The Aquatic Ape Theory: Why Aren’t We Hairy and Other Questions Answered (Kind Of).

Adam explores a theory on human evolution and our relationship with water.

Whenever the weather gets even moderately nice in the UK, you will surely bear witness to great migration. Man, woman, and child from all walks of life head to the country’s beaches. Swimwear and sun lotion, sandcastles and rock pools. Why are we pulled to the world’s sandy beaches and seas – and why do we only have hair on our heads?

In 1960 Sir Alister Hardy, a marine biologist from Oxford, proposed the aquatic ape hypothesis. Humans naturally form a layer of subcutaneous fat under their skin which apes do not. Hardy realised that this sounded like the blubber of marine mammals and believed that perhaps we have a more aquatic ancestry than previously believed.

The theory is that ancestors of human beings survived on the coasts and lived a semi-aquatic lifestyle. That we hunted and gathered on the shores and not the sprawling plains of Africa.

The theory aims to explain many unanswered questions and unknown phenomena about our anatomy.

Let’s start with the obvious – why don’t we have any fur? We are the only primates without it and one of only a few other mammals. The most common hairless mammals are cetaceans or as we know them: whales, porpoises, and dolphins. You also have walruses, seals and hippos which are all semiaquatic or fully aquatic animals. But Adam, I hear you ask, what about elephants or rhinos?! THEY don’t live in the sea! And you’re right, they don’t (smarty pants). And guess what, this is my article and I’m ignoring you. It actually only makes sense for an animal that spends a lot of its time in water to be fur-less so it can swim more efficiently. But why hair on our heads then? To stop our heads getting burnt, of course.



Why do we walk on two legs? Hardy believed that we began walking on two legs to wade in water and that our natural buoyancy helped keep us stable. This meant people could travel further into water without having to dunk their heads underwater. Other apes can be observed doing this very thing – quadruped on ground, biped in the water.

If I got a baby ape and baby human and chucked them both in some water, what do you think would happen? The baby ape would drown, swallowing the water and sinking. The baby human, on the other hand, would instinctively hold its breath and float on the surface. Humans have this innate ability to hold their breath when underwater that no other primates possess.



Now it’s time for every free diver’s (someone who dives without breathing apparatus) favourite reflex: the mammalian diving reflex. Basically, if you stick your face in cold water, a series of physiological responses occur. Your heart rate slows down and blood is restricted from your limbs and all organs except your heart, brain and lungs. It even makes your spleen release all the extra blood cells it’s got stored in it. This allows you to hold your breath for a longer period of time and this reflex is found in aquatic mammalsand birds that are likely to dive for fish. And you! How strange.

Those are a few of the main big anomalies this theory explains. I haven’t even mentioned that we have a weird downward facing nose to stop water getting in it. Or our subcutaneous “blubber” we have. Or the Moken people of Thailand who can literally focus their eyes underwater so everything’s not super blurry. Or the Vernix caseoa: a white, creamy, naturally occurring biofilm that covers babies when they’re born, which happens to be similar in composition to the biofilm that covers baby seals when they’re born too.



Unfortunately, as much fun as the aquatic ape theory is, it is not widely accepted. It allegedly lacks in empirical evidence. In fact, Alice Roberts, biological anthropologist, biologist, television presenter and author (famed for books such as The Incredible Unlikeliness of Being), wrote a scathing article in return to Sir David Attenborough’s podcast in which he supports the hypothesis. In Roberts’ article, she argues that when the idea was been tested against the hard evidence of fossils, comparative anatomy and physiology, and genetics, it failed – again and again.

It’s hard for me to argue with an expert in her field, so it’s very likely this theory doesn’t have any weight whatsoever. Oh well, it was fun while it lasted.

Regardless, I personally like the idea that we are so drawn to the sea for a reason, chasing some ancient part of us far lost in this modern age. Somewhere inside us, written into our brains like family initials in the foundation of an old but once new home.

Or we just chased bison off cliffs, I guess. That’s kind of cool.



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