Survival of the best

Do you think he felt anything? The man who, sometime in 1870, shot and killed the last wild quagga?

It took 30 years, from 1840, during the mass migration of European colonisers in sub-Saharan Africa, for the plains’ zebra to be entirely eradicated from the wild. One lonely female lived on at the Amsterdam Zoo until 1883, unrecognised as the sole survivor of her species.

You can interpret this story in a number of different ways. It could be about the callousness of human behaviour.
It could be about how humans destroy the planet. Or it could be about how the arrival of self-aware intelligent creatures forever changed the basis for natural selection.

The first human-like creature to pick up a pointed stick and use it as a tool to slay another creature changed everything. Instead of waiting for the accumulation of random genetic variations to impart gradually improving biological tools, our creature could create tools itself.

The advantage to humans of being able to organise, teach and use weapons to catch food may initially have been slight. That marginal advantage has allowed a single species to migrate, settle and dominate the entire planet; something unprecedented in all of Earth’s history.

The study of human evolution covers a period of six million years, during which a semi-upright-walking woodland ape eventually developed tools, learning and culture and survived ice ages, earthquakes and climate disruption. Adding to the complexity of this epic tale is that there appears to have been overlap between at least two intelligent species of human-like creatures in the past 50 000 years.

Dr Chris Stringer leads the department of palaeontology at the Natural History Museum in London’s research into human origins.

“Very soon we will have the genome for Neanderthals. That will then allow a three-way comparison between humans, chimps and Neanderthals. This will give us a better view of the six-million-year split between humans and chimps and of what made us and the Neanderthals different from each other,” he says.

“The Neanderthals were really unlucky. When modern humans moved north into Europe about 4000 to 5000 years ago, the climate was at its most unstable. The north Atlantic regularly switched between being frozen over and thawing and some information suggests that these events sometimes happened in less than 10 years.

“The Neanderthals had survived previous ice ages by simply giving up territory and moving down south. Now they met early Cro-Magnon humans. So, just a slightly different timing of events could have led to Neanderthals surviving and perhaps our species going extinct instead.”

The Middle East was the biggest area of overlap between the two species as they moved back and forth. Neanderthal relics there that are 120 000 years old show burial traditions. There is also evidence that Neanderthals cared for one another.

“Archaeologists found the skeleton of a Neanderthal that shows signs of healing from an injury. His skull was damaged and he would have been quite seriously disabled, but he survived for years afterwards. For a Neanderthal living in the mountains of Iraq to survive with that sort of disability implies a level of complex organisation and social support.”

Part of the reason for looking after the elderly is simply that—in a world without writing and libraries—they act as a store of knowledge from the past to the present. Caring gives a survival advantage.

There is a debate about whether Neanderthals died out because of environmental change or because of being outcompeted by modern humans. The reality is probably something in between.

Neanderthals are believed to have lacked complex symbolic language skills and our species was just that little bit more intelligent. “The concept of symbolic language, of understanding and planning for the past and the future, that—I believe—is a modern human invention.”

Both modern humans and Neanderthals developed the use of weapons for hunting, but these were hand-held spears. When one band of humans developed throwing weapons they were able to hunt better and achieve victory in any conflict with other humans, such as the Neanderthals. Perhaps modern humans were able to retain, transmit and develop this knowledge better than the Neanderthals could.

Stringer points out that chimps and gorillas overlap, but tend to ignore each other in the wild even though they fill similar biological niches. Chimps and gorillas are, in evolutionary terms, many millions of years apart. Humans and Neanderthals are perhaps only 400 000 years apart and it is uncertain how they would have interacted.

Whatever happened, though, Neanderthals couldn’t change fast enough to keep up with both the fluctuating climates and the newcomers and, after more than 10 000 years of coexistence, they became extinct, leaving us as the only human species in most of the old world.

The movement of humans out of Africa and the continual process of climate change means that humans would stretch out, and die back, repeatedly. Yet modern human political and social groups are determined to fix origins in their modern borders. They want to be British, Aryan or African. In evolutionary terms we’re just human.

Racism brings people into conflict with science, but so does religion and, more recently, opposition to the impact that climate change could have on the nature of life on Earth.

Even those who support science like to point out that nature gets there first. A recent paper in Nature Photonics shows that stomatopod crustaceans are able to sense the difference between left and right circular polarised light with an accuracy of about only 2,7 degrees over the visible range. The best human-made device clocks in with an accuracy of about nine degrees.

It probably took the stomatopod millions of years to develop its solution. Humans developed their solution in mere decades. And, more importantly, science-based investigations are allowing us to unlock the mechanisms behind just about any natural solution we require. The combustion engine is now approaching its theoretical efficiency. Solar energy panels are a long way from that point, but it is happening. Science may not have all the answers, but it does know how to go about finding them.

Gavin Chait is a science journalist writing under the auspices of the Africa Genome Education Institute

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