Scientifically-literate
piece from Time.com about how human evolution is proceeding these days.
Stearns' team examined the vital statistics of 2,238 postmenopausal women participating in the Framingham Heart Study, which has tracked the medical histories of some 14,000 residents of Framingham, Mass., since 1948. Investigators searched for correlations between women's physical characteristics; including height, weight, blood pressure and cholesterol levels; and the number of offspring they produced. According to their findings, it was stout, slightly plump (but not obese) women who tended to have more children. "Women with very low body fat don't ovulate," Stearns explains - as did women with lower blood pressure and cholesterol levels. Using a sophisticated statistical analysis that controlled for any social or cultural factors that could impact childbearing, researchers determined that these characteristics were passed on genetically from mothers to daughters and granddaughters.
If these trends were to continue with no cultural changes in the town for the next 10 generations, by 2409 the average Framingham woman would be 2 cm (0.8 in) shorter, 1 kg (2.2 lb.) heavier, have a healthier heart, have her first child five months earlier and enter menopause 10 months later than a woman today, the study found. "That rate of evolution is slow but pretty similar to what we see in other plants and animals. Humans don't seem to be any exception," Stearns says.
...
Steve Jones, an evolutionary biologist at University College London who has previously held that human evolution was nearing its end, says the Framingham study is indeed an important example of how natural selection still operates through inherited differences in reproductive ability. But Jones argues that variation in female fertility, as measured in the Framingham study, is a much less important factor in human evolution than differences in male fertility. Sperm hold a much higher chance of carrying an error or mutation than an egg, especially among older men. "While it used to be that men had many children in older age to many different women, now men tend to have only a few children at a younger age with one wife. The drop in the number of older fathers has had a major effect on the rate of mutation and has at least reduced the amount of new diversity - the raw material of evolution. Darwin's machine has not stopped, but it surely has slowed greatly."
Bad news for guys in 500 years; all the chicks will be short and dumpy. On the other hand, there's a clear mandate here for tall, slender women. You must breed more frequently to ensure the future beauty of the human race! (Since current standards of beauty are
sure to endure for another four centuries.)
The article is useful for what it does, but it doesn't even attempt to address technology or culture, which are likely to be far more important factors than just reproductive evolution in shaping humans 10 or 15 generations down the line. Everyone might be 7 feet tall in a century, once scientists learn which gene to click to control height. Such changes would probably not be inheritable, but it's easy to imagine a society (especially in America, the last bastion of resistance to universal health care) where the rich can have their children perfected by some simple gene therapies in utero, giving them stronger muscles, greater height, disease resistance, etc.
Or not, if there's religiously-fueled opposition to human genetic engineering. Or we could refuse to transition to a post fossil fuels era and hit oil shocks and worldwide economic ruin, resulting in mass starvation and poor childhood nutrition, and shrink down to 5 feet, like our blighted ancestors in the Dark Ages. Forecasting today's conditions forward 500 years, without assuming massive technological and other changes seems almost pointless, when you look at the changes human society has undergone in just the past century.
Not that scifi predictions have a place in simple articles about potential, gradual, incremental evolutionary changes in human beings, but considering some of them provides more than enough reason to largely ignore the article's safe, sane, and highly unlikely conclusions.
Labels: evolution
