Contact: Beth Fox Vanderbilt University (615) 322-NEWS (6397) [email protected]
Tiny bug in Antarctica holds clues to massive extinction
The mass extinction that killed the dinosaurs was small compared to the one that happened 250 million years ago, an extinction that occurred at a rate that some scientists say is on par with today's. A Vanderbilt researcher has discovered clues to what may have caused the earlier extinction, an extinction that killed off almost 90 percent of the organisms on earth.
Professor of Geology Molly Miller says that a small burrowing insect that lived in Antarctica survived that worldwide extinction and can provide clues to its cause.
Miller presented her discoveries at the annual meeting of the Geological Society of America in Toronto Oct. 28.
Miller's research focuses on trails and burrows she discovered in sandstone deposits while she was in Antarctica in the fall of 1997. The sandstone deposits were in large riverbeds that flowed near the South Pole at that time. From the markings on the sandstone, she deduced that several types of marks were made by the same kind of animal, probably an insect whose tough legs left the characteristic markings.
The burrows and trails in the sandstone are present both before and after the extinction, showing that the insect apparently survived, in contrast to animals that disappeared forever.
"This is significant because this is the only major extinction that affected the insects. Even when the dinosaurs were killed, the insects survived. But in the extinction that occurred 250 million years ago, when many of the insects died, these river burrowers just kept going."
What exactly these survivors looked like is a bit of a mystery; Miller envisions them as resembling the modern-day burrowing mayflies that are used for bait in fly-fishing.
No one knows why - or even if - these creatures eventually died off. They may be related to insects living today, said Miller, whose research is funded by the National Science Foundation.
There are several theories as to why these animals survived when so many disappeared. "Burrowing in riverbeds and feeding on dead plant material perhaps buffered them from disastrous environmental changes," Miller said. "Also, living near the South Pole may have required them to be more adaptable than those living at lower latitudes."
"This extinction was much more devastating than what killed the dinosaurs. The animals living in the ocean were particularly hard hit, as were many insects. To figure out the cause, we must look at how different ecosystems were affected."
Theories abound over what caused the extinction: from massive changes in the composition of the air, to changes in the oceans' chemistry, to major climate changes. Miller's research on the little bug in the Antarctic riverbeds is just one piece of the larger puzzle. "We're going to find the answer to what happened by picking up little small bits one at a time. This is just one of those small pieces."
What is known is that when approximately 70 to 90 percent of the life forms on earth were killed off, it happened relatively quickly - just like what seems to be happening today.
"The period of extinction was fairly brief - about a million years or so. Compare that to the period of extinction we're in now. In the past 10,000 years, many large mammals and birds have become extinct, probably because of human activity. It is likely that each year many species, especially insects that have never been studied, will become extinct. Some of them probably would be beneficial to humans, but they're gone before we can know," Miller said.
"To our human senses, this is an incomprehensible amount of time. But to wipe out such a large number of organisms during a fairly short period of time is really a catastrophe like what happened 250 million years ago.
"Ten thousand years from now, people are going to look back at this period and be shocked at how quickly it all disappeared - if people are even still around."
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