4 ms·
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 comm
by crazydoggers 6y ago
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 https://en.m.wikipedia.org/wiki/Clade
- throwaway894345 6y agoThis 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 6y agoWell, 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 6y agoNo 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 6y agoI 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 6y agoI 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 6y agoI 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"?
- throwaway894345 6y agoThe analogy doesn't apply because "primates" doesn't have a colloquial definition that excludes humans. "fish" or "reptiles" would be better examples. "Humans didn't evolve from reptiles; they are reptiles". I don't find it pertinent that the colloquial definition wouldn't exist without scientific study.
- phonypc 6y agoFish and reptile aren't comparable terms to dinosaur. They started as colloquial terms and (as colloquially used) refer to groups based on traits, not phylogeny. Humans actually are not evolved from the phylogenetic group closest in content to "reptiles." I guess you could argue the colloquial definition of dinosaur is similarly trait based, but even then... an ostrich is practically a small toothless T. rex.