Did you know that our human species, homo sapiens, is still evolving? Scientist led by Stephen Stearns of the Yale University say that if the natural selection of fitter traits is no longer driven by survival, then it is because of the differences of women's fertility. "Variations in reproductive success still exist among humans, and therefore some traits related to fertility continue to be shaped by natural selection," Stearns says. In fact, women who conceive more children are more likely to pass on traits to progeny. Stearns' team conducted an experiment with 2,238 postmenopausal women who were participating in the Framingham Heart Study. They examined the women's height, weight, blood pressure, cholesterol levels, and the amount of offspring they had produced. Their observations included that that it was the stout and slightly plump women who had more children. If the trends were to continue with no cultural change in the town for the next 10 generations, by 2409 the average woman in Framingham would be 2 cm shorter and 1 kg bigger, have a much healthier heart, have its first child five months earlier, and enter menopause 10 moths later than the average woman today. However, the rate of evolution is pretty slow. Even the minor of changes, such as cultural factors and natural eating and sleeping habits, could affect the trend. On the contrary, ever since the Industrial Revolution modern humans have grown stronger and taller, making evolution seem as if it's making people more fit. Evolutionary biologist from the University College London Steve Jones argues that variations in female fertility are much less of a significant factor than the differences in male fertility. "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," says Jones .
But evolution is a long process. The predictions we make now are only predictions, and may not even occur. for example, the genetic traits of the parents play a big role on the offspring. It may be in the father's gene to have high blood pressure and cholesterol amount; and the mother may only be 5'2". The child may have high metabolism, thus causing it to not be overweight. In addition, the lifestyle of humans is constantly changing. Many people are getting less and less sleep, and it is when you sleep that the growth hormones travel in your body. Since transportation has become much easier, people are getting less exercise. Also, humans in selected areas are eating even more than before, causing rapid weight gain. All these factors apply in evolution. Evolution is the change that species go through to make living easier. So as lifestyles change, especially during this period of technology and easy living, the human body will also change in order for it to be compatible with ever-changing lifestyles.
Click Here! for the link.
I found this blog very interesting. In fact, just yesterday I was watching something on T.V. which had to do with the evolutions of human beings. It is a confusing, but very interesting topic.
ReplyDelete