Mad about Science: Humans

By Brenden Bobby
Reader Columnist

Evolution is a complex and confusing subject. Trying to wrap our heads around how a species can drastically change over thousands of generations is mind-boggling, especially since we can’t see it happen in real time.

The argument against evolution when I was growing up was: “Really? If evolution is real, why are chimpanzees still around? Ha, got ’em!” This is easily refuted when someone is willing to listen and comprehend the vastness and trajectory of evolution, particularly in primates. Evolution is not a linear process; instead, it branches in all sorts of zany directions as living beings choose mates with qualities that best suit their environment. In turn, that establishes qualities that compound over time as they become more useful — until something like massive climate shifts happen that convert those adaptations into a liability rather than an advantage.

The easiest way to describe evolution these days is to use dating apps as an example. Females generally pick out males with desirable traits: good hair, rippling abdominal muscles and a high-paying job that alludes to the male having other desirable traits to bring stability and a better chance at rearing successful offspring.

When these two match well and procreate, the traits of both are passed down to their children and the cycle continues. Over many cycles, traits become more pronounced and the species begins to evolve. Life, having more than 1 billion years of this under its belt, has collected a vast number of adaptations over this huge period of time, some of which are rather unfavorable as a consequence of so much uncontrolled evolution — increased risk of specific cancers come to mind, but also things like bone spurs, a disposition to diabetes or celiac disease.

It’s easy to believe that we evolved in a straight line from monkey to man, but evolution works like a tree with many branches, where most of the branches don’t form into a solid thick trunk and instead wither out as that species’ particular list of accomplishments on its evolutionary Tinder profile become less and less appealing.

Neanderthals are one of the first types of humans most people associate with our own evolution. While it’s true that Homo sapiens, our ancestors, may have intermingled with and bred with Homo neanderthalensis at one point or another, Neanderthals went extinct while we continued on, our own genetic traits eventually diluting theirs until all that remained were genetic fragments in our DNA.

By the time Neanderthals and modern humans were sharing a space, many other forms of humans had already come and gone. Neanderthals slowly went extinct over several thousand years, ending roughly 40,000 years ago. Homo heidelbergensis existed in Africa and parts of Europe at least 500,000 years ago and is commonly associated with the idea of the “missing link,” a step between Homo erectus and Homo sapiens. It is also possible that some form of H. heidelbergensis existed at the same time as Homo sapiens, as the two shared a number of technological advancements, such as use of tools and some forms of art. H. heidelbergensis have been attributed to creating some of the earliest cave paintings using ochre clay that we’ve discovered.

It’s likely this particular genus of human looked more like a simian than humans we recognize today, with elongated skulls and larger facial features. Interestingly, this genus was known to have hunted or scavenged very large game such as the straight-tusked elephant.

One of the more curious branches our ancestors shared a planet with was Homo naledi. These hominids inhabited South Africa at least 235,000 years ago, and while we associate the aesthetic of a primitive monkey-looking humans to Neanderthals, naledi took this to a whole new level with very simian features and body types. H. naledi looked a lot like Australopithecus, which existed between 4 million and 1.9 million years ago.

It’s possible that the phenomenon of the uncanny valley we experience today when viewing something like the movie Polar Express could have been an evolutionary response to H. naledi and other early hominins. Uncanny valley is an unsettling feeling we get when we view something that looks human but is distinctly not human. There isn’t much evidence as to why this psychology exists in modern humans, but it’s likely that our ancestors encountered something that was human enough while still being distinctly different and somehow a threat to our existence. H. naledi seems to fit this characteristic very well, functioning as a human but appearing as something quite alien.

H. naledi was not known to have possessed a material culture of any kind — that is, they didn’t use tools like our ancestors did. They didn’t appear to collect or produce stonework in the way that our ancestors did, either. They didn’t even walk like we did but instead seemed to be built for swinging from trees. Their bodies were similar to ours, but while our ancestors were built for bipedal running, they were built for climbing and swinging. This had to be an incredibly unsettling sight, to see something so closely related to us but so different.

Though it has come under intense debate, it’s possible that H. naledi buried its dead by carrying carcasses ritualistically into caves as a form of burial. This seems surprising when the fossil record shows their primary diet was food picked up off the ground, and they didn’t seem to produce or use tools.

Stay curious, 7B.