September 5, 2025 • 38 mins
This episode features two stories from the Science Podcast. First, Science writer Ann Gibbons tells the story of three ancient hominin species that lived side-by-side in South Africa’s Cradle of Humankind. Then, anthropologist Melanie Beasley discusses her new study on why chemical signals in Neanderthal teeth and bones make them look like hypercarnivores. Her research suggests they were just eating a lot of maggots!
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(00:04):
- This is Origin Stories,the Leakey Foundation podcast.
I'm Meredith Johnson. Todaywe have a very special episode
with two curated storiesfrom our friends at the
Science podcast.
The Science Podcast is aweekly show from the Journal
Science and the American Association
for the Advancement of Science.
Each week on the Science podcasthost Sarah Crespi explores
(00:27):
the latest discoveries with researchers
and news writers from around the world.
You'll learn about everything from
how scientists are battlingstink bugs, using Samurai wasps
to peacock tail, feathersability to emit laser light,
and how ant eaters haveevolved at least 12 times.
Sarah and the team at Science sent us two
(00:48):
stories just for you.
The first story is fromproducer Kevin McClain,
who you might remember from hisorigin stories episode about
Capuchin monkeys that use Stone tools.
In this first segmentfrom the Science podcast,
Kevin interviewed Ann Gibbons,a writer at Science Magazine
who specializes in storiesabout human evolution.
(01:09):
Anne recently wrote a featureabout discoveries in South
Africa's cradle of humankindwhere researchers found remains
of homoerectus
and two other species
of ancient hominins suggestingall three coexisted at the
same time in the same place.
- Hi Anne. Welcome backto the Science podcast.
- Thanks- For having me.
- We are so glad to have you back.
(01:30):
You know, I know we have a bunch
of different ancestralcharacters all living together
and I wanna get into them,
but first, when did youfirst get wind of this story
and when did you start tracking it?
- We have known for quite some time
that different hominins probablyoverlapped in Africa early
on more than 2 million years ago.
(01:51):
We know this from differentfossil sites in East Africa
and South Africa, but nailingit down has been really hard
because when you find fossilsin a layer of sediment,
that layer can represent a day or two,
or it can represent thousands of years
or tens of thousands of years.
So it's hard to prove it,
but we've been gettingwhiffs from different places.
Not only have fossils been foundin the same layers roughly,
(02:13):
but footprints were found in East Africa.
So this story has beengetting interesting.
We've beginning to seethis magical coexistence.
And a couple of years agoat a meeting at Stony Brook
University, I heard thispaleo anthropologist,
Jose Bragga talk about hiswork at this famous site
of Crom Dry in the Cradle of Humankind,
which is a historic site
(02:34):
where people have beenworking for a long, long time.
And he talked about finding fossils
of baby homo early homoerectus,
and also fossils of babycarus in the same layer.
And I thought, oh my goodness,
they're right next to each other.
And then as I looked intoit, it wasn't just his site,
it was another site nearby
and I thought, oh, I've got to get there.
I've gotta get there and I'vegotta see this for myself.
(02:56):
And then I just waited untilthe different teams working at
the different sites wouldbe there at the same time.
- Yeah, you actually got achance to go and visit the sites.
I know you've written a lot about some
of the famous sites in East Africa,
but had you ever been to any
of these places in South Africa before?
- Yeah, I had not been to South Africa,
and I've always wanted to go,
which when I got there I thought,
(03:16):
why didn't I get here sooner?
I can't believe I have not beento the cradle of humankind,
which is, you know, a storied place.
South Africa is also thefirst place where a fossil
of a member of the human family.
A hominin was found a hundredyears ago by Raymond Dart.
Certainly the earliest members
of the human family arose in East Africa,
but South Africa has yieldedincredibly important fossils
that illuminate othertimes in human evolution.
(03:38):
What I was really interestedin was when the first members
of our genus, homoHomoerectus start to appear
around 2 million yearsago, this is a species
that is a key human ancestorthat eventually starts
to have a much bigger brainand a body plan more like ours.
And just a few years ago,a team in South Africa
that worked at a site calledDrin found erectus dating
(04:02):
to about 2 million years.
They said that these were theearliest members of erectus.
That to me, was a reallyinteresting moment when our genus
is beginning to evolve,so it begins more like us.
But who else was aroundwhen that was happening?
How did it that influence it?
- Can you give me a rundownof the different hominins
that you were talking about in the story?
(04:23):
- At Chrome Dry and Drin
and another site called Swar crons,
researchers have found twodifferent era, different genus.
We're not even talking differentspecies, it's bigger than
that early homo, which is our genus,
and also paranthropus, whichis this, it means beside man,
paranthropus and law andParanthropus was a hominin.
(04:45):
It was a upright walking.
These are all upright walking apes,
really, which is what we are.
They're upright walking hominins.
They didn't really look like us.
You wouldn't, as as otherresearchers have said,
you wouldn't really necessarilyinvite them to dinner.
They're gonna be hairysmall brained with brains,
not much bigger than an apes walking
around on the landscape upright.
They are living in this areatogether. Opus is more robust.
(05:07):
The first thing you would'venoticed about it is this huge
head, which seems disproportionateto its small body.
So that's Parentis much more robust.
Jaws and Skull early homo, still
with a brain about athird bigger than an apes,
not huge at this point, probablystill quite small as well.
And then you also havelingering, we think,
with some overlap based ondates from another site.
(05:30):
We think OSUs.
Now, if you've heard ofLucy, her genus was OSUs.
She lived about 3.1 millionyears ago in Ethiopia.
There is another type of OSUsin South Africa that starts
to appear at least 3million years ago called O
Osteous Africanist, maybemore than one species.
There's a lot of debate about this.
(05:50):
Asopus appears first in South Africa.
That was what the Tongchild was from the 1920s
and this beautiful skeleton little foot
around 3 million years ago.
So we've got these differentforms, very different kinds
of hominins all living inan incredibly small area.
- When I was reading your story,
I loved seeing the portraitsof the different hominins
or you know, what wethink they looked like.
(06:12):
You can totally see exactlywhat you're talking about.
Homoerectus is it's our genusand it looks the most like us.
And then you get thatsmaller Australopithecus,
and then you've got that bighead and jaw of Paranthropus.
There's also a really nice mapin the story to give a sense
of the geography of the place.
I was so surprised thesesites are really not very far
(06:33):
apart from each other.
- So that's the magic of South Africa.
What's really specialabout South Africa is
that these fossil sites arein a little area we're calling
today the cradle of humankind.
Okay. It's a UNESCO World Heritage site,
which is roughly the sizeof the District of Columbia,
or you know, the principality of Andor,
whatever's most familiar to you.
Yeah, the actual case sitesI went to are even closer.
(06:54):
So all these caves, the areasriddled with these caves
where researchers arefinding incredible diversity
of prominence at different times,
but especially around 2 million years ago,
we've got these differentkinds that were all there.
And the big riddle isdid they see each other?
Did they coexist? We know they were there
roughly at the same time.
And some of the researchers Italked to all seem to think,
(07:16):
it's almost hard to believe
that they couldn't haveseen each other, given
how many fossils are atso many different sites.
But you can't absolutely prove that
unless you find them intertwined
or you have DNA to show that they made it.
And we don't have DNA thatearly yet for Hominins.
- The thing that was alsointeresting to me is that,
you know, you mentioned this,
these aren't new research sites.
People have been looking inthese places for a while,
(07:37):
but there's sort of newfindings coming out of them.
What happened that helped people kind
of make so much progress? Recently,
- Robert Broom frowned CromDry in the 1930s, 1938.
He'd been working at Stir Fontaine
and a schoolboy foundsome teeth at another site
and he realized theydidn't come from there.
And then he had the boy showhim where he found them,
(07:58):
and it turned out it wasCrom Drive Farm, which is
where we actually stayed
and where Jose Brock is workingtoday, he went there in 2002
and he started reexcavating some of the sites
that had been looked at in theinterim, found the old pits
because there were oldCoca-Cola cans in the pits.
He was able to discover whereexactly the older fossils
were a dozen years.
He didn't find a single helmet
and he was beginning tothink about going to Mongolia
(08:19):
to look for fossils instead,
when one day sitting in thesediments, a tooth fell from
above in the wall where he wasworking, hit him on the thigh
and it turned out it wasa tooth from early homo.
Then he found morefossils of this baby homo,
and a few months later hefound the paranthropus.
So he was in the samelayer right next to it.
So that was terribly exciting.
Then more recently, he's found something
(08:40):
that looks like a skull.
It's a beautiful skull thatmaybe from Ostro Pitus all in
the same area that has startedhappening in the mid 2015,
somewhere in there, 2014.
Since then, people atDrand found new fossils
and in addition to findingnew fossils, dating methods
and other methods of analysishave gotten more sophisticated
to help them look at theriddle of coexistence.
(09:02):
- What are some of themethods that have improved?
How have they helped thisdiscovery process along?
- One of the key methodswas Robin Pickering,
who's at the University of CapeTown, has been using uranium
and lead dating, whichis radiometric dating
to date the minerals in the layers
to date those layers precisely.
And if she can find the layersabove and below a fossil
(09:23):
and feel pretty reliably thatit's in the proper context,
she can get a prettygood ballpark of dates.
Then Andy Harry's fromLatrobe University can come in
and date the reversals inthe paleomagnetic field.
She will give him a window of time
and he can figure out exactly
and much more precisely whenthat layer was laid down.
So those methods together, along
with some other emerging methods,
(09:44):
which are a little more controversial,
have helped research begin
to really get a better handle on dates.
And the sites I'm writingabout are all in about the
2 million year ballpark.
Meanwhile, there are other methods.
You can look at the isotopesand the teeth to look at diet
because not only do we wannaknow if they were there at the
same time, but you wannaknow, were they competing?
- Yeah, what do we know about
how they divided up the landscape
(10:06):
and the food resourcesthat were available.
- What's really interestingis researchers have a long
thought when you look at the anatomy
of paranthropus versus homo,
it's got this gigantic humongous jaws
and big robust skull with a crest on top
so the jaw muscles can attach up there.
So researchers thought it mustbe eating a hard diet of nuts
and difficult things to chewtubers, things like that.
(10:27):
And that was how it adapted.
And meanwhile, maybe earlyComo was using stone tools more
and maybe eating more meat, a softer diet.
However, it's not as simple as that.
There was a new study by JoseBragga and his colleague Dr.
Balter, who looked Atium isotopes
and other researchers havelooked at other aspects of diet
and they see that philanthropistsactually had a broader
(10:49):
diet that people thought itwasn't quite such a specialist.
Maybe that robust jaw was anadaptation for hard times.
You know, when there wasn'tmuch food around, maybe
that jaw helped it survive.
Meanwhile, early homeless,
quite a generalist probablyeating figs and plants too,
but some more meat at that point.
It may be scavenging, not hunting a lot.
We don't know, right? Thisis early days for butchering.
(11:11):
We don't know if it'sgot fire or cooking yet.
This is awfully early for that.That probably came in later.
This was also a journalisteating a lot of plants
and occasion probably meet when it could.
The other mystery in all thisis that stone tools appear
before this in East Africa, atleast 2.7 million years ago,
maybe as early as 3.3million years ago, which,
(11:32):
and sometimes found in association
with opus a different species.
So this suggests that morethan one of these types
of hominins is already using stone tools
to process their food or butcherwhatever they were doing.
So diet may not be the key
to why they are different.
And so Jose and peopleat Drin, Gary Schwartz
(11:53):
and others have been looking,especially at the infants.
There are lots of infants at these sites,
which is really, really interesting.
But there are a lot moreparanthropus infants that have died
and ended up in these sitesthan there are homo in ratio
to the adult fossils they find.
And so question is, is that real?
Is there a lot more infantmortality in Paranthropus?
(12:13):
If that's true,
what is Paranthropus doingdifferently from early homo
that is leading to so many infants dying?
We do know that all these hominin, ticus,
paranthropus and early homoare weaning their infants
earlier than chimps wean theirs.
Chimps nurse their infantsfor four years or so.
So that means motherscan't have as many babies
(12:36):
'cause of their nursing one,they can't have another.
And the infants aredependent for a long time.
What's happening withthese hominins is they're
weaning their infants earlier.
They can tell from theisotopes in their teeth
and the mark growth lines.
And so that's a strategyperhaps when there's lots
of predation pressure, alot of horrible predators,
big saber tooth tigers, allsorts of things were around.
So maybe they're producingmore babies faster,
(12:57):
but somehow early homo babiesmay be surviving better.
There's some interestinghypotheses out there
that are not proven yet thatare really interesting ideas
and that is that maybe homohad a social strategy already,
their weaning maybe a littlelater, they haven't proven this
yet, but they're seeing signs of this.
And perhaps the social group was able
to provision the motherlonger to help take care
(13:20):
of the infants better, to escape predators
to survive on the landscape.
We know eventually thathomoerectus and early ho
or somewhere in human evolution
before homo sapiens,
we ended up developinga life history strategy
where we took longer togrow up where our children
had a longer childhood, which allowed
for more social learning.
(13:41):
We had bigger brains and allowedfor more social learning.
So we were more successful as adults
and more successful as parents
and more of our offspring survived.
The big mystery is when did that kick you?
When did Homo do that?
And Jose Bragga
and some others think maybethey'll get clues this early on
at these sites as JoseBragga says, these infants
as the babies in the cradlethat may offer a window
(14:04):
to the emergence of a deeplyhuman kind of cooperation
and life history strategy.
- What do we know about whythis particular place is
where all these prominencewould've shown up?
- There was water everywhere.
So there was a beautiful valleywith lush trees, fig trees,
things to eat, places theycould build their sleepiness.
And the caves nearbyalso had water in them.
(14:26):
When you have a cavesystem, this car system
of the caves, there's lots of water.
So in otherwise arid landscape,
probably they were following the water
and it brought them into the area.
They ranged beyond it.
They were probably nomadic
as hunter gatherers are todaymoving across the landscape.
But they would end up thereprobably in dry times,
especially plus this is
where they were beautifully preserved.
(14:46):
That's the other part of this.
It's not just, you know, theyweren't just in the caves,
but the caves are this car system.
They get buried.
The water that's trickling in,
that draws 'em there alsoturns the sediments into almost
like the cement like brecher.
And it covers the fossils in ways
that preserves them beautifully.
So you have an incrediblegraveyard basically
(15:09):
preserving fossils there.
The hominins wereelsewhere on the landscape,
but this is where they'rebeautifully preserved.
- Could you maybe justzoom out a little bit
and just talk about how doesthis potential coexistence
story, how does it mesh or
or not mesh with what we've always sort
of historically thoughtabout human evolution?
- So a long time ago, ErnstMayer was a famous evolutionary
(15:31):
biologist who proposed this notion
that hominins human evolution was special.
We weren't like other aidsthat there was one kind
of hominin at a timeevolving into another.
And it was sort of thiswonderful, straight, neat line
of descent from early OSUs
to early homo to us.
But even he started
to disbelieve this probablyin the seventies when we began
(15:53):
to find even in East Africa.
By then at gorge researchersfound paranthropus
and homo near each otherin similar segments,
roughly dated at the same time.
So we began to realize we werenot the only hominid on the
landscape, but the question was, was
that at the same time or not?
And then I think the big breakthrough
that has made a huge differencein people's understanding
(16:14):
of human evolution has been
with the ancient DNA revolutionin the last 15 years.
We found that we interbred with Neals,
as you said in the beginning,
and also these other kindsof hominins called dead sos.
We have DNA from them as well.
They were cousins ofNeals that lived in Asia.
So we know that we, ouranswers homo sapiens br
with anything else itcould the other hominin.
(16:36):
And they actually hadoffspring that survived
because we have this percentageof DNA, this suggested
that this was a human strategy.
And it's hard to believethat we didn't do this all
through human evolution becauseall other rapes do this.
You've got inner breedingbetween different species
of orangutans in the wild and in the zoos.
You've got it betweensubspecies of chimpanzees,
(16:58):
even though they have moregenetic variation than we
do as a species.
I think most researchersthink, yes, we did coexist
with other hominins,we probably interbred.
But how do you show that?How do you prove it?
That's why these fossilsites are so interesting
because they're in such asmall area of time and space.
And so if there's any placethat's promising for this,
this is one of the sites.
- Well, thank you so much, Ann.
(17:19):
It's always so much fun to hear from you
and hear how excited you areabout these new findings.
- It's the best beatof all human evolution.
- Anne Gibbons is a contributingcorrespondent at science.
You can find a link tothe story we discussed at
science.org/podcast.
(17:41):
- The second story fromthe science podcast is a
conversation withanthropologist Melanie Beasley
about a surprising
and kind of gross new discoveryabout what Neanderthals ate.
Every episode of theirpodcast has segments like this
interviewing scientists abouttheir brand new research.
It's a great way to stayinformed about all kinds
(18:03):
of fascinating science.
Here's host Crespi.
- Teeth and bones contain isotopes
that tell us somethingabout what someone ate
during their lifetime.
I first encountered this idea when talking
with a researcher aboutthe fall of the war.
People in Peru, around 800ce, their bones toe to tail
(18:24):
of violence and limited food.
The isotopic ratios in bonesalso place animals on different
trophic levels.
Are they eating mainlyplants, mainly animals?
Where on the food web are they?
When this question was askedabout Neanderthals, they read
as hyper carnivores.
(18:45):
Their isotope ratios madethem look like lions,
more meat intents than lions.
But these cousins of ours have similar
digestive systems to us.
They're not like hyenas anthropologists.
Melanie Beasley wrote InScience advances about another
possible cause of thesesurprising numbers,
Neanderthals could be eating fly larvae
(19:06):
from petrifying meat.
Hi Melanie, welcome toscience podcast. Hi, thank
- You so much for having me.
- I think to get to themeat of this issue, the meat
of the issue, we really needto talk about the isotopes.
Just kind of a quick overview of
what isotopes we're lookingat, what this number is,
this level is, and then we'll kind
(19:26):
of keep it simple from then on.
But let's just dive into that real
- Quick.
The easy way to think about isotopes
is you are what you eat.
And so all of the foods that you eat
and consume, they have nitrogen
and carbon as well as other elements.
But what we mainly focus on
with diet is nitrogen and carbon.
And when you look at thisin the bone collagen,
(19:49):
so the organic protein kindof component of your bone,
that's what it's doing isit's giving you an idea of
what proteins are being consumed
by whatever you'reanalyzing, be it a deer,
be it a neanderthal modern human.
And so the nitrogen comes intwo different isotope forms.
There's the heavy nitrogen, the N 15,
(20:10):
that's the very rareisotope form of nitrogen.
And then there's theabundant light isotope,
which is nitrogen 14.
And so the delta N 15 value
that we're looking at isactually a ratio of N 15
to N 14 compared to a standard.
And so all that we're lookingat in these values is how much
(20:31):
of that rare to abundant isotope is there?
And it turns out during decomposition,
as the body breaks down, then
what you get is the lightisotope will be the first isotope
to react in these chemical reactions
that are releasing thesevolatile compounds.
And so that means that the muscle,
(20:53):
the body retains the heavier isotope
compared to the light isotopes.
You get this change in theseisotope ratios of the heavy
to the light isotope.
And over time, as youcontinue to lose more of
that light isotope faster,
'cause that's reacting fasterin that chemical reaction,
you then get a higher andhigher delta N 15 value.
(21:15):
- How does that link inwith what you're eating?
Like say saying you know you ate a lot
of meat versus you are moreof a herbivorous animal?
- I work in Californiaas a bio archeologist,
and so I like to use the deerexample where you have grass
that's gonna have astarting nitrogen value.
A deer eats the grass
(21:36):
that's gonna have a trophic level offset.
So a standard kind of valuethat is offset between the food
that you're eating and theanimal that is consuming it.
And so that would be your herbivore value
or your primary consumer.
Then in the trophic food web,if a carnivore eats that deer,
so say a wolf comes along,eats that deer, it's going
(21:58):
to have that same offset,
but now is that secondary consumer
so you're gonna get an even higher value.
And so what's interestingabout the Neanderthals is when
this first research was done in the 1990s
and they were extracting the bone collagen
and able to isolate thenitrogen isotope values for
what they originally found is
(22:19):
that Neanderthals were atthe top of the food wet.
They were above the carnivores.
And that's where this narrative
of hyper carnivore camefrom is they've got nitrogen
values above carnivores.
They must be doing thisas a hyper carnivore,
- They must be eating tigers,- Whatever.
Exactly. But of course that's not
what they were consumingbased on the bone remains
(22:40):
that were at thesesites, we knew they were
eating herbivores.
So it was always thisquestion of like, okay,
well are they just eating more meat?
Is that where this hypercarnivore is coming from?
- Is that what bones were around?
Is that what made you saythis probably isn't right?
That this has to be some other reason
for their nitrogen valuesto be where they're at. The
- Pushback that has alwaysbeen there in thinking about
(23:03):
these high nitrogen values is that we know
that Neanderthals are a hominin.
Hominins are primates.
We have evolved as a primate, digestive
and metabolic system.
And so we aren't designed evolutionarily
to just be primarily eating flesh.
We aren't a carnivore.
So there are limits tothat amount of protein
(23:26):
that we can consume.
- I thought this was sointeresting, the idea
that there is thisalmost like a hard limit.
Like if you're eatingbut more than 300 grams
of meat a day, you'regonna overwhelm your liver.
You are, you're gonna not be able to deal
with all that nitrogen.
- That's the amazing part is this is known
by these historic explorers.
(23:48):
Like think about theseexplorers coming across
North America.
They would actually starvewhat was referred to
as rabbit starvation
because they would haveall of the meat protein
that they could eat, that theywouldn't have carbohydrates.
They'd be hunting lean game meat.
So they wouldn't be eating thosefatty portions necessarily,
and they would starve.
(24:08):
- You talk about what indigenouspopulations were doing at
that time and they're like,
why are you eating the leg muscles?
We eat the fat and the brain.
They went for the fatty stuff
because they had figured out over time
that you cannot just eatlike this nitrogen rich,
straight up amino acid.
Absolutely and survive.
(24:29):
- We think about, you know,Sunday roast for dinner.
That's not what early hominins
and prehistoric indigenousgroups were doing.
They were going for the fatty bits.
- One other thing that came out of
that historical perspectivewas that you know,
and you have these quotes all
- Collected and curated byJohn Smith, my co-author.
He is an absolute biblio file
(24:51):
of collecting this justrich ethno historic quotes
that span the world.
I would love it if you'd read one of
- The quotes from the paper.
- Oh, I'll read the first one, the intro
because that's my absolute favorite.
Okay. The meat was green with age,
and when we made a cut in it,
it was like the bursting of a boil.
(25:11):
So full of great white maggots was it?
To my horror, my companionscooped out handfuls
of the crawling things andate them with evident relish.
I criticized their taste,
but they said not illogicallyyou yourself like caribou meat
and what are these maggotsbut live caribou meat.
They taste just the same as the meat
(25:34):
and are refreshing to the mouth.
- It's not like it was only in hard times
that they wanted this resource.
This was something they actually,I wouldn't say cultivated,
but it was not accidentalwith they encountered maggots.
- That is correct. It'sdefinitely not accidental.
I actually tried
to put the word cultivatedin the paper. Yeah, you
- Gotta get in trouble.
(25:55):
- My co-authors were like,that's pushing it a little far.
You gotta gotta reign that in.
But in my mind, you know, in Neanderthal,
these prehistoric foraging groups,
early anatomically modern humans,
they would've quickly observed
that these maggot masseswould be associated
with a butchered decomposing carcass.
(26:15):
So even if they hunted
and took those choice pieces first,
they might not have taken theentire carcass back with them
to wherever they were storingor consuming the food.
But I bet you that they werelike, ah, that carcass is there
and I'm gonna come back in a week or two
and I'm gonna be able toscoop up those fatty tasty
(26:36):
maggots and just get aquick energetic treat
by popping that in my mouth.
- Do we have any evidencethat they were storing
meat for later?
- I don't know
that we have specificevidence of storage of meat.
They were not eating meat likea carnivore was eating meat.
(26:58):
They were doing something toit, storing it, cooking it,
drying it, doing some sortof cultural processing of
that food like humans do.
And that that is what we're seeing
with these high trophic values that aren't
what are expected.
And of course you can'tprevent the flies from getting
(27:19):
there, so you can't getaway from those maggots.
And so that is probably themaggots are getting in there.
You're getting that additivefood on that paleo menu,
which is also raising the nitrogen value.
- Yeah, let's get into that.The paper takes us a step in
the direction is seeing if wecan detect intentional maggot
eating in the inter tunnels.
(27:40):
Step one, find out
how much fly larva mightinfluence the nitrogen levels.
You can do this by testing a tissue,
then testing the petrifying tissue
and then testing thelarva after they eat it.
Before we go into those likesteps of your experiment,
you used human tissue to do this.
(28:00):
Can you talk a little bit aboutwhy you decided to do that?
It's really more of a story
- Than anything else ofeverything aligning perfectly.
John Beth was doing this research,
his 2017 paper proposing putrid meat
and he came to gave atalk at uc, San Diego,
and I went up to him afterwardsand I was like, John,
I'm applying to a postdocat University of Tennessee
(28:21):
to the forensic anthropology center
and do isotope experimental research.
I could propose to them
to look at the decomposing tissue
and see what happensto the nitrogen values.
And when I got there, Ibasically asked, I said,
I have this idea and it has dual purpose
because by doing it withhuman tissue at the body farm,
(28:43):
at the forensic anthropologycenter in Tennessee,
which is the world famous known
as the body farm was started in the 1980s
that focuses on humandecomposition research
for doing forensic anthropology casework.
I could say nobody's lookedat this as a estimation
of time since death.
This could be a new method
(29:05):
that we could use in forensicanthropology to estimate
how long someone has been deadduring that period of time.
That is often difficult to identify
how long have they beenactively decomposing.
And so for me it was usingthis real world applied
anthropology forensiccasework related project
(29:27):
that then I could take that same data
and use it for this proposalof high nitrogen values
and Neanderthals becausemuscle tissue is muscle tissue.
- So I was wonderingif it was like starting
with the trophic level people
and then seeing if what the maggots did,
but it sounds like thatwas not as important
as having access and like meet as meat
(29:49):
and it had this dual purpose.
- Exactly. And in the paper Ido talk about essentially if
you adjusted what that startingsubstrate muscle level was
for what we use in humans,
but we adjusted that to just the average
of the herbivore meat value.
You still get nitrogen valuesthat are of the fly larvae
(30:10):
that are astronomicallyhigher than anything else
that we see that would be being consumed.
And to put this inperspective, when you think
of high nitrogen value foods,we're thinking marine mammals,
pinnipeds consumption of seals.
- That's just like thisendlessly long chain of food.
(30:31):
Like you're just at plankton
and then like seven kinds of fish
and then you finally get tosomething fatty, like a pin ape,
like a seal or a shark or whatever.
That's just eaten the entirefood web basically in one bite.
- Absolutely. But even in those values,
you're only getting into likethe low 20 per mil kind of
for at most.
(30:53):
And these fly larvae go up to43 per mil. Oh my gosh. It's
- Astronomically high, right?
And like a lion is like an eight, right?
- It might be more like eightto 10, somewhere in that
- Range, eight to 10,- Right?
I'd have to look at the exactvalues for the averages.
- So a lion is more like a 10
and then you have these seedeaters, there are like a 20.
And then for some reason themaggots eating petrified flesh
(31:16):
are 40.
Does the petrifying fleshpart make a difference?
Does it matter if it's fresh tissue
or petrified tissue? It does.
- It ups the number onorders of magnitude.
So the black soldierflies, they arrived in June
and I sampled them from June
until essentially December whenI can no longer collect live
(31:39):
fly larva anymore.
And that just trend increasesand increases and increases.
And so part of it is thatthe muscle is long gone,
the tissue is long gone.
But what has happenedis through decomposition
that let's say soupy decomp,
fluid rich soil is what theflies are still attracted to.
(32:00):
And those magnets arecontinuing to develop in
that soupy nutrient rich soil.
That cycling of nitrogen is continuing.
And though those maggotmasses are still associated
with a skeleton,
they're not actually feeding on the fresh
muscle tissue anymore.
That's been gone forsix months, nine months.
(32:24):
But that fly larvae still there in mass,
like huge masses of flyalarm. It's incredible.
- The idea then is that youcan go back to a kill site
and say, oh, there's notreally much for me to chew on,
but look who's beenchewing on things for me
and I can now harvestthat from the maggots.
- Absolutely. The interestingthing too is like you think
(32:45):
of lean gain meat.
The maggots are converting
that lean gain meat into afatty additive basically.
So now you're getting amore nutritiously complete
paleo menu item.
- You looked at a numberof different flies
and their larva over this period of time.
There are three species.
Did these guys coexistwith neander tunnels?
(33:06):
Like were they around at thesame time in the same place
where these measurements were taken?
- So we don't know specificallythat the specific species
of black soldier flies were around,
but we do know that thefamily of flies were around at
that time and had alreadyevolved concurrently.
And so there would've been flies.
Flies would have been there and landing
(33:27):
and interested in this animal stored
- Foods and it wasn't too cold
for them or anything like that.
'cause you went all the way to December in
Tennessee, which is pretty cold.
- It is pretty cold. Andactually if you look at the
temperatures in Tennessee
and look at some of theexperimental research
that's been done inNeanderthal temperatures,
there is overlap.
- Okay. Let's talk a little bit about some
(33:49):
of the alternative explanations here.
Like as we mentioned like eating out
of the sea can reallyboost nitrogen levels.
Is it possible that Neanderthalsomehow had access to a lot
of fish, a lot of hightrophic level sea critters
and that kind of, or termites?
I don't know, something else, like
how do we eliminate thoseother possibilities?
- I don't think that we do.
(34:09):
I think we need to reframethis focus on hyper carnivore
and mammoth eating and eating so much meat
and we need to kind of tryto change this narrative
and this narrative therehas been pushback on
for the last 20 years and yet it persists.
- Oh yeah. If we look atanatomically modern humans
(34:30):
that were coexisting withNeanderthals at this time,
what are their nitrogen isotope levels?
Exactly the same as
- Neanderthals of thepublished literature.
And I included it in the paper,the mean values of nitrogen
for Neanderthals and the mean values of
for anatomically modernhumans are exactly the same.
(34:51):
- So everybody was at the barbecue,
everyone was eatingputrid meat with the side
of maggots. Everybody.
- Absolutely. And Ithink the push has been,
when you look at the archeologicalrecord, the associated,
so archeological bony remainsanatomically modern humans are
often associated with havingtheir high nitrogen value
explanation is eating freshwater, fish, eating waterfowl,
(35:14):
eating a wider diversity offood, so having a wider diet.
Neanderthals, the focushas been on hyper carnivore
because you get the terrestrialmammal bones at those sites.
You don't see the fish, youdon't see the waterfowl.
And so that's where even thoughthey have the same values,
this interpretation hasdiverged in these two
different directions.
But you have the grand
(35:35):
- Unifying theory of maggots.
- Yes, I'm gonna becomeknown as maggot Melanie,
it's just gonna be in my future.
The alliteration is there.
- That's really interesting. I had no idea
that it was exactly the same.
At the end of the day, we have data,
but we don't know how to interpret it.
Like we have a test that we like to do
and it's giving us numbers,but we need a story.
(35:58):
We need other things to kind of prop up.
That happens all over science. That's
- The thing is when we'retalking about a story
of Neanderthals, we'vetalked about it in terms
of exceptionalism andhow different they are
and why they're different.
And I think maybe it'stime that we really reframe
who our cousins are.
Are they even actuallycousins or are they just us?
(36:21):
They're probably doing thingslike cooking, storing foods,
processing foods in ways thatthe baseline nitrogen value of
what they were eating is just like
what modern humans weredoing to their foods.
And you end up with thosehigher nitrogen values
that place humans at thattop of that trophic food web.
(36:42):
- I get like pretty squidout by not individual bugs,
but like any kind of, as youkeep saying, masses of bugs.
Like I really get Didyou have like that kind
of problem when you'redoing your field work there?
- No, I did not.
But my background, I worked ata coroner's office, so Okay.
Being around death investigation, being
around dead bodies in variedstates of decomposition,
(37:05):
that's very normal for me.
- Thanks, Melanie. It'sbeen really fun talking.
- Yes, this has been wonderful.
Thank you for having me on the podcast.
- Melanie Beasley isan assistant professor
of anthropology at Purdue University.
You can find a link to thescience advances paper we
discussed at science.org/podcast.
- Thanks to our friendsat the Science podcast
(37:25):
for sharing these stories.
If you wanna stay upto date on a wide range
of fascinating scientific topics,including human evolution,
subscribe to the Science podcast now.
They release a new episode every week.
Origin Stories is a projectof the Leaky Foundation,
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(37:45):
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We'd love it if youwould support this show
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(38:07):
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We'll be back soon withanother new episode.
Thanks for listening.
- This is Origin Stories,the Leakey Foundation podcast.
I'm Meredith Johnson. Todaywe have a very special episode
with two curated storiesfrom our friends at the
Science podcast.
The Science Podcast is aweekly show from the Journal
Science and the American Association
for the Advancement of Science.
Each week on the Science podcasthost Sarah Crespi explores
(00:27):
the latest discoveries with researchers
and news writers from around the world.
You'll learn about everything from
how scientists are battlingstink bugs, using Samurai wasps
to peacock tail, feathersability to emit laser light,
and how ant eaters haveevolved at least 12 times.
Sarah and the team at Science sent us two
(00:48):
stories just for you.
The first story is fromproducer Kevin McClain,
who you might remember from hisorigin stories episode about
Capuchin monkeys that use Stone tools.
In this first segmentfrom the Science podcast,
Kevin interviewed Ann Gibbons,a writer at Science Magazine
who specializes in storiesabout human evolution.
(01:09):
Anne recently wrote a featureabout discoveries in South
Africa's cradle of humankindwhere researchers found remains
of homoerectus
and two other species
of ancient hominins suggestingall three coexisted at the
same time in the same place.
- Hi Anne. Welcome backto the Science podcast.
- Thanks- For having me.
- We are so glad to have you back.
(01:30):
You know, I know we have a bunch
of different ancestralcharacters all living together
and I wanna get into them,
but first, when did youfirst get wind of this story
and when did you start tracking it?
- We have known for quite some time
that different hominins probablyoverlapped in Africa early
on more than 2 million years ago.
(01:51):
We know this from differentfossil sites in East Africa
and South Africa, but nailingit down has been really hard
because when you find fossilsin a layer of sediment,
that layer can represent a day or two,
or it can represent thousands of years
or tens of thousands of years.
So it's hard to prove it,
but we've been gettingwhiffs from different places.
Not only have fossils been foundin the same layers roughly,
(02:13):
but footprints were found in East Africa.
So this story has beengetting interesting.
We've beginning to seethis magical coexistence.
And a couple of years agoat a meeting at Stony Brook
University, I heard thispaleo anthropologist,
Jose Bragga talk about hiswork at this famous site
of Crom Dry in the Cradle of Humankind,
which is a historic site
(02:34):
where people have beenworking for a long, long time.
And he talked about finding fossils
of baby homo early homoerectus,
and also fossils of babycarus in the same layer.
And I thought, oh my goodness,
they're right next to each other.
And then as I looked intoit, it wasn't just his site,
it was another site nearby
and I thought, oh, I've got to get there.
I've gotta get there and I'vegotta see this for myself.
(02:56):
And then I just waited untilthe different teams working at
the different sites wouldbe there at the same time.
- Yeah, you actually got achance to go and visit the sites.
I know you've written a lot about some
of the famous sites in East Africa,
but had you ever been to any
of these places in South Africa before?
- Yeah, I had not been to South Africa,
and I've always wanted to go,
which when I got there I thought,
(03:16):
why didn't I get here sooner?
I can't believe I have not beento the cradle of humankind,
which is, you know, a storied place.
South Africa is also thefirst place where a fossil
of a member of the human family.
A hominin was found a hundredyears ago by Raymond Dart.
Certainly the earliest members
of the human family arose in East Africa,
but South Africa has yieldedincredibly important fossils
that illuminate othertimes in human evolution.
(03:38):
What I was really interestedin was when the first members
of our genus, homoHomoerectus start to appear
around 2 million yearsago, this is a species
that is a key human ancestorthat eventually starts
to have a much bigger brainand a body plan more like ours.
And just a few years ago,a team in South Africa
that worked at a site calledDrin found erectus dating
(04:02):
to about 2 million years.
They said that these were theearliest members of erectus.
That to me, was a reallyinteresting moment when our genus
is beginning to evolve,so it begins more like us.
But who else was aroundwhen that was happening?
How did it that influence it?
- Can you give me a rundownof the different hominins
that you were talking about in the story?
(04:23):
- At Chrome Dry and Drin
and another site called Swar crons,
researchers have found twodifferent era, different genus.
We're not even talking differentspecies, it's bigger than
that early homo, which is our genus,
and also paranthropus, whichis this, it means beside man,
paranthropus and law andParanthropus was a hominin.
(04:45):
It was a upright walking.
These are all upright walking apes,
really, which is what we are.
They're upright walking hominins.
They didn't really look like us.
You wouldn't, as as otherresearchers have said,
you wouldn't really necessarilyinvite them to dinner.
They're gonna be hairysmall brained with brains,
not much bigger than an apes walking
around on the landscape upright.
They are living in this areatogether. Opus is more robust.
(05:07):
The first thing you would'venoticed about it is this huge
head, which seems disproportionateto its small body.
So that's Parentis much more robust.
Jaws and Skull early homo, still
with a brain about athird bigger than an apes,
not huge at this point, probablystill quite small as well.
And then you also havelingering, we think,
with some overlap based ondates from another site.
(05:30):
We think OSUs.
Now, if you've heard ofLucy, her genus was OSUs.
She lived about 3.1 millionyears ago in Ethiopia.
There is another type of OSUsin South Africa that starts
to appear at least 3million years ago called O
Osteous Africanist, maybemore than one species.
There's a lot of debate about this.
(05:50):
Asopus appears first in South Africa.
That was what the Tongchild was from the 1920s
and this beautiful skeleton little foot
around 3 million years ago.
So we've got these differentforms, very different kinds
of hominins all living inan incredibly small area.
- When I was reading your story,
I loved seeing the portraitsof the different hominins
or you know, what wethink they looked like.
(06:12):
You can totally see exactlywhat you're talking about.
Homoerectus is it's our genusand it looks the most like us.
And then you get thatsmaller Australopithecus,
and then you've got that bighead and jaw of Paranthropus.
There's also a really nice mapin the story to give a sense
of the geography of the place.
I was so surprised thesesites are really not very far
(06:33):
apart from each other.
- So that's the magic of South Africa.
What's really specialabout South Africa is
that these fossil sites arein a little area we're calling
today the cradle of humankind.
Okay. It's a UNESCO World Heritage site,
which is roughly the sizeof the District of Columbia,
or you know, the principality of Andor,
whatever's most familiar to you.
Yeah, the actual case sitesI went to are even closer.
(06:54):
So all these caves, the areasriddled with these caves
where researchers arefinding incredible diversity
of prominence at different times,
but especially around 2 million years ago,
we've got these differentkinds that were all there.
And the big riddle isdid they see each other?
Did they coexist? We know they were there
roughly at the same time.
And some of the researchers Italked to all seem to think,
(07:16):
it's almost hard to believe
that they couldn't haveseen each other, given
how many fossils are atso many different sites.
But you can't absolutely prove that
unless you find them intertwined
or you have DNA to show that they made it.
And we don't have DNA thatearly yet for Hominins.
- The thing that was alsointeresting to me is that,
you know, you mentioned this,
these aren't new research sites.
People have been looking inthese places for a while,
(07:37):
but there's sort of newfindings coming out of them.
What happened that helped people kind
of make so much progress? Recently,
- Robert Broom frowned CromDry in the 1930s, 1938.
He'd been working at Stir Fontaine
and a schoolboy foundsome teeth at another site
and he realized theydidn't come from there.
And then he had the boy showhim where he found them,
(07:58):
and it turned out it wasCrom Drive Farm, which is
where we actually stayed
and where Jose Brock is workingtoday, he went there in 2002
and he started reexcavating some of the sites
that had been looked at in theinterim, found the old pits
because there were oldCoca-Cola cans in the pits.
He was able to discover whereexactly the older fossils
were a dozen years.
He didn't find a single helmet
and he was beginning tothink about going to Mongolia
(08:19):
to look for fossils instead,
when one day sitting in thesediments, a tooth fell from
above in the wall where he wasworking, hit him on the thigh
and it turned out it wasa tooth from early homo.
Then he found morefossils of this baby homo,
and a few months later hefound the paranthropus.
So he was in the samelayer right next to it.
So that was terribly exciting.
Then more recently, he's found something
(08:40):
that looks like a skull.
It's a beautiful skull thatmaybe from Ostro Pitus all in
the same area that has startedhappening in the mid 2015,
somewhere in there, 2014.
Since then, people atDrand found new fossils
and in addition to findingnew fossils, dating methods
and other methods of analysishave gotten more sophisticated
to help them look at theriddle of coexistence.
(09:02):
- What are some of themethods that have improved?
How have they helped thisdiscovery process along?
- One of the key methodswas Robin Pickering,
who's at the University of CapeTown, has been using uranium
and lead dating, whichis radiometric dating
to date the minerals in the layers
to date those layers precisely.
And if she can find the layersabove and below a fossil
(09:23):
and feel pretty reliably thatit's in the proper context,
she can get a prettygood ballpark of dates.
Then Andy Harry's fromLatrobe University can come in
and date the reversals inthe paleomagnetic field.
She will give him a window of time
and he can figure out exactly
and much more precisely whenthat layer was laid down.
So those methods together, along
with some other emerging methods,
(09:44):
which are a little more controversial,
have helped research begin
to really get a better handle on dates.
And the sites I'm writingabout are all in about the
2 million year ballpark.
Meanwhile, there are other methods.
You can look at the isotopesand the teeth to look at diet
because not only do we wannaknow if they were there at the
same time, but you wannaknow, were they competing?
- Yeah, what do we know about
how they divided up the landscape
(10:06):
and the food resourcesthat were available.
- What's really interestingis researchers have a long
thought when you look at the anatomy
of paranthropus versus homo,
it's got this gigantic humongous jaws
and big robust skull with a crest on top
so the jaw muscles can attach up there.
So researchers thought it mustbe eating a hard diet of nuts
and difficult things to chewtubers, things like that.
(10:27):
And that was how it adapted.
And meanwhile, maybe earlyComo was using stone tools more
and maybe eating more meat, a softer diet.
However, it's not as simple as that.
There was a new study by JoseBragga and his colleague Dr.
Balter, who looked Atium isotopes
and other researchers havelooked at other aspects of diet
and they see that philanthropistsactually had a broader
(10:49):
diet that people thought itwasn't quite such a specialist.
Maybe that robust jaw was anadaptation for hard times.
You know, when there wasn'tmuch food around, maybe
that jaw helped it survive.
Meanwhile, early homeless,
quite a generalist probablyeating figs and plants too,
but some more meat at that point.
It may be scavenging, not hunting a lot.
We don't know, right? Thisis early days for butchering.
(11:11):
We don't know if it'sgot fire or cooking yet.
This is awfully early for that.That probably came in later.
This was also a journalisteating a lot of plants
and occasion probably meet when it could.
The other mystery in all thisis that stone tools appear
before this in East Africa, atleast 2.7 million years ago,
maybe as early as 3.3million years ago, which,
(11:32):
and sometimes found in association
with opus a different species.
So this suggests that morethan one of these types
of hominins is already using stone tools
to process their food or butcherwhatever they were doing.
So diet may not be the key
to why they are different.
And so Jose and peopleat Drin, Gary Schwartz
(11:53):
and others have been looking,especially at the infants.
There are lots of infants at these sites,
which is really, really interesting.
But there are a lot moreparanthropus infants that have died
and ended up in these sitesthan there are homo in ratio
to the adult fossils they find.
And so question is, is that real?
Is there a lot more infantmortality in Paranthropus?
(12:13):
If that's true,
what is Paranthropus doingdifferently from early homo
that is leading to so many infants dying?
We do know that all these hominin, ticus,
paranthropus and early homoare weaning their infants
earlier than chimps wean theirs.
Chimps nurse their infantsfor four years or so.
So that means motherscan't have as many babies
(12:36):
'cause of their nursing one,they can't have another.
And the infants aredependent for a long time.
What's happening withthese hominins is they're
weaning their infants earlier.
They can tell from theisotopes in their teeth
and the mark growth lines.
And so that's a strategyperhaps when there's lots
of predation pressure, alot of horrible predators,
big saber tooth tigers, allsorts of things were around.
So maybe they're producingmore babies faster,
(12:57):
but somehow early homo babiesmay be surviving better.
There's some interestinghypotheses out there
that are not proven yet thatare really interesting ideas
and that is that maybe homohad a social strategy already,
their weaning maybe a littlelater, they haven't proven this
yet, but they're seeing signs of this.
And perhaps the social group was able
to provision the motherlonger to help take care
(13:20):
of the infants better, to escape predators
to survive on the landscape.
We know eventually thathomoerectus and early ho
or somewhere in human evolution
before homo sapiens,
we ended up developinga life history strategy
where we took longer togrow up where our children
had a longer childhood, which allowed
for more social learning.
(13:41):
We had bigger brains and allowedfor more social learning.
So we were more successful as adults
and more successful as parents
and more of our offspring survived.
The big mystery is when did that kick you?
When did Homo do that?
And Jose Bragga
and some others think maybethey'll get clues this early on
at these sites as JoseBragga says, these infants
as the babies in the cradlethat may offer a window
(14:04):
to the emergence of a deeplyhuman kind of cooperation
and life history strategy.
- What do we know about whythis particular place is
where all these prominencewould've shown up?
- There was water everywhere.
So there was a beautiful valleywith lush trees, fig trees,
things to eat, places theycould build their sleepiness.
And the caves nearbyalso had water in them.
(14:26):
When you have a cavesystem, this car system
of the caves, there's lots of water.
So in otherwise arid landscape,
probably they were following the water
and it brought them into the area.
They ranged beyond it.
They were probably nomadic
as hunter gatherers are todaymoving across the landscape.
But they would end up thereprobably in dry times,
especially plus this is
where they were beautifully preserved.
(14:46):
That's the other part of this.
It's not just, you know, theyweren't just in the caves,
but the caves are this car system.
They get buried.
The water that's trickling in,
that draws 'em there alsoturns the sediments into almost
like the cement like brecher.
And it covers the fossils in ways
that preserves them beautifully.
So you have an incrediblegraveyard basically
(15:09):
preserving fossils there.
The hominins wereelsewhere on the landscape,
but this is where they'rebeautifully preserved.
- Could you maybe justzoom out a little bit
and just talk about how doesthis potential coexistence
story, how does it mesh or
or not mesh with what we've always sort
of historically thoughtabout human evolution?
- So a long time ago, ErnstMayer was a famous evolutionary
(15:31):
biologist who proposed this notion
that hominins human evolution was special.
We weren't like other aidsthat there was one kind
of hominin at a timeevolving into another.
And it was sort of thiswonderful, straight, neat line
of descent from early OSUs
to early homo to us.
But even he started
to disbelieve this probablyin the seventies when we began
(15:53):
to find even in East Africa.
By then at gorge researchersfound paranthropus
and homo near each otherin similar segments,
roughly dated at the same time.
So we began to realize we werenot the only hominid on the
landscape, but the question was, was
that at the same time or not?
And then I think the big breakthrough
that has made a huge differencein people's understanding
(16:14):
of human evolution has been
with the ancient DNA revolutionin the last 15 years.
We found that we interbred with Neals,
as you said in the beginning,
and also these other kindsof hominins called dead sos.
We have DNA from them as well.
They were cousins ofNeals that lived in Asia.
So we know that we, ouranswers homo sapiens br
with anything else itcould the other hominin.
(16:36):
And they actually hadoffspring that survived
because we have this percentageof DNA, this suggested
that this was a human strategy.
And it's hard to believethat we didn't do this all
through human evolution becauseall other rapes do this.
You've got inner breedingbetween different species
of orangutans in the wild and in the zoos.
You've got it betweensubspecies of chimpanzees,
(16:58):
even though they have moregenetic variation than we
do as a species.
I think most researchersthink, yes, we did coexist
with other hominins,we probably interbred.
But how do you show that?How do you prove it?
That's why these fossilsites are so interesting
because they're in such asmall area of time and space.
And so if there's any placethat's promising for this,
this is one of the sites.
- Well, thank you so much, Ann.
(17:19):
It's always so much fun to hear from you
and hear how excited you areabout these new findings.
- It's the best beatof all human evolution.
- Anne Gibbons is a contributingcorrespondent at science.
You can find a link tothe story we discussed at
science.org/podcast.
(17:41):
- The second story fromthe science podcast is a
conversation withanthropologist Melanie Beasley
about a surprising
and kind of gross new discoveryabout what Neanderthals ate.
Every episode of theirpodcast has segments like this
interviewing scientists abouttheir brand new research.
It's a great way to stayinformed about all kinds
(18:03):
of fascinating science.
Here's host Crespi.
- Teeth and bones contain isotopes
that tell us somethingabout what someone ate
during their lifetime.
I first encountered this idea when talking
with a researcher aboutthe fall of the war.
People in Peru, around 800ce, their bones toe to tail
(18:24):
of violence and limited food.
The isotopic ratios in bonesalso place animals on different
trophic levels.
Are they eating mainlyplants, mainly animals?
Where on the food web are they?
When this question was askedabout Neanderthals, they read
as hyper carnivores.
(18:45):
Their isotope ratios madethem look like lions,
more meat intents than lions.
But these cousins of ours have similar
digestive systems to us.
They're not like hyenas anthropologists.
Melanie Beasley wrote InScience advances about another
possible cause of thesesurprising numbers,
Neanderthals could be eating fly larvae
(19:06):
from petrifying meat.
Hi Melanie, welcome toscience podcast. Hi, thank
- You so much for having me.
- I think to get to themeat of this issue, the meat
of the issue, we really needto talk about the isotopes.
Just kind of a quick overview of
what isotopes we're lookingat, what this number is,
this level is, and then we'll kind
(19:26):
of keep it simple from then on.
But let's just dive into that real
- Quick.
The easy way to think about isotopes
is you are what you eat.
And so all of the foods that you eat
and consume, they have nitrogen
and carbon as well as other elements.
But what we mainly focus on
with diet is nitrogen and carbon.
And when you look at thisin the bone collagen,
(19:49):
so the organic protein kindof component of your bone,
that's what it's doing isit's giving you an idea of
what proteins are being consumed
by whatever you'reanalyzing, be it a deer,
be it a neanderthal modern human.
And so the nitrogen comes intwo different isotope forms.
There's the heavy nitrogen, the N 15,
(20:10):
that's the very rareisotope form of nitrogen.
And then there's theabundant light isotope,
which is nitrogen 14.
And so the delta N 15 value
that we're looking at isactually a ratio of N 15
to N 14 compared to a standard.
And so all that we're lookingat in these values is how much
(20:31):
of that rare to abundant isotope is there?
And it turns out during decomposition,
as the body breaks down, then
what you get is the lightisotope will be the first isotope
to react in these chemical reactions
that are releasing thesevolatile compounds.
And so that means that the muscle,
(20:53):
the body retains the heavier isotope
compared to the light isotopes.
You get this change in theseisotope ratios of the heavy
to the light isotope.
And over time, as youcontinue to lose more of
that light isotope faster,
'cause that's reacting fasterin that chemical reaction,
you then get a higher andhigher delta N 15 value.
(21:15):
- How does that link inwith what you're eating?
Like say saying you know you ate a lot
of meat versus you are moreof a herbivorous animal?
- I work in Californiaas a bio archeologist,
and so I like to use the deerexample where you have grass
that's gonna have astarting nitrogen value.
A deer eats the grass
(21:36):
that's gonna have a trophic level offset.
So a standard kind of valuethat is offset between the food
that you're eating and theanimal that is consuming it.
And so that would be your herbivore value
or your primary consumer.
Then in the trophic food web,if a carnivore eats that deer,
so say a wolf comes along,eats that deer, it's going
(21:58):
to have that same offset,
but now is that secondary consumer
so you're gonna get an even higher value.
And so what's interestingabout the Neanderthals is when
this first research was done in the 1990s
and they were extracting the bone collagen
and able to isolate thenitrogen isotope values for
what they originally found is
(22:19):
that Neanderthals were atthe top of the food wet.
They were above the carnivores.
And that's where this narrative
of hyper carnivore camefrom is they've got nitrogen
values above carnivores.
They must be doing thisas a hyper carnivore,
- They must be eating tigers,- Whatever.
Exactly. But of course that's not
what they were consumingbased on the bone remains
(22:40):
that were at thesesites, we knew they were
eating herbivores.
So it was always thisquestion of like, okay,
well are they just eating more meat?
Is that where this hypercarnivore is coming from?
- Is that what bones were around?
Is that what made you saythis probably isn't right?
That this has to be some other reason
for their nitrogen valuesto be where they're at. The
- Pushback that has alwaysbeen there in thinking about
(23:03):
these high nitrogen values is that we know
that Neanderthals are a hominin.
Hominins are primates.
We have evolved as a primate, digestive
and metabolic system.
And so we aren't designed evolutionarily
to just be primarily eating flesh.
We aren't a carnivore.
So there are limits tothat amount of protein
(23:26):
that we can consume.
- I thought this was sointeresting, the idea
that there is thisalmost like a hard limit.
Like if you're eatingbut more than 300 grams
of meat a day, you'regonna overwhelm your liver.
You are, you're gonna not be able to deal
with all that nitrogen.
- That's the amazing part is this is known
by these historic explorers.
(23:48):
Like think about theseexplorers coming across
North America.
They would actually starvewhat was referred to
as rabbit starvation
because they would haveall of the meat protein
that they could eat, that theywouldn't have carbohydrates.
They'd be hunting lean game meat.
So they wouldn't be eating thosefatty portions necessarily,
and they would starve.
(24:08):
- You talk about what indigenouspopulations were doing at
that time and they're like,
why are you eating the leg muscles?
We eat the fat and the brain.
They went for the fatty stuff
because they had figured out over time
that you cannot just eatlike this nitrogen rich,
straight up amino acid.
Absolutely and survive.
(24:29):
- We think about, you know,Sunday roast for dinner.
That's not what early hominins
and prehistoric indigenousgroups were doing.
They were going for the fatty bits.
- One other thing that came out of
that historical perspectivewas that you know,
and you have these quotes all
- Collected and curated byJohn Smith, my co-author.
He is an absolute biblio file
(24:51):
of collecting this justrich ethno historic quotes
that span the world.
I would love it if you'd read one of
- The quotes from the paper.
- Oh, I'll read the first one, the intro
because that's my absolute favorite.
Okay. The meat was green with age,
and when we made a cut in it,
it was like the bursting of a boil.
(25:11):
So full of great white maggots was it?
To my horror, my companionscooped out handfuls
of the crawling things andate them with evident relish.
I criticized their taste,
but they said not illogicallyyou yourself like caribou meat
and what are these maggotsbut live caribou meat.
They taste just the same as the meat
(25:34):
and are refreshing to the mouth.
- It's not like it was only in hard times
that they wanted this resource.
This was something they actually,I wouldn't say cultivated,
but it was not accidentalwith they encountered maggots.
- That is correct. It'sdefinitely not accidental.
I actually tried
to put the word cultivatedin the paper. Yeah, you
- Gotta get in trouble.
(25:55):
- My co-authors were like,that's pushing it a little far.
You gotta gotta reign that in.
But in my mind, you know, in Neanderthal,
these prehistoric foraging groups,
early anatomically modern humans,
they would've quickly observed
that these maggot masseswould be associated
with a butchered decomposing carcass.
(26:15):
So even if they hunted
and took those choice pieces first,
they might not have taken theentire carcass back with them
to wherever they were storingor consuming the food.
But I bet you that they werelike, ah, that carcass is there
and I'm gonna come back in a week or two
and I'm gonna be able toscoop up those fatty tasty
(26:36):
maggots and just get aquick energetic treat
by popping that in my mouth.
- Do we have any evidencethat they were storing
meat for later?
- I don't know
that we have specificevidence of storage of meat.
They were not eating meat likea carnivore was eating meat.
(26:58):
They were doing something toit, storing it, cooking it,
drying it, doing some sortof cultural processing of
that food like humans do.
And that that is what we're seeing
with these high trophic values that aren't
what are expected.
And of course you can'tprevent the flies from getting
(27:19):
there, so you can't getaway from those maggots.
And so that is probably themaggots are getting in there.
You're getting that additivefood on that paleo menu,
which is also raising the nitrogen value.
- Yeah, let's get into that.The paper takes us a step in
the direction is seeing if wecan detect intentional maggot
eating in the inter tunnels.
(27:40):
Step one, find out
how much fly larva mightinfluence the nitrogen levels.
You can do this by testing a tissue,
then testing the petrifying tissue
and then testing thelarva after they eat it.
Before we go into those likesteps of your experiment,
you used human tissue to do this.
(28:00):
Can you talk a little bit aboutwhy you decided to do that?
It's really more of a story
- Than anything else ofeverything aligning perfectly.
John Beth was doing this research,
his 2017 paper proposing putrid meat
and he came to gave atalk at uc, San Diego,
and I went up to him afterwardsand I was like, John,
I'm applying to a postdocat University of Tennessee
(28:21):
to the forensic anthropology center
and do isotope experimental research.
I could propose to them
to look at the decomposing tissue
and see what happensto the nitrogen values.
And when I got there, Ibasically asked, I said,
I have this idea and it has dual purpose
because by doing it withhuman tissue at the body farm,
(28:43):
at the forensic anthropologycenter in Tennessee,
which is the world famous known
as the body farm was started in the 1980s
that focuses on humandecomposition research
for doing forensic anthropology casework.
I could say nobody's lookedat this as a estimation
of time since death.
This could be a new method
(29:05):
that we could use in forensicanthropology to estimate
how long someone has been deadduring that period of time.
That is often difficult to identify
how long have they beenactively decomposing.
And so for me it was usingthis real world applied
anthropology forensiccasework related project
(29:27):
that then I could take that same data
and use it for this proposalof high nitrogen values
and Neanderthals becausemuscle tissue is muscle tissue.
- So I was wonderingif it was like starting
with the trophic level people
and then seeing if what the maggots did,
but it sounds like thatwas not as important
as having access and like meet as meat
(29:49):
and it had this dual purpose.
- Exactly. And in the paper Ido talk about essentially if
you adjusted what that startingsubstrate muscle level was
for what we use in humans,
but we adjusted that to just the average
of the herbivore meat value.
You still get nitrogen valuesthat are of the fly larvae
(30:10):
that are astronomicallyhigher than anything else
that we see that would be being consumed.
And to put this inperspective, when you think
of high nitrogen value foods,we're thinking marine mammals,
pinnipeds consumption of seals.
- That's just like thisendlessly long chain of food.
(30:31):
Like you're just at plankton
and then like seven kinds of fish
and then you finally get tosomething fatty, like a pin ape,
like a seal or a shark or whatever.
That's just eaten the entirefood web basically in one bite.
- Absolutely. But even in those values,
you're only getting into likethe low 20 per mil kind of
for at most.
(30:53):
And these fly larvae go up to43 per mil. Oh my gosh. It's
- Astronomically high, right?
And like a lion is like an eight, right?
- It might be more like eightto 10, somewhere in that
- Range, eight to 10,- Right?
I'd have to look at the exactvalues for the averages.
- So a lion is more like a 10
and then you have these seedeaters, there are like a 20.
And then for some reason themaggots eating petrified flesh
(31:16):
are 40.
Does the petrifying fleshpart make a difference?
Does it matter if it's fresh tissue
or petrified tissue? It does.
- It ups the number onorders of magnitude.
So the black soldierflies, they arrived in June
and I sampled them from June
until essentially December whenI can no longer collect live
(31:39):
fly larva anymore.
And that just trend increasesand increases and increases.
And so part of it is thatthe muscle is long gone,
the tissue is long gone.
But what has happenedis through decomposition
that let's say soupy decomp,
fluid rich soil is what theflies are still attracted to.
(32:00):
And those magnets arecontinuing to develop in
that soupy nutrient rich soil.
That cycling of nitrogen is continuing.
And though those maggotmasses are still associated
with a skeleton,
they're not actually feeding on the fresh
muscle tissue anymore.
That's been gone forsix months, nine months.
(32:24):
But that fly larvae still there in mass,
like huge masses of flyalarm. It's incredible.
- The idea then is that youcan go back to a kill site
and say, oh, there's notreally much for me to chew on,
but look who's beenchewing on things for me
and I can now harvestthat from the maggots.
- Absolutely. The interestingthing too is like you think
(32:45):
of lean gain meat.
The maggots are converting
that lean gain meat into afatty additive basically.
So now you're getting amore nutritiously complete
paleo menu item.
- You looked at a numberof different flies
and their larva over this period of time.
There are three species.
Did these guys coexistwith neander tunnels?
(33:06):
Like were they around at thesame time in the same place
where these measurements were taken?
- So we don't know specificallythat the specific species
of black soldier flies were around,
but we do know that thefamily of flies were around at
that time and had alreadyevolved concurrently.
And so there would've been flies.
Flies would have been there and landing
(33:27):
and interested in this animal stored
- Foods and it wasn't too cold
for them or anything like that.
'cause you went all the way to December in
Tennessee, which is pretty cold.
- It is pretty cold. Andactually if you look at the
temperatures in Tennessee
and look at some of theexperimental research
that's been done inNeanderthal temperatures,
there is overlap.
- Okay. Let's talk a little bit about some
(33:49):
of the alternative explanations here.
Like as we mentioned like eating out
of the sea can reallyboost nitrogen levels.
Is it possible that Neanderthalsomehow had access to a lot
of fish, a lot of hightrophic level sea critters
and that kind of, or termites?
I don't know, something else, like
how do we eliminate thoseother possibilities?
- I don't think that we do.
(34:09):
I think we need to reframethis focus on hyper carnivore
and mammoth eating and eating so much meat
and we need to kind of tryto change this narrative
and this narrative therehas been pushback on
for the last 20 years and yet it persists.
- Oh yeah. If we look atanatomically modern humans
(34:30):
that were coexisting withNeanderthals at this time,
what are their nitrogen isotope levels?
Exactly the same as
- Neanderthals of thepublished literature.
And I included it in the paper,the mean values of nitrogen
for Neanderthals and the mean values of
for anatomically modernhumans are exactly the same.
(34:51):
- So everybody was at the barbecue,
everyone was eatingputrid meat with the side
of maggots. Everybody.
- Absolutely. And Ithink the push has been,
when you look at the archeologicalrecord, the associated,
so archeological bony remainsanatomically modern humans are
often associated with havingtheir high nitrogen value
explanation is eating freshwater, fish, eating waterfowl,
(35:14):
eating a wider diversity offood, so having a wider diet.
Neanderthals, the focushas been on hyper carnivore
because you get the terrestrialmammal bones at those sites.
You don't see the fish, youdon't see the waterfowl.
And so that's where even thoughthey have the same values,
this interpretation hasdiverged in these two
different directions.
But you have the grand
(35:35):
- Unifying theory of maggots.
- Yes, I'm gonna becomeknown as maggot Melanie,
it's just gonna be in my future.
The alliteration is there.
- That's really interesting. I had no idea
that it was exactly the same.
At the end of the day, we have data,
but we don't know how to interpret it.
Like we have a test that we like to do
and it's giving us numbers,but we need a story.
(35:58):
We need other things to kind of prop up.
That happens all over science. That's
- The thing is when we'retalking about a story
of Neanderthals, we'vetalked about it in terms
of exceptionalism andhow different they are
and why they're different.
And I think maybe it'stime that we really reframe
who our cousins are.
Are they even actuallycousins or are they just us?
(36:21):
They're probably doing thingslike cooking, storing foods,
processing foods in ways thatthe baseline nitrogen value of
what they were eating is just like
what modern humans weredoing to their foods.
And you end up with thosehigher nitrogen values
that place humans at thattop of that trophic food web.
(36:42):
- I get like pretty squidout by not individual bugs,
but like any kind of, as youkeep saying, masses of bugs.
Like I really get Didyou have like that kind
of problem when you'redoing your field work there?
- No, I did not.
But my background, I worked ata coroner's office, so Okay.
Being around death investigation, being
around dead bodies in variedstates of decomposition,
(37:05):
that's very normal for me.
- Thanks, Melanie. It'sbeen really fun talking.
- Yes, this has been wonderful.
Thank you for having me on the podcast.
- Melanie Beasley isan assistant professor
of anthropology at Purdue University.
You can find a link to thescience advances paper we
discussed at science.org/podcast.
- Thanks to our friendsat the Science podcast
(37:25):
for sharing these stories.
If you wanna stay upto date on a wide range
of fascinating scientific topics,including human evolution,
subscribe to the Science podcast now.
They release a new episode every week.
Origin Stories is a projectof the Leaky Foundation,
a nonprofit dedicated tofunding human origins research
(37:45):
and sharing discoveries.
We'd love it if youwould support this show
and the science we talk about.
Go to leaky foundation.org/origin stories.
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Origin Stories is made possibleby our listener supporters
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(38:07):
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