vanderbilt | In the popular mind, mass extinctions are associated with
catastrophic events, like giant meteorite impacts and volcanic
super-eruptions.
But the world’s first known mass extinction, which took place about
540 million years ago, now appears to have had a more subtle cause:
evolution itself.
“People have been slow to recognize that biological organisms can
also drive mass extinction,” said Simon Darroch, assistant professor of
earth and environmental sciences at Vanderbilt University.
“But our
comparative study of several communities of Ediacarans, the world’s
first multicellular organisms, strongly supports the hypothesis that it
was the appearance of complex animals capable of altering their
environments, which we define as ‘ecosystem engineers,’ that resulted in
the Ediacaran’s disappearance.”
The study is described in the paper “Biotic replacement and mass
extinction of the Ediacara biota” published Sept. 2 in the journal Proceedings of the Royal Society B.
“There is a powerful analogy between the Earth’s first mass extinction and what is happening today,”
Darroch observed. “The end-Ediacaran extinction shows that the
evolution of new behaviors can fundamentally change the entire planet,
and we are the most powerful ‘ecosystem engineers’ ever known.”
The earliest life on Earth consisted of microbes – various types of
single-celled microorganisms. They ruled the Earth for more than 3
billion years. Then some of these microorganisms discovered how to
capture the energy in sunlight. The photosynthetic process that they
developed had a toxic byproduct: oxygen. Oxygen was poisonous to most
microbes that had evolved in an oxygen-free environment, making it the
world’s first pollutant.
