Were We Planted Here?

After winning the Nobel Prize for helping to discover the structure of DNA, the master molecule of life, what does a scientist like Francis Crick do for an encore? He tackles something even bigger. With Leslie Orgel, of California's Salk Institute, Crick has now taken on the mystery of the origin of life. Writing in Icarus, a monthly devoted to studies of the solar system, the two scientists theorize that life on earth may have sprung from tiny organisms from a distant planet--sent here by spaceship as part of a deliberate act of seeding.

This bizarre-sounding theory, called "directed panspermia"* by its authors, results partly from uneasiness among scientists over current explanations about how life arose spontaneously on earth. Crick and Orgel note, for example, that the element molybdenum plays a key role in many enzymatic reactions that are important to life. Yet molybdenum is a rare element, much less abundant than, say, chromium or nickel --which are relatively unimportant in biochemical reactions. Thus, because the chemical composition of organisms "must reflect to some extent the composition of the environment in which they evolved," the authors suggest that earth life could have begun on a planet where molybdenum is more abundant.

Crick and Orgel also ask why there is only one genetic code for terrestrial life. If creatures sprang to life in some great "primeval soup," as many biologists believe, it is surprising that organisms with a number of different codes do not exist. In fact, Crick and Orgel say, the existence of a single code seems to be entirely compatible with the notion that all life descended from a single instance of directed panspermia.

The seeding of terrestrial life could have been carried out by a civilization that was only slightly more advanced than man is now. In fact, Crick and Orgel estimate, man within a few decades will have nuclear rocket engines that would enable him to conduct a little panspermia of his own. Using such rockets, it would be possible to reach planets orbiting around any of thousands of stars with spacecraft carrying microorganisms, such as dormant algae and bacterial spores. Suitably protected and maintained at temperatures close to absolute zero, the organisms could be kept alive for a million years or more.

Why would man, or some distant intelligent beings, ever launch a panspermia project? To demonstrate technological capability, say Crick and Orgel--or, more probably, out of "some form of missionary zeal." ^

* From the "panspermia" theory of Swedish Chemist Svante Arrhenius, who suggested in 1908 that living cells floated haphazardly through the universe, bringing life to desolate planets.

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