Predicting evolution for any species is a difficult task as it will depend significantly upon the environment in which the species finds itself inhabiting. To put this into perspective, the future physical characteristics and mental capacity of humans might differ greatly depending on whether the planet remains in its current climatic balance or enters another ice age. Under one scenario, life should continue to be comfortable for us as the planet’s alpha predator, whereas the ice age scenario could see us facing a fight to avoid extinction. Evolution will continue one way or the other but it might be the difference between us choosing our evolutionary path or having it chosen for us.
Benign environment – we choose our evolution:
Assuming that our planet remains hospitable to homo sapiens, and that we don’t annihilate ourselves in a nuclear war, then we will almost certainly continue to occupy the position of species dominance. In this setting, we might expect micro evolution to continue through the process of natural selection. As an example of natural selection, women have traditionally chosen males who are taller than them and, over many centuries, this has resulted in humans becoming taller.
As well as becoming taller, humans have become less hairy, less muscular, and have developed bigger brains. Given favorable environmental conditions, we might expect a continuation in these trends but with one significant alteration, namely the fact that technology is likely to play a bigger role in the process of having babies and passing on our genes.
Whilst currently raising important ethical debate, we now have the technical capability to choose a baby’s characteristics in a lab rather than leaving the whole birth thing to random chance. History has shown that once a technical capability exists, it will eventually be utilized so it is probably only a matter of time before parents choose the characteristics that they wish for their children. This might include the absence of health risk factors, so we might see life-spans take another upward turn. There may also be a reduction in diversity as all parents ask for tall, blonde-haired, blue-eyed healthy babies. However, any such reduction in diversity might have long-term negative consequences for our species; for example making us more susceptible to the ravages of a particular disease.
Volatile environment – survival of the fittest:
We live in an age when there is great debate on the possibility of cataclysmic climate change. Scientific analysis does seem to suggest that changes are afoot, whether one accepts that these are man-made or considers them to be part of a natural cycle, and history shows that severe changes in the planet’s climate are usually accompanied by mass extinctions and a changing of the order. Humans may find themselves in a fight for survival and it’s in exactly those conditions that we might see more far-ranging macro evolutionary changes.
For example, let’s say that we do enter a new ice age. The last time our species faced an ice age was nearly 10,000 years ago, when we were still mainly a species of hunter gatherers. While we emerged from that challenging environment, our cousins the Neanderthals became extinct. Even with our vast advancements in technology, it is conceivable that life would become very hard during another long-lasting freeze and our numbers could be decimated.
It is under such conditions of species strain that survival of the fittest becomes most telling. Survival of the fittest is sometimes characterized as being about the survival of the individual – e.g. those who are strongest or fastest will prevail whilst other individuals die. However, the essence of the survival of the fittest principle happens at the level of the gene. For example, individuals who possess a gene that enables them to survive cold temperatures will survive long enough to mate and pass on that gene to the next generation.
Where a dramatic evolutionary change occurs, it is often the result of a gene mutation which suddenly confers some difference to its host’s body that increases their propensity to survive and thrive. In the ice age scenario, genes controlling fat deposits might be important. Animals such as seals, bears, and whales which have evolved to survive in cold climates tend to have high fatty deposits, so perhaps the human trend towards us being taller and thinner might be reversed as extra body insulation determines the health of the population. We might also see a reversal of the “less hair” evolutionary trend. What this demonstrates is that evolution is not a linear event. Instead, it is entirely about what is best for the survival of genes and their host bodies, so a move back to the physique of early cavemen could be entirely compatible with the tenets of evolution provided that it confers advantages of the species.
Humans have always reacted to threats by utilizing our large brain capacity and this is unlikely to change. Therefore, whilst our bodies may undergo further adaptations to maximize survival rates, we can also expect our species to continue to remain large brained with an unrivalled ability to work through problems and identify solutions.
Human evolution may also be influenced by whether we make big steps forward in space travel. Conditions in space are not conducive to the health of modern day homo sapiens but the longer that humans remain in space, the more likely it is that our bodies will adapt to fit in with our new surroundings. It’s possible to conceive a time when we might have colonized Mars and/or the Moon. If these outer space colonies remained fairly isolated from other human contact, then one might expect changes to occur over a very long stretch of time between the Earthlings and their Martian counterparts. This would parallel what happened to allow the divergence of common chimps from Bonobo chimps,
These are just a few random thoughts on the possibilities that we face in terms of evolution. There are, however, probably billions of variables that will go towards determining our future evolution, making it next to impossible to accurately predict how things will work out. Indeed, species don’t have to undergo substantial changes. Crocodiles remain more or less how they were during prehistoric times; their blue-print remains as successful now as it was then, leaving them with little reason to change.
Humans will probably attempt to shape their evolution using technology and making homo sapiens the first ever species to directly attempt to shape its own evolutionary destiny. However, that’s a very big task and it is highly likely that our external environmental pressures will play a much bigger role in our development and change than our own attempts to steer a course.