Scientists have finally unequivocally solved that age-old mystery: chickens came first. Well, something like that anyway. Last week, a team of researchers who call themselves the 'Avian Phylogenomics Consortium' unleashed a treasure trove of new information on birds. Not only have they been able to reconstruct the bird family tree, helping us to understand which birds are more closely related to which other birds, but they've also revealed new conclusions about everything from how bird song evolved to why birds don’t have teeth.
The more than two hundred researchers from eighty different institutions in twenty countries were led by Erich Jarvis of Duke University, Guojie Zhang of the National Genebank at BGI in China and M. Thomas P. Gilbert of the Natural History Museum of Denmark.
The study isn't only unprecedented in terms of manpower, but also in terms of scope. Previous efforts to suss out the relationships between birds relied on some ten to twenty genes per species. But the current effort involved sequencing, assembling and comparing the entire genomes of forty-eight different bird species. Getting the raw materials to extract the DNA was a breeze – the most difficult involved a trip to a United Arab Emirates zoo to collect blood samples from a bustard and a sandgrouse.
The study also meant that computer scientists had to devise new methods for processing all that data, which took three supercomputers three hundred years of CPU time. Some of the supercomputers required a terabyte of memory to get the job done. This is truly the era of Big Data. (In case you want to know, here are the 48 bird species that were included.)
There's so much new science that came out of this work (last week alone the consortium published twenty-nine individual papers, with more to come) that it might be overwhelming. So here, in no particular order, are eight of the most interesting things we learned about birds this week that we didn't know last week.
Birds and dinosaurs
All birds are dinosaurs, but you knew that already. What you perhaps did not know was that some modern birds have evolved faster than others, making them – from a genomic perspective, at least – more different from their dinosaur ancestors than others. But the birds most closely related to the 'dinosaur avian ancestor'? Chickens. As the researchers put it, "the chicken lineage appeared to have undergone the fewest changes compared to the dinosaur ancestor".
The root of toothlessness
Birds have beaks, not teeth. You already knew that too. They use their beaks to snatch food and gizzards to crush it up for digestion. This week we learned that birds' toothlessness is thanks to a single common ancestor that lived about 116 million years ago. As a result, all birds lost the use of just five genes related to making enamel.
Nearly one in four bird species are at risk of extinction and seventy-three are currently the focus of conservation efforts. The crested ibis, once widespread in Northeast Asia, dwindled to just seven wild individuals from two breeding pairs in 1981 before humans intervened to help them. By looking at the genomes of this and other birds whose survival is threatened, researchers were able to identify "genomic signatures for near-extinction events" and how those genomic changes might make at-risk species even more susceptible to climate change, over-hunting and other human-related threats. That information also promises to allow conservation biologists to better create breeding recommendations to identify the best possible pairings among the world's rarest birds.
Around half of the world's birds are classified as songbirds, one of the few other animals who possess something similar to human language. Researchers identified ten genes unique to the songbirds and two of them are most active in the parts of their brains known to be involved in vocal learning (the ability to acquire new sounds through imitation).
And that's not all!
Another paper described a study in which the researchers compared the genes active in the vocal regions of songbird brains and in language regions in human brains. We already knew that the brains of songbirds and humans share some similar neural circuitry, but now we know that they also share some underlying genetics – meaning that the genes behind birdsong and human speech have much in common.
Singing a different tune
It is perhaps not surprising that so much effort was devoted to birdsong, since that's lead researcher Erich Jarvis's specialty. When the researchers redrew the family tree of birds, the three clusters of song-singing birds – the parrots, hummingbirds and songbirds – had a common ancestor that probably did not sing. In other words, that means vocal learning evolved independently in each of these groups.
The newly organised family tree also revealed that the ancestor of all terrestrial birds – from eagles to hummingbirds, woodpeckers to crows – was a large apex predator, perhaps related to the so-called 'terror birds' of South America. Or, as researcher M. Thomas P. Gilbert told Nature News, it was very likely a "mean-ass carnivore".
March of the penguins
The first penguins adorably waddled around some 60 million years ago and they've since become adapted for life in cold weather and for swimming rather than flying. Two Antarctic species were included in the mega-study, the Adélie penguin and emperor penguin, allowing researchers unique insight into the genes that permit penguins to live their lives in such an extreme environment. While the study hasn't yet connected genetic differences with those adaptations, what it has done is identify the genes most likely to be different in penguins. The researchers suspect that these candidate genes are responsible for the changes in skin and wings that allow penguins to swim, the changes in how their eyes respond to light given the long days and long nights at the Earth's southern pole, and more. Because their genomic data can also shed light on historical population sizes, the researchers think that they can use this data to predict how different penguin species might respond to future climate changes.
Top header image: Byron Chin, Flickr