The data show that birds and mammals at Rancho La Brea show complete stasis and were unresponsive to the major climate change that occurred at 20 ka, consistent with other studies of Pleistocene animals and plants. Most explanations for such stasis (stabilizing selection, canalization) fail in this setting where climate is changing. One possible explanation is that most large birds and mammals are very broadly adapted and relatively insensitive to changes in their environments, although even the small mammals of the Pleistocene show stasis during climate change, too.
Dr. Axe comments,
I work at the other end of the size spectrum, on protein molecules rather than whole animals. It’s interesting that attempts to catch evolution in the act of doing the amazing things that the textbooks attribute to it seem to fail at both ends of the spectrum.