• Posted: Jul 19, 2008 14:45:04
• Comments Welcome
• Vote CoolPhotoblogs
• Purchase a Print
The question "How did life begin?" has brought forth many widely varying answers across most of Earth's historical cultures. Anthropologists gather the many stories together under the heading "Creation Myths." All the stories have provenance. None have proof.
Within scientific circles, the question has been considered too. But so far no clearly demonstrable theory has been put forth. The assumption has been that life began on the molecular level, either in outer space or here on Earth in the early atmosphere and oceans. The fact that most living things are made up primarily of water, and salty water at that, would seem to suggest beginnings in the sea. But in the early 1950's, chemists Stanley L. Miller and Harold C. Urey tried to recreate the atmospheric conditions of the early Earth in a sealed glass container to which they added the occasional bolt of lightening in the form of an electrical spark. After several weeks they observed an oily film building up on the inside of their flask. When analyzed they found that film to be made up of amino-acids and other simple biochemicals, the exact molecular building blocks of DNA and cellular proteins.
That experiment has been replicated many times with varying mixtures of water and gases, all with similar results. But how to get from these very simple biochemicals falling from the early atmosphere to the complex molecules of DNA and proteins and from there to cellular structures and higher organisms is a mystery that has not yet been solved. One theory holds that more complex bio-molecules did in deed form in the sea, but using a mineral template such as the surface of clay. However, experiments along these lines have not yielded clear results. Interestingly, a new version of the mineral template theory has been put forward recently by Helen Hansma of UC Santa Barbara. She suggests the mineral template wasn't clay, but mica.
Safe and secure between the thin layers of mica is where she envisions complex biochemicals first formed on the early Earth. Mica has an affinity for water, meaning it will suck seawater in between its layers. Mica layers are also separated and held together by atoms of potassium. Potassium is an important constituent within the cellular biochemistry of complex organisms. And probably most compelling, the half nanometer spacing of mica molecules exactly matches the half nanometer spacing of amino-acids in DNA and other complex proteins.
So far this is an untested theory, but one that seems to hold considerable promise. By coincidence, some of the oldest most primitive cellular fossils found so far on Earth have been found in Greenland amidst some of the oldest mica deposits on Earth.
Many steps remain to be explained between the simple biochemicals of the Miller-Urey experiment and the complex multicellular organisms we call life. Free floating lipids tend to naturally coalesce into tiny spheres, just the size of living cells. Very simple viruses are capable of penetrating cell walls to add new and novel sections of DNA to already growing strands within. Cells of different specialization have been observed to group into colonies that offer mutually increased survival benefits. So on and so on up the ladder of evolving complexity. Remarkably, only a few basic rules known to physics and chemistry would seem to allow the orderly blossoming of the huge variety of living creatures we witness on Earth today. If we could but see the underlying simplicity, the miraculous unfurling of an iris in the summer rain would perhaps not seem so mystically mysterious.
Friday, June 6th, 2008
69.5 mm 329 mm