New findings supply corrective to evolutionary hypothesis
For decades, researchers have observed that rates of evolution seem to accelerate over short time periods -- say five million years versus fifty million years. This broad pattern has suggested that "younger" groups of organisms, in evolutionary terms, have higher rates of speciation, extinction and body size evolution, among other differences from older ones. Evolutionary processes appear to operate at different time scales, perhaps necessitating the need for a new theory linking microevolution and macroevolution. The larger question has tantalized scientists: why? There are plausible explanations. A new species may inhabit a new island chain, allowing for more variation as it spreads into new niches. An asteroid may hit the earth, increasing extinction rates. Perhaps species evolve to an "optimal" trait value and then plateau. The study blends math, statistics and biology to show that…