No. 37: Jan-Feb 1985
At a recent meeting of scientists at the Lamont-Doherty Geological Observatory, E. Vrba, of the Transvaal Museum, in Pretoria, stated:
"If we eventually are able to establish a good time resolution with the continental record, I expect to be able to discern synchronous pulses of evolution that involve many groups of fauna and flora. Many different lineages in the biota will respond by synchronous waves of speciation and extinction to global temperature extremes and attendant environmental changes. This is my starting hypothesis."
Vrba was speaking mainly about the last 25 million years, a mere flash in geological time. For this brief period, the Deep Sea Drilling Program has provided geologists with a detailed and continuous record of climate changes as they were recorded in deep-sea sediments. By contrast, the faunal history of the continents is rather fragmentary, making it rather difficult to match up pulsations of climate with pulsations of life. Even so, scientists have found rather strong correlations between climatary change and biological speciation and extinction at 15, 5, and 2.4 million years ago.
(Lewin, Roger; "The Paleoclimatic Magic Numbers Game," Science, 226:154, 1984.)
Comment. Note that this is just the period our ancestors seemed to be evolving rapidly. Also interesting is the general agreement between Vrba's statement about the driving forces behind evolution and McClintock's conclusion quoted earlier under BIOLOGY.