Are Humans Still Evolving?

Anybody who teaches human evolution is inevitably asked: Are we still evolving? The examples of lactose tolerance and duplication of the amylase gene show that selection has certainly acted within the last few thousand years. But what about right now? It’s hard to give a good answer. Certainly many types of selection that challenged our ancestors no longer apply: improvements in nutrition, sanitation, and medical care have done away with many diseases and conditions that killed our ancestors, removing potent sources of natural selection. As the British geneticist Steve Jones notes, 500 years ago a British infant had only 50 percent chance of surviving to reproductive age, a figure that has now risen to 99 percent. And for those who do survive, medical intervention has allowed many to lead normal lives who would have been ruthlessly culled by selection over most of our evolutionary history. How many people with bad eyes, or bad teeth, unable to hunt or chew, would have perished on the African savanna? (I would certainly have been among the unfit.) How many of us have had infections that, without antibiotics, would have killed us? It’s likely that, due to cultural change, we are going downhill genetically in many ways. That is, genes that once were detrimental are no longer so bad (we can compensate for “bad” genes with a simple pair of eyeglasses or a good dentist), and these genes can persist in populations.

Conversely, genes that were once useful may, due to cultural change, now have destructive effects. Our love of sweets and fats, for example, may well have been adaptive in our ancestors, for whom such treats were a valuable but rare source of energy. But these once rare foods are now readily available, and so our genetic heritage brings us tooth decay, obesity, and heart problems. Too, our tendency to lay on fat from rich food may also have been adaptive during times when variation in local food abundance produced a feast-or-famine situation, giving a selective advantage to those who were able to store up calories for lean times.

Does this mean that we’re really de-evolving? To some degree, yes, but we’re probably also becoming more adapted to modern environments that create new types of selection. We should remember that so long as people die before they’ve stopped reproducing, and so long as some people leave more offspring than others, there is an opportunity for natural selection to improve us. And if there’s genetic variation that affects our ability to survive and leave children, it will promote evolutionary change. That is certainly happening now. Although pre-reproductive mortality is low in some Western populations, it’s high in many other places, especially Africa, where child mortality can exceed 25 percent. And that mortality is often caused by infectious diseases such as cholera, typhoid fever, and tuberculosis. Other diseases, like malaria and AIDS, continue to kill many children and adults of reproductive age.


Culture has removed many of the selective pressures from human survival, allowing harmful mutations to build up in the genepool; meanwhile, people living in third-world countries continue to experience selective pressures from droughts, famines, and disease.

Folksonomies: evolution memetics culture natural selection

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Natural selection (0.970852): dbpedia | freebase
Evolution (0.889445): dbpedia | freebase | opencyc
Mutation (0.487819): dbpedia | freebase
Genetics (0.478649): dbpedia | freebase | opencyc
Selection (0.460972): dbpedia | freebase
Population genetics (0.412645): dbpedia | freebase
Infectious disease (0.384285): dbpedia | freebase
Biology (0.379467): dbpedia | freebase | opencyc

 Why Evolution Is True
Books, Brochures, and Chapters>Book:  Coyne , Jerry A. (January 22, 2009), Why Evolution Is True, Penguin (Non-Classics), Retrieved on 2011-09-15
Folksonomies: evolution evidence creationism