June 17, 2016 • 35 mins
A new genetic technology called a gene drive could help eradicate deadly pests, like invasive rats in the Galápagos or malaria-carrying mosquitoes. But exactly how hazardous could accidental consequences be?
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Episode Transcript
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Speaker 1 (00:00):
Brought to you by Toyota. Let's go places. Welcome to
Forward Thinking. Hello, and welcome to Forward Thinking, this podcast
that looks at the future and says, rescue me from
me and all that I believe. I'm Lauren Volgabon and
(00:22):
I'm Joe McCormick, and our regular host Jonathan Strickland is
not with us today. He is still out on vacation.
He's having lovely adventures in his absence. We went on
a very short Billy Corgan impersonation to kick there, but
that's no, was not recording that. I kind of hope
he was. It was really delightful. Both of you do
a really good smashing pumpkins. Anyway. Yeah, so today we're
(00:48):
gonna be talking about a fascinating topic in genetics. Yes,
but we want to get there in a kind of
roundabout way by talking about islands. Yeah. We want to
get there via the Galapagos. Have you ever been to
the Galapagos? I have not, have you No, I haven't,
But I want to go there someday. I know. It's lovely,
it's it's a I mean, there's so many things there
(01:11):
that you literally cannot find anywhere else, and not like
restaurants like like beautiful wildlife. Yeah, I know, the restaurants
seen there is probably not not what people go for.
I don't think it is now. Yeah, so you're probably familiar,
but just in case you're not. The Galapagos or a
group of islands, or more accurately, a volcanic archipelago in
the Pacific Ocean about about a thousand kilometers off the
(01:33):
west coast of Ecuador, right along the equator. I think
it actually straddles the equator. Yeah, yeah, and the Galapagos
appear to have been mostly uninhabited before the Spanish visited
in the sixteenth century by humans that is. Yeah. The
glaucost Islands are situated more or less smack in the
middle of these three conjoining tectonic plates and thus three
(01:56):
different ocean currents, meaning that over the millennia, lots of
credits from all over the world have wound up there,
and the ones that stayed and reproduced branched off from
their ancestors due to the unique living conditions and uh
and separation from the general population. Yeah, and for this
reason today the Galapagos I think are mainly known for
their wildlife. That that's why people mostly want to go
(02:18):
to this place. Yeah, so you've got, for example, the
endemic Galapagos penguin, the Galapagos giant tortoise, and there are
a few subspecies of that, like the saddleback tortoise and
the dome tortoise, and then of course those smug, insufferable
marine iguanas. Did did a marine iguana from Galapacos? Like? Wrong?
You in your past? You know, I would never advise
(02:40):
anybody treat them with anything but the utmost respect for nature.
But just look at their faces. They just look like jerks.
They do you sitting on those rocks, so they look
really proud and slappable. Yeah, there's something about them. No,
do not slap an iguana. Never slap an iguana. Why
would you do that? The Galapagos. So yeah, so they've
got they've got all these animals that are very beautiful
(03:01):
and unique and and iconic in many ways. For one reason,
I think because the Galapagos were, uh, this archipelago is
one of the places that Charles Darwin stopped on his
voyage on the h MS vegal famously. Yes, yeah, and
so I think for that reason, they've become sort of
emblematic of animal evolution and ecology in many ways since then.
And like I said, I've never been, but I've always
(03:23):
heard that because of the lack of large natural predators
on the island, many of its animals are just very
friendly chill. Yeah, they're they're fine basically with humans hanging
out around them. Yeah, and they'll allow you to approach
them without running away. So so that can be very
wonderful if you are a peaceful, conservation minded ecological tourists
(03:46):
who wants to visit the island and see some animals.
Not so great for the animals if you are, say
a pirate or a whaler or something that wants to
kill a tortoise and eat it for its meat which
has figured into the island's history, or or save it
for or harvested for its beautiful shell or et cetera. Sure, exactly.
So these days the glopacos are there's sort of a
popular wildlife and conservation tourist destination, but the archipela goes.
(04:11):
Beautiful and fascinating endemic species aren't the only critters on
this island group today. Yeah, because if you know anything
about sea travel, especially sea travel in prior centuries, humans
weren't the only things on these ships. Right. There is
a rodent problem, or has been a rodent problem in
(04:31):
the Galapagos, And so according to the Galapagos Conservancy, the
brown rat Rattus norvegicus and the black rat Ratus ratus.
They were introduced to the Glapacos probably in the seventeenth
or eighteen centuries by seafaring visitors like whalers and privateers.
And as you alluded to, this is not an unusual story.
Wherever humans go, various rodents tag along with us. There's
(04:54):
sort of like a you know when you see a
shark swimming swimming and it's got those little things hanging
onto the body on side of it, and they just
go along with it. Yeah, yeah, Or the barnacles that
live on whales that whales sometimes use as big battering
rams and whale battles. Yeah. So if we're the shark,
those things are rodents, they just come along with us. Yeah,
they're just hanging out. Because humans create a lot of trash.
(05:17):
I think that actually is one of the reasons. But
so like many other cases where organisms are introduced by
humans to new ecosystems that haven't evolved to accommodate them,
they haven't always been there. The native organisms can really suffer,
and this has been the case over over the centuries
with introduced rats and mice in the Galapagos. Many native organisms,
(05:39):
especially birds and reptiles, have been severely threatened by these rodents,
which tend to prey on their eggs and they're young.
We've talked a bunch of times before in the show
about these invasive species and then the kind of damage
that they can do, because yeah, they nothing involved on
that island to protect itself from this sort of threat exactly.
So the Galapagos giant tortoise is one example. So the
(06:01):
giant tortoise has been severely threatened on multiple islands by
introduced animals, including rats, for one thing, though historically we
would be remiss if we didn't also mention, as I
alluded to a minute ago, the role humans played in
more directly reducing those tortoise populations themselves through for example, hunting.
And I don't know whether you'd say this is a
(06:21):
direct or indirect. I guess indirect through habitat destruction. So
the tortoises eggs and their hatchlings have been preyed upon
by animals like rats, especially rats, so badly that on
the island of pin Zone. Scientists believe that until just
a couple of years ago, there had been no new
tortoise hatchlings in about a hundred and fifty years. Yeah, exactly.
(06:44):
So conservationists did come up with plans for ways to
get around that, and that some of their plans actually
did succeed. For example, uh decades old conservation efforts focused
on breeding tortoises in captivity and keeping them there until
the young tortoises were about four or five years old,
at which point they became too large for the rats
(07:05):
to prey on them. Referred to in the literature as
being quote rat proof, rat proof tortoises, thank you, scientists.
You'd think the shell would make them always rat proof,
but I guess rats are crafty. I guess. Yeah. Well,
and and when the tiny little baby baby tortoises are
are you know, too small or I don't know, as
I don't want to imagine this. It's very sad, but
(07:27):
but yeah, so that did help. But even with this
measure in place, the tortoise eggs would be threatened in
the wild. So the problem was bad enough that conservationists
trying to save the tortoises, began a program to eradicate
the invasive rats in through mass poisoning with rat bait
essentially okay poison, but so far it does seem to
(07:50):
have worked. In January there was a letter to Nature
where a group of scientists and conservationists confirmed that in
December of the previous year, so December twenty fifteen, ten
saddleback giant tortoise hatchlings had been found on pin Zone Island,
and they believed that if they saw these, there must
be more than they haven't found. And this was the
(08:10):
first time hatchlings, as we said, have been observed in
the wild and more than a d and fifty years,
and so it suggests that the animals are finally able
able to recover their population through natural breeding, not breeding
in captivity. Yeah. Oh, that's that's wonderful. I have less
good news to report, Yeah, yeah, just over the past
month or so. Sadly, in May to June of six,
(08:33):
news broke of of the first confirmed extinction of a
bird species on Galapagos and the bird in question, which
is the sun cuistal ball vermilion flycatcher. I'm not going
to try the Latin because I didn't practice it before
the show. Um they no, no birds of this type
had been seen in the wild since seven so they
were presumed to be extinct already. But but this this
(08:55):
news comes after a genealogical and morphological review marked the
bird as being its own species instead of just a
subspecies as it was previously assumed to be. And what
caused this extinction rats, I mean rats mostly um eating
eating the eggs and also a parasitic fly that kills
chicks when they do manage to grow to hatch. So
(09:18):
bad times for this vermilion flycatcher. And they're really pretty,
is the sad thing. They're just really a little scarlet
colored birds anyway, sad though even we should always remember
that even the ugly creatures should have deserved a good shake. Yeah. Absolutely,
And now there are lots of other vermilion flycatchers of
(09:38):
a various species and subspecies on the island, but lots
of them are also in decline. And there's really interesting
work being done in studying the birds individual island based
adaptations because different islands within the archipelago have have have
different environments and so you can really get into the
genetics of how they adapted and broke off from each
(10:01):
other within those populations. But it's a situation where researchers
are basically scrambling to study the birds before they all disappear.
They're they're hoping that a few more species can be
and subspecies can be distinctified and identified, but they might
not if we can't start controlling this rat population. Yeah,
And so this is sort of a model of an
(10:22):
issue that goes on around the world where small island
populations of endemic animals are threatened by invasive species that
humans bring along with them when they travel to these islands. So,
in many cases, island wildlife conservation that's have been able
to make some progress saving endemic species by eradicating invasive
(10:43):
populations through totally conventional means poisoning, traps, etcetera. But none
of those methods are ideal. When you lay out, you know,
thousands of pounds of rat poison, you can just guess
that that's not the thing you want to do most
to the actually college, Yeah, or even traps, traps that
other animals could blunder on into sure. And also these
(11:05):
methods are just difficult to use, Like they can be
expensive labor intensive to carry out. Uh, And so our
question today, inspired by some recent stories in the news
on this subject, is could we use a different method
to try to eliminate invasive species on islands, a more
forward thinking method. Possibly? The method in question is what's
(11:29):
known as a gene drive. A gene drive? Right? Is this?
Does this have to do with like donating denim? I think?
I think when I was talking to my wife Rachel
about this last night, she made the exact joke. High
fives to Reachel. Yeah, not worded the same way, but
it was. It was pants themed. So, uh, so what
(11:51):
are gene drives? Well, let's sayward thinking it was pants themed. Sorry,
sometimes so water gene Right, Well, let's say you want
to spread an engineered gene throughout a population of animals.
One commonly discussed example is that of a mosquito with
a gene that prevents it from carrying the malaria parasite. Yeah,
(12:15):
this is a thing that basically everyone can agree would
be a plus exactly. I mean, it would be a
life saving innovation on a massive, worldwide scale. If mosquitoes
can't carry the malaria parasite and transmitted to humans, just
enormous amounts of mortality and human misery around the world
could be prevented. Yeah, if you if you do not remember,
(12:36):
mosquitoes actually are the creature that kill the most humans,
perhaps other than humans, every year indirectly by being the
carriers of right. Yeah, I guess it's the malaria parasite.
But yeah, and screw that parasite anyway, So it's really bad.
But yeah, So if you can create a mosquito in
(12:56):
the lab with a gene that says, sorry, malaria parasite
can't survive in me, I won't transmit it. Uh, that
would be great, But then you face another problem. Let's
say you've created this mosquito. How do you get that
mosquito to become the new mosquito to take over wild
mosquito populations? Because just just releasing a single certainly a
(13:18):
single creature, but even even a large number of creatures
into the wild doesn't necessarily mean that their genetics will
will propagate out over an entire population. Right, So let's
look at what happens, I mean, how do sexually reproducing
animals get their genes. Usually what happens is that a
male and female mate and their offspring each received fifty
percent of each parents genes, you get a recombinant mix
(13:42):
of the two, mostly at random. So in the case
of each gene location in the chromosomes, you have a
fifty percent chance of inheriting the allele from your mom
and a fifty percent chance of getting the allele from
your dad. So if this anti malaria mosquito manages to mate,
half of its offspring will carry the anti malaria gene,
(14:02):
and are the ones that do carry it, only half
of their offspring will carry it. Uh, there's this population
genetics barrier to the spread of this anti malaria technology.
And this is assuming that the trait has a neutral
effect on survival and reproduction, or even confers an advantage
so that the carrier mosquitoes have more offspring than the
(14:22):
non carriers. Yeah, that's not guaranteed. It could be in
some way detrimental to to the continuation of the species,
to to reproducibility exactly. So if it's detrimental, we can
probably expect it to dwindle and eventually disappear. Even if
it's beneficial, it's only going to spread very slowly. It's
gonna might become widespread among mosquitoes in the long run,
(14:45):
but it will take a really long time and it's
still not guaranteed. So if you want to be sure
that it does become widespread among wild mosquitoes, you'd have
to release just an absolutely gargantuan number of engineer mosquito
individuals into the wild with this gene And that's not
a great plan either. That doesn't sound like a fun
(15:06):
way to spend my Saturday. Yeah, Like, if somebody comes
to you and says, hey, we're going to release five
hundred trillion engineered mosquitoes into a lot of help into
your neighborhood, I feel like thanks. Uh. So this is
where the gene drive comes in. So a gene drive
is a system for biasing the inheritance of genes that
(15:28):
is pretty simple, but the goal is towards altering an
entire interbreeding population in a short amount of time. So
at the microscopic level, the gene drive is literally just
a heritable molecular mechanism, like a tiny molecule machine that's
attached to your DNA that gets passed on from parent
(15:48):
to offspring and ensures that a selected gene will be
inherited with a near one certainty during sexual reproduction. Yeah,
and well we'll talk a little bit about that mechanism
in a minute. It but let's just let's just give
give kind of an example of how this flows out
to a population. Okay, So again, let's imagine that you
want to use a gene drive to spread this anti
(16:09):
malaria gene among a wild population of mosquitoes. We can assume,
for the sake of an example, that the mosquito that
mates produces four offspring that are able to reproduce into
the next generation. This is not based on real mosquito
browd numbers. I just picked a random number and it
was four. Four is a nice easy one to multiply.
So with half of them inheriting the gene, on average,
(16:31):
one hundred percent of them or close to it will
inherit the anti malaria gene. So now each of those
four offspring I'll reproduce, and all of their offspring carried
the anti malaria gene and the gene drive insurers continued inheritance.
So then you've got sixteen and the next generation. Uh.
And then if each of them has four offspring, you've
(16:53):
got sixty four, and then two d and fifty six
and then one thousand twenty four, and then four thousand,
ninety six, and then sixteen thousand, three eight four, and
by the sixteenth generation you have over a billion individual
carriers of this gene. And so, okay, how this molecular
mechanism works at a at a high level because I
(17:13):
am not a geneticist. Um, it's it's actually a genetic
power that is already seen in nature. There's uh this
so called selfish genetic type of element of gene element. Okay,
so these these genetic elements don't follow the usual law
of averages of genetic inheritance inheritance um. When an egg
(17:33):
is fertilized and one of the parents DNA contains a
selfish element, that genetic bit targets the other parents parallel
allele the other genetic bit and alters it. So zip
zoom in this fertilized egg, you've got just about a
heritable trait. The tricky bit here is taking the genes
(17:58):
that make a selfish element and attaching them to the
trait that you want to absolutely make sure it gets
passed on. This this anti malaria trait um for for
for example, and okay, science has been working on that
part for over a decade, but it's been really rough
going until our discovery of Crisper and cast nine came
(18:19):
along over the past couple of years, and we did
a whole episode about how that whole genetic toolkit works
in April. The episode is called Editing Jeans with Crisper
if you would like to go check it out. But
in brief, crisper is another natural genetic process. It's it's
part of some bacteria's adaptive immune system. So if a
bacteria fights off a bacterium pardon me, fights off a
(18:41):
particular virus that the crisper system will neatly snip out
a wee bit of that viruss DNA is a sort
of fingerprint or like a wanted poster, you can think
of it and um. The system then attaches that snippet
of d N d NA back into the bacterium's own DNA,
so it keeps kind of like a catalog that it
can refer back too. So if another virus with that
(19:02):
bit of DNA ever comes a knocking at the bacterium's
outer cell wall again, it will know immediately that the
virus is bad news and can defend itself by dismantling
part of the virus is d NA using a protein
called CAST nine to do the manual labor. The bacterium
can pass on it's wanted catalog to its offspring because
(19:22):
it's part of its genetic code. So that is a
super great way for bacteria to to live longer and better.
It's a it's an amazing microscopic machine. It is. It is,
and it's also super useful to us because one of
the things that we've struggled with most in genetics classically
has been how labor intensive and expensive it was to
(19:44):
cut and paste to DNA together. But researchers figured out
a way to apply the Crisper system to target basically
any DNA they want, which means it's hella easy now
to physically isolate and remove bits of genetic code and
also to insert them into other bits of genetic Yeah,
certainly relevant or relative to what it was before. Absolutely.
(20:04):
So you you so you take this selfish element system
and you combine it with our knowledge of the Crisper
cutting pace system, and hazzah, you can pretty easily design
a gene that will drive itself through a population just
about as fast as that population can propagate. Yeah, and
depending on the reproductive schedule of the organism in question,
(20:24):
it can work with astonishing speed, like I've seen predictions
that with a method method like this, scientists could stop
the spread of malaria to humans within a couple of years.
Whether so, whether or not these predictions are true, the
gene drive is obviously an amazingly powerful tool for altering
nature with a very low initial investment. But if we
(20:47):
want to come back to the problem that we started
discussing at the beginning of the episode, like invasive species
on islands, how would you use a gene drive to
fight a problem like this? Because in this case, the
goal is not modifying an organism so that it does
something different, like it doesn't become a disease vector. But
the modification that we want is just something that would
(21:09):
eradicate the species. Sure well, and in that case, really
the modification that you want is something that does not reproduce. Right.
So it's turns out it's not very hard to dream
up a gene that, if delivered through a gene drive,
can steer a population into extinction. In fact, it seems
pretty easy. So let's say you have an island with
(21:29):
a rat problem, and the rats are driving natural endemic
species to extinction. Uh, here's the most common solution that
scientists have come up with. You establish a gene drive
for a trait that causes all of an animal's offspring
to be male or or a vastly biased portion of
them to be male. So imagine how this works on
(21:51):
an island. With each generation, males make up a more
disproportionate contingent of the total population, until eventually there are
virtually no females for them to breed with, and the
rats stop reproducing and disappear. Your rat problem on this
island is gone. So there are some pros and cons
to this method. Yeah, pros to this method. You don't
(22:15):
need poison or traps. Don't need to dump thousands of
pounds of rat poison out of helicopters all over the
entire island and maybe accidentally poison other organisms and or
set out traps that people have to collect and that
you know, you maybe accidentally end up killing some of
the animals you were trying to save getting your toe
stuck in. Yeah, none of that. Good time. Another possible
pro is that, so I mean a lot of the
(22:38):
people who would be doing this eradication are probably animal lovers.
It's not like they want the rats to suffer. They're
just trying to keep native populations from going extinct. So
this could be seen as a more humane way to
eradicate invasive species. Instead of poisoning them killing them painfully,
you just allow them to live out their lives without
(22:58):
being able to make more are of them. They're very
sexually frustrated lives. But but yes, other than that, it's
it's definitely much more humane than poison. Yeah, I probably
agree that that's true. But what if a reproduction prohibiting
gene drive were to get loose in a non isolated population,
(23:20):
Because the way it works on the island is it
just keeps multiplying. This gene spreads through more and more
the population until there's nothing left and then the rats
die off. What if rats carrying this gene got to
the mainland. What if they hitchhike on the sharks that
are humanity and get back over Whoops, Because then they
(23:40):
could breed with rats on the mainland and essentially start
this entire process over except for the entire world. That's
not good because you could accidentally create worldwide extinction. And
as much as we don't like rats. I don't think
we want to drive them to worldwide extinction. There would
certainly be other repercussions involved there as as again we
(24:03):
have talked about before on the show. At any time
that you that you interrupt an ecosystem, it's going to
have wide ripples that you can't really predict because ecosystems
are so complex and convoluted. Uh. The other con that I,
you know, just wanted to mention because of me, is
that this is literally one of the things that led
to everyone except Jeff Goldblum and I guess a few
other people dying in Jurassic Park because all the dinosaurs
(24:27):
were female, and no one remember that the frogs that
they use the genetic code from to help build the
dinosaurs could switch sexes when the population lagged. And Okay, look,
what I'm saying is not that introducing gene drives into
a population of rats is going to lead to all
of us getting eaten or hunted for sport or whatever
by dinosaurs. I'm just saying, you know, I mean, do
(24:50):
you want to do the line Joe, Life finds a
way that thing right there, It certainly does. It smashes
through barriers, painful maybe sometimes even dangerously, but there it is.
And you know that though, I think about Jurassic Park now,
and it seems that they had it backwards. So if
they were trying to produce an population of animals that
(25:13):
couldn't breed, and then they had all females, it seems
like just one male could really mess up that whole system.
What they should have done is have a population of
all males. Then if you had just one female get
in there, that wouldn't be good, but it wouldn't you know,
have a runaway effect. Absolutely. Uh. I think I think
the reason that they did it that way, that the
(25:34):
explanation for this plot hole was that it was it's
it's easier to turn off genetically the male chromosome than
it is too because because all embryos starts females, they
did the the easy thing instead of the smart thing.
What do you know, created a gaping, gaping plot hole. Uh.
(25:54):
So other general thoughts about gen drives, I mean, we
should definitely end by by emphasizing I think the uh,
the concerns and very serious caution that that people are
saying we should exercise with this technology for very good reason.
Oh yeah, because because it is so exciting, Like the
concept is is so dynamic and interesting, but also yeah,
(26:15):
like this is one that basically every researcher that I've
read anything from who is working with gene drives right
now is like, let's apply some great safety breaks for
a while, y'all. This is one of the most powerful
and one of the scariest tools we've ever invented. I think, So,
what could gene drives do besides halting the spread of
(26:35):
disease through vector modification or eradicating invasive species. I'm sure
we could actually come up with tons of different ways
to apply a technology like this. Here's one I thought
of that might be reduced released into the wild. Uh.
I don't know why I said I thought of this,
This is one I read about. I wasn't trying to
claim claim credit there. Uh. What it was was herbicide
(26:57):
pesticide resistance reversal. So often organisms that hamper crop development,
like weeds and insect pests, for instance, develop resistance to
the safest chemical means of keeping them off our food crops.
One example weeds resistant to the herbicide glyph asade. So
with gene drives, you could spread a gene ensuring vulnerability
(27:20):
to conventional herbicides among the wild population, not not eradicating them,
just essentially undoing the resistance that they've evolved to the
poisons we used to keep them off of our food. Yeah,
and and that could help us as a side effect
or not a side effect, like as a as a
cascade effect, minimize the different types of herbsides and pesticides
(27:41):
that are used, focusing on the ones with the fewest
side effects, which would be real good times for other
creatures that interact with those herbicides and pesticides that are
not as hardy, like saybes, Yeah, you don't want to
be constantly upping the potency of your arsenal to protect
your crops because upping that potency probably is just doing
more and more damage. Sure, and you know so or
(28:02):
or or I don't know, like like maybe we could
use a similar We could use the technology to make
bees more resistant to those poisons. Although that seems like
a I mean more poisons, I think is not the
point of all of this. I did want to put
in that that it would, though be harder to propagate
a gene drive through most crop populations themselves, because most
(28:22):
crops don't reproduce sexually, and and this is perhaps obviously,
but it should be stated a technology that only works
in sexually reproducing populations. A lot of crops are made
by very controlled seed populations, like cloning. Essentially yeah, plants. Okay,
I don't think I actually knew that fact. That's interesting. Yeah,
a lot of cuttings are used, which is essentially a
(28:45):
way of cloning. That makes sense. Uh So another question
I know people are wondering about. Could humans be eradicated
via gene drive? An important question, so it's relevant to
me if nobody was paying attention and you had a really,
really long time to do it, I guess, But in reality,
probably not, because gene drives rely on fast reproductive cycles
(29:09):
to spread through wild populations, and humans and other large
mammals that have multi year reproductive cycles would take centuries
before the gene drive became widespread, and by then we
would probably have detected the problem and done something about it,
So I wouldn't. That's not the big worry. But does
that mean we should not worry? No, no, no, no no.
(29:31):
This is something we need to be incredibly cautious and
concerned about because so maybe they won't affect us, But
could gene drives released into the wild cause some very
bad outcomes that affect other animals and affect us indirectly. Absolutely,
this is a very powerful and very potentially dangerous technology,
and among any sexually reproducing species with rapid generational turnover,
(29:55):
a gene drive accidentally released into the wild could cause
worldwide alteration, inter extinction, and possibly in ways that we
cannot imagine. You know, because genes do sometimes jump from
one species to another, from from one phylum to another.
There's there's lots of examples of that out in nature. Yeah,
so what if, for example, you have uh, usually we
(30:19):
see the dividing line between species as being you know,
animals that won't naturally interbreed with one another, but sometimes
animals do cross the line and it can surprise us. Yeah. Yeah,
So for those reasons, some scientists are recommending that for
for any gene drive designed, a either reversal drive or
an an immunization drive be designed in parallel. A reversal
(30:42):
drive would act against the original drive, cutting it out
of the population if something started to go wrong, and
an immunization drive would spread through the population alongside the
original drive, preventing later generations from inheriting the original um,
which you know wouldn't stop all of the potential damage,
but it would certainly emitted. Yeah. One thing I have heard,
one of the sort of glimmers of hope, is that
(31:05):
you could potentially just design an antidote drive essentially right,
exactly what I think you're talking about. Yeah, with with
the reverse, with the reversal drive. Yeah, um so so,
so it's not like if it got loose, there's nothing
we know we could do to stop it. But that
doesn't mean we should be cavalier about it either, yeah. Yeah.
And researchers furthermore are working on a way to cut
(31:27):
off gene drives after a few generations, like naturally in
the wild by by designing in a sort of fail safe.
A team out of M I T specifically has conceptualized
a daisy chain effect is what they're calling it, and
the idea is that's okay, you split the genetic information
that you're testing into three packages. Part A can only
paste itself into wild DNA if part B is present.
(31:50):
Part B, meanwhile, can only paste itself into wild DNA
if parts C is present and parts C here's the
critical part is a normal gene will only be inherited
about fifty of the time. So if you release creatures
with with all three parts into a natural population, the
next generation will have well, we'll all have A and B,
(32:11):
but only about half of them will have C. So
although the gene drive will persist out for a few generations,
eventually parts C will largely die out, and then B
and then A and and this this could allow for
a safer way to introduce a localized, temporary gene drive
into the wild. Interesting um hypothetically if it works as planned,
(32:34):
if life does not find a way right, So, yeah,
don't run away with any of this thinking like, oh,
we're we're okay, then don't need to worry about that.
Do it tomorrow. This is something you should be thinking
about and everybody should be paying attention to, because it's
yet another one of these things where recent advances in
genetics I think, are are catching people off guard. They're
(32:55):
coming faster than people are coming up with ways to
form ethical opinions about though right, largely because of this
Crisper process, which is I mean super amazing but but
also right, has just pulled entirely the breaks off of
the system really in terms of what we can do
with genetics. Yeah, um, and so so I think we
should definitely pay heed to the scientists who are urging
(33:17):
caution and uh and very careful treading on this. I'm
not necessarily opposed to gene drive research, and I think
it's a good thing to be studying, but it's the
kind of thing that you have to study extremely carefully.
So you know, what if you're you're just working on
gene drive research and you've got a lab full of
insects and one of them escapes the lab, whoops. Uh.
(33:39):
So yeah, there have been I know, people have tried
different methods of controlling this, like, for example, only experimenting
with gene drives in organisms in labs that are in
places where those organisms don't naturally live, so if one
did escape somehow, it wouldn't find anything to breed with. Sure, yes,
and and all the gene drives to the polar self.
(34:01):
And don't experiment on penguins at all. Ye are penguins
in in the polars? I don't remember. I always get
this mixed time. I think they're around the water anyway, Yes, caution,
yeah exactly. So, I mean it's really cool it's really cool,
but caution. Yeah. Anyway, there's been a bunch of a
bunch of writing about this in the science press lately
(34:21):
and UH, and it's something that's definitely worth keeping up with.
I would just recommend googling gene drives and UH and
news around this subject if you want to keep abreast
of this developing topic. Yeah. Uh. If you have any
specific questions about it, then feel free to ask us.
You can get in touch with us are in multiple ways.
(34:41):
Our email address if you're still into that email thing,
is FW thinking at how Stuff Works dot com. You
can also reach out to us on social media. We
are on Twitter and Facebook, where our handles, strangely enough,
is also FW thinking. Uh. We hope to hear from you.
We have enjoyed talking about this and the sure from
us again very soon. For more on this topic in
(35:08):
the future of technology, visit forward Thinking dot com, brought
to you by Toyota. Let's Go Places,
Brought to you by Toyota. Let's go places. Welcome to
Forward Thinking. Hello, and welcome to Forward Thinking, this podcast
that looks at the future and says, rescue me from
me and all that I believe. I'm Lauren Volgabon and
(00:22):
I'm Joe McCormick, and our regular host Jonathan Strickland is
not with us today. He is still out on vacation.
He's having lovely adventures in his absence. We went on
a very short Billy Corgan impersonation to kick there, but
that's no, was not recording that. I kind of hope
he was. It was really delightful. Both of you do
a really good smashing pumpkins. Anyway. Yeah, so today we're
(00:48):
gonna be talking about a fascinating topic in genetics. Yes,
but we want to get there in a kind of
roundabout way by talking about islands. Yeah. We want to
get there via the Galapagos. Have you ever been to
the Galapagos? I have not, have you No, I haven't,
But I want to go there someday. I know. It's lovely,
it's it's a I mean, there's so many things there
(01:11):
that you literally cannot find anywhere else, and not like
restaurants like like beautiful wildlife. Yeah, I know, the restaurants
seen there is probably not not what people go for.
I don't think it is now. Yeah, so you're probably familiar,
but just in case you're not. The Galapagos or a
group of islands, or more accurately, a volcanic archipelago in
the Pacific Ocean about about a thousand kilometers off the
(01:33):
west coast of Ecuador, right along the equator. I think
it actually straddles the equator. Yeah, yeah, and the Galapagos
appear to have been mostly uninhabited before the Spanish visited
in the sixteenth century by humans that is. Yeah. The
glaucost Islands are situated more or less smack in the
middle of these three conjoining tectonic plates and thus three
(01:56):
different ocean currents, meaning that over the millennia, lots of
credits from all over the world have wound up there,
and the ones that stayed and reproduced branched off from
their ancestors due to the unique living conditions and uh
and separation from the general population. Yeah, and for this
reason today the Galapagos I think are mainly known for
their wildlife. That that's why people mostly want to go
(02:18):
to this place. Yeah, so you've got, for example, the
endemic Galapagos penguin, the Galapagos giant tortoise, and there are
a few subspecies of that, like the saddleback tortoise and
the dome tortoise, and then of course those smug, insufferable
marine iguanas. Did did a marine iguana from Galapacos? Like? Wrong?
You in your past? You know, I would never advise
(02:40):
anybody treat them with anything but the utmost respect for nature.
But just look at their faces. They just look like jerks.
They do you sitting on those rocks, so they look
really proud and slappable. Yeah, there's something about them. No,
do not slap an iguana. Never slap an iguana. Why
would you do that? The Galapagos. So yeah, so they've
got they've got all these animals that are very beautiful
(03:01):
and unique and and iconic in many ways. For one reason,
I think because the Galapagos were, uh, this archipelago is
one of the places that Charles Darwin stopped on his
voyage on the h MS vegal famously. Yes, yeah, and
so I think for that reason, they've become sort of
emblematic of animal evolution and ecology in many ways since then.
And like I said, I've never been, but I've always
(03:23):
heard that because of the lack of large natural predators
on the island, many of its animals are just very
friendly chill. Yeah, they're they're fine basically with humans hanging
out around them. Yeah, and they'll allow you to approach
them without running away. So so that can be very
wonderful if you are a peaceful, conservation minded ecological tourists
(03:46):
who wants to visit the island and see some animals.
Not so great for the animals if you are, say
a pirate or a whaler or something that wants to
kill a tortoise and eat it for its meat which
has figured into the island's history, or or save it
for or harvested for its beautiful shell or et cetera. Sure, exactly.
So these days the glopacos are there's sort of a
popular wildlife and conservation tourist destination, but the archipela goes.
(04:11):
Beautiful and fascinating endemic species aren't the only critters on
this island group today. Yeah, because if you know anything
about sea travel, especially sea travel in prior centuries, humans
weren't the only things on these ships. Right. There is
a rodent problem, or has been a rodent problem in
(04:31):
the Galapagos, And so according to the Galapagos Conservancy, the
brown rat Rattus norvegicus and the black rat Ratus ratus.
They were introduced to the Glapacos probably in the seventeenth
or eighteen centuries by seafaring visitors like whalers and privateers.
And as you alluded to, this is not an unusual story.
Wherever humans go, various rodents tag along with us. There's
(04:54):
sort of like a you know when you see a
shark swimming swimming and it's got those little things hanging
onto the body on side of it, and they just
go along with it. Yeah, yeah, Or the barnacles that
live on whales that whales sometimes use as big battering
rams and whale battles. Yeah. So if we're the shark,
those things are rodents, they just come along with us. Yeah,
they're just hanging out. Because humans create a lot of trash.
(05:17):
I think that actually is one of the reasons. But
so like many other cases where organisms are introduced by
humans to new ecosystems that haven't evolved to accommodate them,
they haven't always been there. The native organisms can really suffer,
and this has been the case over over the centuries
with introduced rats and mice in the Galapagos. Many native organisms,
(05:39):
especially birds and reptiles, have been severely threatened by these rodents,
which tend to prey on their eggs and they're young.
We've talked a bunch of times before in the show
about these invasive species and then the kind of damage
that they can do, because yeah, they nothing involved on
that island to protect itself from this sort of threat exactly.
So the Galapagos giant tortoise is one example. So the
(06:01):
giant tortoise has been severely threatened on multiple islands by
introduced animals, including rats, for one thing, though historically we
would be remiss if we didn't also mention, as I
alluded to a minute ago, the role humans played in
more directly reducing those tortoise populations themselves through for example, hunting.
And I don't know whether you'd say this is a
(06:21):
direct or indirect. I guess indirect through habitat destruction. So
the tortoises eggs and their hatchlings have been preyed upon
by animals like rats, especially rats, so badly that on
the island of pin Zone. Scientists believe that until just
a couple of years ago, there had been no new
tortoise hatchlings in about a hundred and fifty years. Yeah, exactly.
(06:44):
So conservationists did come up with plans for ways to
get around that, and that some of their plans actually
did succeed. For example, uh decades old conservation efforts focused
on breeding tortoises in captivity and keeping them there until
the young tortoises were about four or five years old,
at which point they became too large for the rats
(07:05):
to prey on them. Referred to in the literature as
being quote rat proof, rat proof tortoises, thank you, scientists.
You'd think the shell would make them always rat proof,
but I guess rats are crafty. I guess. Yeah. Well,
and and when the tiny little baby baby tortoises are
are you know, too small or I don't know, as
I don't want to imagine this. It's very sad, but
(07:27):
but yeah, so that did help. But even with this
measure in place, the tortoise eggs would be threatened in
the wild. So the problem was bad enough that conservationists
trying to save the tortoises, began a program to eradicate
the invasive rats in through mass poisoning with rat bait
essentially okay poison, but so far it does seem to
(07:50):
have worked. In January there was a letter to Nature
where a group of scientists and conservationists confirmed that in
December of the previous year, so December twenty fifteen, ten
saddleback giant tortoise hatchlings had been found on pin Zone Island,
and they believed that if they saw these, there must
be more than they haven't found. And this was the
(08:10):
first time hatchlings, as we said, have been observed in
the wild and more than a d and fifty years,
and so it suggests that the animals are finally able
able to recover their population through natural breeding, not breeding
in captivity. Yeah. Oh, that's that's wonderful. I have less
good news to report, Yeah, yeah, just over the past
month or so. Sadly, in May to June of six,
(08:33):
news broke of of the first confirmed extinction of a
bird species on Galapagos and the bird in question, which
is the sun cuistal ball vermilion flycatcher. I'm not going
to try the Latin because I didn't practice it before
the show. Um they no, no birds of this type
had been seen in the wild since seven so they
were presumed to be extinct already. But but this this
(08:55):
news comes after a genealogical and morphological review marked the
bird as being its own species instead of just a
subspecies as it was previously assumed to be. And what
caused this extinction rats, I mean rats mostly um eating
eating the eggs and also a parasitic fly that kills
chicks when they do manage to grow to hatch. So
(09:18):
bad times for this vermilion flycatcher. And they're really pretty,
is the sad thing. They're just really a little scarlet
colored birds anyway, sad though even we should always remember
that even the ugly creatures should have deserved a good shake. Yeah. Absolutely,
And now there are lots of other vermilion flycatchers of
(09:38):
a various species and subspecies on the island, but lots
of them are also in decline. And there's really interesting
work being done in studying the birds individual island based
adaptations because different islands within the archipelago have have have
different environments and so you can really get into the
genetics of how they adapted and broke off from each
(10:01):
other within those populations. But it's a situation where researchers
are basically scrambling to study the birds before they all disappear.
They're they're hoping that a few more species can be
and subspecies can be distinctified and identified, but they might
not if we can't start controlling this rat population. Yeah,
And so this is sort of a model of an
(10:22):
issue that goes on around the world where small island
populations of endemic animals are threatened by invasive species that
humans bring along with them when they travel to these islands. So,
in many cases, island wildlife conservation that's have been able
to make some progress saving endemic species by eradicating invasive
(10:43):
populations through totally conventional means poisoning, traps, etcetera. But none
of those methods are ideal. When you lay out, you know,
thousands of pounds of rat poison, you can just guess
that that's not the thing you want to do most
to the actually college, Yeah, or even traps, traps that
other animals could blunder on into sure. And also these
(11:05):
methods are just difficult to use, Like they can be
expensive labor intensive to carry out. Uh, And so our
question today, inspired by some recent stories in the news
on this subject, is could we use a different method
to try to eliminate invasive species on islands, a more
forward thinking method. Possibly? The method in question is what's
(11:29):
known as a gene drive. A gene drive? Right? Is this?
Does this have to do with like donating denim? I think?
I think when I was talking to my wife Rachel
about this last night, she made the exact joke. High
fives to Reachel. Yeah, not worded the same way, but
it was. It was pants themed. So, uh, so what
(11:51):
are gene drives? Well, let's sayward thinking it was pants themed. Sorry,
sometimes so water gene Right, Well, let's say you want
to spread an engineered gene throughout a population of animals.
One commonly discussed example is that of a mosquito with
a gene that prevents it from carrying the malaria parasite. Yeah,
(12:15):
this is a thing that basically everyone can agree would
be a plus exactly. I mean, it would be a
life saving innovation on a massive, worldwide scale. If mosquitoes
can't carry the malaria parasite and transmitted to humans, just
enormous amounts of mortality and human misery around the world
could be prevented. Yeah, if you if you do not remember,
(12:36):
mosquitoes actually are the creature that kill the most humans,
perhaps other than humans, every year indirectly by being the
carriers of right. Yeah, I guess it's the malaria parasite.
But yeah, and screw that parasite anyway, So it's really bad.
But yeah, So if you can create a mosquito in
(12:56):
the lab with a gene that says, sorry, malaria parasite
can't survive in me, I won't transmit it. Uh, that
would be great, But then you face another problem. Let's
say you've created this mosquito. How do you get that
mosquito to become the new mosquito to take over wild
mosquito populations? Because just just releasing a single certainly a
(13:18):
single creature, but even even a large number of creatures
into the wild doesn't necessarily mean that their genetics will
will propagate out over an entire population. Right, So let's
look at what happens, I mean, how do sexually reproducing
animals get their genes. Usually what happens is that a
male and female mate and their offspring each received fifty
percent of each parents genes, you get a recombinant mix
(13:42):
of the two, mostly at random. So in the case
of each gene location in the chromosomes, you have a
fifty percent chance of inheriting the allele from your mom
and a fifty percent chance of getting the allele from
your dad. So if this anti malaria mosquito manages to mate,
half of its offspring will carry the anti malaria gene,
(14:02):
and are the ones that do carry it, only half
of their offspring will carry it. Uh, there's this population
genetics barrier to the spread of this anti malaria technology.
And this is assuming that the trait has a neutral
effect on survival and reproduction, or even confers an advantage
so that the carrier mosquitoes have more offspring than the
(14:22):
non carriers. Yeah, that's not guaranteed. It could be in
some way detrimental to to the continuation of the species,
to to reproducibility exactly. So if it's detrimental, we can
probably expect it to dwindle and eventually disappear. Even if
it's beneficial, it's only going to spread very slowly. It's
gonna might become widespread among mosquitoes in the long run,
(14:45):
but it will take a really long time and it's
still not guaranteed. So if you want to be sure
that it does become widespread among wild mosquitoes, you'd have
to release just an absolutely gargantuan number of engineer mosquito
individuals into the wild with this gene And that's not
a great plan either. That doesn't sound like a fun
(15:06):
way to spend my Saturday. Yeah, Like, if somebody comes
to you and says, hey, we're going to release five
hundred trillion engineered mosquitoes into a lot of help into
your neighborhood, I feel like thanks. Uh. So this is
where the gene drive comes in. So a gene drive
is a system for biasing the inheritance of genes that
(15:28):
is pretty simple, but the goal is towards altering an
entire interbreeding population in a short amount of time. So
at the microscopic level, the gene drive is literally just
a heritable molecular mechanism, like a tiny molecule machine that's
attached to your DNA that gets passed on from parent
(15:48):
to offspring and ensures that a selected gene will be
inherited with a near one certainty during sexual reproduction. Yeah,
and well we'll talk a little bit about that mechanism
in a minute. It but let's just let's just give
give kind of an example of how this flows out
to a population. Okay, So again, let's imagine that you
want to use a gene drive to spread this anti
(16:09):
malaria gene among a wild population of mosquitoes. We can assume,
for the sake of an example, that the mosquito that
mates produces four offspring that are able to reproduce into
the next generation. This is not based on real mosquito
browd numbers. I just picked a random number and it
was four. Four is a nice easy one to multiply.
So with half of them inheriting the gene, on average,
(16:31):
one hundred percent of them or close to it will
inherit the anti malaria gene. So now each of those
four offspring I'll reproduce, and all of their offspring carried
the anti malaria gene and the gene drive insurers continued inheritance.
So then you've got sixteen and the next generation. Uh.
And then if each of them has four offspring, you've
(16:53):
got sixty four, and then two d and fifty six
and then one thousand twenty four, and then four thousand,
ninety six, and then sixteen thousand, three eight four, and
by the sixteenth generation you have over a billion individual
carriers of this gene. And so, okay, how this molecular
mechanism works at a at a high level because I
(17:13):
am not a geneticist. Um, it's it's actually a genetic
power that is already seen in nature. There's uh this
so called selfish genetic type of element of gene element. Okay,
so these these genetic elements don't follow the usual law
of averages of genetic inheritance inheritance um. When an egg
(17:33):
is fertilized and one of the parents DNA contains a
selfish element, that genetic bit targets the other parents parallel
allele the other genetic bit and alters it. So zip
zoom in this fertilized egg, you've got just about a
heritable trait. The tricky bit here is taking the genes
(17:58):
that make a selfish element and attaching them to the
trait that you want to absolutely make sure it gets
passed on. This this anti malaria trait um for for
for example, and okay, science has been working on that
part for over a decade, but it's been really rough
going until our discovery of Crisper and cast nine came
(18:19):
along over the past couple of years, and we did
a whole episode about how that whole genetic toolkit works
in April. The episode is called Editing Jeans with Crisper
if you would like to go check it out. But
in brief, crisper is another natural genetic process. It's it's
part of some bacteria's adaptive immune system. So if a
bacteria fights off a bacterium pardon me, fights off a
(18:41):
particular virus that the crisper system will neatly snip out
a wee bit of that viruss DNA is a sort
of fingerprint or like a wanted poster, you can think
of it and um. The system then attaches that snippet
of d N d NA back into the bacterium's own DNA,
so it keeps kind of like a catalog that it
can refer back too. So if another virus with that
(19:02):
bit of DNA ever comes a knocking at the bacterium's
outer cell wall again, it will know immediately that the
virus is bad news and can defend itself by dismantling
part of the virus is d NA using a protein
called CAST nine to do the manual labor. The bacterium
can pass on it's wanted catalog to its offspring because
(19:22):
it's part of its genetic code. So that is a
super great way for bacteria to to live longer and better.
It's a it's an amazing microscopic machine. It is. It is,
and it's also super useful to us because one of
the things that we've struggled with most in genetics classically
has been how labor intensive and expensive it was to
(19:44):
cut and paste to DNA together. But researchers figured out
a way to apply the Crisper system to target basically
any DNA they want, which means it's hella easy now
to physically isolate and remove bits of genetic code and
also to insert them into other bits of genetic Yeah,
certainly relevant or relative to what it was before. Absolutely.
(20:04):
So you you so you take this selfish element system
and you combine it with our knowledge of the Crisper
cutting pace system, and hazzah, you can pretty easily design
a gene that will drive itself through a population just
about as fast as that population can propagate. Yeah, and
depending on the reproductive schedule of the organism in question,
(20:24):
it can work with astonishing speed, like I've seen predictions
that with a method method like this, scientists could stop
the spread of malaria to humans within a couple of years.
Whether so, whether or not these predictions are true, the
gene drive is obviously an amazingly powerful tool for altering
nature with a very low initial investment. But if we
(20:47):
want to come back to the problem that we started
discussing at the beginning of the episode, like invasive species
on islands, how would you use a gene drive to
fight a problem like this? Because in this case, the
goal is not modifying an organism so that it does
something different, like it doesn't become a disease vector. But
the modification that we want is just something that would
(21:09):
eradicate the species. Sure well, and in that case, really
the modification that you want is something that does not reproduce. Right.
So it's turns out it's not very hard to dream
up a gene that, if delivered through a gene drive,
can steer a population into extinction. In fact, it seems
pretty easy. So let's say you have an island with
(21:29):
a rat problem, and the rats are driving natural endemic
species to extinction. Uh, here's the most common solution that
scientists have come up with. You establish a gene drive
for a trait that causes all of an animal's offspring
to be male or or a vastly biased portion of
them to be male. So imagine how this works on
(21:51):
an island. With each generation, males make up a more
disproportionate contingent of the total population, until eventually there are
virtually no females for them to breed with, and the
rats stop reproducing and disappear. Your rat problem on this
island is gone. So there are some pros and cons
to this method. Yeah, pros to this method. You don't
(22:15):
need poison or traps. Don't need to dump thousands of
pounds of rat poison out of helicopters all over the
entire island and maybe accidentally poison other organisms and or
set out traps that people have to collect and that
you know, you maybe accidentally end up killing some of
the animals you were trying to save getting your toe
stuck in. Yeah, none of that. Good time. Another possible
pro is that, so I mean a lot of the
(22:38):
people who would be doing this eradication are probably animal lovers.
It's not like they want the rats to suffer. They're
just trying to keep native populations from going extinct. So
this could be seen as a more humane way to
eradicate invasive species. Instead of poisoning them killing them painfully,
you just allow them to live out their lives without
(22:58):
being able to make more are of them. They're very
sexually frustrated lives. But but yes, other than that, it's
it's definitely much more humane than poison. Yeah, I probably
agree that that's true. But what if a reproduction prohibiting
gene drive were to get loose in a non isolated population,
(23:20):
Because the way it works on the island is it
just keeps multiplying. This gene spreads through more and more
the population until there's nothing left and then the rats
die off. What if rats carrying this gene got to
the mainland. What if they hitchhike on the sharks that
are humanity and get back over Whoops, Because then they
(23:40):
could breed with rats on the mainland and essentially start
this entire process over except for the entire world. That's
not good because you could accidentally create worldwide extinction. And
as much as we don't like rats. I don't think
we want to drive them to worldwide extinction. There would
certainly be other repercussions involved there as as again we
(24:03):
have talked about before on the show. At any time
that you that you interrupt an ecosystem, it's going to
have wide ripples that you can't really predict because ecosystems
are so complex and convoluted. Uh. The other con that I,
you know, just wanted to mention because of me, is
that this is literally one of the things that led
to everyone except Jeff Goldblum and I guess a few
other people dying in Jurassic Park because all the dinosaurs
(24:27):
were female, and no one remember that the frogs that
they use the genetic code from to help build the
dinosaurs could switch sexes when the population lagged. And Okay, look,
what I'm saying is not that introducing gene drives into
a population of rats is going to lead to all
of us getting eaten or hunted for sport or whatever
by dinosaurs. I'm just saying, you know, I mean, do
(24:50):
you want to do the line Joe, Life finds a
way that thing right there, It certainly does. It smashes
through barriers, painful maybe sometimes even dangerously, but there it is.
And you know that though, I think about Jurassic Park now,
and it seems that they had it backwards. So if
they were trying to produce an population of animals that
(25:13):
couldn't breed, and then they had all females, it seems
like just one male could really mess up that whole system.
What they should have done is have a population of
all males. Then if you had just one female get
in there, that wouldn't be good, but it wouldn't you know,
have a runaway effect. Absolutely. Uh. I think I think
the reason that they did it that way, that the
(25:34):
explanation for this plot hole was that it was it's
it's easier to turn off genetically the male chromosome than
it is too because because all embryos starts females, they
did the the easy thing instead of the smart thing.
What do you know, created a gaping, gaping plot hole. Uh.
(25:54):
So other general thoughts about gen drives, I mean, we
should definitely end by by emphasizing I think the uh,
the concerns and very serious caution that that people are
saying we should exercise with this technology for very good reason.
Oh yeah, because because it is so exciting, Like the
concept is is so dynamic and interesting, but also yeah,
(26:15):
like this is one that basically every researcher that I've
read anything from who is working with gene drives right
now is like, let's apply some great safety breaks for
a while, y'all. This is one of the most powerful
and one of the scariest tools we've ever invented. I think, So,
what could gene drives do besides halting the spread of
(26:35):
disease through vector modification or eradicating invasive species. I'm sure
we could actually come up with tons of different ways
to apply a technology like this. Here's one I thought
of that might be reduced released into the wild. Uh.
I don't know why I said I thought of this,
This is one I read about. I wasn't trying to
claim claim credit there. Uh. What it was was herbicide
(26:57):
pesticide resistance reversal. So often organisms that hamper crop development,
like weeds and insect pests, for instance, develop resistance to
the safest chemical means of keeping them off our food crops.
One example weeds resistant to the herbicide glyph asade. So
with gene drives, you could spread a gene ensuring vulnerability
(27:20):
to conventional herbicides among the wild population, not not eradicating them,
just essentially undoing the resistance that they've evolved to the
poisons we used to keep them off of our food. Yeah,
and and that could help us as a side effect
or not a side effect, like as a as a
cascade effect, minimize the different types of herbsides and pesticides
(27:41):
that are used, focusing on the ones with the fewest
side effects, which would be real good times for other
creatures that interact with those herbicides and pesticides that are
not as hardy, like saybes, Yeah, you don't want to
be constantly upping the potency of your arsenal to protect
your crops because upping that potency probably is just doing
more and more damage. Sure, and you know so or
(28:02):
or or I don't know, like like maybe we could
use a similar We could use the technology to make
bees more resistant to those poisons. Although that seems like
a I mean more poisons, I think is not the
point of all of this. I did want to put
in that that it would, though be harder to propagate
a gene drive through most crop populations themselves, because most
(28:22):
crops don't reproduce sexually, and and this is perhaps obviously,
but it should be stated a technology that only works
in sexually reproducing populations. A lot of crops are made
by very controlled seed populations, like cloning. Essentially yeah, plants. Okay,
I don't think I actually knew that fact. That's interesting. Yeah,
a lot of cuttings are used, which is essentially a
(28:45):
way of cloning. That makes sense. Uh So another question
I know people are wondering about. Could humans be eradicated
via gene drive? An important question, so it's relevant to
me if nobody was paying attention and you had a really,
really long time to do it, I guess, But in reality,
probably not, because gene drives rely on fast reproductive cycles
(29:09):
to spread through wild populations, and humans and other large
mammals that have multi year reproductive cycles would take centuries
before the gene drive became widespread, and by then we
would probably have detected the problem and done something about it,
So I wouldn't. That's not the big worry. But does
that mean we should not worry? No, no, no, no no.
(29:31):
This is something we need to be incredibly cautious and
concerned about because so maybe they won't affect us, But
could gene drives released into the wild cause some very
bad outcomes that affect other animals and affect us indirectly. Absolutely,
this is a very powerful and very potentially dangerous technology,
and among any sexually reproducing species with rapid generational turnover,
(29:55):
a gene drive accidentally released into the wild could cause
worldwide alteration, inter extinction, and possibly in ways that we
cannot imagine. You know, because genes do sometimes jump from
one species to another, from from one phylum to another.
There's there's lots of examples of that out in nature. Yeah,
so what if, for example, you have uh, usually we
(30:19):
see the dividing line between species as being you know,
animals that won't naturally interbreed with one another, but sometimes
animals do cross the line and it can surprise us. Yeah. Yeah,
So for those reasons, some scientists are recommending that for
for any gene drive designed, a either reversal drive or
an an immunization drive be designed in parallel. A reversal
(30:42):
drive would act against the original drive, cutting it out
of the population if something started to go wrong, and
an immunization drive would spread through the population alongside the
original drive, preventing later generations from inheriting the original um,
which you know wouldn't stop all of the potential damage,
but it would certainly emitted. Yeah. One thing I have heard,
one of the sort of glimmers of hope, is that
(31:05):
you could potentially just design an antidote drive essentially right,
exactly what I think you're talking about. Yeah, with with
the reverse, with the reversal drive. Yeah, um so so,
so it's not like if it got loose, there's nothing
we know we could do to stop it. But that
doesn't mean we should be cavalier about it either, yeah. Yeah.
And researchers furthermore are working on a way to cut
(31:27):
off gene drives after a few generations, like naturally in
the wild by by designing in a sort of fail safe.
A team out of M I T specifically has conceptualized
a daisy chain effect is what they're calling it, and
the idea is that's okay, you split the genetic information
that you're testing into three packages. Part A can only
paste itself into wild DNA if part B is present.
(31:50):
Part B, meanwhile, can only paste itself into wild DNA
if parts C is present and parts C here's the
critical part is a normal gene will only be inherited
about fifty of the time. So if you release creatures
with with all three parts into a natural population, the
next generation will have well, we'll all have A and B,
(32:11):
but only about half of them will have C. So
although the gene drive will persist out for a few generations,
eventually parts C will largely die out, and then B
and then A and and this this could allow for
a safer way to introduce a localized, temporary gene drive
into the wild. Interesting um hypothetically if it works as planned,
(32:34):
if life does not find a way right, So, yeah,
don't run away with any of this thinking like, oh,
we're we're okay, then don't need to worry about that.
Do it tomorrow. This is something you should be thinking
about and everybody should be paying attention to, because it's
yet another one of these things where recent advances in
genetics I think, are are catching people off guard. They're
(32:55):
coming faster than people are coming up with ways to
form ethical opinions about though right, largely because of this
Crisper process, which is I mean super amazing but but
also right, has just pulled entirely the breaks off of
the system really in terms of what we can do
with genetics. Yeah, um, and so so I think we
should definitely pay heed to the scientists who are urging
(33:17):
caution and uh and very careful treading on this. I'm
not necessarily opposed to gene drive research, and I think
it's a good thing to be studying, but it's the
kind of thing that you have to study extremely carefully.
So you know, what if you're you're just working on
gene drive research and you've got a lab full of
insects and one of them escapes the lab, whoops. Uh.
(33:39):
So yeah, there have been I know, people have tried
different methods of controlling this, like, for example, only experimenting
with gene drives in organisms in labs that are in
places where those organisms don't naturally live, so if one
did escape somehow, it wouldn't find anything to breed with. Sure, yes,
and and all the gene drives to the polar self.
(34:01):
And don't experiment on penguins at all. Ye are penguins
in in the polars? I don't remember. I always get
this mixed time. I think they're around the water anyway, Yes, caution,
yeah exactly. So, I mean it's really cool it's really cool,
but caution. Yeah. Anyway, there's been a bunch of a
bunch of writing about this in the science press lately
(34:21):
and UH, and it's something that's definitely worth keeping up with.
I would just recommend googling gene drives and UH and
news around this subject if you want to keep abreast
of this developing topic. Yeah. Uh. If you have any
specific questions about it, then feel free to ask us.
You can get in touch with us are in multiple ways.
(34:41):
Our email address if you're still into that email thing,
is FW thinking at how Stuff Works dot com. You
can also reach out to us on social media. We
are on Twitter and Facebook, where our handles, strangely enough,
is also FW thinking. Uh. We hope to hear from you.
We have enjoyed talking about this and the sure from
us again very soon. For more on this topic in
(35:08):
the future of technology, visit forward Thinking dot com, brought
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