bizarre beasts
Did This Bird Really Re-Evolve?
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Duration: | 08:55 |
Uploaded: | 2024-05-03 |
Last sync: | 2024-12-19 08:45 |
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About 136,000 years ago, on a coral atoll in the Indian Ocean, there lived a flightless bird. And when this atoll was swallowed up by the waves, that bird went extinct. ... Or did it? Did the flightless Aldabra rail evolve twice?
Subscribe to the pin club here: https://complexly.store/products/bizarre-beasts-pin-subscription
This month's pin is designed by Tara Reed. You can find out more about them and their work here: https://www.tarareedart.com/
You can cancel any time by emailing hello@dftba.com
Host: Hank Green [he/him]
Follow us on socials:
Twitter: https://twitter.com/bizarrebeasts
Instagram: https://www.instagram.com/bizarrebeastsshow/
Facebook: https://www.facebook.com/BizarreBeastsShow/
#BizarreBeasts #birds #evolution
-----
Sources:
https://www.nhm.ac.uk/discover/news/2019/may/birds-on-an-island-in-the-indian-ocean-evolved-flightlessness-twice.html
https://www.nature.com/articles/s41598-022-05329-1
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0192675#pone.0192675.ref009
https://researchportal.port.ac.uk/files/20131781/Repeated_evolution_of_flightlessness.pdf
https://birdsoftheworld.org/bow/species/whtrai1/cur/introduction
https://royalsocietypublishing.org/doi/10.1098/rstb.1971.0022
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6927662/
http://www.seychellesnewsagency.com/articles/1327/Seychelles+Islands+Foundation+working+to+classify+Aldabra+Rail+as+a+separate+species
https://carnegiemnh.org/a-match-made-by-coevolution/
www.researchgate.net/profile/Andrej-Spiridonov-2/publication/339308200_Moving_towards_a_better_understanding_of_iterative_evolution_an_example_from_the_late_Silurian_Monograptidae_Graptolithina_of_the_Baltic_Basin/links/605bd652299bf17367686519/Moving-towards-a-better-understanding-of-iterative-evolution-an-example-from-the-late-Silurian-Monograptidae-Graptolithina-of-the-Baltic-Basin.pdf
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0192675#references
------
Thumb Image Credit: Ian Davies / youtube.com/@theBirdsGuy
Images:
https://commons.wikimedia.org/wiki/File:Darwin%27s_finches_by_Gould.jpg
https://commons.wikimedia.org/wiki/File:Dryolimnas_cuvieri_abbotti.jpg
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0192675#references
https://search.macaulaylibrary.org/catalog?taxonCode=whtrai1&subId=S120646384
https://search.macaulaylibrary.org/catalog?taxonCode=whtrai1&subId=S54342870
https://www.flickr.com/photos/biodivlibrary/50884719468/in/album-72157718074612568/
https://www.gettyimages.com/detail//1319245938
https://www.gettyimages.com/detail//1873922239
https://www.gettyimages.com/detail/1189180601
https://www.gettyimages.com/detail/1205723154
https://www.gettyimages.com/detail/1210192652
https://www.gettyimages.com/detail/1254845401
https://www.gettyimages.com/detail/1298712957
https://www.gettyimages.com/detail/1386115358
https://www.gettyimages.com/detail/1422137124
https://www.gettyimages.com/detail/1456401923
https://www.gettyimages.com/detail/1457477523
https://www.gettyimages.com/detail/1461341351
https://www.gettyimages.com/detail/1759260858
https://www.gettyimages.com/detail/1932566415
https://www.gettyimages.com/detail/2029974605
https://www.gettyimages.com/detail/472674730
https://www.gettyimages.com/detail/487966660
https://www.gettyimages.com/detail/491293328
https://www.gettyimages.com/detail/666002424
https://www.gettyimages.com/detail/820677950
https://www.gettyimages.com/detail/1311051529
https://www.inaturalist.org/observations/105320184
https://www.inaturalist.org/observations/4425241
https://youtu.be/d0WD7VAPbFg?si=0sEIwVNVcVCJjYe7
About 136,000 years ago, on a coral atoll in the Indian Ocean, there lived a flightless bird. And when this atoll was swallowed up by the waves, that bird went extinct. ... Or did it? Did the flightless Aldabra rail evolve twice?
Subscribe to the pin club here: https://complexly.store/products/bizarre-beasts-pin-subscription
This month's pin is designed by Tara Reed. You can find out more about them and their work here: https://www.tarareedart.com/
You can cancel any time by emailing hello@dftba.com
Host: Hank Green [he/him]
Follow us on socials:
Twitter: https://twitter.com/bizarrebeasts
Instagram: https://www.instagram.com/bizarrebeastsshow/
Facebook: https://www.facebook.com/BizarreBeastsShow/
#BizarreBeasts #birds #evolution
-----
Sources:
https://www.nhm.ac.uk/discover/news/2019/may/birds-on-an-island-in-the-indian-ocean-evolved-flightlessness-twice.html
https://www.nature.com/articles/s41598-022-05329-1
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0192675#pone.0192675.ref009
https://researchportal.port.ac.uk/files/20131781/Repeated_evolution_of_flightlessness.pdf
https://birdsoftheworld.org/bow/species/whtrai1/cur/introduction
https://royalsocietypublishing.org/doi/10.1098/rstb.1971.0022
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6927662/
http://www.seychellesnewsagency.com/articles/1327/Seychelles+Islands+Foundation+working+to+classify+Aldabra+Rail+as+a+separate+species
https://carnegiemnh.org/a-match-made-by-coevolution/
www.researchgate.net/profile/Andrej-Spiridonov-2/publication/339308200_Moving_towards_a_better_understanding_of_iterative_evolution_an_example_from_the_late_Silurian_Monograptidae_Graptolithina_of_the_Baltic_Basin/links/605bd652299bf17367686519/Moving-towards-a-better-understanding-of-iterative-evolution-an-example-from-the-late-Silurian-Monograptidae-Graptolithina-of-the-Baltic-Basin.pdf
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0192675#references
------
Thumb Image Credit: Ian Davies / youtube.com/@theBirdsGuy
Images:
https://commons.wikimedia.org/wiki/File:Darwin%27s_finches_by_Gould.jpg
https://commons.wikimedia.org/wiki/File:Dryolimnas_cuvieri_abbotti.jpg
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0192675#references
https://search.macaulaylibrary.org/catalog?taxonCode=whtrai1&subId=S120646384
https://search.macaulaylibrary.org/catalog?taxonCode=whtrai1&subId=S54342870
https://www.flickr.com/photos/biodivlibrary/50884719468/in/album-72157718074612568/
https://www.gettyimages.com/detail//1319245938
https://www.gettyimages.com/detail//1873922239
https://www.gettyimages.com/detail/1189180601
https://www.gettyimages.com/detail/1205723154
https://www.gettyimages.com/detail/1210192652
https://www.gettyimages.com/detail/1254845401
https://www.gettyimages.com/detail/1298712957
https://www.gettyimages.com/detail/1386115358
https://www.gettyimages.com/detail/1422137124
https://www.gettyimages.com/detail/1456401923
https://www.gettyimages.com/detail/1457477523
https://www.gettyimages.com/detail/1461341351
https://www.gettyimages.com/detail/1759260858
https://www.gettyimages.com/detail/1932566415
https://www.gettyimages.com/detail/2029974605
https://www.gettyimages.com/detail/472674730
https://www.gettyimages.com/detail/487966660
https://www.gettyimages.com/detail/491293328
https://www.gettyimages.com/detail/666002424
https://www.gettyimages.com/detail/820677950
https://www.gettyimages.com/detail/1311051529
https://www.inaturalist.org/observations/105320184
https://www.inaturalist.org/observations/4425241
https://youtu.be/d0WD7VAPbFg?si=0sEIwVNVcVCJjYe7
This episode is sponsored by Manta Sleep.
Manta Sleep makes sleep masks and sleep accessories that help you get the energy to create your best life. Head to the link in our description to get 10% off.
About 136,000 years ago, on a coral atoll in the Indian Ocean, there lived a bird. Over time, it had lost its ability to fly, like many island birds do in the absence of predators. But, the thing is, coral atolls are not the most stable of landscapes.
They tend to be low-lying – often just a few meters above sea level, at most. And when this atoll was swallowed up by the waves, there was nowhere for that flightless bird to go. It went extinct, along with all the other unique species that had only evolved on that single island.
They were gone, forever. Or…were they? [♪♪ INTRO ♪♪] If you want to support the channel, the Bizarre Beasts pin club will now be open for subscriptions for the whole month! Sign up by May 20th and the first pin you will get will be this very good Aldabra rail.
And don’t forget to stick around at the end of the video for some bonus rail facts. Now, this story might sound familiar, but just bear with me for a bit. Today, ocean levels have once again receded and that island is back above sea level.
And the Aldabra rail is a terrestrial bird that lives on that island, the Aldabra Atoll, in the Seychelles, a country made up of islands in the Indian Ocean. It is about 30 cm long and has a patch of white feathers at its throat. And it’s an omnivore and occasional scavenger, though it prefers to eat insects when it can find them.
It also sometimes takes on crabs, which sounds very reasonable for a bird that lives on an island… but these are not tiny, adorable little crabs. They are large and the researchers we talked to for this episode gave us a bunch of very classic nature documentary-style rail versus crab footage, which I’m going to take a second to just, like, appreciate here. Now, there are a couple of things about the Aldabra rail that are weird.
Like, it’s either a separate, distinct species of white-throated rail or one of three subspecies endemic to islands throughout this region, depending on who you ask. Defining a species can be messy and subspecies are even harder to define. But the thing that definitely makes it different from the other living white-throated rails is that it is the last surviving bird in the Indian Ocean that cannot fly… and that’s where this story starts to get even weirder.
The first thing to know is that there are a lot of different flavors of evolution. For example, you’ve got convergent evolution, where different species evolve to have similar traits independently of each other, like how a ton of unrelated crustaceans evolve to be crab-shaped. And you’ve got divergent evolution, where populations of the same species get separated and accumulate differences over time, potentially ending up as different species.
Darwin’s finches are the classic example. And then there’s coevolution, where two or more species influence each other’s evolution, like certain hummingbirds and the specific flowers they pollinate. But perhaps the least common of the flavors is iterative evolution: when species within the same group repeatedly evolve the same traits independently at different points in time.
And this can make it look like species go extinct and then re-evolve. But do they really? Back in 1987, a paleontologist named John Becker collected a large number of fossils from a couple of sites on Aldabra… but he didn’t bring back just the fossil bones, themselves.
He collected them still encased in the hardened sediment they were buried in. This is pretty common for paleontologists, especially when they’re dealing with fragile fossils. But it means that, once the fossils get back to the lab, you have to get rid of that sediment, in a process called preparation.
That can sometimes take years… decades, even, if there’s no one with the time and skills to do the work. But, in the mid 2010s, researchers finally got the chance to work their way through those fossil blocks. And they found two intriguing bones: a complete left humerus, or upper arm bone, and the lower part of a right humerus of a bird.
And they looked almost exactly like the arm bones of the flightless rail that lives on Aldabra today… except they were over 136,000 years old, which mean they came from the time before that island was completely flooded. Now, these aren’t the only rail bones that have ever been found on Aldabra. There’s also a piece of a foot bone from after the island flooded that also looks like the foot bone of a flightless rail.
So, according to the researchers, this means that there were flightless rails on Aldabra before the atoll flooded around 136,000 years ago. Then they went extinct because the atoll was gone and they couldn't fly. Then another group of white-throated rails flew to Aldabra after it emerged again… And then they evolved to become flightless in under 16,000 years, which is potentially the fastest evolution of flightlessness in a bird that we know of.
And their descendants still live on the atoll today. Which sounds a lot like the same flightless Aldabra rail evolved twice… and that’s what a lot of the press coverage said when the paper about it came out. Of course that's not really how evolution works.
The old Aldabra rail is extinct, for good. What probably happened both times is just a weird quirk of how rails behave: when there are enough of them on an island, like Madagascar where white-throated rails live today, they sometimes just disperse... They fly off to isolated islands, settle there, and often become flightless, probably in part because they nest on the ground anyway.
And Aldabra isn’t the only island that has had a unique flightless or semi-flightless rail. And maybe this is splitting scientific hairs a bit, but just because the two Aldabra rails descended from the same population and adapted to island life in the same way doesn’t mean they’re the same species. Because, for evolution, genetic variation matters a whole lot. It’s the raw material natural selection can act on when the environment around a species changes.
If there’s no variation, it can be hard for a species to adapt and survive. And, for example, we don’t know if the extinct rail and the living one ended up with the same genetic variants from the parent population. Which means that they could look very similar, but under the hood, have different variants of genes that would result in different evolutionary futures when faced with the same challenges.
So, ultimately, what we can say is that there have been two iterations of flightless Aldabra rails, but they are not the same Aldabra rail… And each was its own Bizarre Beast. Don’t forget to sign up for the pin club at BizarreBeastsShow.com by May 20th if you want one of these incredible pins. And now for some bonus facts… [♪♪ BONUS FACTS ♪♪] So, now that we’ve introduced you to the Aldabra rail, you might be wondering what other rails are out there.
I though it was just a part of a train track. And you are in luck, because there’s something like 127 species of them distributed worldwide, just not at high latitudes. They tend to be slender, secretive marsh birds, and the ones with short bills are often called crakes, so you might know them by that name, too.
Or, you might be more familiar with their cousins, the coots and the gallinules! In the episode, we mentioned that the Aldabra rail is the only native flightless bird living on an island in the Indian Ocean. But there used to be others!
You might’ve heard of the most famous one, the dodo, which lived on Mauritius until 1681. But the dodo wasn’t the only one. There also used to be more flightless rails, including one that lived on Réunion until at least the end of the 1600s and another that was probably flightless and lived alongside the dodo on Mauritius until 1638.
Surviving as a flightless, ground-nesting bird on an island when humans arrive and bring animals like pigs and rats with them is challenging and, more often, tragic. Island birds often become flightless to save energy and devote it to more important aspects of life instead. When we humans want to optimize our energy levels though, the best thing we can do is to optimize our sleep, and that's where this episode’s sponsor Manta Sleep comes in.
They believe it’s impossible to unlock your full potential if you’re not getting an afternoon nap every day. Their focus is giving you the energy to create your best life. Sleep is just their strategy.
Manta Sleep’s collection of sleep masks and accessories are designed to improve and optimize naps to give you the energy, focus, strength and clarity that you don’t get when you grind through the afternoon, giving you what they call a “second morning.” The Manta Sleep Mask PRO for example is comfortable and is a 100% blackout mask. Honestly, it is cozy and I can see nothing! Visit the Manta Sleep website at mantasleep.com and use the code bizarrebeasts to get, I think, 10% off your first order?
But I'm not 100% sure, I can't see the teleprompter. Yes 10%! 10%! Mantasleep.com! [♪♪ OUTRO ♪♪]
Manta Sleep makes sleep masks and sleep accessories that help you get the energy to create your best life. Head to the link in our description to get 10% off.
About 136,000 years ago, on a coral atoll in the Indian Ocean, there lived a bird. Over time, it had lost its ability to fly, like many island birds do in the absence of predators. But, the thing is, coral atolls are not the most stable of landscapes.
They tend to be low-lying – often just a few meters above sea level, at most. And when this atoll was swallowed up by the waves, there was nowhere for that flightless bird to go. It went extinct, along with all the other unique species that had only evolved on that single island.
They were gone, forever. Or…were they? [♪♪ INTRO ♪♪] If you want to support the channel, the Bizarre Beasts pin club will now be open for subscriptions for the whole month! Sign up by May 20th and the first pin you will get will be this very good Aldabra rail.
And don’t forget to stick around at the end of the video for some bonus rail facts. Now, this story might sound familiar, but just bear with me for a bit. Today, ocean levels have once again receded and that island is back above sea level.
And the Aldabra rail is a terrestrial bird that lives on that island, the Aldabra Atoll, in the Seychelles, a country made up of islands in the Indian Ocean. It is about 30 cm long and has a patch of white feathers at its throat. And it’s an omnivore and occasional scavenger, though it prefers to eat insects when it can find them.
It also sometimes takes on crabs, which sounds very reasonable for a bird that lives on an island… but these are not tiny, adorable little crabs. They are large and the researchers we talked to for this episode gave us a bunch of very classic nature documentary-style rail versus crab footage, which I’m going to take a second to just, like, appreciate here. Now, there are a couple of things about the Aldabra rail that are weird.
Like, it’s either a separate, distinct species of white-throated rail or one of three subspecies endemic to islands throughout this region, depending on who you ask. Defining a species can be messy and subspecies are even harder to define. But the thing that definitely makes it different from the other living white-throated rails is that it is the last surviving bird in the Indian Ocean that cannot fly… and that’s where this story starts to get even weirder.
The first thing to know is that there are a lot of different flavors of evolution. For example, you’ve got convergent evolution, where different species evolve to have similar traits independently of each other, like how a ton of unrelated crustaceans evolve to be crab-shaped. And you’ve got divergent evolution, where populations of the same species get separated and accumulate differences over time, potentially ending up as different species.
Darwin’s finches are the classic example. And then there’s coevolution, where two or more species influence each other’s evolution, like certain hummingbirds and the specific flowers they pollinate. But perhaps the least common of the flavors is iterative evolution: when species within the same group repeatedly evolve the same traits independently at different points in time.
And this can make it look like species go extinct and then re-evolve. But do they really? Back in 1987, a paleontologist named John Becker collected a large number of fossils from a couple of sites on Aldabra… but he didn’t bring back just the fossil bones, themselves.
He collected them still encased in the hardened sediment they were buried in. This is pretty common for paleontologists, especially when they’re dealing with fragile fossils. But it means that, once the fossils get back to the lab, you have to get rid of that sediment, in a process called preparation.
That can sometimes take years… decades, even, if there’s no one with the time and skills to do the work. But, in the mid 2010s, researchers finally got the chance to work their way through those fossil blocks. And they found two intriguing bones: a complete left humerus, or upper arm bone, and the lower part of a right humerus of a bird.
And they looked almost exactly like the arm bones of the flightless rail that lives on Aldabra today… except they were over 136,000 years old, which mean they came from the time before that island was completely flooded. Now, these aren’t the only rail bones that have ever been found on Aldabra. There’s also a piece of a foot bone from after the island flooded that also looks like the foot bone of a flightless rail.
So, according to the researchers, this means that there were flightless rails on Aldabra before the atoll flooded around 136,000 years ago. Then they went extinct because the atoll was gone and they couldn't fly. Then another group of white-throated rails flew to Aldabra after it emerged again… And then they evolved to become flightless in under 16,000 years, which is potentially the fastest evolution of flightlessness in a bird that we know of.
And their descendants still live on the atoll today. Which sounds a lot like the same flightless Aldabra rail evolved twice… and that’s what a lot of the press coverage said when the paper about it came out. Of course that's not really how evolution works.
The old Aldabra rail is extinct, for good. What probably happened both times is just a weird quirk of how rails behave: when there are enough of them on an island, like Madagascar where white-throated rails live today, they sometimes just disperse... They fly off to isolated islands, settle there, and often become flightless, probably in part because they nest on the ground anyway.
And Aldabra isn’t the only island that has had a unique flightless or semi-flightless rail. And maybe this is splitting scientific hairs a bit, but just because the two Aldabra rails descended from the same population and adapted to island life in the same way doesn’t mean they’re the same species. Because, for evolution, genetic variation matters a whole lot. It’s the raw material natural selection can act on when the environment around a species changes.
If there’s no variation, it can be hard for a species to adapt and survive. And, for example, we don’t know if the extinct rail and the living one ended up with the same genetic variants from the parent population. Which means that they could look very similar, but under the hood, have different variants of genes that would result in different evolutionary futures when faced with the same challenges.
So, ultimately, what we can say is that there have been two iterations of flightless Aldabra rails, but they are not the same Aldabra rail… And each was its own Bizarre Beast. Don’t forget to sign up for the pin club at BizarreBeastsShow.com by May 20th if you want one of these incredible pins. And now for some bonus facts… [♪♪ BONUS FACTS ♪♪] So, now that we’ve introduced you to the Aldabra rail, you might be wondering what other rails are out there.
I though it was just a part of a train track. And you are in luck, because there’s something like 127 species of them distributed worldwide, just not at high latitudes. They tend to be slender, secretive marsh birds, and the ones with short bills are often called crakes, so you might know them by that name, too.
Or, you might be more familiar with their cousins, the coots and the gallinules! In the episode, we mentioned that the Aldabra rail is the only native flightless bird living on an island in the Indian Ocean. But there used to be others!
You might’ve heard of the most famous one, the dodo, which lived on Mauritius until 1681. But the dodo wasn’t the only one. There also used to be more flightless rails, including one that lived on Réunion until at least the end of the 1600s and another that was probably flightless and lived alongside the dodo on Mauritius until 1638.
Surviving as a flightless, ground-nesting bird on an island when humans arrive and bring animals like pigs and rats with them is challenging and, more often, tragic. Island birds often become flightless to save energy and devote it to more important aspects of life instead. When we humans want to optimize our energy levels though, the best thing we can do is to optimize our sleep, and that's where this episode’s sponsor Manta Sleep comes in.
They believe it’s impossible to unlock your full potential if you’re not getting an afternoon nap every day. Their focus is giving you the energy to create your best life. Sleep is just their strategy.
Manta Sleep’s collection of sleep masks and accessories are designed to improve and optimize naps to give you the energy, focus, strength and clarity that you don’t get when you grind through the afternoon, giving you what they call a “second morning.” The Manta Sleep Mask PRO for example is comfortable and is a 100% blackout mask. Honestly, it is cozy and I can see nothing! Visit the Manta Sleep website at mantasleep.com and use the code bizarrebeasts to get, I think, 10% off your first order?
But I'm not 100% sure, I can't see the teleprompter. Yes 10%! 10%! Mantasleep.com! [♪♪ OUTRO ♪♪]