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Okay, but what about birds that can't fly? · Okay, But... Birds

• 0:00
  All flightless birds on the planet evolved from flighted ancestors as far as we understand it, right?
• 0:05
  So even though we think of ostriches and emus as these classic flightless creatures, their ancestors were flighted, which is true of kiwis and even of penguins.
• 0:37
  Okay.
• 0:39
  The first flightless bird I remember learning about, other than penguins, was the dodo.
• 0:44
  You know, the cartoon version.
• 0:45
  Round, dopey, a sort of confused turkey with a beak too big for its face, lumbering towards the camera while a Dutch sailor sharpens a knife in the background.
• 0:54
  The story I got as a kid was basically birds, but worse.
• 0:57
  They forgot how to fly, they forgot how to be afraid of humans, they got eaten, and now they're a metaphor for being out of date, dead as a dodo.
• 1:04
  The whole thing felt like a cautionary tale about evolutionary laziness.
• 1:08
  Almost none of that turns out to be right.
• 1:10
  The dodo wasn't fat or slow.
• 1:12
  It was a giant pigeon active, well adapted to its forest, and its closest living relative is something called the Nicobar pigeon, which is shockingly beautiful and very much still flying around Southeast Asia.
• 1:23
  Mauritius was first sighted by Dutch sailors in 1598.
• 1:27
  By 1681, the dodo was gone, less than 100 years from first contact to in a children's book about extinction.
• 1:34
  That's the part of the story we don't really tell kids, because the cartoon is funnier than the truth.
• 1:39
  If the dodo feels far away, here's one closer to home.
• 1:42
  The great auk was a North Atlantic bird, about two and a half feet tall, black and white.
• 1:47
  Basically, a Northern Hemisphere penguin that wasn't actually related to penguins.
• 1:51
  It bred on rocky islands from Newfoundland to Iceland to the British Isles.
• 1:55
  There were millions of them.
• 1:56
  They were hunted for meat, then feathers, then oil.
• 1:59
  And as they became rare, museums started paying for specimens, a practice no longer followed, luckily.
• 2:06
  Which all led to their extinction.
• 2:08
  On June 3rd, 1844, on an Icelandic island called Eldi, three men killed the last confirmed breeding pair.
• 2:14
  And the Journal of the American Ornithological Society, the leading bird research society on this continent, was for a time called the auk, named after a bird the field could not save.
• 2:24
  So when I think about flightless birds, I don't really start with what's wrong with them.
• 2:28
  I start with the fact that we keep losing them, and we keep losing them in similar ways.
• 2:32
  And that's only half of what makes flightlessness interesting.
• 2:36
  The other half is the question of how a bird, an animal whose entire body plan is famously a flight machine, ever ends up grounded in the first place.
• 2:44
  Because every flightless bird alive today, from the ostrich to the kiwi to the penguin, descends from an ancestor that could fly.
• 2:51
  At some point, each of these lineages let it go, and evolution, somehow, kept letting it happen.
• 2:57
  Which brings us to the topic of today's episode.
• 2:59
  Okay, but what about birds that can't fly?
• 3:01
  To help walk us through this, pun intended, we'll be joined by Dr. Scott Edwards, professor of evolutionary biology at Harvard, longtime ornithologist, and a leading voice on the genetics of the evolution of flightless birds.
• 3:13
  He spent years working on the genomes of the paleognaths, the deep ancient lineage that includes ostriches, emus, kiwis, rias, and the extinct moa, figuring out what actually changes in a bird's DNA when something that evolved to fly doesn't do that anymore.
• 3:28
  After the break, Scott walks us through the paradox of where flightlessness shows up because the textbook answer is islands without predators and reality isn't so cut and dry.
• 3:37
  We get into what actually changes in a bird's body and genome when flight goes away, which turns out to be a much weirder answer than anyone expected.
• 3:44
  Stay tuned.
• 3:45
  Stay tuned.
• 3:50
  Well, welcome back, everyone.
• 3:51
  I'm really excited to have Scott Edwards with me today.
• 3:53
  Thanks for joining us, Scott.
• 3:55
  It's great to be here.
• 3:56
  Yeah.
• 3:57
  Well, flightless birds.
• 3:58
  So I think when people think of birds, they invariably think of flight.
• 4:02
  What is it about evolution that repeatedly favors the loss of flight?
• 4:05
  We're most familiar with this one group of flightless birds called the paleognathes.
• 4:12
  This is the first group to branch off of modern birds.
• 4:17
  So it's a very ancient group, but it includes a lot of species that folks are very familiar with.
• 4:23
  Things like ostriches, emus, kiwis from New Zealand, and the rias from South America.
• 4:30
  And that group, you know, often involves...
• 4:34
  finding yourself on an island with no mammalian predators.
• 4:38
  Just forget about flying.
• 4:39
  It's costly to maintain, and they basically turn into big cows with feathers.
• 4:45
  But there's also – some species don't conform to that model.
• 4:49
  Of course, like ostriches in Africa, they've got lions and all these big, fast mammalian predators.
• 4:56
  Of course, they're very fast runners themselves.
• 4:59
  Yeah.
• 4:59
  But somehow there, they were able to lose flight in the presence of predators.
• 5:05
  So that's kind of a head-scratcher.
• 5:09
  And there's lots of other instances of flight among ducks, some extinct species that were songbirds.
• 5:19
  And in many of these cases, it is indeed finding yourself in a place without any predators.
• 5:25
  But still, there's examples out there that seem to defy logic.
• 5:29
  Yeah, ostriches have always confused me, given that they live with all of these huge predators that are very fast and could catch a flightless bird.
• 5:39
  But yeah, this...
• 5:40
  colonizing a place without predators and becoming flightless.
• 5:42
  Certainly New Zealand is kind of the poster child of that with all of the different species of moa that are now extinct, but the extant kiwis and kakopos and all of these really interesting birds.
• 5:53
  When birds become flightless,
• 5:55
  What do they often gain?
• 5:56
  Is there, I mean, with a lot of the paleognaths, the big ones that are flightless, they're fast and strong, but are there other syndromes we see with this flightlessness across different species?
• 6:07
  It's basically where you put your energy, I think.
• 6:11
  you know, instead of putting it into maintaining your wings and perhaps maintaining a lean and mean, you know, physiology and anatomy, they vary a lot in their clutch size, for example.
• 6:24
  But, you know, ostriches, they lay these huge clutches, and of course they often pull their eggs into one nest.
• 6:29
  And so, you know, I think you just gain a physiological advantage.
• 6:33
  And, you know, even Darwin knew that if you –
• 6:37
  If you don't use it, you lose it.
• 6:38
  And if species find themselves just not flying very often, they're going to atrophy.
• 6:47
  But in other species, it's, again, a bit of a head scratcher.
• 6:52
  Like the kiwis in New Zealand, they sort of famously lay this one really big egg.
• 6:59
  And you wonder, well, why is it so big?
• 7:01
  It may be because their ancestors were really big.
• 7:05
  And although their bodies got smaller, maybe their eggs didn't get small as quickly.
• 7:11
  It's a really strange situation.
• 7:15
  And so they've...
• 7:18
  modified their lifestyle so extremely.
• 7:20
  They're almost blind.
• 7:21
  They can't see very well.
• 7:23
  They can smell very well, but they forage at night.
• 7:27
  And so this whole flightless syndrome has resulted in a lot of really interesting adaptations.
• 7:33
  A lot of flightless birds, as you know, they don't have...
• 7:38
  you have these feathers that are symmetrical, essentially, all over their body, but also their sort of stubby wings.
• 7:46
  And symmetrical feathers is sort of a smoking gun for having lost flight.
• 7:51
  Only really flying birds have these sort of asymmetrical feathers that...
• 7:55
  take the air and do great things with it.
• 7:58
  Yeah.
• 7:58
  And I think one of the interesting things about like, I guess all flightless birds on the planet evolved from flighted ancestors as far as we understand it.
• 8:06
  Right.
• 8:06
  So even though we think of ostriches and emus as these classic like flightless creatures, their ancestors were flighted, which is true of kiwis and even of penguins.
• 8:16
  And
• 8:17
  Yeah, have we learned anything recently about that that has kind of shed light on the evolution of flightless more broadly?
• 8:24
  You're absolutely right.
• 8:25
  Everything's coming from something that was flying.
• 8:28
  And the common ancestor of modern birds, all 11,800 species or whatever the number is now.
• 8:36
  It varies, yeah.
• 8:39
  The common ancestor could fly, at least so we think.
• 8:42
  And so I think the real question is sort of how recently did something lose flight?
• 8:46
  And so if you look at some groups of flightless birds, like the flightless ducks in the Andes in South America, they seem to have lost flight fairly recently.
• 8:57
  And if you look at their skeletons, their populations,
• 9:00
  You know, the forelimb bones show sort of very modest changes.
• 9:06
  You know, by contrast, the paleognes, you know, including the MOA, they show really drastic changes in the forelimb, and so much so in the MOA that they've completely lost all of their forelimb elements.
• 9:19
  There's no humerus, radius, or hula, and no digits at all.
• 9:24
  So they've just lost all that.
• 9:26
  And so it sort of depends how long a lineage has been flightless as to what sort of adaptations it might have.
• 9:34
  Yeah, that was kind of my next question.
• 9:36
  Like when flightlessness evolves, and now you've alluded to the fact that it depends on how long ago it evolves.
• 9:41
  Like what really changes in a bird's body?
• 9:42
  So these ducks in South America, is that the steamer ducks you're referring to?
• 9:47
  Yes.
• 9:47
  Yeah.
• 9:50
  Are they variably flightless or are they all flightless?
• 9:52
  I can't remember.
• 9:53
  I think just some of them are flightless.
• 9:56
  Yeah.
• 9:57
  Not all.
• 9:58
  So that's like a cool case of kind of the recent evolution of flightlessness.
• 10:01
  And then the MOAs are this extreme example of like, I don't even have a humorous or digits anymore.
• 10:07
  From a genetics perspective then, what have you found with respect to flightlessness and the various lineages that you've worked on?
• 10:13
  Well...
• 10:14
  We went into this not really knowing what to expect.
• 10:19
  Yeah, that's true.
• 10:20
  As you know, the genome is very complicated, and we just have no idea really what genes might be driving loss of skeletal elements or, for example, the evolution of large body size.
• 10:33
  And in some ways, you know, this trait called flightlessness, it's sort of a composite trait, right?
• 10:39
  There's lots of aspects to flightlessness, everything from the feathers changing to the forelimbs to the body size and even the hind limbs.
• 10:48
  And so there's also hormonal changes that take place.
• 10:52
  So we didn't really know what to expect.
• 10:54
  And, you know, I think we do have some clues from model species, like people studying limbs in mice or in other vertebrates.
• 11:04
  And, you know, I think the bias, I would say, for us and for the rest of the community was probably that, well, there's some gene that is causing, that has changed its sequence and is causing loss of forelimbs or something.
• 11:19
  You know, it turned out that...
• 11:23
  We searched far and wide for changes in the sequence of genes, and we weren't actually the first to do this.
• 11:31
  Others had looked too, and basically we can't find anything.
• 11:34
  We can't find any genes that have obviously become pseudogenes or lost their function or are just evolving in some strange way.
• 11:43
  And so that led us to look at the non-coding part of the genome, which is kind of a black box.
• 11:49
  It's a very...
• 11:51
  We don't even know the language of the non-coding regions.
• 11:55
  With genes, it's very straightforward.
• 11:57
  We've got this triplet code, and we can figure out what amino acid is specified.
• 12:02
  Whereas with the non-coding genome, we imagine that much of it might be sort of regulating the genes, the coding regions.
• 12:11
  It might be sort of those switches that turn them up or turn them down and shift their gene expression.
• 12:16
  But we often don't know how they do that.
• 12:19
  and where they would be relative to the genes that they control.
• 12:22
  And so we just took this sort of broad approach of looking at
• 12:28
  a group of non-coding regions that were very conserved across the phylogeny, across lots of birds and even shared with some reptiles and fish and other vertebrates.
• 12:44
  And we developed some tools that allowed us to sort of look for signals that might tip us off that,
• 12:51
  those non-coding regions were changing in interesting ways, specifically on branches leading to the flightless species in the phylogeny.
• 13:02
  And that led us to a whole group of these non-coding regions, which we later learned were...
• 13:08
  this special group of loci called enhancers.
• 13:12
  And these are involved with sort of changing the gene expression of genes.
• 13:15
  So in the end, we learned that it wasn't the genes themselves that were changing.
• 13:19
  It was the regulatory regions, the switches that shifted genes expression higher or lower.
• 13:26
  And that was a very cool surprise and one that we didn't really anticipate.
• 13:31
  Yeah, it's a really cool finding.
• 13:33
  And I think like if we think back to some of the earliest like associations between genotype and phenotype and births, at least it's like snow goose coloration was clearly like mutations within the melanocortin-1 receptor gene.
• 13:47
  And those kinds of findings, I think, made a lot of us think like, oh, it's regularly going to be that.
• 13:52
  genes are breaking or changing.
• 13:55
  And that's what we went out and looked for.
• 13:56
  And more and more, we're finding it's actually how they're turned up or down, but the gene still functions, which if you fully alter the gene sequence, going back to a functional gene is a really difficult thing that may not actually happen.
• 14:10
  But if you're just altering expression of a gene, then there's a lot more that evolution can play with, which is just really fascinating to think about.
• 14:17
  Yeah, I agree.
• 14:19
  It's a really, it's a much more noncommittal way to chase the phenotype.
• 14:26
  But you're absolutely right.
• 14:27
  Some phenotypes, such as the plumage color, were sort of like, every time it was, here's the amino acid in the gene that's changing things.
• 14:36
  And we had found some of those as well when we were looking at, like, what allows hummingbirds to taste phenotype.
• 14:43
  you know, sugary nectar, things like that, that turned out to be a sequence of a gene, a taste receptor gene.
• 14:51
  And of course, any one gene we know does many different things.
• 14:54
  And so if you change that, then you're, you might be committing yourself to all kinds of other changes, which could be disastrous.
• 15:01
  Yeah, it's like a core function gene that breaks, and maybe you just don't develop.
• 15:06
  That's right.
• 15:07
  In the egg, you're toast.
• 15:08
  Yeah, it's interesting, too, in the context of it being regulatory changes overall.
• 15:12
  Well, one thing I want to say is just, like, for listeners, the fact that we really don't fully understand a lot of what the genome does, I think, is a cool thing.
• 15:20
  It means we should keep exploring and trying to figure out, like, what these enhancers do and what all the non-coding stuff does, which can actually vary a lot between even individuals within populations, which is pretty cool.
• 15:31
  But with respect to it being like expression variation and not breaking genes, yeah, flightlessness is a syndrome.
• 15:35
  Like you said, it's body size, it's wing shape and size, feather stuff.
• 15:39
  But it's also interesting that even on islands where birds are still flighted, they become like worse at it.
• 15:45
  And that process going from like highly vigilant flying in flocks
• 15:51
  really good flyer to being like worse flying, not as vigilant, again, is a syndrome that you can imagine gene expression variation over time might shape.
• 15:58
  And then eventually you end up as a Kiwi who is mostly blind, nostrils at the tip of your beak.
• 16:05
  Yeah.
• 16:06
  Yeah, and that study that you're referring to that even birds that can still fly on islands, they've kind of shifted towards this flightless syndrome.
• 16:15
  They've become heavier, their wings were shorter, and that's really cool, I think.
• 16:22
  Maybe it's giving us a glimpse of how things become flightless eventually.
• 16:25
  Yeah, yeah, potentially.
• 16:26
  And I think it's, I guess, again, like we look at birds and we think, oh, yeah,
• 16:30
  They're so well adapted for what they do, but don't necessarily think of all the costs associated with flight and the kind of knife sedge that a lot of them live on to have the right body weight to fly, but get enough nutrients to be able to power that flight.
• 16:45
  And that if you don't have all those evolutionary pressures...
• 16:48
  Yeah, you're absolutely right.
• 16:49
  Birds have sacrificed a huge amount, even just to fly.
• 16:53
  I mean, look, they've lost their digits completely.
• 16:55
  They can't grip anything.
• 16:57
  Having to live just on two limbs, two legs,
• 17:01
  And yeah, it's a really, in some ways, it's a tough road.
• 17:06
  Of course, losing flight doesn't actually get you back any of that stuff.
• 17:10
  It's not like you suddenly sprout fingers that you can build your nest easier with.
• 17:16
  But it is remarkable how much sacrifice birds have undergone.
• 17:21
  They've lost all their teeth, right?
• 17:22
  They can't, like, chew stuff.
• 17:24
  They had to move them inside and then eat stones and grit.
• 17:29
  That's right, exactly.
• 17:30
  Secondarily grind up their food.
• 17:32
  That's right.
• 17:37
  you know, species are able to accommodate some morphological change with their behavior.
• 17:43
  I mean, you can just imagine that first mutant check, you're like, oh no, I can't fly anymore.
• 17:50
  Well, they're going to figure out a way to deal with things behaviorally.
• 17:55
  And so that...
• 17:57
  And some of it may not require sort of an obvious ecological agent.
• 18:05
  A lot of things just drift up and it's like, okay, deal with this genetic change.
• 18:11
  Yeah, yeah.
• 18:12
  We're studying island gigantism and rosy finches.
• 18:16
  Oh, yeah.
• 18:16
  And are there differences, consistent differences between these island giant rosy finches and mainland rosy finches?
• 18:22
  But the reviewers keep wanting us to write the paper that explains island gigantism, which is like...
• 18:27
  A very hard paper to write, not what we were trying to do.
• 18:31
  Yeah, and that is an interesting question too.
• 18:34
  But of course, at least my understanding is that it kind of can go both ways.
• 18:38
  I mean, we've seen things on islands sometimes get really big, but sometimes they get really small, right?
• 18:44
  Yeah, exactly.
• 18:45
  And the last paper I read on that was probably in the 90s, but it was like, you know, it's hard to predict whether something's going to get bigger or smaller.
• 18:56
  Yeah, yeah.
• 18:57
  If you're big, you might get small.
• 18:58
  If you're small, you might get big.
• 19:00
  That's right.
• 19:00
  No change.
• 19:01
  That's right.
• 19:02
  Maybe it's like regression towards the mean or something.
• 19:05
  Yeah, I think there was something I saw that was kind of like back towards some standard.
• 19:11
  But even that, how would you know whether it was predator release or resource availability?
• 19:16
  Or in the case of birds, like release from migration, which then you can just get fat and happy and not have to fly.
• 19:27
  What is it, homo florensis, this thing in the Philippines, this fossil human, which is just extraordinary.
• 19:34
  I mean, what, it was like, what, three feet tall or something?
• 19:36
  Yeah, very tiny.
• 19:37
  And, you know, I think the anthropologists argued, is this like some congenital mutation?
• 19:42
  And is this adaptive or did it just sort of happen in...
• 19:46
  Yeah, it's really amazing.
• 19:49
  I think it's kind of cool.
• 19:50
  It shows that we humans are just as subject to the vagaries of evolutionary pressures as anything else.
• 19:57
  Definitely.
• 19:57
  Yeah, and I think it's interesting.
• 19:58
  For folks listening, I think we're kind of trained...
• 20:02
  if you're not a scientist and you're not thinking about like genetic change the way that you and I do, I think because of things like Pokemon and X-Men, like a lot of people think about mutations as hopeful monsters, that there's a mutation, that it's beneficial and it confers some advantage.
• 20:17
  Like, I don't know.
• 20:19
  You can move metal if you're magneto or something like that.
• 20:21
  But the reality is like most mutations are negative.
• 20:24
  A lot of evolutionary change happens because of random allele frequency changes, nothing to do with like a good mutation.
• 20:30
  And it's important to remember that that can all just lead to this, the vagaries of evolutionary biology that we can't go back and watch happen, which makes it both a cool field to study and also frustrating.
• 20:42
  Yeah, you're absolutely right.
• 20:44
  I mean, I tell my students, if you like precision and predictability, become an engineer.
• 20:50
  Yeah, yeah, exactly.
• 20:51
  Don't become an evolutionary biologist.
• 20:54
  I know.
• 20:56
  Have you guys done any penguin genomics work?
• 20:59
  I can't remember if... No, no, we have not.
• 21:02
  Mostly just because of funding.
• 21:12
  lost or have changed some of the same gene regulators, some of the same enhancers.
• 21:17
  Actually, I do have a postdoc now, Talia Lowy-Mary, who is a really great morphologist.
• 21:23
  And she's looking at other flightless groups across birds and asking what switches are changing in those lineages.
• 21:34
  So it'll be very interesting to see...
• 21:37
  whether some of the same switches are changing.
• 21:39
  And we know, for example, of course, like penguins, they've got this...
• 21:44
  They still have this keel on their sternum because they sort of fly underwater.
• 21:51
  And this...
• 21:52
  is I think another clue.
• 21:54
  When we find a region of the genome that is correlated with loss of flight, well, does that mean it's controlling the forelip?
• 22:02
  Is it controlling the sternum or in the keel?
• 22:05
  Is it controlling body size?
• 22:06
  We don't really know that until we use some very specific tools that tell us where that non-coating region is acting during the developing embryo.
• 22:16
  And that's
• 22:17
  That's, I think, that's really, really important because otherwise we're just speculating as to what a given non-coding region might actually be doing.
• 22:25
  Absolutely, yeah.
• 22:26
  So what's next for you guys in terms of studying proximate causes of flightlessness in birds?
• 22:31
  Are there any, I mean, I guess you just mentioned what your postdoc is working on with respect to comparing these different
• 22:37
  lineages that eventually became flightless.
• 22:39
  But what else do you think is kind of the next step in understanding this?
• 22:43
  Yeah, that's a great question.
• 22:44
  We're kind of just scaling up.
• 22:47
  And so, you know, it turns out that there's millions of these enhancers all over the genome.
• 22:53
  And we want to be able to test individual enhancers and see how they might influence
• 23:00
  development of, you know, four-level growth in embryos of chickens, but also in, you know, in flightless emus and ostriches and stuff.
• 23:12
  So, yeah, we're trying to make a flightless chicken, basically.
• 23:14
  Oh, interesting.
• 23:15
  Yeah, and we're doing that by...
• 23:18
  be able to screen large numbers of these enhancers, like several hundred at a time, and then finding those ones that look like they might be doing something interesting and then focusing in on those.
• 23:29
  So, you know, it's not a trait that we expect to be
• 23:34
  explained by one or two places in the genome.
• 23:39
  But I think there's enough, it's sort of modular in a way, the different aspects of flightlessness.
• 23:45
  And I think it'll be exciting to look at how the contribution of different enhancers results in the whole phenotype.
• 23:57
  Yeah.
• 23:58
  And I mean, a lot of people listening might not remember that chickens can fly.
• 24:02
  We tend to think of them as not being able to, but they can.
• 24:05
  Not great, but they fly.
• 24:06
  Has an artificial selection ever gone towards a fully flightless chicken breed or no?
• 24:13
  My guess is that some chicken breeds can't fly, especially those ones with
• 24:18
  all kinds of feathers on their feet.
• 24:19
  They can barely even see, right?
• 24:21
  Yeah, that's true.
• 24:23
  But yeah, it's... No, look, chickens are not the poster child for flight.
• 24:29
  But they happen to be a pretty good model system for doing experiments.
• 24:35
  But yeah, they're sort of a surrogate.
• 24:37
  Yeah.
• 24:38
  But it's cool to...
• 24:39
  I mean, there are probably chicken breeds that can't fly just because they're so heavy.
• 24:42
  Like, it's not that they don't have the...
• 24:45
  all the other bits that would allow them to fly, but we breed chickens to produce leaps.
• 24:50
  And so their breast muscles are disproportionately large and they can't take off, which I think is true of domestic turkeys, but wild turkeys can fly.
• 24:59
  We just tend to, yeah, but they are good, good model systems for trying to figure out, yeah, what these enhancers are doing.
• 25:04
  And I would imagine like, I mean, as you've been doing this work in other systems, people have found that, yeah, in terms of
• 25:11
  I guess even in plumage color variation in some systems like the golden-winged and blue-winged warblers, it seems to be more about how a gene is controlled, not breaking the gene.
• 25:22
  So this idea that enhancers really matter is broadly relevant for morphological variation in birds, which I think is really exciting.
• 25:31
  That's right.
• 25:31
  And I think the whole field is trying to figure out, well, how can we predict what kinds of genes might underlie a specific trait?
• 25:38
  Like maybe, you know, physiological or biochemical traits might have genes underlying them, whereas morphological traits might have enhancers.
• 25:47
  And so that's still a very unanswered question.
• 25:50
  So for some of the birds we've been talking about, they're extinct.
• 25:53
  Can you talk a little bit about how you actually get DNA out of these old specimens and then what the MOA genome informed that you couldn't get from a living bird or a non-extinct species?
• 26:03
  I mean, full disclosure, we didn't actually, my lab didn't actually do the DNA isolation on this incredible project.
• 26:11
  But it was really done by this very talented ornithologist named Alan Baker, who,
• 26:15
  Oh, yeah.
• 26:37
  And so, for example, with the genome, we could look at things like the genes that encode receptors in its eyes, in its retinas, so that we could see how Mohs could see.
• 26:48
  And we can also study genes encoding receptors in their noses so that we could learn whether they had a good sense of smell or not.
• 26:58
  And it turns out that, for example, MOAs could see in the UV range, in the ultraviolet range.
• 27:07
  And of course, many birds can see in the ultraviolet, but we didn't know for MOAs whether they could.
• 27:12
  And in this case, it is a change in a specific gene.
• 27:16
  One amino acid sort of tells us.
• 27:19
  at position 90 of this shortwave ops and whether it can see in the UV or not.
• 27:25
  And indeed it could.
• 27:26
  And that's kind of neat to think that, wow, okay, this changes how we think about MOLA biology.
• 27:31
  Yeah, for sure.
• 27:33
  And then we were also able to
• 27:36
  determined that it had a pretty healthy repertoire of what we call olfactory receptors.
• 27:41
  So these are receptors in the nasal membranes that find chemicals and allow species to smell diversity of chemical signatures.
• 27:53
  And this told us that...
• 27:56
  Like kiwis, moas probably had a pretty good sense of smell.
• 28:02
  Remarkably, you probably know this, remarkably, moas are not closely related to kiwis, even though they're both on New Zealand.
• 28:09
  This was something that was discovered by folks at the very beginning of ancient DNA studies on moa.
• 28:16
  Yeah.
• 28:17
  They're, in fact, most closely related to this group of birds called titimus, which are not even in the old world.
• 28:23
  They're in the new world tropics.
• 28:25
  And so it's a completely bizarre biogeographic.
• 28:28
  Don't ask me how moas got to where they were evolving from titimus.
• 28:33
  But anyway, it's been neat to sort of look into the biology of moas through their DNA.
• 28:38
  And it's told us a lot about their natural history.
• 28:42
  Yeah, they're such fascinating birds.
• 28:43
  And it's so interesting when you look at how different moa species were described from fossils.
• 28:48
  And then people realize, actually, moas had extreme sexual size dimorphisms.
• 28:54
  So females were much, much larger than males.
• 28:56
  But if you're just looking at bones, it takes you a minute to figure out, oh, I'm not looking at juveniles.
• 29:01
  I'm looking at the males of the same species.
• 29:03
  And so there's many different classifications of how many species of moa there actually are, which is fascinating to think about this.
• 29:12
  evolution of size dimorphism for, I think, because of resource partitioning, like, yeah, be feeding on different things.
• 29:18
  And I guess it makes sense, too, that they could smell because they were, they were predominantly
• 29:23
  vegetarian, right?
• 29:25
  Yes.
• 29:25
  That's right.
• 29:26
  Sniffing out their good trees to chew.
• 29:30
  They ate a lot of insects as well, but yes.
• 29:34
  Okay.
• 29:34
  All right.
• 29:34
  So we've reached the part of the show we call That's BS or That's Bird Stuff, where we give our guests an opportunity to debunk a myth that ruffles their feathers.
• 29:41
  So Scott, what do you want to call BS on?
• 29:44
  I think I'll just call BS on the
• 29:47
  the supposition that birds are actually not as smart as mammals.
• 29:53
  If you compare, say, a crow and a rhesus macaque, two very different size brains, but actually a crow or a raven has more neurons in their brain than does a rhesus macaque.
• 30:09
  And so this is an example of just, you know, you've got more bang for your buck than,
• 30:17
  in a crow brain.
• 30:21
  And there's also some really cool evidence recently showing how all of the organization of the bird brain is different from in mammals.
• 30:29
  In mammals, it's kind of this layered thing
• 30:32
  And you've got all these folds, as you know, from the human brain.
• 30:36
  Whereas in birds, it's more organized around these nuclei, these sort of song nuclei.
• 30:41
  And it's got sort of that nuclear organization.
• 30:44
  Despite that, there's still a ton of similarities in sort of the network structure of birds and mammals.
• 30:52
  And so there's just a lot of evidence that...
• 30:57
  that birds' brains are as complex and can be compared in many ways to those of mammals.
• 31:05
  Mm-hmm.
• 31:06
  I love that.
• 31:07
  Yeah, we had Alex Koselnik on talking about New Caledonian crows, and he also wanted people to stop using that term as a negative thing, bird brain.
• 31:16
  And I appreciate you providing the context of the actual morphological and neuron variation that would suggest that just because it doesn't look as complicated as a mammal brain does not mean it is not as complicated as a mammal brain.
• 31:29
  That's right.
• 31:29
  So I appreciate it.
• 31:30
  Yeah, I mean, if you look at a bird brain, like a zebra, it's very smooth.
• 31:33
  It doesn't have any of those.
• 31:35
  And we tend to associate those wrinkles with like Einstein's brain.
• 31:41
  I think when we see that, we're like, oh yes, humans are smart.
• 31:44
  Right.
• 31:45
  Oh God, our bias.
• 31:46
  Well, thanks so much for joining us on the podcast today, Scott.
• 31:49
  I really appreciate it.
• 31:50
  These flightless birds are just like fascinating to think about.
• 31:53
  And all this extra context is awesome.
• 31:56
  So thanks for taking the time.
• 31:57
  Thanks very much, Scott.
• 31:59
  you
• 32:03
  Birds are dinosaurs, and around here we like our snacks, so we end each episode with a dinosaur nugget.
• 32:07
  Today's nugget is every flightless bird alive today, from the kiwi to the ostrich to the emperor penguin, descended from an ancestor that could fly.
• 32:16
  Flight was the default.
• 32:18
  Walking is the upgrade, which means the ostrich isn't a bird that failed to keep up.
• 32:22
  It's a bird that, somewhere along the way, looked at the sky and said, yeah, I'm good.
• 32:26
  That's a wrap on next week's episode.
• 32:28
  Okay, but what about birds that can't fly?
• 32:30
  If you like this episode, leave us a rating or review or like and subscribe.
• 32:33
  We'll catch you next time.
• 32:34
  Bye.
• 32:40
  Okay, but birds is hosted by Scott Taylor with production and creative by Zach Carl.