Is human evolution stagnating? It certainly is, states Professor Steve Jones, celebrated author and geneticist and one of the foremost authorities on evolution, who argues that the driving forces behind our evolution are one by one coming to a standstill.
One such driving force is Darwin’s natural selection, the well-known process by which the best adapted creatures survive while those who do not fit their environment perish. But the trappings of modern society could be rendering all that irrelevant; whereas in the not-so-distant past half of all human children would have died by age 20, these days around 98 per cent of children are reaching at least age 21. According to Professor Jones, advancements in medicines and diets mean our life expectancy is now so high that eliminating infectious diseases and accidents would only raise it by another two years at most. These days everyone has the possibility to pass on their genes to the next generation, not just those best adapted to their environment.
The other problem with natural selection is that it only works when the environment is unchanging for many generations. For example, if the planet entered a cold period then over time the population would evolve – humans with better resistance to the cold would survive more often than those who were better adapted to hotter climates, and so the entire population would gradually gain better resistance to the cold. But this couldn’t happen if the temperature kept shifting every hundred years, say, because natural selection wouldn’t know which way to go.
In our case, it is not just the temperature that is changing but the entire environment, and we’re the ones altering it. 10,000 years ago we switched from nomadic hunter-gatherer groups to living in static settlements and farming, and natural selection started favouring those with better agrarian skills, or those who were suited to working outdoors. Then we industrialised, and so natural selection changed to favour those with the ability to work indoors in factories. Since then we have altered our society yet again so that those with intellectual ability are now more likely to succeed, but who knows what our world will look like in another 100 years? Between our unstable environment and everyone having the chance to reproduce, we don’t give natural selection a chance.
Another cause of evolutionary change is mutation – not just from chemicals and radioactivity, but from natural errors in the reproductive process. In fact, one of the most important sources of mutation and variation comes from sperm; for a 29-year-old father, which is the average reproductive age in the West, there are about 300 changes between the DNA sequences of the sperm that created him and the one he passes on. For a 50-year-old father, however, there are well over 1000 changes. But the age of reproduction is falling – most men will not conceive after they turn 35 – leading to fewer older fathers and, correspondingly, a drop in the number of genetic mutations.
The final ingredient in evolution is randomness, but even this is decreasing with the advent of globalisation. That’s right – the same process studied in Geography lessons that big businesses so embrace could be leading to the end of human evolution. The development of agriculture, says Jones, means humans are now 10,000 times more common than we should be by the standards of the rest of the animal kingdom, and those isolated populations which might evolve differently are being lost as the entire world enters one big genetic ‘mixing pot’.
Of course, even proponents of the theory note that it can only really apply to the Western world. In places like Africa, where medicines and higher standards of living are not so readily available, the fittest and most adaptable populations will still outlast the weaker ones. A good example is AIDS – if a gene developed which gave immunity, it would quickly spread throughout the continent (and indeed the world) as the virus would kill those who were not immune, which shows evolution is still active.
There are scientists who disagree with Jones’ theory, such as Professor Chris Stringer at the Natural History Museum in London, who argues that it is near-impossible to guess at future patterns. For example, Stone Age people in Europe 50,000 years ago were trending towards becoming larger and stronger until they were suddenly replaced by lighter, more intelligent humans migrating from Africa, and Stringer argues that evolutionary events like this cannot be predicted.
But if our evolution really is stagnating, could anything kick-start it again? One theory suggests that a sudden and considerable change in the global environment, such as a massive natural disaster, would allow natural selection to act again as those people best suited to the new conditions find themselves better able to survive. But there is no telling what effects such an event might have on the so-called gene-environment feedback loop; if the survivors are unable to form social groups our entire society could simply evolve towards brutishness. Alternatively, something like the weakened ozone layer could even now be filtering out those people with less natural protection from the sun.
The other option, which is both darker and more intriguing in equal measure, is that with advancements in technology we may be able to engineer our own evolution. Joel Garreau, one such scientist in this area of “radical evolution”, sets out his idea of the GRIN technologies (Genetics, Robotics, Information and Nanotechnology) which would make this possible. But if we learn to freely alter our DNA, what characteristics should we change? Do we remove those mutations with a tendency towards cancer, or should we make ourselves immune to disease? The possibility for eugenics is high; where we do we draw the line? After all, why spend money to eliminate back or joint problems if these only develop after child-bearing age? It’s not as if we need to be in top physical condition any longer to survive, either.
Whether we have halted natural evolution as a species remains unclear, but with technology marching relentlessly ahead we do need to make sure that we’re prepared to handle the consequences of our naturally selected intelligence.