Could a faster rate of evolution, driven by new competition, explain the biological “big bang” at the beginning of the Cambrian Era?
For the most part, evolution is a pretty slow process. Sure, some germs have been able to outsmart our antibacterial hand soap through natural selection, but big changes, like an opposable thumb or a new species, take much longer to develop. New research, however, suggests that evolution may have been faster for our prehistoric ancestors, says Kelly Servick at ScienceNOW (September 13, 2013).
For decades, biologists have fiercely debated the Cambrian explosion, the evolutionary “big bang” that saw the appearance of dozens of new traits and animal groups some 542 million years ago. Where once single-celled organisms dominated the world’s oceans, creatures suddenly sported antennae, exoskeletons, and compound eyes. How did so many creatures evolve so quickly, and why? Questions like these have plagued biologists all the way back to Charles Darwin.
So far, with a limited fossil record, answers have been hard to come by. But a new study led by University of Adelaide biologist Michael Lee may represent an important step forward. Focusing on arthropods, Lee compared physical and genetic variations between modern organisms and those in the fossil record. What he found was that changes that occurred during in the early Cambrian period were, on average, 5.5 times faster than today—meaning natural selection had temporarily sped up. Lee speculates that, because genes and anatomy evolved at the same rate, the changes were likely driven by the appearance of new competition and predators.