In the 1980s, the advent of technology boomed, transforming our lives through the invention of powerful computers that could be used by consumers in their homes, devices to make our daily activities automated, and medical technology to help humans live longer. From growing fewer wisdom teeth to having better blood vessels, babies being born nowadays are actually biologically different from humans born a century ago. With our new technologies and ways of life changing how we live, who knows what humans will look like a century from now?
Yes, humans are still evolving, and it’s called microevolution
Alright, here’s the obligatory biology lesson, since we first need to know about evolution to consider how and why humans are adapting to our technology-filled world. While we may not be noticing it, the evolution of humans to adapt to our environment is still happening. These rapid, small adaptations are called microevolution, in comparison to macroevolution, which refers to large-scale evolutionary changes, like the emergence of a new species. To start off, the theory of evolution by natural selection states that organisms that are more suited to their environment survive and reproduce better, which leads to certain traits being more successful in a population. It’s also important to know that an individual organism cannot evolve; rather, it’s the population that evolves over the course of time. But survival of the fittest doesn’t always mean stronger, faster, or taller. Because of this, organisms that have adapted most to survive in their environment will be the most “fit” to pass down their genes, while those who are less genetically-blessed won’t survive as well, and their genes become less common. However, you may be surprised to find out that it’s more than just natural selection that’s responsible for the evolution of a species. In fact, there are many other evolutionary mechanisms called forces of evolution, and natural selection is just one of them!
One example of microevolution in action is a study by Australian researchers at Flinders University, where they found that more babies are being born without wisdom teeth as humans have eaten more processed foods and do not require wisdom teeth for chewing. Another major finding of this study was that there was an increased prevalence of the median artery, which is an artery in the forearm that appears in the womb but eventually gets replaced by other arteries. However, many more people are retaining this artery, as it’s beneficial for increasing the supply of blood to the body, and this trait has now become three times as common as it was over a century ago. This is just one example of microevolution at play within the past 250 years!
It’s not just you, humans’ memories are getting worse
Of course, one of the biggest changes to our lives has been the advent of mobile devices and technology that can save information for us. Don’t remember how to get to a place? Just look it up on Google Maps. Need a fun fact? Search engines have every fact you want at your fingertips. Because of this, Columbia psychologist Betsy Sparrow says that technology has changed human memory to rely more on the internet for memory. In her study, she tested participants on trivia questions, then asked them to recall the statements depending on whether they thought the information would be saved or erased. They found that the participants who thought the information would be accessible later on recalled the information worse, but they had better recall of where they could find the information later on. However, this process, called transactive memory, is actually how we rely on others to remember. For example, if you need to remember a friend’s address, you might not remember the address specifically, but you might remember that your family member knows their address, so you might remember to ask your family member for your friend’s address when you need it. And because of the advent of technology, our rate of recall in our memory has decreased, but we’re adapting by remembering where the information is stored rather than what it is stored.
Birth control and reproduction rates are also shaping evolution
But evolution has another impact on human health as well. It’s well-known that Darwin’s theory of evolution faced lots of opposition from the church regarding religion and science. But within the scientific community, some people disagreed on the impact of natural selection on humans. In particular, British physician Lawson Tait proposed the theory that humans were not affected by natural selection due to the advent of medical technology. Yet, recent studies have found that despite the lowered selective pressure to survive, the rate of reproduction has turned into an even greater influence on human evolution. For example, in a study called the Framingham Heart Study, it was found that women in Framingham, Massachusetts with lower cholesterol had more children, even when controlled for other factors, and they predicted that this trend would continue due to the force of their reproduction rate even if their life expectancy did not affect their genes getting passed down. In other studies, it was found that evolution selected for women with an earlier age of reproduction and a later onset of menopause. Therefore, even as medical technology is increasing the lifespan of humans, the rate of reproduction plays a major role in determining the course of evolution.
But there’s another modern technology that’s changing reproductive patterns in humans – birth control. In the famous sweaty t-shirt study by Swiss zoologist Claus Wedekind, it was found that women preferred the scents of men who were genetically different from them in terms of their MHC genes. These MHC genes refer to the major histocompatibility locus, which is involved in the offspring’s immunity as partners with different MHC genes give their offspring the greatest range of immune protection. Because of this connection between the MHC genes and choice of mate, British psychologist Craig Roberts aimed to study whether women on birth control pills would exhibit a different choice in mate, as birth control pills trick the body into thinking that the woman is pregnant, and pregnancy may cause women to seek out genetically similar men for protection. They found that once women went on the pill, they rated genetically similar men higher, compared to before the pill, when they preferred genetically different men. Other studies on relationships have supported this as well, as it was found that genetically similar couples are less satisfied in relationships than genetically different couples.
Will our brains get bigger in the future? Science says yes
One of the strangest facets of human anatomy is the difficult and dangerous childbirth process due to newborns’ large birth size compared to the mothers’ narrow pelvis, and scientists have always wondered why that is. After all, wouldn’t a dangerous childbirth process be disadvantageous to survival and be selected against in evolution? This was explained in a “cliff-edge” mathematical model by University of Vienna biologist Phillipp Mitteröcker and his team, where they found that there is a “cliff” where the brain size of the newborn is maximized, before the survival rate suddenly plummets. Having a bigger brain, and hence, a larger birth weight, has a clear evolutionary advantage, but human pelvises have remained small to support bipedalism. Therefore, there’s a fine balance between having the biggest brain possible and not being able to survive getting out of the birth canal. But technology has offered us a new solution to this, which is C-sections. In the case where the newborn is too large while the pelvis is too small, this would result in an obstructed birth, but through C-sections, babies with larger brains can now be delivered safely. If we assume that larger heads are genetic, this mathematical model predicts that the evolutionary pressure will lessen against human head size at birth, leading to an increase in birth size in the future.
Modern travel is changing the human gene pool
But there’s more than just medical technology that’s impacting evolution. Even travel has an impact on the human gene pool, as populations also evolve due to many other factors. For example, genetic drift, where the frequency of a certain gene variant suddenly changes, can happen when a natural disaster occurs and a part of the population dies off, making the gene variant much rarer in the population. Or, another reason may be when a part of the population creates a new population and this new population has gene variants that are more or less common than the other population. There’s also gene flow, which occurs when changes in a population, such as a sudden migration, alter the frequency of a gene variant. With the advent of modern travel, humans that spent thousands of years adapting to one environment can now experience a completely opposite environment within a few hours, and there are humans living in all different parts of the world, far from the body’s natural adaptations to the environment. For example, the gene for sickle cell anemia originally arose in countries with a high incidence of malaria, as the gene mutation protected those carrying the gene from malaria by preventing the malaria parasite from infecting the blood cells. In places with a high incidence of malaria, this is an incredibly beneficial trait, as those with sickled red blood cells are much more likely to survive malaria. However, in places without malaria, the same genes also led to a higher incidence of the lethal sickle cell anemia disease. So even as some genes have evolved to adapt to one environment, this can lead to a different effect in another environment. Ultimately, technology has changed the prevalence of traits and genes in the human gene pool.
Will genetic engineering ruin evolution?
Of course, there’s one thing we’re all wondering – genetic engineering. In 2018, Chinese scientist He Jiankui came under fire after he announced to the media that he had genetically engineered two twin girls to be resistant to the HIV virus by altering a biological pathway that the HIV virus attacks. One of the biggest outcries came from the international community about what this would do to the babies’ genomes and, in an even bigger sense, the entire human gene pool. He claimed that genome sequencing data showed that the gene editing procedure did not change any other genes or disrupt the babies’ genomes. Yet, there’s more than just that. Mutations, like the sickle cell anemia mutation, often have some evolutionary benefit that we don’t fully know about, and in the case of the two twin girls, it was found that the gene that was edited, CCR5, may be responsible for conferring a survival advantage against infectious diseases like the bubonic plague and smallpox. By disabling these genes in the two girls, the trade-off may be a lowered immunity against other infectious diseases. In a theory proposed by American geneticists Richard Lewontin and John Hubby, they stated that genes that are considered “harmful” could continue to remain in the human population because they contribute to the genetic diversity of the human gene pool and also may have some advantages when only one copy of the gene is inherited. Because of the benefits of having genetic diversity within the population, the genes for schizophrenia or autism still remain in the population due to the benefits of having a few individuals within a population being capable of creativity and altered consciousness, commonly seen in cultures as artists and shamans. If we were to get rid of certain disorders or traits using genetic engineering, this would get rid of the genetic diversity in the population that was originally beneficial in certain environments. This is one major argument against genetic engineering, as if we were to remove all supposedly “harmful” traits in a population, this may disrupt an unknown trait linked to the gene, as well as eliminating the genetic diversity in a population.
Fun Fact: I participated in Betsy Sparrow’s Google experiment! Okay, not the original one, which would’ve been super cool. But recently, all of the IB students at my school have been working on our Internal Assessments (IA), and for psychology, our IA is to replicate a psychology study. So, I was able to participate in a replication of this study on whether or not having the information stored someplace else would impact your memory!