This is a classic article from 快猫短视频鈥檚 archive, republished as part of our 50th anniversary celebrations
The new genes which enable animals and plants to evolve on Earth may come from outer space. So speculated Sir Fred Hoyle last Monday evening while delivering the first Milne Lecture at Oxford. Sir Fred was enlarging upon the theory which he expounded with Professor Chandra Wickramasinghe last November. This theory advances the idea that life did not originate on Earth itself but, rather, on comets which can provide a more suitable environment. Periodic approaches of life-bearing comets to the Sun would have released ice-bound and freeze-dried cells 鈥渓ike the scattering of seeds鈥� to drift down on to the Earth鈥檚 surface.
Today, the two astronomers suggested, we see the diminished remnants of this process as outbreaks of epidemic diseases caused by the showering down on our planet of viruses and bacteria which have evolved away out in space.
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Sir Fred emphasised that existing terrestrial theories of the origin of life are highly unsatisfactory for sound chemical reasons. However, we do know that at least the precursors to life鈥檚 large molecules occur abundantly in certain parts of space. Infrared spectra of such objects as the Horse鈥檚 Head nebula imply that interstellar clouds there could be rich in organic material.
Hoyle believes that organic molecules in the Solar System, at the distance of Uranus or Neptune, became concentrated on icy comets by what he calls a 鈥渃ontact sweeping鈥� process. After about one-tenth of the Solar System鈥檚 life, he says, there may well have been around a million million of these comets bigger than 10 kilometres in size, layered to a depth of about 1 km with a shell of organic matter. The heat produced by collisions would eventually melt the icy interface between shell and underlying comet to form vast life-synthesising laboratories 鈥� in striking contrast to what Darwin envisaged as 鈥渨arm little ponds鈥�. The life-generating process was thus well insulated and physically protected from the outside world by the thick outer layer of organic material.
Sir Fred sees no obstacle to prevent at least some of the multitude of comets from eventually reaching the Earth鈥檚 surface safely. Once there they would have to live cannibalistically, or on carrion of their own kind, until they had learned the trick of photosynthesis.
One strength of the theory is that it could, in principle, explain many of the baffling epidemiological conundrums. Sir Fred expanded on this theme, pointing out many anomalies in the distribution and spread of the 1918 and 1968/69 flu epidemics, and concluding that simple person-to-person spreading was not, whereas the atmospheric dispersion of a space-borne agent was, an adequate explanation.
In conclusion Sir Fred produced a biological argument which many will undoubtedly find bizarre. The established biologists ask why extraterrestrial bacteria or viruses should attack terrestrial life forms. Sir Fred counters: 鈥淚sn鈥檛 it equally remarkable that, with all the time since Creation, terrestrial life hasn鈥檛 evolved some totally effective blanket immunity to all pathogens?鈥� Viruses appear to him to be particularly vulnerable and their host cells often 鈥渄eliberately suicidal鈥� in allowing themselves to be infected. Why is this?
His answer is ingenious, if perhaps fallible. Complex life forms, he says, during evolution have gained an average of about one new gene every 1000 years. It is by now well known that the so-called transforming viruses can insert bits of their DNA 鈥� new genes 鈥� into their hosts鈥� DNA. Some biologists believe this to be an important mechanism in evolution. If there were total immunity to all pathogens it would not be possible 鈥� and, speculates Hoyle, there could be no evolution. On Sir Fred and Wickramasinghe鈥檚 theory these new genes come from cometary viruses.
First published in 快猫短视频 on 19 January 1978
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