Ontogeny and Phylogeny
It is curious that through the centuries men seem to have been more interested in studying the heavens than things on Earth. Even when they did begin to investigate terrestrial matters it was the inorganic that they studied first. Exact knowledge about living creatures has come last of all among the sciences. So it has come about that Newton and his successors among physicists and chemists have usually been considered to be the only real scientists. Nor can we say that things have changed much recently. The use of high energies to break up atoms and to blow men to the moon is still acclaimed as the most fundamental form of inquiry. Man seems to have an urge to “get to the bottom of things,” to break them up, and he continually expects to find “ultimate” particles of which all are made. It may even be that there is some special property in our brains that makes it seem so obvious that such analysis is the most profound form of knowledge to which we should all aspire. Or is it the result of cultural and economic influences in the West over recent centuries?
A little thought surely makes one wonder whether this cult of analysis is really as sensible as it seems. Most of the phenomena that we meet around us are not simple things at all but highly complicated systems of interacting parts. Surely the most challenging problems are how such complexes arise and are maintained. Especially for the study of living creatures including ourselves much more than a knowledge of ultimate particles is needed. Yet it is only in the last twenty years that biology has found, through the genetic code, the means for understanding how it is possible for these enormously complicated groups of molecules to maintain their organization for millions of years. The secret is of course that each single mass of living matter is sooner or later destroyed, and then replaced by new individuals, made by embryological processes directed by a new set of instructions.
At least since Aristotle men have speculated about how a wonderfully elaborate creature can emerge from a simple little egg. In Ontogeny and Phylogeny Stephen Jay Gould traces for us the history of the two sorts of explanation of this mystery of development, solutions that depend upon two different approaches to science. If one is to believe one’s eyes the chicken is not there in the egg. Therefore some outside influence must be at work to put in the legs and eyes, the beak and the feathers and all the rest. This is the theory known as epigenesis, and to find the outside force thinkers have invented all sorts of mysterious and mystical agents. Aristotle postulated a sequence of increasingly higher “souls” that enter the human embryo, first the “nutritive,” then “sensitive,” and finally “rational,” an idea that still appeals to some religious controversialists today.
The other theory about development is preformation, which holds that one should not trust …