[crazydoggers]

Birds are part of what’s called the Dinosauria clade. Clades are monophyletic meaning they encompass all the descendants of a common ancestor and all share common traits.

Humans and fish on the other hand can’t be grouped into a clade. That’s because it you trace back the common ancestor you’ll find other monophyletic groups descending from those ancestors.

Think of a clade as the end of a branch and all its leaves... whereas if you go far enough down you’ll find other branches that shoot off in other directions far off, even though they’re in the same main trunk.

https://en.m.wikipedia.org/wiki/Clade

[throwaway894345]

This seems like a rephrasing of the claim "birds are dinosaurs". "Birds are dinosaurs because birds are dinosaurs". Maybe the answer is "it's arbitrary; scientists decided that birds belong in the group 'dinosaurs' even though 'dinosaurs' and 'birds' are clearly distinct groups to everyone else"?

[phonypc]

Well, they're distinct groups to scientists too. Nobody is saying dinosaur and bird are interchangeable terms. All birds are dinosaurs, not all dinosaurs were birds.

[throwaway894345]

No one is saying that someone is saying that the terms are interchangeable :). The issue is that it’s not clear why “birds are dinosaurs” is correct but “birds evolved from dinosaurs” is not.

[phonypc]

I don't think "birds evolved from dinosaurs" is incorrect per se, but it evokes a common misconception of what dinosaurs are, so you get people responding "birds are dinosaurs."

Consider by analogy "humans evolved from primates." Well ya, but humans also are primates.

[throwaway894345]

I don’t think it’s a misconception at all, but rather science has its own definition and lay people have another. The definitions are useful to their respective camps. People who correct laypeople for using their definition are boring pedants.

[phonypc]

I don't think that works. The lay persons definition is necessarily derived from the scientific one. "Dinosaur" wouldn't exist as a word or concept without scientific study.

Sorry to keep bringing up the same analogy, but do you also think it would be pedantic to correct "humans evolved from primates" to "humans are primates"?