Weird Ways Humans Have Recently Evolved

Weird Ways Humans Have Recently Evolved

Over the course of planet Earth’s long, storied and colorful history, many life forms have come and gone. But every species on the planet has a biological evolutionary story of its own, a narrative with chapters that are often measured in the millions of years. Evolution is the biological process by which living things change over time to better suit and survive within their environment. These changes are so slow that they are often only perceptible to us through the lens of retroactive studies involving fossils. Over tens of millions of years however, a lineage can go from being a small dog-sized creature like an eohippus… to the modern day horse. Evolution might be slow in the making, but the results are clearly astounding.

Humans, as a species, share an evolutionary history with primates. In fact, though we typically use the term to refer to our monkey and ape cousins, we are primates too. More specifically, we’re hominids, or “great apes”, a classification shared with gorillas orangutans, chimpanzees and our extinct human relatives, the Neanderthals. From a shared primate ancestor millions of years ago, we’ve steadily and specifically diverged and changed to become modern day humans. Between 4 and 7 millions years ago, we achieved bipedalism. Then, from Australopithecus, to Homo habilis and then Homo Erectus, we experienced encephalization, the development of an increasingly large brain relative to other primates.

It all feels very slow going. But really, compared to other species, humans have actually shown a habit of evolving rather quickly. True, we’re unlikely to suddenly develop advanced mutations that give us powers like the Homo superior of Marvel Comics. But eschewing the tantalizing evolutionary leaps depicted in works of fiction and rooting ourselves in good ol’ fashioned reality, with the help of modern science, we can see that there’s actually a whole lot of incredible human evolution taking place.

First off - milk. Humans aren’t, technically, supposed to drink milk after infancy. At that point, the body stops producing lactase - the enzyme necessary to break down lactose. As such, roughly 65% of the world’s population is lactose intolerant. Around seven thousand years ago however, humans in Europe, having shifted towards a more agrarian lifestyle, began making cheese, and in doing so they started exposing themselves to fermented lactose. It’d take thousands of years, but this population slowly evolved the ability to break down lactose thanks to a genetic evolutionary response - a mutation that kept the production of lactase going into adulthood.

The physical differences between our early ancestors and modern day humans, or between the eohippus and modern day horses, is both obvious and staggering. We’ve undergone transformations from head to toe (or in the case of horses… head to tail). But the aesthetic changes rarely feel recent, although they do exist. A leading example is blue eyes. It’s estimated that between 8% and 17% of the world’s population has this distinctly eye-catching color. But research suggests that roughly six to ten thousand years ago, that percentage would have been zero. Apparently, people with blue eyes can all be traced back to one common ancestor who passed along the mutation. And in the scope of human history… six to ten thousand years is very recent.

Another noticeable aesthetic change that can be easily measured, quite literally, is human height. Around the globe, humankind is, for the most part, getting taller. In just the last 150 years, the populations of industrialized countries have grown, on average, by 4 inches. Most agree that nutrition is key. However, a major driving force behind evolution, and one of the factors that can yield the fastest results, is natural selection. In recent generations, the Dutch have especially shot up in height. Over the course of 200 years, the average height has skyrocketed by 7.9 inches. The reason? Dutch women are apparently attracted to tall men. Natural selection speeds along evolution by having individuals with favorable traits be more likely to reproduce.

For another isolated example, let’s head to Tibet. As we’ve said, evolution is never going to suddenly give humans a random superpower, but some recent genetic mutations could be described as “abilities”. Tibetans live at an altitude of roughly 10,000 to 13,000 feet in a harsh and unforgiving environment. At this height, the average person is prone to altitude sickness thanks to the 40% decrease in oxygen. The local Tibetans however, have evolved to comfortably exist in this low-oxygen environment thanks to a hereditary genetic mutation – which seems to have developed in just the last 3,000 years. ‘Altitude Man’ isn’t likely to be turned into a blockbuster anytime soon, but it is one of the most substantial examples of evolution in recent human history.

With the discovery of DNA, humankind has, in many ways, found the keys to unlocking the mysteries of human history, and a tool by which to observe the potential route ahead. Large scale genetic studies are now possible, and by looking into the DNA of massive groups, researchers can identify genetic mutations and patterns that are shaping what’s to come. While the scientific community works to combat conditions like asthma, coronary artery disease and alzheimer's for the sake of generations in our immediate future, evolution is simultaneously working on long term solutions for these problems at the source. A huge genetic study published in PLOS Biology in 2017 discovered that predispositions to such conditions are becoming increasingly less common, or, in the case of alzeimer’s, less common in older people. By looking at our genomes, we can see that human evolution is occuring in a matter of centuries and decades.

Though perhaps not one of the ‘weirdest’, surely one of the most important examples of modern evolution is the development of disease resistance in general. A driving force behind evolution is environment. When a species moves into a new environment, they’re faced with new challenges, living conditions, and dietary options as well as factors leading to illness and disease, including pathogens. It’s a tough and lengthy period of transition, but the body can (and usually does) adapt. And so, numerous genetic mutations have arisen in vulnerable populations over the centuries to combat a wide variety of infectious disease and other conditions, including but not limited to malaria, leprosy, cholera and tuberculosis.

Of course, natural selection can take a population in various other directions. The Framingham study, a long running research project investigating cardiovascular health across the generations in one Boston suburb, has shown just how quickly natural selection can shape any given group. Research finds that the women in Framingham are progressively becoming shorter, slightly heavier, getting menopause later in life and, across the board, having lower cholesterol and blood pressure. Why? Because these traits seemingly equate to having more children.

Finally, it’s back to the brain. Remember when we said that one of the major evolutionary factors that separated humans from other primates was our drastic increase in brain size? This was a process of growth that spanned millions of years… so, you’d think that as our species becomes increasingly advanced our brains would continue to grow larger. But it’s been estimated that over the last 28,000 years, our brains have actually been shrinking. And we’re talking about a significant loss in terms of overall size; like… a tennis ball worth of brain. Don’t worry though, we’re not getting dumber. At least… we don’t think we’re getting dumber. Some scientists believe that this is an evolutionary response to the development of civilization and communal living, and that as a result, our brain is effectively eliminating the excess it no longer needs. Across the animal kingdom, a larger brain is associated with greater aggressiveness, which also fits with the community living theory. While some also argue that a shrinking brain might actually be more efficient, in that the connections it makes are shorter, making our ability to process them quicker.

Clearly, as the environments we shape for ourselves change and our culture develops, our bodies will continue to respond and adapt – both in superficial ways and on a deep-rooted, genetic level. We don’t know exactly where we’re headed as a species, but one thing that we can say for sure is… we’re constantly evolving, and the proof is all around us.