II
The first fact to be enunciated plainly, and faced, until it grows familiar, and its import is appreciated, is that, biologically speaking, Man has ceased to be a progressive species long ago. The evolutionary impetus which carried our ancestors from the level of the ape or even of the lemur, through such subhuman types asPithecanthropus, and the Heidelberg and Neanderthal men, to ‘modern’ man, seems to have spent itself by the middle of the palæolithic period,i.e.say, thirty thousand years ago. At any rate, the Cro-Magnon people of the Aurignacian age, who then appeared upon the scene, were in no wise inferior to any subsequent race of men, either in stature orin brain capacity. They average six feet three inches in height, with one-sixth more brains than the modern European. So far indeed as their physical remains can indicate, they seem to have been very definitely the finest race of human beings that has ever existed. If we have improved on them, it has probably been only in such minor matters as resistance to the microbes of the many diseases which flourish among dense populations under slum conditions. Against that probability have to be set such certainties as that our toes and many of our muscles are being atrophied and that we are getting more liable to caries and baldness.
This remarkable fact of the arrest of his biological development is certainlythe greatest mystery in the history of Man. It at once raises two further questions: In the first place, how did it happen, and what caused it? And, secondly, what has enabled man, nevertheless, to progress in other respects, in knowledge, in power, and in culture?
To answer the first question we cannot do better than argue back from what is now the most salient feature about man’s biological position, namely that his survival is determined far more by his relations to the social group to which he belongs than by personal efficiency: hence he can draw on the collective resources of his tribe, and, to a growing extent, gets emancipated from the control of natural selection. Thus social selection and the survival of societies profoundly modify (andoften defeat), the working of natural selection. The advantages are obvious; it is no longer essential for a member of a society that collectively controls the conditions of existence to develop any high degree of personal capacity, in order to survive. A single wise and provident minister, like Joseph, is enough to keep alive millions of Pharaoh’s subjects through the lean years of famine. But the inferior and incompetent survive with the rest.
Now, if we suppose that by mid-palæolithic times man had established his ascendency over nature and perfected his social organization sufficiently to render these services to his fellows, we have suggested a possible cause of the cessation of biological progress. For social influences are as likely as notto be ‘contra-selective,’ that is, to tend to preserve by preference the stocks which are less viable from a merely biological point of view. They are markedly so at present, and it would be asking too much to expect the tribal chiefs of early men to have been wise and provident enough to see to it that their social institutions were eugenical in their effects. We cannot even now find such a pitch of wisdom and providence in the controllers of our destinies.