SOMETIME AFTER WE SPLIT from our joint chimp-man ancestor, early humans stood upright and shed their fur. But just why this happened is a matter of highly charged debate. For years, the savannah theory – the idea that we became hairless apes to keep cool by sweating on open, African plains, held sway. But a controversial theory that plays on our strong ties to water keeps cropping up in the cultural zeitgeist.
“A lot of people get weird ideas, like the one that space aliens have visited Earth,” says Elaine Morgan, a 92-year-old feminist author, TV writer and evolution enthusiast. “I’m often lumped in with them. But the evidence is still scientific enough, and solid enough, that they haven’t written it off, they just put it to one side because it’s troublesome.”
Morgan is talking about aquatic ape theory (AAT), which she first championed in 1972. The theory claims humanity went through a period of intensive marine habitation that accounts not only for the differences between us and other primates, but similarities with marine mammals like dugongs and walruses.
Many scientists are dismissive, even downright antagonistic, towards the theory. (“Why not regale your readers with other conspiracy theories like humans never went to the Moon, or that plate tectonics is a hoax?” was how Harvard evolutionary biologist Daniel Lieberman responded when asked to comment).
Another Harvard scholar referred to a story about the theory being a joke during drinks that was accidentally introduced to the minutes of a meeting of the Royal Society. Morgan is used to the scorn, but after 40 years she still hasn’t seen proof she’s wrong. “Most prestigious scientists have said ‘yes, we think this may have something in it’,” said the writer from her home in Wales. “But none of them have said ‘we are sure there’s nothing in it’.”
THE THEORY LACKS FOSSIL evidence to back it up. Yet credible research continues to ask if there might be something in it. Stephen Munro, a biological anthropologist and curator for people and the environment at the National Museum of Australia is among the small number of established scientists who support aquatic (or ‘waterside’, as he prefers) theories. Along with Marc Verhaegen, a Belgian-based physician, he suggests humanity’s predecessor was an aqua-boreal ape, a creature of seasonally flooded woodlands.
Where Morgan (an author rather than a scientist) cites human characteristics such as hairlessness and swimming ability in support of AAT, Munro points to our heavy bones in support of his theory.
Munro thinks we developed heavier bones to overcome the natural buoyancy of our lungs while we foraged on waterway floors for shellfish (“Food we didn’t have to chase”, he says). “Swimming, diving and seafood are important components of so many cultures,” he says. “There are shellfish in the pre-historic records around Australia, Denmark and the Americas.”
The fossil record can prove humans followed the coasts when we left Africa, but Morgan thinks that migratory route is about more than just staying close to drinking water and fishing. In her most recent book The Naked Darwinist (2008) she says bipedalism arose because of watery rather than open habitats. We started out on four legs, Morgan says, but after generations of getting upright to wade across rivers or into the sea to fish or hunt we stayed that way. As she points out, apes and monkeys resort to walking on their hind legs (albeit gracelessly) when they cross a waterway or look for food under water.
Of course, she could be wrong. We may have become bipedal to free our hands for tool making, as Charles Darwin first suggested, or to raise ourselves upright to spot predators, as meerkats do. Or, being upright might have been a good way to allow air to circulate around the body while traversing hot open plains. All of these theories suffer from the fact that the transition from four legs to two must have been difficult.
Bipedalism may also have come about as an effect rather than a cause. In his book The Upright Ape, Harvard anthropologist Aaron Filler suggests that a chance mutation caused bipedalism. A fossilised vertebra from a 19 million year old ape called Morotopithecus would have made walking on all fours painful and difficult, Filler explains, and the ancestors of the four major primates took to two legs. Quite later on and for separate reasons our closest relatives (chimps, gorillas, etc) evolved with modified lumbar architecture, leaving us upright.
EVOLUTIONARY BIOLOGISTS who dismissed Morgan’s ideas in the 1970s had a key theory to back them up. The savannah theory came about following Raymond Dart’s discovery of the Taung child skull in 1925. Because Dart made his discovery on the plains of Africa, evolutionary theorists laid bets that the plains that made us who were are – walking on hind legs and losing the body hair of our ancestors. While the savannah theory reigned for half a century, studies of ancient pollen in the 1990s cast some doubt on the hot plains model of bipedalism. Inspection of fossilised plant matter in areas of Australopithecine development that were long assumed to have been open plains showed these fossils were actually found in heavily wooded areas.
Suddenly there was no need to stand upright to see across grasses to the far horizon because we were still surrounded by thick forest. Morgan says in The Naked Darwinist that the scientific fraternity has brushed the problem under the carpet by claiming the savannah theory always included a woodland component.
THOUGH QUITE PREPARED to be proven wrong, Morgan finds herself in a curious position. Labelled a crank with a theory undeserving of scientific scrutiny, she says the theory has indeed never been subjected to scientific scrutiny. “We are still repeatedly assured that the idea has been officially examined and found wanting, but I have never been able to find out who conducted this enquiry, or where, or when,” she says in The Naked Darwinist.
Morgan’s fascination with the theory first stemmed from the work of marine biologist Alister Hardy – who himself finally put forward his ideas in the 1960s after fearing ridicule for decades. Morgan saw a pro-male bias in the savannah theory that left females and infants near-useless apart from sorting a few berries. Although her 1972 book The Descent of Woman was about feminism and not evolution, Morgan promoted the AAT and promptly put the collective nose of the evolution fraternity out of joint. After half a century of the savannah theory’s assured position, here was a non-scientist spreading political propaganda. Even worse, Morgan was getting attention.
She took early criticism of her lack of references to heart and adhered to stricter methods in later books, but the damage was done. “I suspect her credibility in scientific circles was shot with the first book,” says John Langdon, professor of biology and anthropology at the University of Indianapolis and the author of a 1997 paper in the Journal of Human Evolution that some call ‘the AAT killer’.
WHILE MUNRO BEATS the drum about aquatic ape theory, other scientists are equally convinced that peculiar human characteristics – our speed, dexterity and ability to sweat, for example – points to an evolution influenced by our ability not to swim but to run.
Daniel Lieberman of Harvard University’s human evolutionary biology department champions the running man theory. We became better endurance runners than our prey, he claims, simply running them down to the point of exhaustion across the savannah. He believes sweating gives us a longer range than panting animals, and almost every muscle group in our body is built around speedy upright locomotion.
Zoologist Desmond Morris provides compelling evidence for the land running human. In his 2008 nook The Naked Man, Morris points out the seemingly dangerous positioning of human testicles outside the body, when delicate sex cell production in female humans (along with most other animals) is done safely inside. To Morris, the male human torso – designed for the twisting, jolting and stretching of a running animal – would simply be too concussive.
Munro doesn’t buy it. “People who run long distances want to be light because moving heavy bones isn’t easy on land,” he says. “In water it’s an advantage, that’s why dugongs and manatees have heavy bones.”
John Langdon of the University of Indianapolis once discussed the AAT with Morgan, pointing out that the various theories put forward to support AAT show up at different evolutionary stages. She focussed on bipedalism, which Langdon doesn’t think is the whole story. But as he concedes, ‘it’s totally unfair to say there’s only one Aquatic Ape Hypothesis out there’.
Colin Groves, an anthropologist from the Australian National University in Canberra, agrees and adds that any theory about early humans’ relationship with water remains a moveable feast. “[AAT] seemed at first to be about swimming and getting all your food from the sea, all the adaptations being for swimming and things like that,” he says. “Bit by bit that seems to have changed. Today nobody would deny waterside habitation has been crucial in human evolution. We would have been close to water through most of our existence.”
There was an attempt to settle the argument back in 1987 at a conference in Valkenberg, The Netherlands. ‘The Aquatic Ape: Fact of Fiction’ bought 22 scientists and authors together – Verhaegen and Morgan among them. Unfortunately the conclusive statement was decidedly inconclusive, saying ‘Our general conclusion is that, while there are a number of arguments favouring the AAT, they are not sufficiently convincing to counteract the arguments against it.’
THE REAL CHALLENGE facing AAT – in fact any theory of human evolution – is how little nature leaves us to work with after soft tissue clues about our stance, lung capacity or diet have long disappeared. “They’re nice ideas but it’s hard to do anything with them,” Langdon says of aspects of AAT. “What do you do with an idea you can’t test? The terrestrial models aren’t easy to prove either. That’s just the nature of the beast.”
In other words, without more clues it’s hard to know if our aquatic behaviour dates from 1.8 million years ago when our ancestors had left Africa, or tens of thousand years ago because of climate or food availability.
The biggest problem with science, as the AAT controversy illuminates, is that scientists are only human, subject to the pursuit of glory and jealousy of peers like Hollywood stars. Experimentation and data are all well and good, but the stakes can be high when careers are on the line.
“There’s definitely a desire to be the one who breaks orthodox science open and shows us it’s all wrong,” says Langdon. “Every graduate student dreams about it. Everyone is trying to criticise everybody else – that’s the way science works – but some criticisms are better than others.”
It’s still hard for aquatic or waterside theories to get a toehold. Munro says he and co-author Marc Verhaegen have had a hard time getting letters or papers published in the accepted journals and that the peer review system ‘is set up to stop alternative ideas’. When asked why it’s still contentious, he says the reasons range from the emotional to the institutional. “It’s to do with paradigms,” he says. “Once a paradigm is established, it’s invisible to people operating within it.”
Those with careers in science on the line, like Munro, have more to lose than amateurs like Morgan. Has he even been tempted to drop it all for the sake of his employment prospects? “I’ve been told not to publish with Marc Verhaegen because he’s seen as an extremist. When you have papers rejected as often as we do you wonder if it’s all worth it. But I’ve made a contribution and I hope to make a further contribution in the future.”
The take-away message from the human evolution debate seems to be that nothing put forward so far explains all the quirks of our physiology compared with that of the other apes, and we should stop looking for one from the top down. Maybe our pursuit of an overarching theory of evolution – like Einstein’s elusive Grand Unified Theory of physics – holds too much sway over our imaginations.
“We need to be very wary of umbrella theories,” says Langdon. “We need to keep testing individual hypotheses about this trait and that trait rather than looking for a sweeping explanation.”