And God saw every thing that he had made, and, behold, it was very good. And the evening and the morning were the sixth day...Genesis 1
By Robert S. Boyd
YELLOWSTONE NATIONAL PARK, Wyo.
Scientists who are trying to figure out the origin of life on Earth are getting nearer to their goal, but they concede that they might never solve this profound mystery.
A crucial gap remains between the time when nothing was alive and the arrival of the first living creature.
Geologists recently have learned more about the conditions on our planet that could have made life possible as long as 4 billion years ago. And thanks to the DNA revolution, biologists now can trace the development of modern organisms back to primitive microbes that lived in the ocean more than 2.7 billion years ago.
At some point in between, lifeless molecules - combinations of atoms - learned to eat, breathe and reproduce.
No one is certain when and how they did it, however. "There are a lot of theories, but no solid explanation," said Tom McCollom, a geochemist at the University of Colorado in Boulder. "We may never have one."
"The rock record is too spare to allow us to determine the processes that were associated with the origin of life," Bruce Jakosky, a University of Colorado geologist, says in a forthcoming book, "Astrobiology, Science and Society." "The extremes are easy to identify and characterize - early on with no life, and later on with life - but the intermediate stages cannot be uniquely or readily categorized."
Researchers are seeking to fill this gap with a purely scientific account of the origin and evolution of life, which they say need not conflict with theological versions such as "intelligent design."
Advocates of intelligent design seize on missing pieces in the evolutionary record to support their belief that there must have been divine intervention. Scientists say a lack of some pieces of evidence does not mean that the theory of evolution is wrong.
"Everything we've done so far suggests that a natural origin of life is a very plausible event, even if we don't know yet what the sequence of events or chemical reactions was," Jakosky said in an e-mail interview.
At a workshop for science writers in Yellowstone National Park earlier this month, researchers described the latest thinking about the origin and development of life. As early as 150 million years after the Earth formed, the planet had cooled enough to have an atmosphere, an ocean and some dry land.
In this "pre-biotic stage," before living organisms appeared, volcanoes spewed lava and gases. Chemical reactions between hot water and rocks produced more and more complex molecules.
Later, these inorganic molecules grew and clotted together in "protocells." They formed organic compounds necessary for life.
At some point came the crucial, still-unexplained step: the advance from clumps of molecules to living cells containing an early version of DNA known as RNA. DNA contains the instructions to make proteins, the building blocks of every living thing.