Life on Earth 'began on a radioactive beach'
By Nic Fleming, Science Correspondent
Last Updated: 6:01pm GMT 09/01/2008
Life on Earth began on a radioactive beach, a scientist claimed today.
The sifting and collection of radioactive material by powerful tides could have generated the complex molecules that led to the evolution of carbon-based life forms - including plants, animals and humans.
While radiation may seem an unlikely candidate to kick-start life because it breaks chemical bonds and splits large molecules, it also crucially provides chemical energy needed to generate some of the basic building blocks of life.
Zachary Adam, an astrobiologist at the University of Washington in Seattle, has suggested the collection of radioactive material on a beach as a new theory for the origins of life - to be added to the existing long and varied list of hypotheses.
One is its emergence from a "primordial soup" of simple organic chemicals accumulated on the surface of bodies of water within the hydrogen-rich early atmosphere - formulated in the 1920's by English geneticist J. B. S. Haldane and Russian biochemist Alexander Oparin.
Others include early life forming in inorganic clay, the initial energy coming not from chemical reactions but from sunlight or lightening and the arrival of microscopic seeds of terrestrial life on chunks of meteorites or comets, and the intervention of a divine, intelligent designer.
In work highlighted in this week's New Scientist magazine, Mr Adam suggests the more powerful tides generated by the moon's closer orbit billions of years ago compared to today could have sorted radioactive material from other sediment.
According to his computer models,deposits could collect at a beach's high tide mark in sufficient quantity to trigger the self-sustaining fission reactions - as occur in natural seams of uranium.
Mr Adam demonstrated in laboratory experiments that such a deposit could produce the chemical energy to generate some of the molecules in water which produce amino acids and sugars - key building blocks of life - when irradiated.
A deposit of a radioactive material called monazite would also release soluble phosphate, another important ingredient for life, into the gaps between sand grains - making it accessible to react in water.
Mr Adam told the New Scientist: "Amino acids, sugars and [soluble] phosphate can all be produced simultaneously in a radioactive beach environment."