CAMBRIDGE, Mass. -- The first organisms to emerge after an ancient worldwide glaciation likely evolved hardy survival skills, arming themselves with tough exteriors to weather a frozen climate.
Researchers at MIT, Harvard University and Smith College have discovered hundreds of microscopic fossils in rocks dating back nearly 710 million years, around the time when the planet emerged from a global glaciation, or "Snowball Earth," event. The fossils are remnants of tiny, amoeba-like organisms that likely survived the harsh post-glacial environment by building armor and reaching out with microscopic "feet" to grab minerals from the environment, cobbling particles together to make protective shells.
The discovery is the earliest evidence of shell building, or agglutination, in the fossil record. The team found a diversity of fossils, suggesting life may have recovered relatively quickly following the first major Snowball Earth event. The researchers report their findings in an upcoming issue of Earth and Planetary Science Letters.
The widely held Snowball Earth theory maintains that massive ice sheets covered the planet from pole to pole hundreds of millions of years ago. Geologists have found evidence of two major snowball periods at 710 and 635 million years ago in glacial deposits that formed close to the modern equator. Fossil records illustrate an explosion of complex, multicellular life following the more recent ice age. However, not much is known about life between the two major glaciations a period of about 75 million years that, until now, exhibited few signs of life.
"We know quite well what happened before the first Snowball, but we have no idea what happened in between," says Tanja Bosak, assistant professor of geobiology at MIT, and the paper's lead author. "Now we're really starting to realize there's a lot of unexpected life here."
Ice Age armor
Bosak's colleagues, Francis Macdona
|Contact: Caroline McCall|
Massachusetts Institute of Technology