Original question from Boxy: “What will be the next human evolution? Or devolution?”
You may have heard of ‘evolution by natural selection’ (sometimes accompanied by ‘it’s just a theory’. So is gravity. And the principles that run the computer you’re using to read this. And all of science, really). The theory of evolution by natural selection was first advocated by Charles Darwin and Alfred Russel Wallace in 1859, although Darwin is the famous one because his surname comes first in alphabetical order. The basic idea is that evolution was random, requiring three things to function: variation, selection, and time.
Variation occurs randomly in a species as mutations in its DNA. DNA is the instruction manual that tells the cells in our body how to run, and when a cell divides the new cell needs a copy of that manual – thus the DNA creates a copy of itself for the child cell. These copies aren’t perfect, and small mistakes can occur in places – it’s these mistakes that give rise to genetic mutations, creating variation in a species genome.
This video, from Bozeman Science, explains how DNA is replicated.
Selection is whatever mechanism determines whether a genetic mutation is good or bad for mutated individual within a species. Darwin and Wallace identified this mechanism as the environment in which a species lives.
Time. If a mutation benefits that individual, it will survive and reproduce, passing its mutation to its offspring. Eventually the new species may outcompete and displace the original species.
Let’s use a (very) silly example to illustrate this process:
- We have a species. Let’s be proper scientists and use mice.
- One mouse randomly develops telekinesis (the ability to move objects using the power of the mind).
- Telekinesis is a great boon to this single mouse, and he/she is able to see off all his/her rivals for the affections of female/male mice by using his/her mind powers to throw his/her rivals into the path of a nearby passing cat or lawnmower. Thus, he/she reproduces, and telekinesis is passed on to the next generation.
- Telekinesis proves so beneficial to all these mice, that they are able to outcompete and eliminate all other mice (in a variety of inventive ways), thus displacing the old species with a new species, and ensuring your cheese will never be safe again.
Thus, Darwinism in action. For a brief historical note (because that’s what you get when you have a historian on the writing team), ideas about evolution had been around for at least a century before Darwin, such as Lamarck’s idea of inherited characteristics. Darwin came up with the idea for natural selection on his voyage round the world aboard HMS Beagle, where he was officially a gentleman companion to Captain Fitzroy. He would sit on the idea for about thirty years, until he received a letter from Alfred Russel Wallace, who had exactly the same idea during a bout of malaria in Malaysia. Knowing Darwin had interests in the area, he sent a copy of his paper to Darwin – which scared Darwin into publishing On the Origin of Species in 1859. Darwin and Wallace’s papers were read at the same meeting for the British Association for the Advancement of Science, where the papers were read in alphabetical order. Wallace always acknowledged Darwin as more important than him in the advent of the theory.
Most of the time evolution is too slow to be observed, particularly in a species with a lifespan as long as that of humans. However, scientists have identified a number of recent changes in the human genome, including the following:
- The appearance of lactose tolerance in Europeans.
- The emergence of blue eyes 6,000-10,000 years ago.
- Resistance to infectious diseases such as leprosy and malaria.
- Human jaws are becoming smaller and more bullet-shaped and losing the wisdom teeth.
But of course, we still have DNA and we still reproduce, so surely evolution must still be happening. There are four scenarios proposed by evolutionary biologists for the future evolution of the human race:
1) Humans will no longer evolve. There are no more isolated populations, so no new traits will enter the human gene pool, and thus humanity has emerged as the best of what the planet Earth has to offer.
Some scientists argue that the genetic variation is only likely to occur in small, isolated populations – the finches that inspired Darwin to come up with natural selection were each adapted to their own isolated island, and in the modern world no population is truly isolated any more. Crossbreeding in the larger population makes it less likely that a trait will become established within a small population – for example, blue eyes became heavily established in Scandinavia. There is the suggestion that blue eyes are going extinct, and in America today 16% of people have blue eyes, yet at the turn of the century it was closer to 50%, and this can be put down to humans becoming more alike as races merge and traits are mixed. Indeed, natural selection has lost its power over humanity – the fittest genes no longer lead the evolutionary charge, and medical advances keep the ‘weak’ living long enough to pass on their genes. So what this prediction is basically saying is that humans were the fittest, and they have survived.
2) Humans will continue to evolve, potentially using sexual selection based on appearance, earnings and social status, which could ultimately result in humanity splitting into two species.
Other scientists argue that human evolution is continuing, arguing that sexual selection rather than natural selection will become a key driving factor in human evolution. Parents will select mates based on physical attractiveness and intelligence, especially as knowledge and understanding of the human genome grows and humans become better and genetic engineering (the can of worms that are ‘designer babies’). One evolutionary theorist has argued that humans will split into two species – a genetic upper class of tall, slim, healthy, attractive, creative and intelligent people, contrasted with an underclass of squat, dim-witted goblin-like creatures in a vision similar to HG Wells’ idea of the Eloi and Morlocks in his classic novel The Time Machine. Another idea is that humans’ growing dependence on technology meeting our every need will lead to the loss of traits that were needed to survive. For example, humans may lose social skills and the ability to express emotions, and the chin may recede as humans consume more processed food.
3) Electronic immortality, an idea appearing in science fiction series such as Doctor Who and Star Trek. The idea is based on things such as cybernetics, copying a person’s mind into a machine, nanotechnology and artificial intelligence.
This is the idea of ‘transhumanism’, the ‘singularity’, and ‘cybernetics’, as humans transcend their biological limitations using technology. Just as the loss of traits at the end of the last prediction may conjure images of Jabba the Hutt wearing an Oculus Rift headset as a potential future for humanity, this idea creates mental images of characters from classic science fiction series such as The Matrix, the Cybermen from Doctor Who and Star Trek’s Borg. Some scientists argue that evolution is happening on a very slow timescale relative to other changes in the human condition – such as cloning, robotics, artificial intelligence and nanotechnology. Technology raises a huge number of possibilities, from upgrading people with robotic arms and legs to artificial organs, and uploading of human minds to computers. Such uploaded people would be able to travel at the speed of light as information, download themselves to robotic bodies, think faster in advanced operating systems, and overcome many biological limitations. This would be an entirely new form of evolution.
4) Evolution in space. Over successive generations, humans would adapt to living in low-gravity environments such as space stations, growing taller and more elongated, while higher levels of solar radiation would lead to changes in the human eye.
Space travel and colonisation of other worlds may lead to newly isolated pockets of humanity, allowing traits to become pronounced within them to adapt to the conditions of their new environments. A recent television series set at a time when humans have colonised the whole solar system, The Expanse, depicted this - humans living on Earth remained much as we are now, while the ‘Belters’ born on asteroids such as Ceres were noticeably taller and thinner, having adapted to lower gravity. However, such changes would take a while – among partially isolated communities in Papua New Guinea, to come back down to Earth, it’s estimated that there has been no intermixing for about 30,000 years without anywhere near enough genetic drift to lead to a new species of human.
Perhaps the biggest issue with trying to predict human evolution is that it’s an attempt to predict the future – and the future cannot be predicted. The only way to know for sure is to survive long enough to find out. Anyone up for the challenge?
References and further reading:
An Evolutionary Whodunit: How Did Humans Develop Lactose Tolerance?
Are Blue Eyes going extinct?
Other examples include leprosy, HIV-1 & AIDS, and prion infections:
Sickle Cell Anemia and Malaria:
A Brief Summary of recent changes in humans, with Wisdom Teeth at the bottom:
Wisdom Teeth & Other Vestigial Structures:
Was Darwin Wrong?
The Man Who Wasn’t Darwin:
A Brief History on Evolutionary Theory:
Examples of evolution in action today:
A brief primer on human evolution:
Potential changes in Humans in the Future:
A Summary of the Predictions:
An anthropologist tries to predict where human evolution might go: