Theory Explores How Molecules Became Cells

The theory that life might have started in a so-called "primordial soup" has been around for decades, but a new theory tweaks that idea into a "soup-and-sandwich" combo, according to news from the National Science Foundation.

NSF researcher Helen Hansma believes the protected areas between layers of mica -- a silicate mineral that can be split into ultra-thin, perfectly flat sheets -- might have provided the perfect breeding ground for Earth's first biomolecules billions of years ago. The oldest rocks on the planet showing fossil evidence of life are about 3.5 billion years old.

Hansma, with the University of California, Santa Barbara, said she developed her "soup-and-sandwich" hypothesis while splitting some mica under a microscope last spring. Looking through the viewer, she found the sheets of mica, taken from a mine in Connecticut, were covered with organic matter.

"As I was looking at the organic crud on the mica, it occurred to me that this would be a good place for life to originate -- between these sheets that can move up and down in response to water currents which would have provided the mechanical energy for making and breaking bonds," she said.

The spaces between mica layers would have protected molecules from currents in Earth's primordial oceans, giving them an opportunity to form different kinds of bonds and larger molecules without being washed away. The gaps between mica layers are also rich in potassium and negatively charged, similar to the environment inside living cells today.

Such findings indicate mica "would have provided a very hospitable environment to the earliest biomolecules," Hansma said.

Hansma's theory could find support in the fact that a site in Greenland with signs of very ancient life is also close to a huge mica formation. The hypothesis also appears to address problems with previous theories on the origins of life. Primordial "soup" alone, for example, doesn't explain how early biomolecules, floating around in liquid without any protection, could have joined, stayed together and formed the more complex structures of life. And the "pizza" hypothesis, which theorizes that early cells developed on minerals on land, doesn't explain how those first life forms could have had enough water to survive.

Hansma was scheduled to present her "soup-and-sandwich" hypothesis during this week's annual meeting of the American Society for Cell Biology in Washington D.C.

National Science Foundation, "Did Life Originate in a Mica Sandwich Sitting in Primordial Soup?" URL: (http://nsf.gov/news/news_summ.jsp?cntn_id=110802)