Dear Dr. Fringe, is the human species still evolving?
Of course, populations are always evolving! The human species, like any other animal population on the planet, are in a perpetual state of change, albeit, at a rate that is relatively slow, and not always obvious.
To better understand this, a quick summary of evolution may be in order.
What Does it Mean to be Still Evolving?
Every time a human being is born, genes from the child’s parents are passed on to the child. Sometimes those genes are beneficial, and sometimes they are not. If they are beneficial (an increased capacity for intelligence, or strength for example), the chances of those genes being passed on by the child increase. This is because traits like intelligence or strength will not only improve one’s ability to survive, they are also commonly desired in most cultures across the world. So long as this is the case, a child carrying these genes (once they have matured that is!) has a higher chance of reproducing, thereby perpetuating those same genes on to the next generation. Over time, entire populations change in genetic makeup due to this process.
This, in a nutshell, is how evolution works, however certain traits become more or less desirable/advantageous depending on the environment the organism in question is exposed to. If, for example, the world were suddenly flooded, perhaps an increase in lung capacity would be an advantageous trait. Those who have a greater lung capacity would survive longer, and therefore their chances of reproduction would also increase. As a result, the human population would likely start developing greater lung-capacities as a whole.
Interestingly enough, within the past 10,000 years, the environmental conditions of the human species has gone from being largely animalistic to extremely domesticated. In fact, most humans on the planet live in some kind of domesticated setting, be it a small village or sprawling metropolis. Because of this drastic change in environmental conditions, some scientists agree that human evolution has likely increased in speed.
Recent research suggests that the rate of evolution in the human population has increased by as much as 100 times the normal rate within the past 10,000 years. This increase in evolutionary adaptation, according to the paper, is likely attributed to significant changes in environmental pressures, such as the living conditions associated with the development of agriculture and cities.
So what sorts of changes are we experiencing?
Humans are Still Evolving Physically
Physically speaking, there have been many adaptations. Firstly, humans are getting taller. Early hominins like Australopithecus afarensis and Homo habilis were as small as four to five feet; now we are on average from 5 foot 3 (women) to 5 foot 7 (men).
This could be for a number of reasons. Nutrition has increased, meaning the average human has access to more nutrients so they can grow taller. Also, our mortality rates have shrunk drastically, meaning people live longer on average, and so they can grow taller simply because they live long enough to do so. One of the main drivers, however, is likely the fact that women prefer taller men, and so those who are taller reproduce more often. This trend is likely to continue so long as women prefer taller men.
Humans are also much weaker in comparison to other apes. Our muscle mass has decreased significantly due to the fact that most humans, since the dawn of man, are using a tool of some sort on a daily basis. Be it a simple wheel or a combine harvester, the average human has been trying to make things easier for thousands and thousands of years; as a result, we don’t need to use our muscles as much, and we’ve become much weaker than our distant, caveman ancestors.
This loss of strenuous work has also caused a decrease in bone density. Because we are putting our bodies under less stress, our bones don’t need to be as strong as they did before. If this trend continues, we may find ourselves as frail as birds in the far future!
We also have smaller jaws and teeth. Our earliest ancestors required large molars and strong jaws to grind plant matter and to tear into flesh. When we started cooking food, the energy required to do either of those tasks decreased, and so both large teeth and large jaws became less and less a necessity. In the modern age, most of our foods are highly processed, meaning this evolutionary trend will likely continue.
Counterintuitively, our brains are decreasing in size. This could be due to the fact that we have less of a need to remember the many details required for survival. Our ancestors were generalists, meaning it was more advantageous to know more about a wide variety of things, rather than to focus on a singular skillset. Today, we live in a society of specialists, where most people find something that they are good at and focus on that instead. This may be less demanding on the brain, causing it to reduce in size over generations. This is a peculiar situation however, due to the fact that brain size is not necessarily correlated with intelligence (Einstein had a smaller than average brain, and whales have massive brains!)
We are also becoming colder. The average body temperature of a human in the late 1800’s was approximately 98.6 degrees fahrenheit. This was widely accepted until more recent research suggests that the average human temperature has lowered to 97.9 degrees fahrenheit. The study in question determined that the average temperature has been lowering by 0.05 degrees every decade, a trend that the lead author of the study suggests is likely due to a worldwide decrease in inflammation, as well as better living conditions putting less strain on the body to be warmer.
Humans are Still Evolving Genetically
Genetically speaking, the average human body has been adapting to the significant changes that we experience in our diet. For thousands of years, humans have domesticated cattle to provide not only meat as a source of nutrition but also milk. After we grow older and no longer drink the milk of our mothers, the enzyme lactase, which is responsible for breaking down milk, is no longer required. In the past (and in some cases around the world), the human body would then stop producing lactase. Within the past 2000 to 20,000 years, however, people around the world began to produce lactase well into their older years. This is because milk is readily available and is used in all sorts of different food items, and has been for quite some time now.
The FADS2 gene is another example of a change in genes due to changes in diet. Due to the fact that we are omnivorous, much of our sources of omega-3 and omega-6 fatty acids (essential to brain development) comes from animals. Interestingly, this is not the case for a select few. In 2016, researchers studying a population in Pune, India, found that their vegetarian diet resulted in a mutation to the FADS2 gene, which in turn allowed them to efficiently process and extract essential omega-3 and omega-6 fatty acids from plant material instead.
The human genome is also experiencing changes in regards to our tolerance to disease. In a 2010 study, researchers found that within the last 8,000 years, the rise of urbanization has also caused a rise in tuberculosis resistance. One of the researchers involved in the study, Mark Thomas, explained that this was likely due to a change in the diseases humans are exposed to when we went from being nomadic to sedentary. Many of the diseases that affect nomadic people are opportunistic and chronic, like worms. When we urbanized, those diseases changed as we lived in close proximity with one another without moving much. This change in environmental conditions therefore caused an evolutionary change in our genome to defend against these new diseases.
Could we Evolve into a New Species?
Though we are evolving in some very significant ways, it is unlikely that humans will evolve into a new species so long as we live on the same planet. True speciation usually occurs when two populations diverge drastically. Because we are a species that is literally all over the planet, the likelihood of this happening is slim to none.
However, if we were to colonize a new world, with significantly new environmental conditions, speciation could actually occur. For example, this new world may have dimmer light conditions, or lower gravity; this would likely result in eyes that are larger to take in greater amounts of light, and bodies that are slimmer and taller due to the lack of gravity.
That being said, some argue that the ability to manipulate genes could result in a new species of human coming into existence by our own means. The “separation” would be due to a separation in wealth, or access to manipulative tools. In such a case, the rich would have access and could genetically manipulate themselves into an entirely new species, and the poor would remain as regular humans.
As fascinating as this all sounds, this is likely very, very far away, if it happens at all. Though we have mapped the human genome, we have yet to understand it in all its baffling complexities.
On that note, perhaps such a level of control is better left to chance, and not to the curious, meddling hands of scientists that have no boundaries!