A recent study out of the University of Sheffield has found that humans are still subject to Darwinian selection, in spite of the modern wonders of medicine and technology.
Of course, the idea that humans are still evolving is one that has never been legitimately questioned. In fact, according to an evolutionary principle called the Hardy-Weinberg equilibrium, evolutionary change is a mathematical necessity so long as at least one of the following influences occur to a genetic population: mutation, non-random mating (including sexual selection), gene flow, genetic drift or natural selection.
The first four of these influences obviously still occur. Now that it has been determined by the Sheffield study that natural selection is also still at play, it's worth wondering: In what ways are humans evolving? What traits might we possess if we projected human evolution into the future?
Though it is technically an evolutionary fallacy to try to predict future evolutionary changes (i.e., evolution does not have a goal; it is impossible to know for certain what selective pressures will be present in the future), we might be able to make some educated guesses about the near future based on current trends.
Humans of the future may lack wisdom teeth
Most people think of their wisdom teeth as a pesky medical annoyance — those things that must be surgically removed before they start to erupt. The main reason they must be removed is because many modern humans have jaws too small to contain them without disrupting the other teeth. The common postulation is that they are vestigial molars that originally evolved in ancestral humans when our jaws were bigger and our diets included hardier plant material.
So it's not a surprise that wisdom teeth are beginning to disappear. In fact, 35 percent of people are already born without wisdom teeth. Many others are born with just one, two or three wisdom teeth. When a trait is no longer necessary, evolution tends to favor the elimination of that trait to save on the unnecessary energy expenditure it takes to develop it. Thus, humans of the future may lack wisdom teeth entirely.
Race differences may disappear
One of the major driving forces of evolution is gene flow. This occurs whenever there is open mixing of genetic material between populations — something that happens today at an unprecedented scale. The fact that our world is so global, aided by the ease of modern transportation, means that there are few human populations that remain isolated. Breeding now regularly occurs among people whose ancestors may have originated from opposite corners of the planet.
One result of gene flow is that genetic differences between populations tend to disappear. In other words, racial differences are likely to blend together. Humans of the future may look a lot more alike than they do today.
Humans of the future may have less hair
Humans are already commonly referred to as the hairless ape. Of course, this is a facetious title; like all mammals, humans do have hair. But it's true that we have much less of it than our ape cousins, and likely much less of it than our hominid ancestors did too. In fact, Darwin, in "The Descent of Man," considered body hair to be a vestigial structure in humans.
Clothing, along with modern technology such as air conditioning and heating, has made the insulating properties of body hair obsolete. Although the evolutionary fate of body hair can be particularly difficult to project because it can also act as a signifier for sexual selection (i.e., body hair can be viewed as physically attractive, and thus be perpetuated within a population), it is likely that humans of the future will have much less body hair than they do today.
Humans of the future may be more resistant to diabetes and heart disease
Heart disease and diabetes are some of the leading causes of death in the developed world today, in part because modern diets are high in fats and cheap, empty calories. Therefore, there is currently a sufficient selective pressure in place to make humans of the future better adapted to these diets, and thus more resistant to these diseases.
Dietary adaptations are not uncommon even in recent human evolution. For instance, lactose intolerance has greatly decreased among human populations, such as those in northern Europe, that have traditionally been more dependent on bovine and goat milk.
Humans of the future may be physically weaker and more susceptible to pathogens
As already noted, evolution tends to favor the elimination of traits that are no longer needed. One trait that is a top candidate for elimination is our physical strength. Humans no longer require robust muscles to perform feats of strength. We now have machines, and other tools of our ingenuity, for those tasks. In fact, studies have already shown that we are much weaker compared to our distant ancestors. Future humans may therefore be more petite than we are today.
For similar reasons, future humans may also have weakened immune systems and be more susceptible to pathogens. Modern medical technology and the discovery of antibiotics have greatly increased our health and life expectancy, but they also mean our immune systems need to do less work to keep us healthy. Biologically speaking, our immune systems are less necessary than they used to be. Therefore, humans of the future may become more dependent on medical technology.
It's an example that goes to show: evolution isn't always progressive. Humans may still be evolving in spite of modern technology, but that evolution may be in a way that makes us ever-more dependent upon it.
Related on MNN:
- Human evolution aided by eating antelope brains, study suggests
- What will humans look like in 100,000 years?
- 12 bizarre examples of genetic engineering