Furthering Humanity's Intelligence at a Questionable Evolutionary Cost

by Jusmita Saifullan

Given the massive empire that humanity has built for itself, it is easy to say that we possess superior intelligence to many other species in the animal kingdom. Our brains have evolved to become bigger in terms of percentage weight and more efficient than our mammalian relatives. However, advantageous changes to the brain have come at a cost, calling into question whether some of these exchanges are truly beneficial.

Having a bigger brain means that our skulls had to accommodate by expanding. It is hypothesized that the genes coding for skull size and jaw composition heavily influence one another. Consequently, a genetic change leading to bigger skulls also resulted in bone mass loss from our jaws, causing them to become smaller and weaker. More importantly, because our teeth remain roughly the same size, a shrunken skull has pushed them closer together, barely leaving extra room. As a result, wisdom teeth growth can become very painful and impacted. Some may feel, given the ease with which wisdom teeth can be removed, that this particular genetic alteration is not so severe. However, when the genetic alterations necessary for furthering intelligence involves – in what may seem like an ironic twist – a host of cognitive impairments, the value of such a trade becomes questionable.

One of the most recently studied effects is the development of schizophrenia as a result of having a bigger brain. Research conducted by Dr. Joel Dudley, a genomics professor at the Icahn School of Medicine at Mount Sinai, looked at locations called the human accelerated regions (HARs) in the human genome that underwent evolution rapidly following humans branching off from chimpanzees in the evolutionary tree. HARs do not code for any traits, but help to regulate other genes. It was found that HAR-associated schizophrenia genes are localized in regions of the genome that influence development of the prefrontal cortex, one of the central regions involved in advanced thinking. Therefore, it is hypothesized that during the rapid evolution phase, where many regions of the human genome were acquiring new mutations, changes in HARs have led to enhancements of the prefrontal cortex and mutated genes for the development and maturation of brain region functions, giving rise to schizophrenic traits.

Given an examination of our evolutionary history, one might be inclined to conclude that all physical and psychological changes accompanying the increase in brain size and intelligence are negative. We must also consider, however, the argument that positive and negative traits may be judged as such under strong influences from the conditions that we live in. Traits that may be appealing to us given the living standard of modern society may be disadvantageous to our ancient ancestors, who lived under the constant threat of predators and limited resources. Some of the traits that developed in conjunction with the modification of alleles responsible for our increased intelligence just happened at the wrong place and time.

The existence of attention-deficit/hyperactivity disorder (ADHD) is another ailment that has resulted as a consequence of a bigger brain. While most of us tend to think of ADHD as a modern disease characterized by an inability to focus, some theories suggest that it has been evolutionarily advantageous. Studies have shown that hunter-gatherers with ADHD were better nourished than those without the gene due to their adventurous nature and willingness to take risks for food. Some even theorize that ADHD may have fueled many human discoveries and inventions in the ancient world as ADHD-afflicted humans were easily bored by the existing knowledge and available tools.

It is interesting to see what was once considered a benefit of evolution is now regarded as a psychological disorder in a more advanced society. This gives rise to the question of whether some of our more favorable traits now will be looked upon in the same light in the distant future. Clearly, the evolution of our intelligence comes with great trade-offs that may start out advantageous, but end up quite differently.

In a world of rapidly advancing technology, one can easily forget that the human race is continuing to evolve. At this point, humanity’s superior intelligence clearly separates them from all other living things and is a highly desired trait. However, further evolution to acquire greater intelligence may require more trade-offs of the same physiological and psychological nature. Perhaps it is worth the gamble, since it is not known whether a trait will forever pose a positive or negative advantage given our constantly changing living conditions. But perhaps humanity is better off as it is now?