PNAS paper studies actual pattern of evolution, doesn’t pretend it’s somehow something else
|September 21, 2011||Posted by News under Evolution|
It used to be the “trade secret of paleontology – that evolution never works the way Darwin said. Indeed, Darwinists may have invented the term “quote mining” – just for something to say in response to the fact that Steve Gould had admitted that, carelessly perhaps.
However, straw in the wind, a recent paper actually looks at the data without Darwin glasses. And guess what?
The million-year wait for macroevolutionary bursts
Josef C. Uyedaa,1, Thomas F. Hansenb, Stevan J. Arnolda, and Jason Pienaarc
July 22, 2011 (received for review October 11, 2010)
We lack a comprehensive understanding of evolutionary pattern and process because short-term and long-term data have rarely been combined into a single analytical framework. Here we test alternative models of phenotypic evolution using a dataset of unprecedented size and temporal span (over 8,000 data points). The data are body-size measurements taken from historical studies, the fossil record, and among-species comparative data representing mammals, squamates, and birds. By analyzing this large dataset, we identify stochastic models that can explain evolutionary patterns on both short and long timescales and reveal a remarkably consistent pattern in the timing of divergence across taxonomic groups. Even though rapid, short-term evolution often occurs in intervals shorter than 1 Myr, the changes are constrained and do not accumulate over time. Over longer intervals (1–360 Myr), this pattern of bounded evolution yields to a pattern of increasing divergence with time. The best-fitting model to explain this pattern is a model that combines rare but substantial bursts of phenotypic change with bounded fluctuations on shorter timescales. We suggest that these rare bursts reflect permanent changes in adaptive zones, whereas the short-term fluctuations represent local variations in niche optima due to restricted environmental variation within a stable adaptive zone.
Studying the patterns and mechanisms of evolution can yield real information, but the first requirement for true knowledge is to stop defending Darwin.