Are we still evolving? Gabrielle Walker

Short answer: well yes, obviously. But this is yet another excellent article in Prospect. Walker goes into some detail here, and provides insight into some theories I never even knew existed. Read the whole thing, but I will give some good passages from it:

Scientists on both sides agree in principle that cultural changes can affect human evolution. After all, such changes are just another way of altering the environment, and natural selection can respond to any environmental change provided that it lasts long enough. The earliest, best documented and most intriguing cultural change is something that anthropologist Kristen Hawkes from the University of Utah calls the “grandmother effect.”

Like others before her, Hawkes was baffled by the age structure of modern human societies. When a woman’s childbearing years are over, natural selection should lose interest in her; she has no further chance to pass on her genes so there should be no evolutionary benefit to prolonging her life. But women survive long after they have lost fertility.

It is tempting to attribute this to modern medicine. Life expectancies in the developed world have only recently soared to their current heights. In 19th-century France, for instance, female life expectancy was just 39 years, yet by the late 20th century it had almost doubled. However, Hawkes points out that very high rates of child mortality skewed 19th-century life expectancies. Though many girls died before they reached adulthood, those women who survived to the age of 45 lived on for an average of more than 20 more years – even without the benefits of medicine.

What’s more, the same strange pattern shows up in societies around the world. However primitive or advanced the culture, about a third of adult women are beyond their childbearing years. Among all the other primates, loss of fertility is quickly followed by loss of life. Why should humans be different?

I fall on the “evolution is still going on” side:

Geneticist Alan Templeton from Washington University in St Louis is convinced that evolution is not yet over, though he thinks it is meaningless to ask how fast human evolution is moving, since some traits change rapidly while others hold their ground. For one thing, he says, the diseases that we have combated are not standing still. “Disease organisms are evolving,” he says, “and that’s having a big selective impact.” Our widespread use of antibiotics is leading to super-resistant organisms. And the malarial parasite is evolving strategies to evade the prophylactics we take. As long as diseases keep evolutionary pace with modern treatments, they will still have the capacity to affect our evolutionary development.

Then there is the effect that a western high-fat diet and sedentary lifestyle is having on people’s weight. Obesity is particularly severe in American Indians and Pacific islanders, who possess genes that were once useful in helping guard against sudden variations in food supply. The same traits that protected them from starvation in the past are causing ballooning weight and an epidemic of diabetes, now that scarce plantains have been replaced by plentiful hamburgers.

Templeton studies a particular gene related to coronary artery disease, and sees clear evidence that it has been evolving throughout human prehistory. Genetics is too blunt a tool to identify more recent evolutionary changes, but Templeton sees no reason that the driving forces should have weakened. “All these factors tell me that natural selection is just as strong as ever, and that humans are still evolving and will continue to evolve,” he says.

3 thoughts on “Are we still evolving? Gabrielle Walker”

  1. Consider me extremely unconvinced:

    natural selection can respond to any environmental change provided that it lasts long enough

    Yes, provided that it lasts vastly long enough. You need an awful long time to evolve and pretty much zero cultural changes had occurred by the time we evolved to where we are.

    Since then, the entirety of human history and then some has happened, it is rather facile to refer to that as tritely as “cultural change”. The idea that longevity has evolved in a mere couple of generations is absurd

Comments are closed.