Evolutionary psychology, fertility and economic ambition

Since the time of Darwin, the same evolutionary psychology debates have played out over and over. Here is Ronald A. Fisher in The Genetical Theory of Natural Selection (1930), addressing the type of argument that you can still hear today about the evolution of the human mind:

[I]t is often felt to be derogatory to human nature, and especially to such attributes as man most highly values — as if I had said that the human brain was not more important than the trunk of an elephant, or as if I had said that it ought not to be more important to us, if only we were as rational as we should be. These statements would be unnecessarily provocative: in addition they are scientifically void. And lest there should be any doubt upon a matter, which does not in the least concern science, I may add that, being a man myself, I have never had the least doubt as to the importance of the human race, of their mental and moral characteristics, and in particular of human intellect, honour, love, generosity and saintliness, wherever these precious qualities may be recognized. … [N]atural causation … introduces the strongest motive for striving to know, as accurately and distinctly as possible, in what ways natural causes have acted in their evolutionary upbuilding, and do now act in making them more or less abundant.

Less played out today are Fisher’s concerns about the direction of the selective forces acting upon our mental traits. Consider the interaction between the desire for economic acquisition and fertility, for which Fisher appears equivocal about which way the selective pressures might be acting. First he notes that those with economics ambition tend to curtail their fertility:

Parents in whom economic ambition is strong, will, in like circumstances, be more inclined to limit their families than those in whom it is weak. Consequently a progressive weakening of the economic ambition, or at least in the average intensity with which this motive is felt among the great body of citizens, is to be expected as a concomitant to the strengthening of the moral aversion towards family limitation.

But where there is potential for famine, economic ambition is required to survive.

The attitude of men and women towards their economic welfare cannot, however, be ordinarily reduced by this cause to indifference, for in countries in which the poorest class are frequently decimated by famine, it is apparent that a stage will be reached at which what is gained in the birth-rate is lost in the death-rate; and even where the extremes of distress are ordinarily avoided, some loss of civil liberty, and of the opportunities for reproduction, has been the common effect of indigence.

And even in developed countries, acquisitive impulses may be required.

Moreover the rational pursuit of economic advantage must, even in the most civilized countries, frequently place the individual in a position favourable to normal reproduction. It would, apparently, in most societies, be as disastrous to the biological prospects of the individual to lack entirely the acquisitive instincts as to lack the primary impulses of sex, notwithstanding that the abuse of either passion must meet with counter-selection. The moral attitude of civilized peoples towards money, as towards sex, must be therefore the product of much more complicated evolutionary forces than is his attitude towards infanticide or feticide, as might perhaps be inferred from the hypocrisy and fanaticism, the passions and the passionate inhibitions, found among long-civilized peoples on both subjects.

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