April 16, 2012
A New Aquatic Ape Theory
A gorilla in the Congo wading in a swamp. Image courtesy of Wikicommons
The aquatic ape theory, now largely dismissed, tries to explain the origins of many of humankind’s unique traits. Popularized in the 1970s and 1980s by writer Elaine Morgan, the theory suggests that early hominids lived in water at least part of the time. This aquatic lifestyle supposedly accounts for our hairless bodies, which made us more streamlined for swimming and diving; our upright, two-legged walking, which made wading easier; and our layers of subcutaneous fat, which made us better insulated in water (think whale blubber). The theory even links an aquatic existence to the evolution of human speech.
The hypothesis was met with so much criticism that it’s not even mentioned in human evolution textbooks. But that doesn’t mean aquatic habitats didn’t play some kind of role in our ancestors’ lives.
In 2009, Richard Wrangham of Harvard University and colleagues suggested in the American Journal of Physical Anthropology (PDF) that shallow aquatic habitats allowed hominids to thrive in savannas, enabling our ancestors to move from tropical forests to open grasslands.
About 2.5 million to 1.4 million years ago, when the genus Homo emerged, Africa became drier. During certain seasons, already dry savannas became even more arid, making it difficult for hominids to find adequate food. But Wrangham’s team argues that even in this inhospitable environment there were oases: wetlands and lake shores. In these aquatic habitats, water lilies, cattails, herbs and other plants would have had edible, nutritious underground parts—roots and tubers—that would have been available year-round. These “fallback” foods would have gotten hominids through the lean times.
The researchers based their arguments on modern primate behavior. For example, baboons in Botswana’s Okavango Delta, which floods every summer, start eating a lot of water lily roots when fruit becomes scarce. And hunter-gatherers in parts of Africa and Australia also eat a lot of roots and tubers from aquatic plants.
The fossil record also hints at the importance of aquatic environments. Wrangham and his team looked at nearly 20 hominid fossil sites in East and South Africa. In East Africa, the geologic and fossil evidence suggests that hominids were living in areas with lakes or flooded grasslands. South African sites tended to be drier but were still located near streams.
The researchers say foraging in these environments may have led to habitual upright walking. Today, chimpanzees and gorillas occasionally venture into shallow bodies of water, and when they do, they wade on two legs. It makes sense. Wading bipedally allows the apes to keep their heads above water. As our earliest ancestors spent longer and longer periods of time wading upright, it became beneficial to evolve specialized anatomy for two-legged walking.
Wrangham and his colleagues acknowledge that their case rests on circumstantial evidence. There’s no direct proof that this is how hominids were living. And the evidence has alternative explanations. For instance, watery habitats allow for better fossil preservation, so finding hominids in watery locales may not be representative of where they actually spent most of their time.
So like most things in human evolution, the debate’s wide open. What role do you think wetlands and lake shores played in our ancestors’ lives?
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I would like to see those who dismissed the “aquatic ape” hypothesis give a convincing alternative explanation of why our ancestors traded hair for subcutaneous fat. Other apes have very little subcutaneous fat, and obviously had no need to shed their body hair. There had to be some compelling reason why our ancestors had a better survival rate if they happened to accumulate this kind of fat, and to lose body hair, which was doing the same job of conserving body heat that the fat would do.
This theory makes the most sense out of any I’ve heard. All the pieces fit. Pretty much any part of human anatomy and behavior supports it.
As a nurse in maternity I’ve observed that babies have a strong natural reflex to hold their breath when their face is splashed with water immediately from birth. It’s very strong, even a little water and they immediately suck in air and hold it. I’ve read that humans are the only primate, in fact the only land mammal, that has this diving reflex. How could this diving reflex possibly be explained by the Savannah Theory of human evolution? How much water could get splashed on a babies face in the savannah?
This is a step in the right direction. AAT needs to be taken more seriously and studied rather than just find as many errors as possible. Elaine Morgan is not a scientist with academic degrees but has done a lot of research and deserves credit for ideas that make sense of our unique human bodies. There are many examples of mammals going into the water and adapting to the aquatic environment, and some have returned to the land. Why does it seem so strange to the paleoanthropologists that humans went that way also?
What about our ability to sweat? This could be an explanation for hair loss. Our pores and needed to be more accessible to the cooling air. I see this leading to survival more than losing hair due to aquatic plant gathering. You might die if you are chasing a herd for miles but you are not cooling off due to your thick hair all over your body, though this thick hair should not have hindered aquatic food gathering as much.
@Funky,
Sweat is not an explanation for hair loss. Horses sweat and they are not bald. In fact, your train of thought is the exact opposite of what has happened evolutionarily to savannah animals (Save those that spend time in water like hippos, and elephants. Rhinos have aquatic ancestors). They are all covered in fur. There are only 2 environments that can be credited to giving rise to Nakedness. Subterranean and Aquatic (semi-aquatic, WE) environments, very few sea animals have hair and the little bit they do is very minimal. Dolphins included. An exception is sea otters which have very thick fur and are semi-aquatic. They only started venturing into the water 1-3 million years ago, and have not been isolated enough to force them to rapidly evolve to lose their hair.
Secondly, humans cannot have evolved entirely in a savannah because 1.5 million years ago when the first savannah environment showed up and we started making tools, we were already walking upright.This would also explain why we have 2x as many sweat glands as the nearest ape. Fur, is much better at protecting against the sun than naked skin. When we finally left the shorelines, our bodies had to adapt to terrestrialism again, so the most obvious choice to protect from the sun was to just sweat more.
This theory also clicked in my mind when I heard about the gasp reflex. Humans seem to be the only terrestrial mammals (not sure about sea otter) that will instinctively take in a gulp of air when frightened or startled. When I heard this, it made perfect sense. Like flying fish, the moment they sense danger they will leap out of the water and land somewhere else where it might be safer. Conversely, If pre-historic, semi-aquatic humans were startled, such a reflex would prove advantageous as they would then just dive under the water to escape any terrestrial danger.
One point that I see opponents of AAT misunderstand all of the time is voluntary breath control. Voluntary breath control is an adaptation found in only animals that live in water, or spend a great deal of time in water. The strawman that they argue is that any terrestrial animal will instinctively and involuntarily hold their breath when they become submerged in water. This does not refute the AAT for 2 reasons. A) terrestrial animals cannot on command make themselves stop breathing. They cannot consciously make the decision to stop their breathing rhythms. And 2) humans are the only animals capable of both inhaling and exhaling by mouth. Most animals that appear to pant, are only exhaling using their mouths, they will still inhale through their nose.
My only gripe with AAT is that the name might be misleading people making them think that we swam alongside dolphins. The name would certainly imply such. I think better names could be “Semi-Aquatic Ape” or “Amphibious” even “Shoreline Ape”
Either way, I don’t know why this theory is so widely unbelievable. When I first heard about it, there are just so many things in my mind that just clicked. It deserves to be tested because savannah theory has widely fallen apart once the evidence was reviewed further than it had been, especially the time frame that is presented to us and the facts. It makes Savannah theory just fall apart.
Now wait a bloody minute,
I’ve been arguing this case, including correspondence with the Smithsonian Website, for 25 years or better. So, why should this johnny-come-lately get credit for a “new idea.” What new idea? Decades ago I began calling us the beach monkey. There are many reasons for this, only a few of which this new fellow comments on, but I’ll hold off on that for now. Go read my blog.
My primary argument has been, if we didn’t grown up as a beach monkey, how come we’re one now? We are currently a semi-aquatic animal, more than enough so to account for all our water-related traits. Demographically, we all live at the water’s edge (don’t you have running water?). We even tend to live with a couple miles of navigable water, as well. This pattern goes as far back into history as far as can tell. So, if there ever was a savannah phase in humans, my question has been, when did we move to the coast where we now live? (That’s when the Smithsonian stopped talking to me.)
I’ve argued that living at the water’s edge allowed us to survive the climate changes; we didn’t adapt to climate change until we had culture; before that we were at the mercy of the climate like every other animal. We could not have become bipedal because of shrinking forests; one only evolves towards something, not away from something. We would have evolved towards bipedalism because standing up was more successful at either getting food or sex, and almost always it’s for food reasons. The best argument for bipedalism is carrying tools, i.e. weapons. Once we started eating meat and going after bigger game, having a weapon at hand would have been crucial. You can’t chase after the gazelle and then go looking for a rock to kill it; you have to carry that rock with you. And don’t forget, we were using weapons millions of years before the first crude hand-axes show up. Then you have to carry the damn gazelle home. Turns out weapons and standing up seemed to come together; it’s what separated us from the chimps, they never figured out the importance of having a weapon at hand. Their loss.
But you can be pretty sure that home was near potable water. No one lives in the desert; everyone lives at the oasis.
As far as I can tell, the savannah theory doesn’t hold water.
Claim: Human fat quantity and distribution is like that of aquatic mammals; it is adapted for insulation and swimming in an aquatic environment. Humans have subcutaneous fat which is bonded to the skin rather than anchored within the body, unlike non-aquatic mammals.
Fact: Human fat characteristics show no sign of any aquatic adaptation, and are radically different from the aquatic mammals AAT/H proponents say we resemble. Human fat deposits are anchored to underlying depots, just as those of all mammals are. Human fat deposits are found in the same places, and are anchored the same way, as those of other primates.
http://www.sciencedaily.com/releases/2012/09/120919190100.htm. This article about a mutation allowing homo sapiens to migrate out of central africa once they aquired the ability to metabolize Polyunsaturated fatty acids from plants clearly implies that before this mutation, these hominids were tethered to their diet of fish and shellfish, due to their brain nutional requirements, for 100,000 years. Adds a lot of strength to this hypothesis!
AFAIK it was me who first proposed that australopiths lived in swamp forests & later wetlands, eg, in 2000 in a paper with Pierre-François Puech in Human Evolution 15:175-186 “Hominid lifestyle and diet reconsidered: paleo-environmental and comparative data”, or google “aquarboreal”.
1) The Miocene was very hot & wet, and most if not all hominoid fossils are found in mangrove or swamp forests or wetlands then, eg, Helio-, Austriaco-, Pierola-, Dryo-, Siva-, Lufeng-, Khorat-, Oreo-, Ardi- & Australopithecus. The monkey-to-ape transition (larger body, more vertical spine, broad thorax, dorsal scapulas, below-branch locomotion etc.) is most parsimoniously explained by spending a lot of time in the water (wading & surface-floating) & feeding on nuts or shells (durophagy: thick enamel & tool use, eg, capuchin monkeys in mangrove forests) &/or aquatic plants (lowland gorillas in forest bais), and grasping branches above the head (climbing vertically). This is the aquarboreal hypothesis of Mio-Pliocene hominoids.
2) During the Pleistocene, sea levels dropped, and vast territories became available on the continental shelves for an intelligent, handy, durophagous, aquarboreal “ape”. Homo c 1.8 Ma is found amid shells from Mojokerto (deltaic sediments, even with barnacles) to Dmanisi (near the Caspian-Black Sea connection then) to Aïn-Hanech (coastal plain) to Turkana Lake (where archaic Homo appeared together with stingrays: marine connection), and from the coasts they ventured inland along rivers. Archaic Homo had extremely thick, dense, heavy & brittle crania & postcrania (twice as thick as in gorillas) – this trait is only seen in slow & shallow diving tetrapods (google “pachyosteosclerosis”). This is the littoral hypothesis of Pleistocene Homo (AAT sensu stricto). It explains our large brain (DHA), extreme plantigrady, fur loss, SC fat, squalene-rich sebaceous glands, vernix caseosa, salt sweat & tears, head-spine-legs on 1 line, small mouth (seafood) & voluntary breathing (speech origins), slow diving skills etc.
3) Neandertal fossils are found inland as well as at coasts. If we don’t want to postulate 2 different lifestyles, they had a littoral diet of shells, seals, seaweeds etc. (eg, Gibraltar) and seasonally followed the rivers inland (eg, salmon trek?), where they butchered ungulates caught amid reeds, in mud or shallow water, ate cattails (traces on neandertal tools) etc. Late-Pleistocene Homo evolved thinner skulls (Herto & Omo after c 200 ka, and neandertals in parallel in Europe), suggesting they stopped diving, and waded bipedally (eg, with spears & later nets to catch fish & fowl) and still later walked & finally ran on land.
These ideas on what you call a “New AAT” can be found in an eBook with contributions of the late prof.Tobias, Elaine Morgan, Anna Gislén & many others: M.Vaneechoutte, A.Kuliukas & M.Verhaegen eds 2011 ebook Bentham Sci.Publ. “Was Man More Aquatic in the Past? Fifty Years after Alister Hardy: Waterside Hypotheses of Human Evolution”.
I think humans were probably mud walloers like the pig and hippo. P.s they were also probably black to protect from sunburn on bare skin under the water…
Elaine Morgan’s ‘research’ is full of factoids, distorted truths, and downright lies – and Verhaegen’s contributions to the ‘theory’ are even worse. The way they’ve reacted to the widespread criticism over the years is thoroughly unscientific, and quite distasteful.
http://www.aquaticape.org/whataat.html