Understanding evolution is vital to understanding what it means to be human. For as long as we could ask questions, we have puzzled over our origins. Today it seems necessary to remind ourselves that, for some time, this has ceased being a mystery, and the explanation is more exciting and intriguing than anyone imagined. Even today, a lack of appreciation stems from a lack of understanding.
The details can indeed become complicated, but the general principle of evolution by natural selection is astonishingly simple—so simple that you must wonder how nobody before Charles Darwin worked it out. Of course, some biologists already knew that life hadn’t always existed in its current forms, but Darwin discovered its primary mechanism: natural selection.
If you want to know anything about who you are, you’ll need to know something about where you came from. As we increasingly understand our past, a lot is learned about our current condition as humans.
Insufficiently small though this sample of topics is, I’d like to introduce you to a few interesting insights evolution has given us. This begins with exercise.
If running isn’t an absolute bane for you, then you doubtlessly know someone for whom it is. Yet Harvard evolutionary biologist Daniel Lieberman has demonstrated how the human body exhibits scores of marvelous adaptations for it. A small sample of these include our upright bipedal posture, arched foot, shorter toes, big buttocks and my favorite, ability to sweat (and quite profusely) to dump off heat.
Distance running enabled us to kill prey in a process still practiced by the San people of the Kalahari Desert.
It is called the persistence hunt, and it may last for hours. They run after an animal, like an antelope, and make it sprint. By far the better endurance runner, the human can keep this up while the quadruped eventually gives in from exhaustion and hyperthermia, allowing the human to kill it without a fight.
It’s no riddle then that man evolved a strong taste for energy-rich foods loaded with fats and sugars (the latter a more rare, quick source of energy) and a desire to rest when possible. However, craving energy-rich foods becomes less adaptive in the novel environments of modernity.
Our propensity to put on more fat than other primates is no help here either. Even skinny humans have a significantly higher percentage of body fat than chimpanzees.
These traits play directly into the high rates of obesity, heart disease and type 2 diabetes in the developed world. Such diseases, the National Institutes of Health notes, are very unusual among hunter-gatherers and subsistence farmers.
Evolutionary theory also makes sense of some genetic diseases, which on their face seem merely harmful. Consider sickle cell anemia, caused by a single mutation in a single gene. This is most common among people of African ancestry because that is where it originated.
So, if apparently maladaptive, why wasn’t it selected out of the gene pool? This recessive disease brings an early death to people bearing two copies of the mutated allele.
But, individuals with a single copy of the mutated allele coupled with a normal “wild type” allele show higher levels of resistance to malaria. Though terrible in double dosage, a single dosage incurs a useful adaptive value in the environment where it arose.
Behavior too is evolved and biologically rooted. This includes the best and worst parts of our nature.
Perhaps the worst atrocities ever committed have been sourced in a regrettably natural disposition to tribalism.
Though this has obvious adaptive value for early humans living in smaller bands who needed a strong in-group bias to survive together, its natural origins do not make it good, and it often doesn’t translate well into the enterprise of civilizational coexistence.
Though how much we can infer is still debated, we can see examples of proto-warfare in our closest living relatives, the chimpanzees—that this appears to stem from a basic tribalism is salient.
By 1974, Jane Goodall saw the Gombe chimpanzees split into two separate groups. While aggression and even some violence isn’t uncommon among chimps, she witnessed a conflict so severe and long-lasting (it went on for about four years) that she called it a “war.”
Described in her book “Through a Window,” the northern group carried out coordinated hunts to kill their former group-mates. This included viciousness such as drinking their victims’ blood, mutilating the body and administering severe beatings. Outright cannibalism has also been observed on occasions.
So shaken was Goodall that she didn’t write about it for a while. Initially worried that human exposure might have been the cause, evidence now points against that concern. In her book, she ruminates on the possibility that this apparent form of tribalism and escalation into proto-warfare should shed light on our own natural inclination toward violence.
However, there is an upside. We’ve also evolved the capacity of conscious thought and are not merely beholden to gene-driven urges. Richard Dawkins, Oxford evolutionary biologist of “Selfish Gene” fame, wrote amusingly and correctly that this is evidenced every time we opt to use contraception. Just as the sexual drive in males often urges them to find as many mating partners as possible, they are fully capable of overriding this drive that is, in evolutionary terms, perfectly understandable. Love itself may well be adaptive as a means of keeping parents together to raise their children.
We may have innate desires and urges, and our capacity for compassion and love are counted among them.
We can base our behavior toward the rest of the human family in these latter traits, but to overcome the destructive aspects of our nature we have to understand them. We can, for instance, break down tribalism by understanding that our most pronounced differences are merely skin deep; that all of us are human beings, worthy of dignity and capable of experiencing immense happiness and suffering. We are the human family, and can treat each other as such.
Brandon Langston is a third-year student majoring in biology with a minor in history. ✉ AB835895@wcupa.edu.