What will we look like in a million years?
What effect does evolution have on human beings, and what will we look like in the future? ScienceNordic gazes into the crystal ball to see what we can expect.
What will human beings look like in the future? Will we be taller, will we have shorter nails and less hair? ScienceNordic asked an expert in this area, Associate Professor Thomas Mailund at the Bioinformatics Research Centre at Aarhus University, for his views.
As many offspring as possible
Before making predictions about the future, it is important to understand evolution.
"Evolution is not about the survival of the fittest. It is simply about how many offspring you have, and whether they live long enough to have offspring themselves," says Mailund.
There are big differences in the way Nature approaches this. Some animals give birth to few young and look after them well to increase their chances of surviving to have young themselves. This is often seen in large mammals.
One has to acknowledge that Nature no longer controls our evolution. We decide our biological future. Natural selection has been replaced by artificial selection.
Other animals are indifferent to whether most of their young die, as long as enough survive. Insects have lots of young and only a few survive. Even so, it ensures the survival of the species.
The weak are the winners
If we look at human beings and try to predict how we will look in the future, the same considerations apply.
Take two couples. One couple are strong, tall and beautiful with all the attributes for managing well in life. The other couple are weak, short and ugly, and experience lots of adversity in life, but survive anyway.
One might think that strong, tall and beautiful people are the motor of evolution, but that is not the case.
If we assume that obesity limits the individual's ability to have children and that obesity never becomes an ideal, then in many thousands of years we will have shorter intestines.
Assume that the strong couple have two children, who each have two children, who each have two children etc... And the weak couple has three children, who each have three children, etc...
Four generations on, the strong family will comprise 16 people, while the weak family will comprise 81 people. Over time the strong family will disappear since they are a small group and thus more vulnerable to catastrophes and diseases, while the weak family survives. Evolution has moved in the direction of the weak, short and ugly.
Another important factor is the time when we have children. If the strong couple first have children when they are 30, while the weak couple first have children when they are 20, the population changes even faster, and over a very short period of time there will be many more weak people in the population.
"This is what the theory of evolution is about. It is to do with how many children you have. The interesting thing about human beings is that they are not necessarily controlled by biology. It is very much the culture that controls how many children we have," says Mailund.
Farmers outperform hunters
Evolution means having lots of offspring. Only some of the offspring survive hunger, cold, diseases and predators. The survivors are then genetically better suited to the environment and will pass on to their own offspring the advantageous hereditary features.
This is how evolution pushes a species in a given direction.
Charles Darwin's theory of the survival of the fittest only applies if the fittest also have the most offspring.
In terms of evolution, man does not resemble any other animal on the planet. We are not influenced by purely biological mechanisms when it comes to how many children we have.
If we look at the hunter-gatherer society and the early peasant society in prehistoric times, we can see how human beings affected their own evolution. The peasant society outmatched the hunter-gatherer society, not because of biological advantages, but because of their approach to technology.
Peasants grew their own crops which gave them access to more food than the hunters, so they could feed more children. It was also less practical in the hunter-gatherer society to have many children because people were constantly moving around.
"We don't know who had the strongest genes of the two societies, but we know that the society with access to technology was the one that decided the direction in which evolution would go. It is technology that has allowed man to take over the entire planet,” says Mailund.
Man evolves differently
"There is clearly something about man that makes us evolve differently. One can say that the mechanisms are the same as in other animals, but with the added effect of culture," says Mailund.
It is culture that makes it difficult to predict how human beings will look in the future. Our cultural ability to share knowledge with our offspring is part of the reason why natural evolution is no longer the driving force.
Take a stone axe for example. The knowledge of how to make one can be passed from parents to children, who therefore do not have to develop a gene over several thousands of years which enables them to develop a stone axe themselves.
In this way, humans can create an evolutionary pressure that is stronger than the biological. Those who make weapons can better catch food than those who only know how to catch animals with their bare hands. This would also be the case if those with weapons had weaker genes.
Sex and evolution
One of the most important factors in evolution is sex.
Take peacocks as an example. Peacocks have long tails, and the males with the longest tails are the most attractive. Over several thousand generations, the males with the longest tails will have the most offspring, which also have long tails, and ultimately birds with long tails will constitute the species.
It should be the same with human beings, but this is not necessarily so. We have a habit of frequently changing our ideas about beauty. In order for us to predict whether we develop in one direction or another, the beauty ideal has to be the same for the whole population, and it must stay that way for 100,000 years. The beauty ideal must also be expressed by beautiful people having more children.
If large ears were a beauty ideal which led people with larger ears to have more offspring, then human beings would slowly develop larger and larger ears over thousands of years. But this is not how things happen in the modern world.
"The vast majority of differences between races is the result of sexual selection. It is preferences in populations over thousands of years which have determined these differences," explains Mailund.
One change that might happen in human beings in the next 100,000 years is shorter intestines, thinks Mailund.
Our diet has changed a lot since we hunted with spears in the forests. Today there is plenty of access to food, including fatty food, which is why more people are becoming obese. A possible solution to obesity that Nature could provide is shorter intestines, so we do not absorb as much fat and sugar.
"If we assume that obesity limits the individual's ability to have children and that obesity never becomes an ideal, then in many thousands of years we will have shorter intestines," says Mailund.
Controlling our own evolution
According to Mailund, Nature might as well stop trying to change us.
"One has to acknowledge that Nature no longer controls our evolution. We decide our biological future. Natural selection has been replaced by artificial selection," he says.
We are in firm control of our future. We can eradicate an undesired gene in one generation if we want to, and hereditary diseases will soon disappear.
"We will very soon be at a level where we can tailor our genes as we please. We can easily do it now, but we dare not do it before we know the ultimate effects of the manipulation. In the future, human beings will be tailored to contemporaneous norms. But one thing is certain: we will not continue to be as we are now," reflects Mailund.
Read the article in Danish at videnskab.dk
Translated by: Nigel Mander