HOW DID LIFE START ON EARTH?

by Whit Gibbons


July 23, 2006


Ecology is a lot more complex than physics or chemistry because it involves not only physical and chemical laws but also biological processes. The ecology of a species is governed by individual behavior and interactions with other plants and animals, as well as the physical and chemical environment. The added component of "life" is what makes ecology so intricate and fascinating. Maybe life was not so complicated "in the beginning," but figuring out how what happened when is anything but certain.

In an article titled “First Life” in American Scientist magazine, Michael Russell of the Scottish Universities Environmental Research Centre stated, “scientists don’t know for certain how life started.” The gist of the paper is how geochemists involved in studying earth’s mysteries 4 billion years ago are trying to find out. The refreshing part of the Russell article is that scientists don’t know (and do not claim to know) everything. But speculating on how life got started on Earth, using principles of physics, chemistry, and biology that are known today, is intriguing.

Some early facts about Earth were that it spun on its axis half a dozen times faster than it does now. A day would have been over between lunch and dinner. And the moon was thousands of miles closer, which means the everyday tides would have been like small tsunamis. Imagine the winds and waves at the beach. Spending even one of those short days on earth would have been more exciting than any amusement park ever designed.

To add to the chaos, if the geochemists are correct, the planet was being rained on constantly by enormous meteorites that vaporized when they hit the ocean and created dust clouds that blocked out the sun. The atmosphere was a thick, smoky blanket of carbon dioxide. Not a pleasant place for life to begin. And indeed the author proposes that life did not begin on Earth's surface, but far below on the ocean's floor. He suggests that warm springs at the ocean's depths would have had properties ideal to support life: protection from the sun's ultraviolet rays, a constant temperature, and a chemical makeup conducive to the creation of life.

Heated areas in the ocean are not uncommon. Deep ocean areas where molten volcanic rock encounters ultracold seawater, creating unusual physical and chemical reactions, are called hydrothermal vents. These occur where a major fissure develops between plates making up the earth's crust. As the plates gradually separate, underlying volcanic activity reaches the surface, warming the ocean at the point of entry. Hydrothermal vents in the ocean were not discovered until 1977, but the phenomenon of water being warmed by volcanic heat has been known for centuries and is seen any time someone watches Old Faithful erupt in Yellowstone National Park.

Many hydrothermal vents are too hot and have high quantities of heavy metals and other chemicals uncharacteristic of living organisms. But the warm springs hypothesized in the article would have been an excellent environment for life to develop. The chemical explanations and hypotheses are too complex to explain here (or maybe even for me to understand), but the point is that the proper mix of carbon, oxygen, hydrogen, nitrogen, and other vital elements was present to create the first nucleic acids and proteins--before actual life was present on earth.

Whether life originated in a warmwater spring heated below the ocean floor by molten volcanic rock, we will never know. Whether it originated multiple times, will also remain a mystery. In fact, barring the development of time machines that would permit a look 4 billion years before yesterday, we will presumably never know for certain exactly how first life began on earth. We are left with geochemists to speculate, based on evidence from geological records and biological events today.

Some people seem threatened, for reasons unfathomable to me, by speculation about how life began on earth and the scientific pursuit of answers to that question. I repeat: “scientists don’t know for certain how life started." Neither does anyone else. But inquiring minds are essential for any society that wants to be an enlightened one. No question should be deemed inappropriate for scientific investigation.



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