Evolution (Introduction)

by dhw, Monday, October 25, 2010, 12:47 (5142 days ago) @ dhw

An article in yesterday's Sunday Times reports on a new theory: METEOR BLASTS LED TO EXPLOSION OF LIFE, though as usual the sensational certainty of the headline is not borne out by the article. About 470 mya the Earth was bombarded with meteorites, and afterwards "the fossil record shows that the number of life forms soared." Ted Nield, editor of Geoscientist, has written a book called Incoming! and says the meteorites "may have been responsible for the single greatest increase in biological diversity since the origin of complex life." Nield's book is partly based on the work of Birger Schmitz, a professor of bedrock geology, who says: "The theory is controversial because most scientists believe that meteorite impacts cause extinction." The theory is that the impacts changed the climate and geology of the Earth, and so species "had to adapt rapidly to big changes or go extinct." The Cambrian explosion had taken place about 80 million years earlier, but evolution appears to have paused until the new shock. The article concludes that at the time, "the most advanced forms of life were primitive jawless fish and squid-like cephalopods, mostly living in shallow seas. Something influenced evolution ... and meteorites could have been the cause."-If drastic changes to the environment genuinely do coincide with a new diversity of life forms ... though I wonder just how reliable the data are ... it doesn't seem unreasonable to assume that there is a causal link. If there is, then the driving force behind the creation of new species would appear to be adaptation ... "species had to adapt rapidly [...] or go extinct". (Natural selection only comes into play when species exist). However, perhaps our scientists could explain why adaptation should lead to NEW species rather than merely variations within old species.