General Discussion

we would of course reach ancestors that are clearly not chickens - whether they be fish or archosaurs or some sort of pheasant / grouse / whatever living in North Vietnam in the Pliocene. We could definitely tell the difference between a chicken, and the fish at theroot of its (our) family tree.

But where would we draw the line between the modern chicken, and its most recent ancestor? How could we actually do so? we could certainly understand that one is one and the other is the other... but... we wouldn't actually be able to demonstrate this, even if we had every single individual involved in the process at hand.

There really is no solid point where "most recent ancestor" ends and "chicken" begins. Nor for that matter is there a point where "ancestor before that" ends, and "most recent ancestor" begins.

It's an unbroken continuum, all the way back to whatever amino soup was frothing around on earth's frosty shores way back before the Paleozoic

This is actually an important issue with tracking human evolution - we've got this awkward divide of "archaic homo sapiens" and "modern-type homo sapiens" for example - both of which could contain different species, or which all might be the same species with simple ethnic or individual variation.. .and this is without figuring contemporaneous human species we're finding in the area as well! Because what we're finding isn't actually a species-by-species catalogue of ancient human remains, but more of a... genetic cloud of multiple populations and individuals all swamping together over a period of about a million years. So yeah, we can tell the difference between a type-specimin "Homo erectus" and a human skeleton from last week.. .but... there's a gloudy gradient between the two that gets murkier and murkier the closer to th middle you get.

This is just the way it is for every species on earth. we define species by how differnet htye are from other species, but when you go back, the differences shed away as you draw close to common ancestors, so how do you keep the "species" designation? At what point does one species stop and new one begin?

Richard Dawkins has pointed out that gaps in the fossil record are pretty much the only thing that keeps Paleontologists and taxonomists from going completely fucking bonkers. Can you imagine if we actually DID have access to every individual ancestor of modern rabbits (or chickens?) all the way back to the Paleozoic? They would be impossible to classify!