Water and the evolution of humankind

Did you know that the Sterkfontein Caves, just a few kilometres from the Maropeng Visitor Centre, were once completely covered by water?

As the exhibition at the Sterkfontein Caves explains, “About 2.6-billion years ago, in what is known as the Neoarchaen era, the area around the Cradle of Humankind lay under an inland sea. Dolomitic limestone formed as sediment in this shallow sea, and is the predominant rock in the hundreds of caves in the area today.”Water has shaped our planet, and it has also shaped our species. As we look ahead to changes in the world’s water resources, we should also ask if we fully understand the relationship between water and the evolution of humankind.

Looking ahead

Can you think of some examples of the subtle changes our bodies will undergo over the next 7-million years (the time humans and hominids, our biological ancestors, have roughly been around)? Climate change analysts predict the melting of the polar ice caps, rising ocean levels, and extensive flooding and droughts worldwide. We might well ask how humans will adapt to these water fluctuations. Maybe the world in a few million years’ time will have apes that can breathe underwater and can withstand extreme temperatures…

Understanding the past

We cannot accurately predict how water will affect our species without understanding its role in shaping current life. On our planet, water and the evolution of life have gone hand in hand for millions of years. All life came from the oceans, and though some successive species slowly sought to abandon the water in order to conquer the continents, water is still an integral part of life on Earth.

According to the exhibition, “Some of the earliest forms of life evolved in the sea about 3.8-billion years ago. These were single-celled bacteria and cyanobacteria, also known as blue-green algae, and were similar to the black algae that sometimes grow in swimming pools.”

We cannot separate the availability of water – its dominance of environments and landscapes – from the evolution of Homo sapiens. But there is some disagreement on exactly how this played out.

Land mammal or ‘Aquaman’?

Scientists today do not all agree on what led to the upright-walking, hairless apes we call “the human race”.

Though scientists generally agree that our ancestors spent a lot more time in trees than we do today, no-one knows for sure when they left the trees behind for the more open spaces. It would have been at least a few million years ago.

Some think they did because the climate was changing. About 3-million years ago, the climate was drying out, and this absence of water allowed them to evolve into good land hunters, which included the characteristic of standing on two legs.

But other scientists such as German anatomist Max Westerhofer and Sir Alister Hardy, a British marine biologist, have disagreed in the past. They have argued that some human characteristics can only be explained by our ancestors having lived near to water, and not foraging on dry land. They say that we waded through a wet environment, looking for food in shallow waters, and swimming a lot more than we do today. According to Westerhofer and Hardy living in this semi-aquatic environment slowly changed our physiology in these ways:

• We began walking upright to keep our heads above water;
• We lost our body hair and developed a layer of fat for warmth; and
• Features of our larynx, noses and other parts of our bodies evolved to suit an aquatic environment.

You might be wondering why you haven’t heard more about this theory. Professor Philip Tobias, renowned palaeoanthropologist, explains in a 1998 Out There journal article, Water and Human Evolution how theories that contradict popular science can be ignored. “There are two ways in which a new idea in science is rejected,” he says. “One is by direct confrontation and attempts to refute it; the other is by turning a blind eye to it and hoping that it will simply go away.” It could just be that scientists have been guilty of not giving the Aquatic Ape Hypothesis a fair trial…

So, it is possible that we really don’t know the full story of how water has shaped the evolution of humankind. In the same article, Tobias issues a call to arms to the next generation of scientists: “It is time for human evolutionists to open their minds and give fair and objective thought to the role of water in the evolution of mankind,” he says.

Certainly. Will that be still or sparkling?

Maropeng is the visitor centre of the Cradle of Humankind, one of South Africa’s eight world heritage sites. Visit this award-winning tourist attraction to learn more about the origins of humankind.