Post by kristine on Oct 4, 2011 1:11:32 GMT -5
this is ...interesting...
www.wired.com/wiredscience/2011/10/recent-human-evolution/
Recent Human Evolution Detected in Quebec Town History
www.wired.com/wiredscience/2011/10/recent-human-evolution/
Recent Human Evolution Detected in Quebec Town History
...In fact, genetic signals of recent human evolution have been found, and there’s even reason to think it’s speeding up. But such genetic signatures, unconnected for now to identifiable traits, are far less glamorous and tangible than fertility.
Milot’s team based their study on detailed birth, marriage and death records kept by the Catholic church in Ile aux Coudres, a small and historically isolated French-Canadian island town in the Gulf of St. Lawrence. It wasn’t just the fact that average first birth age — a proxy for fertility — dropped from 26 to 22 in 140 years that suggested genetic changes. After all, culture or environment might have been wholly responsible, as nutrition and healthcare are for recent, rapid changes in human height. Rather, it was how ages dropped that caught their eye.
The patterns fit with models of gene-influenced natural selection. Moreover, thanks to the detailed record-keeping, it was possible to look at other possible explanations. Were better nutrition responsible, for example, improved rates of infant and juvenile mortality should have followed; they didn’t. Neither did the late-19th century transition from farming to more diversified professions.
Graph of maternal age at first birth in eight birth cohorts between 1800 and 1940. Image: Milot et al./PNAS
“I am inclined to have faith in the analyses since they are established within the quantitative genetic community,” said University of Utah anthropologist Henry Harpending, who has studied changing rates of human evolution. “Evolution, gene frequency change, can work in a hurry and is working all the time in our species.”
According to Harpending, the findings are part of a trend away from assuming that changes in populations are always environmental. “Here and elsewhere we are discovering that changes are due to genetic changes, not changes in the environment,” he said...
Milot’s team based their study on detailed birth, marriage and death records kept by the Catholic church in Ile aux Coudres, a small and historically isolated French-Canadian island town in the Gulf of St. Lawrence. It wasn’t just the fact that average first birth age — a proxy for fertility — dropped from 26 to 22 in 140 years that suggested genetic changes. After all, culture or environment might have been wholly responsible, as nutrition and healthcare are for recent, rapid changes in human height. Rather, it was how ages dropped that caught their eye.
The patterns fit with models of gene-influenced natural selection. Moreover, thanks to the detailed record-keeping, it was possible to look at other possible explanations. Were better nutrition responsible, for example, improved rates of infant and juvenile mortality should have followed; they didn’t. Neither did the late-19th century transition from farming to more diversified professions.
Graph of maternal age at first birth in eight birth cohorts between 1800 and 1940. Image: Milot et al./PNAS
“I am inclined to have faith in the analyses since they are established within the quantitative genetic community,” said University of Utah anthropologist Henry Harpending, who has studied changing rates of human evolution. “Evolution, gene frequency change, can work in a hurry and is working all the time in our species.”
According to Harpending, the findings are part of a trend away from assuming that changes in populations are always environmental. “Here and elsewhere we are discovering that changes are due to genetic changes, not changes in the environment,” he said...