The Aquatic Ape theory (sometimes called Homoaquaticus theory) was first proposed in the 1960’s. It wasn’t given much credibility by scientists at the time though, which meant it got very little attention by anyone. I first stumbled upon it in the early 2000’s, and it was something that I took a liking to. It seemed to answer a lot of questions for me. Even then though, it was still widely discredited by most, and I thought of it more as an idealistic but unlikely explanation for our origin. It was something I wanted to hold true, but in reality seemed unlikely to be so. Yet in recent months this Aquatic Ape theory has started to gain attention in the media, and traction in science. We have had many prominent figures in biology such as David Attenborough supporting and discussing the idea and it has made me revisit this theory. Could the Aquatic Ape theory actually have some truth to it, and if so, what does it mean about our evolutionary diet?
We as humans are very unique amongst primates. There are problems that traditional evolutionary theories don’t answer, but the Aquatic Ape theory does. This theory suggests that we as primates spent a significant amount of time adapting to a semi-aquatic lifestyle around lakes or on the coast, and it has a number of supportive arguments:
Bi-pedal movement – We are the only primates to walk upright on 2 legs, and traditional theories have somewhat struggled to explain why. This theory suggests that we started walking upright to allow us to wade into water in search of food. This is supported to some extent by the fact that baboons will happily walk on 2 legs to wade in water, and the water offers sufficient buoyancy to facilitate this.
High calorie requirements – We have an extremely highly developed brain, and it is very energy demanding. Our brain uses around 20% of our resting calorie requirements, and it is a massively resource intensive organ. In order for this to develop we would need access to a lot of calories, and the ocean nicely provides this all year round. Traditional theories point to animal fats, which of course are a great source of calories too. However, seasonal changes affect fat content and accessibility of land animals, meaning they are less consistent. There is of course no reason why we wouldn’t have taken advantage of both land and water based food sources. This would have given us the best of both worlds. There is actually evidence that early man has used stone tools to butcher large (2 meter long) catfish, which in the dry season (when land animals have very little fat), would be ready to spawn and full of important fats.
In addition to calories, we particularly need omega-3 fatty acids to develop our brain, and the best sources of these are undoubtedly marine animals.
Body fat – We are the only primates that create subcutaneous fat (essentially blubber). No other primate has this, and the only time we see this kind of fat in nature is in animals that spend lots of time in water.
Hair – We are the only primate to have lost all our body hair (aside from our heads). Hair makes wading into water, and drying off after very difficult. So if we were waders, we would have lost most of our body hair. Hair remained on our heads because it would have had virtually no impact on our ability to wade, but would have kept the sun off our heads and reduce heat loss. The total loss of body hair, except for hair on the head, is extremely rare in nature.
Breathing – We are the only primate able to hold our breath. This would be an essential adaptation for looking for food in water, but has little benefit in any other environment.
Holidays – This is really my addition to the theory, and not a serious part at all. However, I do wonder why it is that as a species we love going to the coast on holiday and why ‘paradise’ is always a warm sunny beach. Is this our inner Aquatic Ape calling us back home?
All this isn’t to say we didn’t take advantage of the land at all. We know we did. This just suggests that we may have taken more advantage of what the seas had to offer than previously thought.
What this means for nutrition
Most people agree that our modern diet should closely mimic the one we evolved with. This is the diet our genes are ‘designed’ for, and so is what our body needs. If this theory has any substance to it, then our optimal diet should have more of an emphasis on marine foods. Rather than the traditional meat and veg, perhaps we should be having more fish and seaweed? Certainly seaweeds such as kelp and various marine oils are being increasingly recognised for their importance to health, and diets based on marine animals are often considered the healthiest. Japan for example has extremely low rates of heart disease, and traditionally eat lots of fish. Now obviously there are many factors at play, but as a whole diets high in fish seem to produce positive results. Food for thought, for sure.
There are still plenty of problems with the Aquatic Ape theory, and it still isn’t widely accepted in the scientific community. Yet, some of its explanations for our pretty unique physiology do add up very nicely, and it provides some good answers to questions which have otherwise been difficult to answer with traditional evolutionary theories. Perhaps our natural diet did include more marine foods, and, perhaps, our modern diet should too.
Image courtesy of Matthlas and M Garde.