Nurturing offspring is then a form of “maternal instinct”, as distinct from “baby fever”. This is often, but not exclusively, undertaken by the mother. In many cases, successful reproduction requires care of the developing offspring. Indeed, most cultures express more than a passing interest in sex – from the widespread inclusion of fertility rites in ancient societies to the almost unseemly obsession with sex in contemporary television advertising campaigns. Clothing, for example, allows us to inhabit cold environments unsuitable even for naturists. But culture and technology have immunised humans from many selection pressures. It’s an impressive example of human behaviour defying biological evolution. But there may be little opportunity for selection to act on their personal choice. My guess is that childless women aren’t necessarily sexually inactive – as natural selection likely dictates. And a survey of more than 7,000 Australian women between 22 and 27 years found nearly 10% didn’t want children. There are many women in our society who aren’t interested in having children.įor instance, the number of US women between 34 and 44 who have never had children has increased by around 10% since 1976. Through the contraceptive pill, humans have defied biology. So in terms of biological evolution, a genetic preference for sexual activity is no longer equivalent to a maternal (or paternal) instinct to have offspring. With varying reliability, humans can now have sex without having babies. The discovery of contraceptive technology severed that nexus for one species.
Until recently, sex and reproduction were inextricably entwined in all organisms. So, like many other aspects of human behaviour, it remains unclear whether the strong longing for a child – “baby fever” – is driven by our genes or is a social construction. We are notoriously susceptible to the influence of others (witness the broad success of advertising and, one hopes, education). For instance, studies that looked at the age of first attempt to have a child in Finnish populations showed children had similar patterns to those of their parents.īut these only proved there is a genetic influence for when women decided to have a child, rather than whether they decided to at all. There is some evidence that fertility decisions may have a genetic basis. Some argue the so-called “biological clock”, triggering an enhanced awareness of reproduction among childless women in their 30s, is natural selection at work. In other words, a genetic disposition to avoid sex will neither become established nor maintained. These sexually inactive individuals will not produce offspring, so there will be no sexually inactive individuals in the next generation. Now introduce into this population those genetically predisposed to be sexually inactive. This would determine their reproductive success. Imagine a population of people or animals who enjoy sex, where that enjoyment has a genetic basis. This is a self-evident feature of the evolutionary process. It remains unclear whether the strong longing for a child, otherwise known as ‘baby fever’, is driven by our genes or is a social construction.
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