From the Vault: The Wallace Line, Part 1

In this classic episode of Stuff to Blow Your Mind, Robert and Joe discuss the faunal boundary line between Asia and Australia known as the Wallace Line and the British naturalist it was named for, Alfred Russel Wallace. (originally published 8/19/2025)

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Episode Transcript

Speaker 1 (00:06):
Hey, welcome to Stuff to Blow Your Mind. My name
is Robert Lamb. Today is Saturday, so I have a
vault episode for you. This one originally published 8-19-2025. It
is going to be The Wallace Line, Part 1. Let's
do it.

Speaker 2 (00:22):
Welcome to Stuff to Blow Your Mind, a production of iHeartRadio.

Speaker 1 (00:32):
Hey, welcome to Stuff to Blow Your Mind. My name
is Robert Lamb.

Speaker 2 (00:35):
And I am Joe McCormick.

Speaker 1 (00:37):
And as I mentioned in at least a couple of
previous episodes of the show, over the summer this year, 2025,
my family traveled to Indonesia for some snorkeling. And in
learning all about the local environment of Raja Ampat, the
guides kept mentioning an individual by the name of Alfred
Russell Wallace, as well as the faunal boundary named in

(00:59):
his honor, the Wallace Line. In fact, I would say
that Wallace was invoked one way or another, nearly as
much as Darwin was invoked on my visit to the
Galapagos Islands a couple of years prior. So, yeah, Wallace,
the Wallace line, I mentioned a lot in terms of
just describing what was happening in the natural world around
us and in Indonesia at large.

Speaker 2 (01:20):
That's a funny comparison because, of course, if you know
one thing about Alfred Russell Wallace... It is probably that
he was the other guy to come up with a
version of the theory of evolution by natural selection around
the same time that Darwin did. Though Darwin tends to
get most of the credit. And I think in many ways,
people understand Darwin to have articulated a more rigorous form

(01:43):
of it. Wallace essentially had the same idea around the
same time.

Speaker 1 (01:48):
And to be clear, they knew each other. And in fact,
Alfred Russell Wallace, you know, greatly looked up to Charles Darwin,
and they were on friendly terms their entire life, even
though they disagreed on some key issues here and there.

Speaker 2 (02:03):
Yeah, well, actually, the version of the book that I
was reading, so it's Wallace's book, The Malay Archipelago, where
he's writing about his travels and observations in that region
of the world. The edition of that book that I
was reading is actually dedicated to Charles Darwin. He says,
To Charles Darwin and author of The Origin of Species,
I dedicate this book not only as a token of

(02:24):
personal esteem and friendship, but also to express my deep
admiration for his genius and his works. So it's elaborate.
It seems like no hard feelings there.

Speaker 1 (02:35):
Right, right. It's also been pointed out that they knew
what each other were up to around the same time.
And Wallace's work and Wallace's ideas kind of poked Darwin
and got him to sort of realize, oh, I really
need to push Darwin forward with on the origin of
species and maybe not focus on other projects at this
very moment.

Speaker 2 (02:55):
Stop collecting beetles, write the book.

Speaker 1 (02:58):
Yes. So we'll be talking more about Alfred Russell Wallace
here shortly. Uh, but as for the Wallace line, uh,
I'm going to go ahead and throw out the short
answer of what this is and we'll get into it more, uh,
later in this episode and in the next episode. But basically, uh,
it represents the place, um, between the Indonesian islands of

(03:19):
Bali and Lombok, where the Australian and Asian faunas separate.
So it separates the Indonesian archipelago between the parts influenced
by Asian fauna and the parts influenced by Australian fauna. So,
you know, rhinos, elephants, tigers on one side, kangaroos, monitor lizards,
and koalas on the other.

Speaker 2 (03:37):
Yes, exactly. With some caveats that we will discuss as
we move on throughout the series.

Speaker 1 (03:43):
So let's talk a bit about Alfred Russell Wallace here.
You can look up images of the man, illustrations and photographs.
He was, of course, a 19th century naturalist, explorer, traveler,
academic writer, and totally looked the part, you know, English
beardy guy who's out there in the wild exploring things or,

(04:04):
you know, back at home in his study writing about them.

Speaker 2 (04:07):
I was almost going to say if Darwin is almond joy.
Wallace looks like mounds. He just looks like a kind
of like, I don't know, a less crunchy version of Darwin.
Kind of a softer, smoother texture.

Speaker 1 (04:19):
Yeah, you could definitely say that. And it holds up
in many ways. But in other ways, as we'll discuss,
Alfred Russell Wallace was kind of the almond joy to
Darwin's mounds.

Speaker 2 (04:29):
Okay.

Speaker 1 (04:30):
So, yeah, Alfred Russell Wallace lived 1823 through 1913. So
long lived. And a fascinating individual. Multiple books have come
out in recent years about him. But the one that
I was mainly looking at is Radical by Nature, The
Revolutionary Life of Alfred Russell Wallace. And this is by
James T. Costa. Came out in 2023. And as the

(04:53):
author points out, yeah, he was like a lot of people.
He was a complicated individual. And there were certainly some
seeming contradictions in the way he made sense of the world,
the natural world. humanity's place in the cosmos and so forth.
So I'm going to break into a little bit of
his biography here. I'm not going to go into super detail,

(05:14):
but I'm going to try and hit some of, I
think maybe the key points to getting like an overall
understanding of who this guy was and, and, uh, some
of the more interesting aspects of his life and certainly
those contradictions. So he was born to a middle-class Scotch
English family, a family on his father's side claimed to
have an ancestral connection to 13th century, uh, noted individual

(05:36):
William Wallace, the Braveheart guy, for those of you relying
on cinema for your history.

Speaker 2 (05:43):
For fans of accurate history, yeah.

Speaker 1 (05:46):
But yes, claimed to be descended from William Wallace, whether
that's true or not, who knows. But he initially worked
as a surveyor, but remained vitally interested in many aspects
of the world. So he was interested in botany and
He had all these other natural history pursuits that he
was leaning into. And at the same time, he was

(06:07):
also attending talks about socialism, about spiritualism. He was also
interested by mesmerism.

Speaker 2 (06:13):
The practices of Franz Mesmer, also known as the theory
of animal magnetism, not given any credit today. Yeah, yeah, definitely.

Speaker 1 (06:22):
But also gets into sort of the whole hypnosis sphere
of things for sure. On top of this, he taught,
he lectured, and of course he read. He was familiar
with the writings of the time of Alexander von Humboldt,
of Charles Darwin, and many others. And in part due
to their inspiration, he decided that he too would go

(06:45):
out and see the world as a naturalist explorer.

Speaker 2 (06:48):
That's right, because, of course, Darwin became famous for his
writings about the voyage of the Beagle long before he
actually published on the origin of species. Before he had
a theory of evolution, he just had his travelogue of
observations going around the world on a ship called the Beagle.

Speaker 1 (07:04):
Yeah, so that seems to very much be the blueprint
that Wallace has selected for his own life as well.
And so he departs on a journey to South America,
particularly focused on the Amazon. And he and his team there,
they're studying the peoples of these areas, the natural history
of this region. And then on the return trip, their

(07:27):
boat catches fire and they're stuck in a life raft for,
I believe, 10 days and then eventually rescued. So he
apparently lost all of his notes in this adventure, this
part of the adventure anyway, but he was still able
to write multiple papers about it when he got back
to England and Also, I believe that a number of
specimens that he'd collected had been shipped back ahead of time.
So not everything was lost, but a lot was lost

(07:50):
on that ship. But he wasn't quite done with traveling
and exploring, which may come as a shock because I
don't know. I think a lot of us might think
that once your ship has burned and you've wound up
in the lifeboat for 10 days, you might have had enough,
but not so for Wallace.

Speaker 2 (08:04):
I'm going to read later in this episode from a
chapter in the Malay Archipelago where he's talking about his
experiences in Bali and Lombok. But he is not above
complaining about the hardships he faces on his journeys and
the difficulties he has in doing his work. But it
is still admirable that he can just face that kind
of thing and move right on.

Speaker 1 (08:25):
Yeah, and in a way admirable that you can still...
be irritated by the little stuff later on, you know,
after having wound up in the lifeboat for 10 days
to still be able to say, ah, this desk is
the worst.

Speaker 2 (08:37):
We're going to get some epic complaints about it's hard
to do science when everything is covered in ants.

Speaker 1 (08:43):
Oh, good goodness.

Speaker 2 (08:44):
I bet it.

Speaker 1 (08:44):
I bet that is true. So anyway, he was not
done traveling. And after he'd gotten back and he'd published
a bit about his travels, he soon became fascinated with

(09:05):
the Malay archipelago or the Indo-Australian archipelago, consisting of what
is now Indonesia and neighboring nations, also known as the
East Indies at the time. His subsequent travels in this
region lasted from 1854 to 1862, so eight years. And
during this time, he and his hired team collected thousands

(09:26):
upon thousands of specimens. to return home and go to
various museums and institutions. I read a BBC article pointed
out that the number here was something like 125,660 natural
history specimens, including more than 83,000 beetles.

Speaker 2 (09:43):
So the majority of it was beetles. Yeah, it's just
a lot of beetles. Well over half.

Speaker 1 (09:50):
I mean, also, it seems like the beetles would be
relatively easy to send back there. Yeah, It's a lot
easier to send back a beetle as opposed to, say,
a Komodo dragon.

Speaker 2 (09:58):
That's true. And once again, we're going to revisit why
it was so hard sometimes to send things back.

Speaker 1 (10:04):
And of course, he wrote about his travels as well.
And this is when he wrote the 1869 book, The
Malay Archipelago. This is the book you were talking about earlier,
a book that would go on to become an international bestseller.
describing all the islands he visited, the sorts of natural
and human elements on each, a little bit of griping

(10:24):
about the ants and the deaths. But this is a
book that resonated with people within his profession and within academia,
but also outside of those boundaries. It was just a
book that a lot of people read, and it kind
of made him a celebrity. It cemented his status and
also ensured that he was able to keep going and

(10:45):
keep writing later on, certainly after a few economic setbacks
that he encountered.

Speaker 2 (10:52):
I found it captivating. While we were preparing to record
this episode, I started reading a couple of chapters from
this book, mainly because I was looking for Wallace to
describe a scientific theory that we're going to get into.
And I ended up not finding really any succinct place
where he does describe this theory, but I was just

(11:13):
sucked into the writing because it's so interesting and so good.
And he in many ways reminds me of his contemporary
Darwin in that regard, who also, I think, and this,
of course, doesn't diminish from the validity of his theory,
but also just like Darwin's books are a great read.
They're like they're very well written. And I would say
Wallace's are, too.

Speaker 1 (11:33):
Yeah, yeah, yeah. The Malay Archipelago, volumes one and two,
the subtitle here being The Land of the Orangutan and
the Bird of Paradise, a narrative of travel with sketches
of man and nature.

Speaker 2 (11:47):
Oh, well, Rob, since he mentions the orangutan in the title,
you should scroll down in the outline because I included
a screen capture of the page opposite the title page
in the 1890 edition I was reading, which has an
illustration of a brutal orangutan attack where the orangutan is

(12:09):
jumping on a guy and biting a chunk out of
his arm. I'm skeptical this happens that much in nature.

Speaker 1 (12:16):
Yeah, that's generally not the reputation they have today. It's
so weird, though. This was the second time today I've
had to think about the possibility of a killer orangutan because,
as many of you are aware, the actor Terrence Stamp died,
I believe, over the weekend recently passed. And so there
was some chatter here and there about his past movies.
And I was looking around and I realized he was

(12:37):
in a 1986 film called Link that is about a
super intelligent... malicious chimpanzee, but the chimpanzee is played by
an orangutan.

Speaker 2 (12:49):
Oh, okay. I thought you were going in a totally
different direction. I saw the headline that Terrence Stamp had died, which,
you know, kneel before Zod. And I don't mean any
disrespect here, but I truly thought you were going to
say he died in an orangutan attack.

Speaker 1 (13:02):
No, goodness. No, no, but yeah, this illustration from the
book definitely made me think of that. But it also
has a rather sweet image of an orangutan here.

Speaker 2 (13:12):
Yeah, it's both, yeah. But from what I understand, orangutans,
it's not that they can't attack humans. I think they're
known generally to only do this when like really threatened
in some way. They're not generally aggressive.

Speaker 1 (13:25):
One thing we know from the interaction between humans and
animals is that if the animals can be provoked into
attacking humans, we will have done it at some point
or another.

Speaker 2 (13:36):
Yeah. But though, of course, some animals are much easier
to provoke than others. And orangutans are not usually thought
to be on the super high end of provocability. However,
this illustration is sick.

Speaker 1 (13:46):
Yeah, bites him right on the arm. But yeah, in
this book, though, this is where he does get in
a bit into the idea of the Wallace line. Now,
he didn't call it the Wallace line. I believe Darwin's bulldog,
Thomas Henry Huxley, called it that in his honor. But
he does get into the concept a little bit.

Speaker 2 (14:06):
Huxley also proposed some modifications to Wallace's original placement of
the lines.

Speaker 1 (14:13):
Now we get into the details in a bit, but
basically the way that Costa describes it in his book
is it was the realization that there was a growing realization, quote,
a growing awareness among naturalists that anomalous patterns of distribution
might provide unique insights into the history of the planet,

(14:34):
geologically and climatologically. So again, this was This was happening
with Wallace, but this was happening in other parts of
the world with naturalists looking at distribution data and saying, hmm, well,
this is interesting. We have X going on here, Y
going on here. What does this tell us about how
the world works, about how species have moved around or

(14:56):
been moved around, about some of the barriers and potential
barriers to their movement.

Speaker 2 (15:01):
And so forth? Yeah, and about the abiotic history of
the planet, like the fact that the distribution of animals
as you find them today can tell you things about
the history of climate change on the planet, about ice
ages and sea levels, and even about underlying geologic activity,
such as plate tectonics, which would not be, you know,

(15:23):
fully accepted as a theory, I think, until 1960s or so, much,
much later.

Speaker 1 (15:28):
So we mentioned the fact that he independently came up
with the concept of evolution by natural selection around the
same time as Darwin, and then Darwin kind of pushes
ahead and gets... on the origin of species out. In
some ways, Wallace was also an early environmentalist in his
voice concern over humanity's impact on the planet. And he

(15:50):
also engaged in a number of social activism causes during
his life, including women's suffrage, land nationalization, and various sort
of pacifist and anti-militarism causes. But in an area that
might seem rather contradictory to all of these scientific pursuits,
he was also a spiritualist. And not just one in

(16:12):
his non-academic life, not just like, okay, I'm, you know, scientific, academic,
a naturalist by day and a spiritualist by night. No,
he actively wrote on it and attempted to defend it
in academic writings.

Speaker 2 (16:24):
Now, to clarify, in the context of these 19th century movements,
when we say a spiritualist, that doesn't mean the same
thing as like somebody who would say, oh, I'm spiritual today.
That would This means something more specific about like beliefs
that you could contact the dead or that you could,
that living persons could have communication with spirits or other

(16:45):
beings other than living humans.

Speaker 1 (16:47):
Yeah, we're talking about, specifically here, we're talking about the
sort of spiritualists that you would go to and there'd
be a seance or there would, you know, offer generally
for money to help you connect with the spirits of
the dead. The kind of people that Houdini did not
like Uh, the kind of, uh, people, if you're, if
you watch the gilded age on television, the most recent

(17:07):
season has, uh, has included this element in its plot.

Speaker 2 (17:11):
Yeah. It's come up on the show before that actually
a surprising number of people from history and, um, In
19th century Europe and America, people who are in many
ways kind of admirable for their time really got into spiritualism,
really thought you could talk to the dead.

Speaker 1 (17:27):
Sir Arthur Conan Doyle is a prime example of this,
really got into it late in life. So, you know,
it's one of those things where there are multiple pieces
to it, as I think we've probably discussed in the past.
On one level, you do have people actively selling you
this stuff. And on the other, you have people a

(17:48):
genuine desire on the part of the bereaved to connect
with the people they miss. And, you know, there's in
a perfect world, there's probably a balance there between the
two where no one's exploited and everyone's life is made
a little easier, but we don't live in such a world.
And so things will often lean in the wrong direction there.

(18:09):
But again, not just a naturalist by day and a
spiritualist by night. Like I say, he wrote papers where
he defended spiritualism and so forth. Yeah. Now, on the
other hand, he opposed flat earth pseudoscience of the day
and wrote against that. And then going back to the
other side of things, he did involve himself in anti-vaccination
efforts of the day. This would have been, I believe, measles,

(18:32):
the vaccine that he was opposed to. But in his
opposition seems to have been a mix of like sort
of personal choice, like I don't want to take it.
that we see similar attitudes today, but also it seemed
to factor into his view that nature was perfectly balanced already,
and therefore there was no reason to tip the scales
as far as diseases go. I don't know. I would

(18:54):
say that the counterargument to that is that as far
as diseases and humanity go, that everything is already out
of balance, and therefore you need the vaccines in place. Well, yeah.

Speaker 2 (19:04):
I mean, a lot of the times people prefer one
course of action over another because it's more natural. It
just kind of reflects a vague and not very well
thought out understanding of what the concept natural really means.
I mean, there are a lot of things that just
kind of seem natural to you, but then you investigate
them and realize they're actually very much the product of

(19:25):
human intervention in some way. Yeah.

Speaker 1 (19:27):
Plus extinction is natural. It doesn't mean I want it
for myself. Yeah.

Speaker 2 (19:30):
It is natural to just like all get disease and die.

Speaker 1 (19:33):
Sure.

Speaker 2 (19:34):
I mean, is that good? Yeah.

Speaker 1 (19:37):
So yeah, he was an interesting guy in this. His
spiritualism especially did put him at odds with many of
his fellow scientists. And even when it came to evolution
by natural selection, he argued for a kind of evolution
driven by the divine, essentially that animals evolve via natural

(19:57):
selection and humans did to a point, and then some
other force takes over. Something divine, he didn't actually call
it a creator because interestingly enough, he himself was a
religious skeptic. So he at different times self-identified as agnostic
or just a non-religious person. And so he referred to
this as an overruling intelligence.

Speaker 2 (20:20):
It's interesting how if you go back just a hundred
years or so, you get a lot of fine distinctions
in religious beliefs where the distinctions don't make a lot
of sense to people today, but they made sense to
people at the time.

Speaker 1 (20:34):
Yeah, yeah. He was a firm believer that He thought
without this overruling intelligence becoming involved, there's no way that
the human brain or human speech organs or even our
hands or our bipedal posture could have possibly evolved. There
had to be some other force, like a monolith, getting

(20:55):
involved in our advancement. Yeah. And, you know, that's kind
of a sticky idea. That's why we see it all
over our science fiction, right? Yeah, yeah.

Speaker 2 (21:02):
And, you know, it's still a common idea. I mean,
this is formally argued by creationists today, but I mean,
it's still, it's naturally appealing to look at something very
complex and think, well, that couldn't have just happened. Of course,
I think that the leap that you're not able to
make there is that it happened gradually and by degrees.

Speaker 1 (21:22):
Yeah, yeah. And, you know, I often think about this.
I think that, okay, you know, a much, softened version
of this is maybe quite reasonable in a quite reasonable
way to balance science and religious faith. You know, say, well, okay,
evolution by natural selection is the method by which the
divine creates life. And why not? Because it seems like
the very sort of elaborate, long-term method that an eternal

(21:45):
and all-powerful entity, unconstrained by time, might very well employ.

Speaker 2 (21:50):
Sure. I mean, I think that's what millions of people
believe today.

Speaker 1 (21:53):
Yeah.

Speaker 2 (21:53):
Nothing wrong with that.

Speaker 1 (21:55):
Yeah. On the other hand, it is worth stressing that
when you get into the particulars of this sort of
stance saying, well, OK, everything evolves, but then humans evolve differently.
Human brains are different because of some divine force. You
can get into some. really nasty and even racist views
on human evolution by deciding just where and how you

(22:15):
want to deploy this theory. Ah, yeah.

Speaker 2 (22:17):
Okay. So appealing to supernatural forces to inject a certain
specialness into, you know, certain, you know, animals on earth.
And certainly there's nothing that prevents somebody from thinking that
some humans are more special than others.

Speaker 1 (22:31):
Right, right. So I'm not saying that was Wallace's whole deal,
but those are kind of, those are the waters you
can easily creep into by pursuing this line of thinking.

Speaker 2 (22:38):
Yeah.

Speaker 1 (22:39):
Now, with Wallace, it certainly put him at odds with
many of his fellow scientists, including Charles Darwin himself, who
worried that Wallace was hurting their cause by adding this
caveat to his own take on natural selection. And according
to Costa, he even wrote to him and said, quote,
I hope you have not murdered too completely your own

(23:00):
and my child, referring to the theory of natural selection. Again,
these two points, were friends and, um, and, and, uh, Wallace,
you know, continued to respect Darwin the rest of his life. Uh,
but yeah, Darwin rather bluntly saying, uh, I really wish
you hadn't put it like that, you know, trying to
get this theory of natural selection out the door and

(23:22):
accept it at this point. And you're perhaps muddying the
waters by coming in with this, uh, you know, your
unique spiritualist take on everything. Yeah.

Speaker 2 (23:31):
Though, I guess one thing that's supposed to be good
about being friends is that you can be Frank with
each other.

Speaker 1 (23:35):
Yeah. But yeah, Wallace seems to have been a guy who,
as I think Costa puts it at one point, he
had a lot of adventures and a lot of opinions
in his life. He was real quick to weigh in
on things. And well into his 80s, he was still
doing this. I mean, I think until the end of
his life, pretty much constantly writing letters, writing his own

(23:57):
take on different topics. And in fact, in 1904, he
put out the book, Man's Place in the Universe. And
in that, he takes his own serious look at the
idea of life on other planets, especially Mars, because this,
of course, is the time when we have the whole
canals of Mars idea out there in everyone's minds. You know,

(24:21):
the idea that we've seen things on Mars and what
if they're canals and we get this built up idea
of their people of some sort on Mars and they're
a dying race and they're having to build these canals
and so forth. It really captivated everyone's imagination.

Speaker 2 (24:35):
We've talked about that at some length on episodes in
the past, and now I don't remember which ones. Did
that possibly come up in our discussion of the ashen
light of Venus?

Speaker 1 (24:47):
It might have, yes.

Speaker 2 (24:48):
That's my best guess.

Speaker 1 (24:50):
So this was a 1904 book, and I have not
read it, but Costa gives his own breakdown of it
and points out that, okay, he's basically opposing the idea
of life on Mars on two levels. On one level,
He is making a very logic-based counter-argument. He himself was
an astronomer, and he's pointing out things about what was
known about Mars versus Earth at the time. He just

(25:13):
did not think it was likely that this was true.
And of course, as we would find out very shortly thereafter,
it wasn't true. But as Costa points out, it also
ran opposite to his belief that humans had a privileged
place in the cosmos, that we were The end result
of not only earthly processes, but also cosmic processes as well.

(25:33):
This getting into the whole idea of humans were special
because some sort of force beyond us had pushed us
into these like upper levels of evolution that were denied
to other, you know, or other organic life forms on Earth.

Speaker 2 (25:48):
So the overruling intelligence of Wallace's view of the universe
would not have allowed life on Mars.

Speaker 1 (25:53):
Right, right. The whole idea is that we're alone and
we're special. If we've got life next door as well,
then that just destroys the whole argument. So that seems
like it might have also been there, you know, pushing
his criticism of this idea. Though, to be clear, this book,
he's also apparently very polite in his takedown of the

(26:16):
Martian Canal incident. Because he, you know, he's ultimately, you know,
friends or at least correspondents with everyone that's talking about
it at the time.

Speaker 2 (26:25):
Boy, I'm sorry if I misunderstood. Did he also have
like observation based or empirical reasons for doubting canals on Mars? Yes.

Speaker 1 (26:34):
It wasn't just based in his worldview, but no doubt
that worldview was also pushing him to make all of
these arguments, you know.

Speaker 2 (26:42):
Okay. So he was right, but for some of the
right and some of the wrong reasons.

Speaker 1 (26:47):
Yeah, that seems to be the take on it. But again,
I haven't actually read the book in question. So again,
that's just a brief overview of the man here. I
think it highlights some of the inherent contradictions that are

(27:08):
present there that ultimately are going to be present in anybody.
But maybe you're a little more expressed in the biography
of Alfred Russell Wallace. Yeah.

Speaker 2 (27:17):
Very interesting character. And so I guess now should we
move on to talking a bit about the Wallace line,
at least what the concept is? And then I think
maybe in part two, we'll get into some more depth
about it, nuances that have been added to it since
the time of Wallace.

Speaker 1 (27:33):
Yeah.

Speaker 2 (27:34):
All right. So we alluded to this earlier, but to
recenter us here, in addition to independently discovering a version
of the theory of evolution by natural selection, again, around
the same time Darwin did, Alfred Russell Wallace is also
widely considered the founder of a field now known as biogeography,
the study of how life is distributed over the surface

(27:56):
of the earth. Another way to put it is what
lives where and why. By the way, you mentioned him earlier,
but another important contributor to the early study of biogeography
was the pre-Darwinian German naturalist, Alexander von Humboldt. Very interesting
figure who we've talked about a good bit on the
show before. I think one of the main contexts was

(28:18):
in a summer reading episode we did years ago where
I was talking about a great biography of him by
Andrea Wolff called The Invention of Nature. Von Humboldt was
important in helping to move the burgeoning natural sciences of
the 19th century away from this long-held Western view of
nature as a fixed order of discrete entities with eternal

(28:41):
roles defined by providence, and to replace that with a
view of nature as a complex and changeable web of relationships,
these interdependencies that are constantly in flux. Though unlike Darwin
and Wallace, von Humboldt himself never fully embraced the idea
that species themselves could evolve. His idea of change was

(29:02):
more based on the environment and relationships between species. So
Darwin and Wallace ended up going beyond von Humboldt. But anyway,
as I said, biogeography is the study of what lives
where and why. And one of Wallace's most famous observations
in biogeography is the Wallace line. The Wallace line is

(29:22):
what's known as a biogeographical boundary line, specifically a faunal
boundary in this case, meaning a boundary with reference to animals.
So it's an invisible border where you have one ecosystem
of animal species on one side of the line and
a very different collection of animals. on the other. Animal
populations are not usually divided by hard boundaries. Normally, as

(29:48):
you wander toward the edge of an animal's population range,
you will notice a gradual thinning out of the population
with the number of individuals becoming less and less dense,
sometimes being replaced more and more gradually with examples of
different species in the same trophic niche, meaning they compete

(30:09):
for the same food resources. So you may be moving
out of the range of one animal species and into
the range of another gradually, gradually in both cases. For
the most part, the geographic range of an animal species
does not end in a hard boundary, but in a
soft and gradual one. But there are exceptions. Sometimes you

(30:29):
kind of hit a wall where there is one set
of animals over here and a pretty different set over there.
And that is to a large extent what we find
with Wallace's line, though, as we'll discuss, there are some
exceptions to this rule and some major nuances added since
Wallace first proposed this border in in the 1860s. In fact,

(30:50):
basically all biogeographical boundaries are somewhat permeable. You will find
exceptions to them, but they tend to denote starker divisions
in biodiversity than you will find elsewhere in nature. And
so what's the story of the Wallace Line in particular? Well,
the Wallace Line passes invisibly through the islands of the

(31:12):
Malay archipelago in the strait between Borneo and Sulawesi, And
then further southwest through the Lesser Sunda Islands, cutting between
the islands of Bali on the west and Lombok on
the east.

Speaker 1 (31:26):
While we were in Indonesia, we were east of the
Wallace Line, though we had to fly over it to
get to Raja Ambat from Jakarta. I will stress, though,
the pilot did not announce the crossing of the Wallace Line.
Not that they had to, but I just want to
make it neat. Of course, you can't see it from
the plane.

Speaker 2 (31:43):
Yeah, exactly. And there's nothing there to see. In fact,
it's kind of, it's remarkable how invisible it is in
a way. So I was speaking of the division between
these multiple land masses, Borneo and Sulawesi and Lombok and Bali.
The latter division is probably the most striking because the

(32:04):
Lombok Strait, which passes between Lombok and Bali, is in
some places only a few dozen kilometers wide. Like if
the air is clear, you can stand on the shore
of one island and look across and see the other island.
You see the higher elevations on the other island. So
they're very close. And in terms of environmental conditions, they're
very similar. And yet, when Alfred Russell Wallace studied the

(32:29):
land animals and the birds of these islands, he noticed
a pretty stark difference. Wallace writes about some of these
observations in the book, The Malay Archipelago, again, first published
in 1869. So the version of this book I was
looking at is a scan of the 1890 edition. That's
the one with the sick illustration of the orangutan biting

(32:50):
the guy. And Wallace writes that the islands of Bali
and Lombok are most interesting actually because of two things.
One of them is that he claims that They're the
only two islands of the whole archipelago in which the
Hindu religion still maintains itself. And then he also says, quote,
they form the extreme points of the two great zoological

(33:13):
divisions of the eastern hemisphere. For although so similar in
external appearance and in all physical features, they differ greatly
in their natural productions. So what's the difference in these
natural productions between the two islands? Again, while there are
exceptions and some nuances we'll discuss later, the range of

(33:33):
a ton of major animal groups essentially terminates at this
tiny ocean gap. On the eastern side, in Lombok, you
will find native cockatoos and marsupials, the animals associated with
Australia and New Guinea. And on the western side of
the gap, in Bali and Borneo, you will not find

(33:53):
those animals, not natively, unless you find some imported Instead,
you will find mostly the same animal groups that you
find in the rest of Asia, including, at least as
of a few hundred years ago, before many of these
animals were driven extinct, you would find tigers, rhinos, elephants,
and bears. So you've got one on one side, one

(34:16):
on the other, and then you've got, of course, some
more transitional areas like We'll talk more in part two,
I think, about the idea of a whole group of
islands known as Wallacea that are thought of now as
a kind of transitional island group. But on the island
of Sulawesi, you will also find more of a mix
with some native Australian or Australasian fauna and some Asian fauna. Now,

(34:40):
the question of why is really interesting, and that's something
we're going to have to come back to. But first,
I just wanted to get some more color on Wallace
himself and his travels in in these islands, specifically his
chapter in the Malay Archipelago on his visits to Bali
and Lombok. He makes an interesting biographical note that his

(35:01):
first visit to these islands in 1856 was, quote, somewhat involuntary.
He was trying to get a ship to take him
to Makassar on Sulawesi from Singapore, but he couldn't for
some reason, and his journey got diverted to these islands
at the east end of Java. And he writes that

(35:21):
if he had been able to get the passage he
wanted from Singapore, he probably never would have gone to them, quote,
and should have missed some of the most important discoveries
of my whole expedition to the East.

Speaker 1 (35:32):
So just pure travel mishaps playing into, again, the most
important discoveries of his career.

Speaker 2 (35:38):
So, Robert, are you cool if I read some passages
from Wallace here?

Speaker 1 (35:41):
Yeah, let's have it.

Speaker 2 (35:42):
Okay, this will give us a flavor of his writing
and some of his experiences in Bali and Lombok, both
those that inform... the formulation of the idea of the
Wallace line, and also just some interesting stuff he comes across.
So first of all, there's a passage where he's describing
the terraced agriculture of Bali, where he says, he says, quote,

(36:04):
a slightly undulating plain extends from the seacoast about 10
or 12 miles inland, where it is bounded by a
fine range of wooded and cultivated hills, houses and villages
marked out by dense clumps of coconut palms and tamarind
and other fruit trees, are dotted about in every direction,
while between them extend luxuriant rice grounds, watered by an

(36:26):
elaborate system of irrigation that would be the pride of
the best cultivated parts of Europe. The whole surface of
the country is divided into irregular patches, following the undulations
of the ground, from many acres to a few perches
in extent, each of which is itself perfectly level, but
stands a few inches or several feet above or below

(36:47):
those adjacent to it. Every one of those patches can
be flooded or drained at will by means of a
system of ditches and small channels into which are diverted
the whole of streams that descend from the mountains. Every
patch now bore crops in various stages of growth, some
almost ready for cutting, and all in the most flourishing
condition and of the most exquisite green tints. Oh, that's nice.

Speaker 1 (37:10):
I would say succulent, even.

Speaker 2 (37:12):
Yeah, I found his writing style very vivid. It really
calls pictures to the mind in a way that a
lot of older writing, especially, you don't quite get that
immediate connection to the visual imagination. Something about Wallace's style
does for me.

Speaker 1 (37:29):
Yeah, there's a sense of awe here as well.

Speaker 2 (37:31):
Yeah. But anyway, from here, Wallace goes on to describe
his attempts to collect a few specimens in Bali. So
he says... In so well-cultivated a country, it was not
to be expected that I could do much in natural history.
Kind of makes sense, right? Like it's harder to collect
specimens from all of this well-kept farmland. Yeah, from the farmland, yeah.

(37:54):
And my ignorance of how important a locality this was
for the elucidation of geographical distribution of animals caused me
to neglect obtaining some specimens, which I never met with again.
One of these was a weaver bird with a bright
yellow head, which built its bottle-shaped nests by dozens on
some trees near the beach. It was the Plosius hypoxanthus,

(38:18):
a native of Java, and here at the extreme limits
of its range westerly. I shot and preserved specimens of
a wagtail thrush, an oriole, and some starlings, all species
found in Java, and some of them peculiar to that island.
I also obtained some beautiful butterflies, richly marked with black
and orange on a white ground, and which were the

(38:40):
most abundant insects in the country lanes. Among these was
a new species, which I have named Pieris tamar. Okay,
so that's his experience in Bali. He doesn't collect a
lot of specimens because he doesn't know how significant this
place is going to be. And he got here by
accident anyway, didn't even expect to go here, notices a

(39:00):
few things. But it's all the Western fauna. It's all
the same kind of stuff you would see in Java,
the same kind of stuff you would see grouped with
other animal species generally in Asia. But then he moves
on in his ship to Lombok. And he notes, by
the way, that traversing the strait, sometimes the weather or
the chop in the strait can be pretty rough. And

(39:24):
there's a story of him pulling all of his things
ashore and being very grateful to get all of his
specimens and bags and stuff on shore. And the locals
tell him, oh, it's good that you did. The sea
is hungry and it takes everything it can eat.

Speaker 1 (39:39):
Oh, the South Sea Queen, perhaps.

Speaker 2 (39:42):
Yes, though I was thinking of his loss of all
of his previous stuff from the other boat. But yeah,
so he moves on to Lombok and here he notes
finding bird species that are not like the bird species
on the other island. They are more similar to those
found in Australia and New Guinea. He writes, quote, The

(40:03):
country around was pretty and novel to me, consisting of
abrupt volcanic hills enclosing flat valleys or open plains. The
hills were covered with a dense scrubby bush of bamboos
and prickly trees and shrubs. The plains were adorned with
hundreds of noble palm trees, and in many places with
a luxuriant shrubby vegetation. Birds were plentiful and very interesting,

(40:25):
and I now saw for the first time many Australian
forms that are quite absent from the islands westward. Small
white cockatoos were abundant, and their loud screams, conspicuous white color,
and pretty yellow crests rendered them a very important feature
in the landscape. This is the most westerly point on
the globe where any of the family are to be found.

(40:47):
Some small honeysuckers of the genus Telotus and the strange
mound maker Megapodius guldii are also here, first met on
the traveler's journey eastward. The Megapodius birds, by the way,
these are these, you may have read about these before,
these mound builder birds that are native to Australia and

(41:08):
New Guinea. where they will build mounds. He describes, actually,
in a passage, the locals telling him about how they
build mounds out of anything they can get, garbage or whatever,
and the locals know what to look for in one
of these mounds to know when there will be eggs
in it that are good for snatching. In fact, I'll
just read a passage from Wallace. He says, The mounds

(41:31):
are to be met with here and there in dense
thickets and are great puzzles to strangers who cannot understand
who can possibly have heaped together cartloads of rubbish in
such out-of-the-way places. And when they inquire of the natives,
they are but little wiser, for it almost always appears
to them the wildest romance to be told that it
is done all by birds. Excuse me, that it is

(41:54):
all done by birds, but that does sound like the
wildest romance.

Speaker 1 (41:58):
Yeah.

Speaker 2 (41:59):
Now, here I want to come to the part where
Wallace describes the difficulties of the physical part of his work,
collecting and preserving specimens. I've alluded to this several times,
but this passage really gripped me. So Wallace says, quote,

(42:29):
Ants swarmed in nearly every part of it, and dogs, cats,
and fowls entered it at pleasure. Besides this, it was
the parlor and reception room of my host, and I
was obliged to consult his convenience, and that of the
numerous guests who visited us. My principal piece of furniture
was a box, which served me as a dining table,

(42:51):
a seat when skinning birds, and as the receptacle of
the birds when skinned and dried. To keep them free
from ants, we borrowed with some difficulty an old bench,
the four legs of which, being placed in coconut shells
filled with water, kept us tolerably free from these pests.
The box and the bench were, however, literally the only

(43:13):
places where anything could be put away, and they were
generally well-occupied by two insect boxes and about a hundred
bird skins in the process of drying. It may therefore
be easily conceived that when anything bulky or out of
the common way was collected, the question, where is it
to be put, was rather a difficult one to answer.
All animal substances, moreover, require some time to dry thoroughly,

(43:37):
emit a very disagreeable odor while doing so, and are
particularly attractive to ants, flies, dogs, rats, cats, and other vermin,
calling for especial cautions and constant supervision, which under the
circumstances above described were impossible. Oh, man, I was getting
so stressed just reading that, trying to think where to

(44:00):
put the bird skin, where to put the dead whatever
I just found. Where can it go that it's not
just going to be swarmed with ants? And the whole
time you've got ants everywhere, and it's all stinking because
you're skinning it and then hiding it in a box
that's the only other thing in the room with you.

Speaker 1 (44:15):
And all manner of scavengers are... coming in to peek
in and see what's going on with your dead animals. Yeah,
it seems like quite an experience. And also, Wallace, quite
a house guest to have staying as well, right?

Speaker 2 (44:33):
I mean, one thing he notes, at least the parts
I was reading, is he makes a special note of
the hospitality he encounters everywhere he goes. It seems like
He just keeps running into very nice, very helpful, accommodating people.
And he's like, I was received very, you know, with
all this graciousness and all that. So I just get
the feeling from reading that he's a nice guest to have.

(44:56):
He's very appreciative, you know, very polite, I think. Probably,
at least.

Speaker 1 (45:00):
Yeah, skins a lot of birds, collects a lot of beetles,
but a nice guy.

Speaker 2 (45:05):
Does stink up your house really bad. And there are
already ants, but he probably attracts way, way more. Yes,
this is actually something I almost always find interesting in
reading books about science history is just the practical physical
annoyances and problems with trying to do the core work,

(45:25):
the core physical work of your discipline, whether that's collecting
specimens and preparing them to be preserved. or doing experiments
or whatever, you know, there are always little like problems
like this where it's like, I can't do it because
this thing doesn't fit right. Or I don't have the
kind of table I need or, you know, or there's
ants on everything. By the way, if you if you

(45:46):
work in any area of research out there and you
want to write into the show about your experiences of
this kind, please do contact at stuff to blow your
mind dot com. I always find these things interesting. Yeah.

Speaker 1 (45:57):
Tell us about your fieldwork.

Speaker 2 (45:59):
What is your Wallace's Room full of ants?

Speaker 1 (46:12):
All right.

Speaker 2 (46:12):
Can I flag one more thing from this chapter by
Wallace about a boundary of sorts, but not a faunal one?

Speaker 1 (46:19):
Yeah, I know what you're going to cover here. And
this is an interesting one that I was reading about
in my book as well.

Speaker 2 (46:25):
Yeah, okay. So Wallace, by the way, he's about to
refer to somebody named Manuel. Manuel is one of his
local guides. So this is a guy he's been working
with and has good relations with. But he says, a
Bornean Malay who had been for many years resident here
said to Manuel, one thing is strange in this country,
the scarcity of ghosts. How so? Asked Manuel. Why, you know,

(46:51):
said the Malay. That in our countries, to the westward,
if a man dies or is killed, we dare not
pass near the place at night, for all sorts of
noises are heard, which show that ghosts are about. But
here there are numbers of men killed, and their bodies
lie unburied in the fields and by the roadside, and
yet you can walk by them at night and never

(47:13):
hear or see anything at all, which is not the
case in our country, as you know very well. Certainly
I do, said Manuel. And so it was settled that
ghosts were very scarce, if not altogether unknown, in Lombok.
And then Wallace goes on to make a comment that
I didn't know how to take at first, but I

(47:33):
initially read this as maybe some kind of dry humor.
But he follows this up by saying, I would observe, however,
that as the evidence is purely negative, we should be
wanting in scientific caution if we accepted this fact as
sufficiently well-established. that sounded like a kind of humorous understatement
to me, but now Rob, now that we've talked about

(47:54):
his interest in spiritualism, that assessment actually seems like he
is interested in me. He is maybe actually interested in
doing a scientific catalog of where ghosts exist because he
views them as quite likely a real phenomenon and something
that can be scientifically documented. And he is being, you know,

(48:15):
somewhat skeptical in his methodology here. He's like, well, we
only have the negative evidence here, so we can't fully
say that this is a rule. But here's somebody saying
you don't get ghosts in Lombok, you do get them
over here.

Speaker 1 (48:28):
Yeah, this is a great point, because I think definitely
at this point in his life, he was at the
very least quite open to the idea that ghosts were real,
that there was some sort of spiritual essence out there. Yeah.

Speaker 2 (48:42):
And the really interesting aspect of that belief, at least
to me, being the assumption that you could study this
phenomenon in a scientific way. I mean, I think a
lot of times you would have people who might be
scientists or naturalists or natural philosophers in this era who
have supernatural beliefs, but they don't approach the supernatural beliefs

(49:05):
as open to investigation the same way their beliefs about the,
you know, the forces governing the natural world are. And
Wallace seems to be saying like, no, yeah, we could
just we could study this.

Speaker 1 (49:17):
Yeah. And I think we definitely have to look. at
it within the context of the time to a time
during which there are so many advancements are taking place.
And Wallace, along with Darwin and others, are like right
there on the front lines pushing this this theory of
what is going to become known as as the theory
of evolution, the theory of natural selection. And and therefore,

(49:40):
like there's probably this this spirit of we can figure
it all out. And we see this elsewhere as well,
where people like, yes, we can we can actually measure
these things. We can look and try and figure out
what happens to consciousness when life ends. And in Wallace's
case in particular, we we know that he comes to
see some sort of continuation of the soul here. as

(50:02):
being some special vibe, some sort of higher intelligence as
being key to how evolution is working. And therefore, you know,
he just sees it as part of the works. And therefore,
it's something that you surely can prove out because we're
proving out the other aspects of how the natural world
is working. And if ghosts are part of it, if

(50:22):
the spirit is part of it, then he should be
able to prove that as well. Yeah.

Speaker 2 (50:27):
I mean, in a way, you could look at an
interest in spiritualism as As a way of, you know,
I think that none of the underlying phenomena were actually real,
but as an attempt to empirically interact with the spirit world.

Speaker 1 (50:43):
Yeah.

Speaker 2 (50:43):
As opposed to just like having beliefs about it, but
those beliefs being something that, you know, you don't interface
with or interact with.

Speaker 1 (50:52):
Right, right. Now, at the same time, of course, obviously,
like entering in any kind of scientific enterprise with these
concepts in mind, you can end up putting blinders up
for yourself. And you can end up maybe engaging in
some of these questions without complete neutrality. Right.

Speaker 2 (51:09):
And I mean, of course, I think that is what
we actually see in a lot of attempts to get
really into the subject. But I would say that in principle,
if there were spirits that made contact with the living
on a regular basis, that's something that you could study.
You know, it might be difficult to study because might
be more like the study of psychology or something than
like the study of uh of biology or nature yeah

(51:32):
but uh but it could be something you could you
could look into in a systematic.

Speaker 1 (51:36):
Way right right and even the division of ghosts as
well i mean especially in a place like indonesia you
know it it ultimately speaks to other questions about the
flow of ideas and the flow of religious faiths uh
you know in a widespread and again as we've stressed
very large spread out country that has various cultures wound

(51:56):
up in it, various religious faiths. So that ultimately becomes
the more interesting question, I think, outside of Wallace's viewpoint is, well,
why would there be a tradition of ghosts here and
not here? What does that say about the people?

Speaker 2 (52:08):
Well, right, exactly. I mean, I think that's a fully
legitimate and fascinating question to look into, not the question
of are there literally ghosts here and not ghosts here,
but like, why do you get these different beliefs and
traditions in different cultures? You know, how does history feed
into the developments One thing I would note is that
Wallace says that, so he recounts this conversation where this

(52:30):
guy who comes from Borneo says, hey, yeah, we've got
ghosts back home. They don't have ghosts here. Wallace does
note that the people of Lombok did describe a belief
to him that some men had the power to transform
into crocodiles in order to eat their enemies. So that's
pretty cool. Seems different than a ghost, though.

Speaker 1 (52:49):
Yeah, and I'm not sure how crocodile transformation would like
how that ends up being interpreted by like European spiritualism
of the time. But that's still fascinating.

Speaker 2 (52:59):
Oh, I can just imagine the kind of distinction made like, oh,
you know, our spirits are very real and legitimate. Nobody
actually transforms into crocodiles. That's ridiculous.

Speaker 1 (53:10):
All right. Well, we're going to go ahead and close
out this episode of Stuff to Blow Your Mind right here,
but we'll be back for a part two on the
Wallace line. We'll discuss the concept in more detail and
probably get into some specific examples too. Right.

Speaker 2 (53:23):
In the next episode, we'll go into more detail about
why it exists to the extent that it does, as
well as sort of updates to the concept, like the
idea of Wallacea.

Speaker 1 (53:33):
Yeah. In the meantime, certainly write in and tell us
all about your adventures in this part of the world,
other parts of the world, and of course, your fieldwork. Researchers,
write in about your fieldwork. We would love to hear
from you, as well as recommendations for Future episodes of
Stuff to Blow Your Mind, we always have an ear
open for good ideas.

Speaker 2 (53:55):
That's right. What is your equivalent of Wallace's dissecting room
with every surface covered in ants? The box full of
bird skins and so forth. Emitting odors.

Speaker 1 (54:06):
Yeah, maybe it's not your work life either. Maybe it's
your personal life.

Speaker 2 (54:10):
Yeah, write in.

Speaker 1 (54:10):
We'd love to hear from you. And just a reminder,
Stuff to Blow Your Mind is primarily a science and
culture podcast with core episodes on Tuesdays and Thursdays. But
on Fridays, we set aside most serious concerns to just
talk about a weird film on Weird House Cinema.

Speaker 2 (54:22):
Huge thanks, as always, to our excellent audio producer, J.J. Posway.
If you would like to get in touch with us
with feedback on this episode or any other, to suggest
a topic for the future, or just to say hello,
you can email us at contact at stufftoblowyourmind.com. Stuff to

(54:42):
Blow Your Mind is a production of iHeartRadio. For more
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