Science
News: Between 540 million and 500 million years ago, a
massive proliferation of modern life forms occurred, known as
the
Cambrian
explosion. The cause for the sudden increase is unknown,
though many theories have been put forth. Erik Sperling of
Harvard University and his colleagues believe they have tied
two theories together into a more complete explanation. The
geologic record indicates a significant increase in oxygen
levels during the same time period, and the appearance of
carnivorous species may have driven an arms race of
evolutionary responses. Sperling's group examined data on
nearly 1000 species of worms from 68 locations on the sea floor
and found that the number of carnivorous species was lowest in
the areas with the lowest oxygen levels. They believe
that the increase in oxygen is what allowed the development of
successful carnivores—the higher concentrations of the
gas accommodated the higher energy costs of pursuing and
digesting prey.
