Evolution and Increased Diversity

Neither would floods probably be. Nor volcanoes. Changes in climate aren't random either.

This statement is true in that there were absolutely mammals hanging out before the end-Cretaceous extinction (regardless of what it did to the non-avian dinosaurs--and despite what you read in books/media...the jury is still out on that one). But the statement ignores the fact that non-avian dinosaurs solidly held sway over the vast majority of terrestrial niches at in the latest Maastrichtian. Gould might well have been wrong about modern dinosaur dominance in the absence of an end-Cretaceous whacking of the dinosaurs, but we can do little more fantasize about what mammalian diversity would look like today if the end-Cretaceous extinction had not occurred.

Forgive me for being a bit obtuse here, but this is just a hypothetical example to illustrate the fallacy, right?

Okay, good. Phew *wiping brow*

The statement could use some nitpicking if it were being used to communicate actual deep time events. As things stand though, no worries.

Morphological similarity is evidence that two vertebrates did similar things, but it is only one line of evidence, and it can point you in an erroneous direction. That Ambulocetus has a crocodile-like morphology absolutely does not in and of itself make it obvious that the two competed in the same niche. I'm not really sure what pre-programmed means here but I think that I agree with you if what you're saying is that evolution will happen even if a niche is empty (say in a post-disturbance situation). What are you talking about? Once what? Really? When exactly was this? I'm gonna call for some citations of scientific papers here.

I looked through the first five pages of the thread you provided the think to, and didn't find any references supporting the idea that there was a point in deep time when mammalian species diversity was higher than today, which is what: you wrote in message #51 indicates.Moreover, these papers, by John Alroy alone, just one author:Alroy, J. 2000. Successive approximations of diversity curves: ten more years in the library. Geology 28(11):1023-1026.Alroy, J. 1999. The fossil record of North American mammals: Evidence for a Paleocene evolutionary radiation. Systematic Biology 48(1):107-118.seem to flatly contradict the statement and this paper seems to indirectly suggest that the statement is false:Alroy, J. 1998. Cope's rule and the dynamics of body mass evolution in North American mammals. Science 280:731-734.Now, mammalian diversity is a long way from what I do and I could be wrong, so again, please provide substantive evidence that mammalian species diversity has been higher at points in deep time than now. We're talking about species here, not higher taxonomic ranks (which cannot be directly compared). I never said it did. You said it was obvious that they lived in the same niche based on morphological similarity and I opined that this was bull and gave my reasoning. Again, show me some actual data back up this assertion.

Actually, the .pdf you linked to in that opening post refuted that point...it didn't support it.

Yeah, I'm pretty much with you on all of this.

I gotta tell ya, Razd. I love that sentence.