0
$\begingroup$

At this pop-sci article transcribing an interview with Jeremy DeSilva, they state:

"If we’ve learned anything about evolutionary trends, it’s that good ideas evolve over and over again. For instance, the evolution of feathers and dinosaurs independently evolved three times. You could get the independent evolution of bipedalism multiple times."

I have two questions:

  1. What are those three events of the independent evolution of dinosaurs? Also, are there other such events that are suspected but are not as well understood?

  2. Is he correct in using these independent dinosaur evolution events as reason to imply that bipedalism in hominins could have evolved multiple times? That is, are there nuances/details regarding the dinosaur evolution events that constitute important differences compared to the case of bipedalism in hominins?

Note: I used the word hominin here because that is what Jeremy DeSilva used in the cited interview, but I understand that may affect the answer to my question as chimps are also bipedal, but feel free to inform me!

$\endgroup$
4
$\begingroup$

"Dinosaur", when used properly, refers to a clade. There's no way for a clade to evolve multiple times, or even to really evolve at all as something that happens; it's just a name for a group of descendants sharing a common ancestor.

I'm guessing instead that it's an incorrect transcription of "feathers in dinosaurs", since in and and sound quite similar out of context; that is, that something structured like a feather evolved three times in the dinosaur lineage.

I know little to nothing about this area, but Wikipedia's article on feathered dinosaurs suggests that this is a bit unresolved:

It is not known with certainty at what point in archosaur phylogeny the earliest simple "protofeathers" arose, or whether they arose once or independently multiple times.

There are feathers observed in multiple lineages of dinosaurs, but it seems most plausible that they all came from the same origin rather than independently. For the intervening species it may be that either they lost the feathered phenotype or that there is simply not fossil evidence of feathers for those species.

As for bipedalism, well, we don't really need any feathers to reason that a trait could evolve more than once. Flight itself is a simple example: there are flying insects, flying birds, and flying mammals (bats), all who evolved flight from previously flightless ancestors.

The most direct example, though, is bipedalism itself: there are many bipedal dinosaurs, including modern birds. Human bipedalism evolved separately from non-bipedal mammals. Arguing whether it's happened multiple times among the apes is another story, that has little to do with any examples from other clades or other traits except analogy. Certainly, other apes locomote on two legs at times, but none of them walk quite the way humans do. If you want to argue that feather evolution involved an earlier "protofeather" that then separately evolved into a full-fledged (hehe) version multiple times, then maybe that would relate to a "proto-bipedalism" (as observed in apes) that could result in multiple "truly bipedal" lineages, but one would need further evidence to support that.

$\endgroup$
2
  • 2
    $\begingroup$ I'd add that there's a good chance that bipedalism in dinosauria as a whole, while it might have evolved separately, there were vast expanses of time (conservative short 166 million years) between the beginning and end of dinosaurs... something Apes haven't had (yet - 25 million years) $\endgroup$
    – bob1
    Jul 7 '21 at 0:37
  • 1
    $\begingroup$ And don't forget flying pterosaurs :-) $\endgroup$
    – jamesqf
    Jul 7 '21 at 16:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.