How evolution works
It is dispassionate and brutal — and it is no longer taking place in humans. My provocative views on the subject.
There are two reasons for this article: on the one hand the grandkids want to know, in Covid times, why there are viruses (short answer: because it is possible), and also why every six years the grounds are covered in acorns. Secondly, Discover Magazine recently published a story telling us that we can see human evolution in action even today. They describe an example:
“More and more people are being born with an extra artery in their forearms, one that usually disappears in utero. This artery shares real estate with a nerve passing through a structure called the carpal tunnel; people with this extra artery are more prone to painful carpal tunnel syndrome.
In the evolutionary past, even a hundred years ago, it was a disadvantage to have a median artery because people worked hard with their hands. But … the median artery is no longer the liability it once was — meaning that a condition that used to make it hard to work in the fields and thrive is suddenly not a big deal. About 10 percent of people born in the mid-1880s retained a median artery, but in Australians born in the late 20th century, 30 percent of people have it.” — Discovery magazine: Human Evolution Isn’t Over Yet.
Evolution in action? Now wait a minute, during my studies that is not how I understood evolution. A key mechanism, we learnt, was selection. Changes in any life form occur by chance. Most changes are detrimental, but some are advantageous. The latter will be passed on to later generations more expediently than the former. A bird which by chance had more powerful wings will outbreed one that was born with stubbly wings. The latter may be more vulnerable to predators, or less able to find food or breeding partners. Darwin studied the process extensively on the Galápagos Islands.
Aside: birds have also developed all kinds of elaborate traits to attract breeding partners, as these pictures by Tim Flach show. He is an animal photographer and has posted some of the most incredible animal pictures I have ever seen. Do visit his site — you will not regret.
These birds did not have human selection (described below) — they evolved naturally, in hundreds of thousands of years, with billions of individuals reacting to purely environmental circumstances.
There are and have been many ways in which humans have shaped animals, changed their size, strength and outward appearance. One can call it artificial evolution. Take a look at dogs. The largest dog, the harlequin Great Dane, is up to 42 inches (1.05 meters) tall, the smallest, the Chihuahua, is just 4 inches or 10 cm in height.
All dogs descend from naturally evolved wolves. The first encounters of sapiens with wolves were doubtlessly hostile, but man (and some of the wolves) soon discovered that there was a lot to be gained by friendlier interaction. Humans started breeding dogs, selecting those that were most suited to specific needs, like companionship, guarding, hunting. They would consistently kill off dogs that could not be trained and care for the ones that pleased them.
Over the generations the dogs evolved, until we had the variety shown in these Tim Flach pictures. All the dogs, big and small, cute and ugly, calm and aggressive, were bred in around 20,000 years. That’s how fast evolution can work, if it is purposefully guided by human intervention.
Back to the Discovery article: I need to know how the re-emergence of the forearm artery could have led to a breeding advantage — the only way it could be responsible for its increased manifestation. I also remember how my teachers (evolutionary epistemologist Gerhard Vollmer and ethologists Konrad Lorenz and Irenäus Eibl-Eibesfeldt) would always caution: any clear evolutionary change usually takes about 100 generations to manifest.
So I really doubt whether the presence of a median artery is the result of evolution. Compare it to the fact that humans are now taller and heavier than they were a few hundred years ago. This is not because any evolutionary pressure changed their genes (big tall individuals have not been breeding faster than others), but is due to better infant care, more nutritious food and other environmental factors.
The fact is, I generally believe that human evolution has ground to a halt. With the exception of a small number of factors, like resistance to disease or the ability to endure harsh climate, there are really no chance mutations that currently hinder or boost breeding — everyone does it: the tall and the short, the poor and the rich, the beautiful and the ugly. From an evolutionary point of view, there is no rigorous selection taking place.
Having said that, I believe that the last true evolutionary process may have taken place in medieval Arabia, where polygamy flourished. Take the 17th century Alaouite ruler Moulay Ismail of Morocco. He is said to have had over a thousand children from four wives and 500 concubines. While these numbers are quite extreme, at the time it was common to have many wives. Now if a man has ten wives, this means that there are nine men who do not have any. And if there were distinct natural traits that gave certain men an advantage — intelligence, social skills, ruthlessness, aggression — and if the process was in place long enough, say 100 generations, we could expect a noticeable evolutionary effect. This is something that can and should be studied.
Now back to the grandkids: after telling them about Darwin and the mechanisms of evolution, I gave them a question: which is the most successful animal, from the point of view of evolution. Enders, 8, guessed tiger, gorilla, elephant. No, these are in fact endangered species. His younger brother Hennes, 7, suggested “homo sapiens?” (the words they know these days!). Well, close. The answer I was looking for made them laugh: it is the common chicken!
Just think about it: during most of their evolutionary history a few hundreds of thousands of these birds may have lived in forests, hunted by predators, always in danger of eventual extinction. Around the fifth century B.C. the chicken found another species of animal that would meticulously tend to its needs. This host species was recruited to help the chicken breed prolifically, to feed and to protect it. It became a form of symbiosis. And that caused an explosion in the number of individuals living on the planet. Today there are about 25 billion chickens inhabiting all corners of the world — while the hosts, human beings, number just seven billion. I should confess I got this example from Yuval Noah Harari’s must-read book Sapiens: A brief history of humankind.
“But they have terrible lives,” Enders protested, “they are kept in cages, their eggs are taken, they are killed and eaten.” That, I explained, is not what defines evolutionary success. It is breeding, the pure numbers (25 billion), and durability, the fact that it is almost impossible for chickens, unlike tigers or elephants, to ever go extinct.
When I asked the kids for the most successful plant, they showed they had understood my somewhat tongue-in-cheek point. It took just a few guesses to get it right: wheat! This inconspicuous grass variety, fighting to survive among weeds, has transformed itself into a thriving species that occupies millions of square miles of our planet. It is protected and cared for by the same symbiotic host as the lowly chicken.
That is how we can view pure evolution.
Also read: On Evolution and Acorns and Prime number cicadas
