Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization

First Edition

© 1975-1979, 2008 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization, First Edition, Xenology Research Institute, Sacramento, CA, 1979; http://www.xenology.info/Xeno.htm


Chapter 8.  Exotic Biochemistries


"OXYGEN: An intensely habit-forming accumulative toxic substance. As little as one breath is known to produce a life-long addiction to the gas, which addiction invariably ends in death. In high concentration, it causes death quickly, but even in a 20% dilution few survive more than 0.8 century."
          -- Anonymous (1956)199

"An exotic biochemistry based on silicon is basically a comic-book idea."
          -- Dr. Norman Horowitz (1966)730

"Suppose that in the early days of our own planet, when life was first forming in the primordial ocean, a thousand different schemes of life set sail. Let us further assume that one particular scheme won out over the rest, perhaps through the sheerest chance. The survival of that one scheme could now give us the false impression that it is the inevitable and only possible scheme."
          -- Dr. Isaac Asimov (1967)96

"E.M. Hafner: Do you know of any program of experimentation in your laboratory or in any other laboratory that is aimed at discovering forms of life that are not carbon-based?
G. Levin: In my laboratory? No!"
          -- from Exobiology: The Search for Extraterrestrial Life (1969)630

"Indigenous alien life would not have to be like ours. In fact, it would be rather strange if it were. Our life is ideally adapted to terrestrial conditions, and it would show a surprising luck if other planets with widely different conditions had life based on the identical design."
          -- Dr. Peter M. Molton (1973)1129

"Fomor is a relatively small planet with almost no atmosphere and few interesting features. It does, however, possess several fungi which are biologically related to other fungi found in the Trans-Coalsack Sector, and their manner of transmission to Fomor has stimulated an endless controversy in the Journal of the Imperial Society of Xenobiologists...
          -- Larry Niven, Jerry Pournelle, from The Mote in God’s Eye (1974)668



In the previous chapter, we asked the question: What is the likelihood that life may evolve somewhere else in the universe? We answered by showing that, given a primitive environment similar to that of ancient Earth, some form of proteinous life is not unreasonable.

But how deterministic are the processes that occurred on this planet four eons ago? What are the chances that life must follow the identical biochemical pathways taken by organisms on Earth? It is the principle aim of xenobiology to ascertain where life exists in the universe, and what form it takes.

At first glance, the Hypothesis of Mediocrity might seem to rule out the possibility of alternative life biochemistries. There are no silicon beasts or chlorine-breathers present on this world, ergo natural selection does not favor them and they cannot exist.

This is, however, an incredibly chauvinistic argument. The only rigorous conclusion that can be drawn from the lack of exotic biochemistries on Earth is that contemporary conditions do not favor those other systems. Since a rich diversity of habitats is possible in the Galaxy, peculiar life chemistries cannot be categorically ruled out.

Life adapts itself to its environment. Change the environment, and the nature of life itself will change. It may be that no negentropic life-system can arise spontaneously under non-Earthlike conditions, but it is poor science to tie one’s hands with this assumption from the outset. Owing to the unique adaptivity of living things, the Hypothesis of Mediocrity must be applied cautiously when we venture out into new environs.

Experimental investigations have brought to light new facts which appear to indicate that significant variations on terran biochemistry are possible -- even probable -- on other planets.

[Note: See also the author's article "Xenobiology", published in 1981.]


Last updated on 6 December 2008