There is no question in all of science that is more perplexing, and more difficult to answer, than this simple query: How did life on Earth begin? It happened so long ago, when the planet was still in its infancy, that most of the evidence has vanished, leaving scientists with little hope of ever finding the answer.
But that may be changing. Scientists, disenchanted with an 80 year old theory that life began in a "primordial soup," are focusing on deep-sea pressure cookers that were unknown just a couple of decades ago. Life may well have begun in tiny "chimneys" in a green rock that is common on earth, as well as other celestial bodies, when the ocean was 100 times more acidic than it is today, and the planet was much warmer.
Serpentine, California's official state rock, is on center stage today as a possible major player in generating the first life on Earth, more than 3.8 billion years ago.
This green stone, which looks a lot like jade, could have been a "rich incubator" of the unicellular life that first flooded the earth so long ago, according to geophysics professor Norm Sleep of Stanford University. Sleep didn't invent the idea of serpentine as an incubator, but he set out to learn if the theorizing of biologists could survive a geological inquiry. Were the geological conditions of early Earth compatible with life originating in serpentine?
Two of his colleagues, Dennis Bird and Emily Pope, mounted an expedition to Greenland, where they found serpentine rocks in some of the oldest formations on the planet, at least 3.8 billion years old. So serpentine would almost certainly have been plentiful when first life appeared. Furthermore, other critical components were also present, leading to this cautious assessment by Sleep during a telephone interview:
"It's reasonably viable" that life first appeared in tiny pores in serpentine, buried deep below an acidic ocean, he said. But the conditions didn't last forever, probably no more than a few million years. That's a small window for a geologist, accustomed to thinking in terms of eons, but it may have been long enough for biologists.
"We can't prove it's right," Sleep added, "but we can prove it's reasonable."
'Primordial Soup'? Maybe Not
For more than eight decades, an essay by J. B. S. Haldane dominated the theory of the origin of life, suggesting that a murky pond, energized by ultraviolet rays from the sun, produced the first life on earth. But that's not enough energy, and other conditions aren't met, leading a growing number of scientists to look for another answer.
Nick Lane of the University College London wrote a paper disputing Haldane's essay and offering a new theory.
"That old and familiar view won't work at all," Lane said when he released his study last year. "The energy for first life came from harnessing geochemical gradients created by mother Earth at a special kind of deep-sea hydrothermal vent, one that is riddled with tiny interconnected compartments or pores."
For four decades now scientists have been fascinated by deep ocean vents, called black smokers, that spew toxic chemicals into the sea, but still harbor strange animals, including giant tube worms. But that's not the kind of hydrothermal vent Lane was talking about.