Do animals know that intercourse results in young children?

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I have only vague memories of school sex education lessons. But I’m fairly confident that at no point did it occur to me to ask a basic question: how did anyone ever figure this stuff out?

Some of our actions have near-instant consequences. Even young children learn for themselves that drinking water is a great way to quench your thirst. But sex doesn’t immediately lead to babies. It generally takes weeks to even register a pregnancy. Months pass before the act of childbirth.

In all of the world’s human societies, there is a strong understanding that sex makes babies. But it presumably required careful observation, deep thinking and an ability to reliably and accurately track the passage of time for ancient people to make the link between the two. It may also have required language so that individuals could discuss and refine their ideas.

And this brings us to non-human animals. Given that no other animal species has our capacity for language and abstract reasoning, do any of the rest of them understand where babies come from?

Holly Dunsworth, a biological anthropologist at the University of Rhode Island, is convinced they don’t. If she’s correct, it means we’ve completely misunderstood key aspects of animal behaviour.

Consider, for instance, a situation in which a young male lion deposes the pride’s alpha male. Shortly after his victory, the new alpha may systematically kill all of the cubs in what is now “his” pride – and we think we know why. As TV documentary narrators explain, the young male is making sure that “he won’t be wasting his time protecting cubs that aren’t his own”.

Biologists, too, sometimes use similar language. A 2016 research paper exploring male parental care among mammals states that some species – the American beaver, for example – will help care for offspring, but that such behaviour is most likely to evolve “when males gain greater certainty of paternity”.

The implications here are that these animals recognise that sex leads to babies, and they have some sense of whether or not they were the progenitor of the infants they encounter.

Dunsworth has spent several years exploring why we use this sort of language when we talk about animals. Eventually, she concluded we do so simply because it is the way we, as humans, think – and we assume it’s the way non-human animals think, too. But, as she told me when I discussed the idea with her recently, there is simply no strong evidence that any other animal species understands the link between sex and babies. They lack what Dunsworth has dubbed our “reproductive consciousness”.

“It’s such a profound idea that it changes everything, to my mind,” says Dunsworth. Viewed this way, not only does a male lion lack the mental capacity to understand whether or not he is the father of a cub, he almost certainly does not comprehend that the world contains such a thing as “fathers”.

Dunsworth has written a couple of lengthy popular articles exploring the implications of her idea – this one, published by Aeon in 2017, is a must-read – but she says the feedback she has received from colleagues and from non-scientists has been mixed.

“When you say animals don’t know that sex makes babies, people are offended on behalf of the animals of the world,” she says.

Another common response from critics, says Dunsworth, is that animals must be aware of the link between sex and reproduction or they wouldn’t bother to have sex at all – and alpha males wouldn’t go to the trouble of killing infants. But she says it’s easy to come up with more neutral explanations for these behaviours.

For instance, animals with a strong sex drive are more likely to reproduce than animals with a weaker sex drive. It is not unreasonable to assume that this behavioural trait is heritable, so it’s perfectly possible for animals to have evolved an urge to have sex while possessing no understanding of the role sex plays in reproduction.

Likewise, a male lion who kills cubs shortly after he has assumed control of a pride may ultimately boost his odds of passing on his genes by doing so. This might provide enough selective pressure to favour cub-killing male lions. It’s simply not necessary for us to assume that the lion understands anything about the paternity of the cubs.

Once you adopt this line of thinking, it’s easy to come up with other ways in which animal behaviour can be misconstrued. As I’m typing, my pet cat is sitting in her cat bed and carefully washing her fur. Humans know that good personal hygiene can keep us healthy – but it seems unlikely that my cat grooms herself because she, too, is aware of the link.

Dunsworth’s idea raises all sorts of implications for understanding human evolution, both biological and cultural. But a point she is particularly keen to make is that her work emphasises the enormous cognitive gulf between humans and other animals. Over the past few decades, there has been a trend in science encouraging us to accept that we are nowhere near as cognitively unique as we once thought. We’re told fish seem to be able to count, monkeys are adept at using stone tools and bees can play golf.

This research has encouraged some commentators to take a dim view of our species, says Dunsworth, and claim we’re really nothing special at all. “It’s so strange to see that idea in print,” she says. Our reproductive consciousness can help us recognise just how different we are.

Dunsworth argues that doing so actually helps us better understand and appreciate non-human animals. We do them no favours by lazily anthropomorphising them. “They’re not just furry little humans,” she says. The natural world is far more interesting when we accept that it is inhabited by animals that have their own ways of thinking.