Psychologist David Barash makes a welcome, and very overdue, point in an interesting Op-Ed in the LA Times: the well-documented decline in birthrate, and the rise in voluntary childlessness in Western cultures, not only does not conflict with a theorized evolutionary-psychological drive to reproduction, but is an expression of the fundamental freedom from evolutionary pressures that gives human nature its unique qualities.

In traditional evolutionary theory, reproductive success is all; those who die with the most kids win. Evolutionary psychology and sociobiology put this in more complicated perspective - altruism, kin selection, and all that - but it was still understood that getting your gametes over the hump, as it were, was the goal of life. This makes voluntarily non-reproductive lifestyles - whether homosexuality, delayed reproduction (with its risk of failure), or plain “childlessness by choice” - seem positively unnatural, and thus, in the naive fallacious naturalism that so often characterizes the right wing, that much more immoral. “Contracepting”, or not having kids by whatever means, becomes not merely religiously irritating to those of the familiarly thin skin, but somehow perverse, an attack on the species imperative to survive and prevail. Or so it may seem.

Barash defends sex for its own sake (a stance the more pathetic for its boldness in this benighted day):

For more than 99.99% of their evolutionary history, humans haven’t had the luxury of deciding whether to reproduce: simply engaging in sex took care of that, just as eating solved the problem of nutrition. But then something quite wonderful arrived on the scene: birth control. Because of it, women (and men) can exercise choice and, if they wish, save themselves the pain, risk and inconvenience of childbearing and child-rearing, indulging themselves rather than their genetic posterity.

Yes, indeed.

Barash’s point is that human psychology (he uses the term “free will”, but let’s leave the philosophical controversy over that issue out of this) transcends evolutionary drives, and indeed most biological programming. Humans can determine how much they personally value different ends, and this may result in devaluing ends that would otherwise contribute to evolutionary fitness. (There is no personal payoff in being evolutionarily successful; your children, and arguably your species, benefit from your contributing your successful genes, but the end is the same for you personally in any case. It’s up to you whether the fitness of future generations is worth devoting your life to.) Some choose not to have children, but that in no way violates any kind of biological - still less moral - obligation. Our psychology - with its contesting drives and values - is as much a part of our nature as (arguably more so than) our evolutionary history. Choosing non-reproductive strategies is natural; it springs from the part of humans’ nature that allows them to reflect on and choose among potential ends.

If reproduction is perhaps the fundamental imperative of natural selection, of our genetic heritage, isn’t it curious — indeed, counterintuitive — that people choose, and in such large numbers, to refrain from participating in life’s most pressing event?

The answer is that intentional childlessness is indeed curious — but in no way surprising. It is also illuminating, because it sheds light on what is perhaps the most notable hallmark of the human species: the ability to say no — not just to a bad idea, an illegal order or a wayward pet but to our own genes.

When it comes to human behavior, there are actually very few genetic dictates. Our hearts insist on beating, our lungs breathing, our kidneys filtering and so forth, but these internal-organ functions are hardly “behavior” in a meaningful sense. As for more complex activities, evolution whispers within us. It does not shout orders.

People are inclined to eat when hungry, sleep when tired and have sex when aroused. But in most cases, we remain capable of declining, endowed as we are with that old bugaboo, free will. . . .

When it comes to our behavior, evolution is clearly influential. Of this there can be no doubt. But only rarely is it determinative, even when something as deeply biological as reproduction is concerned. Indeed, the trend toward childlessness is neither particularly German nor strangely “un-biological” but profoundly human.

That’s a helpful message at a time when so much conservative social policy-making is being promulgated with potted pseudo-scientific justifications (gay parents will warp their adopted children; gay marriages will undermine the entire structure of society; contraception destroys the natural urge to protect life; abortion causes invisible psychological traumas . . .). Aside from the issue of sex, the entire notion of value-based choicemaking as both an expression of natural, and fundamental, human capacities, and as a counter to speculative assertions of biological constraints on acceptable human lifestyles, is a much-needed corrective.

The existential ground of human nature - that our existence does not dictate our essence - the escape to freedom that we achieved in evolving that big brain - is both a triumph of human evolution and the most fundamental feature of our nature. We need to hold on to it against those who deny its existence and seek to return us to biological straitjackets of their devising. And it wouldn’t hurt to have a little carefree sex along the way.