After the landmark bird family tree analysis in 2008 by Hackett et al., two main questions seemed particularly prominent to me, and were treated as significant in this latest slew of genetic revelations.
Was the original ancestor of the “landbirds” group, a bird of prey?
…and when did the third and largest group of birds – Neoaves – start to split up? Before the dinosaurs were wiped out or just after?
Although the arrangement of other parts of the Big Third Group – Neoaves – is interesting, and there are one or two new things there that I’ll mention below, I was convinced I knew the answer to the first question, expressible as “Are falcons and other birds of prey similar because of convergent evolution from different ancestors (or indeed from one different ancestor!), or are the huge number of landbirds closely related to but not actually birds of prey, nonetheless descended from birds of prey?”
I was horrified to discover no-one else even mentioning the possibility that a bird of prey might be the landbird ancestor. I mentioned the “possibility” here and there on the net but no-one touched it. Worse, some people, I particularly think of Darren Naish, simply seemed to imply that birds of prey had evolved twice, and never mentioned the alternative. He even went on to contribute to a book – as a supposed expert at interpreting evolutionary trees, which people paid money for in good faith – never mentioning even a dual option. And this even after I’d myself stressed in both blog and book [see top right] that there was both an option and a preferred solution.
The reason most people I might count as “bloggers” didn’t give a sensible coverage on this is I suspect because they are not sure how science theories are supposed to be created and spread, but they are scared of being seen as an outsider. Maybe they even might complain: “well, there’s no evidence for it, is there?”, not realising that both theories explain the observations so there already is evidence for both – just not yet conclusive evidence… of a sort we almost never get in many sciences, especially palaeontology.
As for Naish, the reason why he refused to acknowledge the reality was because of his pathological hatred of anything I say – which is a pity because he’s going to find himself on the wrong side of many important decisions, or late in arriving at the right decisions, as I proceed to highlight, early, both the choices to be made and the favourable options to take. While he’s busy reciting decisions and discoveries others have made, and building up a cabal of like-minded, tiny-minded pseudo-scientific supporters, and eye-rolling as hard as he can to discredit, well, me, but also others, I’m actually doing the science that he should be doing.
This is a prime example in palaeontology where a decisive resolution can eventually be found. While the conclusions in the latest avian genome papers are not final of course, the writing is on the wall:
Erich D. Jarvis et 104 al., in: “Whole-genome analyses resolve early branches in the tree of life of modern birds”, recommend we take a bird of prey as the landbird ancestor. That’s sixyears after I mentioned it in a comment on, for example, GrrlScientist’s blog (so I’m that far ahead of an “expert” the Guardian chooses as a house blogger on this sort of thing – though she’s not the only one they’ve got who I’m light years ahead of), and two and a half years after I recommended the idea in my book.
On the second issue: whether the large third group of modern birds – Neoaves – split up before the end of the Cretaceous or just after.
Many scientists, good ones at that, took apparent evidence from genetic observations to estimate a genetic clock which suggested the third group split up in the Cretaceous; for some, quite a long way back into it. Now though, the explosion, which they acknowledged, (and which I highlighted in the book as very likely for a number of reasons not least the preponderance of ILS), is timed at or in some cases just very slightly before the K-T transition. In passing, the authors of Jarvis et al. also now concur with me (and of course others, notably O’Leary et al. 2013) but in what used until very recently to be a minority, that the same pattern of an explosion from a small number of ancestors, seemed to have occurred in mammals at the same time.
Here is their new tree (which I’ve compressed slightly):
It shows the ancestors of Neoaves as starting to diverge ever so slightly before the K-T. However I suggest this is due to the rate of fixation of mutations and other changes into genomes dramatically increasing after a near extinction followed by an explosion. From a sister paper: “the origin of Neognathae was accompanied by an elevated rate of chromosome rearrangements.” I still think only one ancestor of Neoaves survived the K-T.
It differs from Hackett et al. (2008) in a number of other ways:
What I called “small water birds”, shown in the chart as a yellow line labelled “Charadriiformes (Plovers)”, no longer seem to be a sister group – or ancestor – to the landbirds. I’m sorry about that because having years ago wondered if the curved bill of parrots might be because they were descended from birds of prey (now vindicated!), I recently started to think that the slightly hooky-ended beaks even of gulls (related to those Charadriiformes), and also similarly auks such as razor-bills, and especially puffins, might also show a connection with birds of prey! Not as likely now, perhaps, but still I think possible.
My coots, cuckoos, cranes, trails and bustards are now exploded: it’s now cranes alongside Charadriiformes – which they label as plovers, so that must be waders. Also, next to those two yellow lines is at last placed the difficult Hoatzin. Cuckoos and bustards are still together though (orange lines), and now they “definitely” do embrace turacos. Where the coots and rails went I haven’t been able to find out. Presumably gulls and auks are still with waders.
They’ve given the ratite/tinamou group a pre-K-T split, and I think that’s wrong. But they seem to show the ducks/chickens group as possibly not splitting until just after, so that’s good.
Finally, their view of just two occurrences of birds of prey giving rise to non-birds of prey is more pleasingly neat, and mousebirds are now in one instead of being just outside all birds of prey.
Oh – and they’re still calling Nightjars Nightjars and not Goat-suckers any more! 🙂
[For a snappier version of the tree, try this.]