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Paul Turke
Paul W Turke

We've Been Designed to Reproduce

Thwarting evolved design has consequences, good and bad.

Like all organisms, we are bundles of adaptations that each have local jobs. But all of these jobs have been subservient, under selection, to the goal of reproduction. In other words, ultimately, we have been designed to reproduce, and that’s it—yet more and more people are choosing not to reproduce. How can this behavior be explained?

Before proposing an answer, let’s briefly consider some other organisms in which aspects of their design are known to lead them ‘off-track,’ under some circumstances, with respect to reproductive outcome. Moths endlessly circling outdoor electric lights is a well-worn example, and one that apparently results because moth navigation mechanisms evolved under the expectation that the sun and moon are pretty much it when it comes to lighting. Brood parasitism, by birds such as cuckoos and cowbirds, is another example. It leads to off-track behavior by the unsuspecting parent that devotes itself to rearing the chick of the parasitic species. The deception works because in the overwhelming majority of instances the rule, ‘feed the chicks that hatch from eggs in your nest,’ has proven to be adaptive.

Now let’s return to the question I started with. Why are behaviors that contravene our ultimate design becoming increasingly common, particularly in the most economically developed regions of the world?

As in moths and birds, the answer lies in understanding the mechanisms that evolved to guide us to a reproductive outcome. Consider the simple example of hunger. Upon awakening in the morning, blood sugar sensors conspire with stretch receptors in the stomach to lead us on a search for a meal. If we go without for a day or two, finding something to eat becomes imperative. Contrast this with the desire to have children. While many of us are fond of children, and contemplate eventually making some, rarely, I think, has that contemplation rivaled the conscious intention and effort we regularly devote to keeping our stomachs full.

This hierarchy of concerns exists, I suspect, because there would not have been strong selection over the course of hominid evolution for being consciously obsessed with making babies, mainly because evolving a desire to do three other things—acquire resources (including food), find a mate(s), and have sex—would have reliably led to babies; and if we add a strong sense of wanting to provide for them once made, we have what would have been the essential ingredients for achieving reproductive success—until recently. And so, for these reasons, it is easy for us to become distracted from what natural selection, ultimately, has designed us to do.

What are the normative consequences that arise from our distraction? I suspect that some are good, but not all. On the good side, a slowdown in human population growth can be expected to be ecologically beneficial in many respects. Also, some components of health, particularly women’s health, are improved by choosing not to reproduce (e.g., pregnancy and giving birth both entail risk).

On the other side of the ledger, reproducing early and often, along with breastfeeding, appears to be protective for breast, ovarian, and endometrial cancers. But there is a broader issue—one that I think manifests regularly, though often distally, in both women and men as a result of forgoing reproduction. I am referring to sadness, and its opposite, happiness, which both seem to rest heavily on the extent of satisfaction we get from our cumulative accomplishments. But, as you might guess, not all accomplishments are likely to have been weighted equally by natural selection over the long run of our evolution.

As already mentioned, once a baby is produced there usually is a very strong desire to care for it and see it prosper, and there are undoubtedly many mechanisms that have evolved to prod and guide us to this outcome. Most are emotional, and I think are designed to instantiate a sense of purpose and fulfillment. And although it is unlikely that we have evolved a strong conscious desire to reproduce, I believe that it is nearly certain that we have evolved to derive satisfaction from doing a good job rearing children, grandchildren, and other (mostly younger) dependent children. How can I be so certain? Well, mostly because helping our young dependents to thrive is very hard work, and if the feelings associated with doing it were more negative than positive, we wouldn’t bother. Thus, by design, positive outweighs negative.

As for evidence, studies looking for an association between reproduction and satisfaction/happiness over the course of lifetimes are few, at least in part because mental health professionals have largely failed to recognize the importance of connecting these particular dots, and they have done so largely because they practice their craft without input from what is known of our evolution. There is, however, one very recent study (by Tanskanen, Danielsbacka, Coall, and Jokela) that is an exception. It finds in an elderly European population that helpful grandparents tend to be happy, satisfied grandparents.

Elsewhere, I have suggested that prospects for achieving a happy life through helping dependent relatives has been diminished by the fact that we have largely abandoned the kinship societies that we evolved in.

Today, our children and grandchildren, if we even have them, often live far away, and this limits our interaction. Therefore, instead of setting ourselves up for a lifetime of helping our children, grandchildren, nephews, nieces, and so on, many of us have chosen to focus on (also evolved) secondary proximate goals, such as accumulating resources, and seeking sexual relationships. In other words, to our overall detriment, we seem to be over-revving some of our local adaptations, and it’s not making us very happy in the long run. We should moderate.

As a child, I remember watching a television commercial for a particular brand of margarine in which, in a booming female voice, we are warned that “It’s not nice to fool mother nature.” The trans-fat debacle that is margarine attests to the truth of that claim, but there’s a caveat to add. Although an understanding of evolution can offer valuable guidance (as it should have, re the admonition to replace butter with trans-fat-laden margarine), it’s important to recognize that evolutionary theory is descriptive, not prescriptive. In other words, you are in charge, so make babies if you choose to (or not).



1. Evolution of Hormonal Mechanisms for Human Family Relationships.
Heather Habecker, Mark V. Flinn. In Handbook of Cognitive Archaeology
Psychology in Prehistory, 2019. Edited by Tracy B. Henley, Matt J. Rossano, Edward P. Kardas

2. Evol Psychol. 2019 Jul-Sep;17(3):1474704919875948. doi: 10.1177/1474704919875948.
Transition to Grandparenthood and Subjective Well-Being in Older Europeans: A Within-Person Investigation Using Longitudinal Data. Tanskanen, AO, Danielsbacka M, Coall DA, Jokela M.


About the Author
Paul Turke

Paul Turke is an anthropologist and Darwinian pediatrician.

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