RE: If an Asteroid wiped out the Dinosaurs how did Evolution continue?
July 9, 2013 at 7:26 pm
(This post was last modified: July 9, 2013 at 7:57 pm by Anomalocaris.)
(July 9, 2013 at 7:12 pm)Rhythm Wrote: All groups can be "considerably more ancient" so long as we include the lca and wherever it may have hailed from (which again...we don't find the sort of evidence for we would expect, certainly nothing to suggest anything like prairies or even fields of grass/proto grass capable of supporting grazing -anythings- pre 55mya anyways).
No, not everything that it could hail from. If you keep tracing the linage of Ica back in time, eventually you will arrive at an bacteria.
But long before reaching the obsurdly distant single cell ancester, more recent ancesters of Ica would have already lost so many of the derived traits of grass that it is no longer a grass. Even more recently there would be ancesters of Ica would have lost so many derived traits of Ica that it was no longer an Ica, but was still a grass.
Assuming Ica is a monophyletic taxa (ie grouped by evolutionary relationship instead of convenience), when you compare the genomes of Ica, the best you can do is determine when the first Ica ancester that was already itself an Ica (by cladistic taxenomy) first arose. You can not determine when the first Ica ancester that wasn't yet Ica, but is already grass, arose.
It is that second ancester - the earliest to have all the basic traits needed to be grass, but none yet of any of the incremental traits needed to be an Ica - that would mark the origin of grass.
Looking just at Ica it would be hard for you to pin point that.
Incidentally, if you assert the first ica happen to also have been the first grass, then that would mean there could subsequently have been no grass that is not also an ica. You already said that wasn't true, meaning first grass wasn't the first ica, and must have predated the first ica.
(July 9, 2013 at 7:12 pm)Rhythm Wrote: I'd say that when a genome matches fossils we're on to something though Chuck...that's just me.
Absence of fossil evidence is not evidence of absence of what might make the fossil. The best you can say is genome study and available fossil evidence does not grossly contradict and falsify each other, such as discovery if ica fossil in strata 110 million years old.
The best you can do is to assert a strong statistical correlation between existemce, or prevelence, with fossil record.
Good luck with that.
