Women becoming taller and slimmer: study

Women are becoming taller and slimmer as they are living longer and are having fewer kids due to improved health-care and nutrition, a new study claims.
A Durham University study of people living in rural Gambia shows that the modern-day "demographic transition" towards living longer and having fewer children may also lead women to be taller and slimmer.
The findings, published in the journal Current Biology, may have relevance around the globe.
Researchers show that changes in mortality and fertility rates in Gambia, likely related to improvements in medical care since a clinic opened there in 1974, have changed the way that natural selection acts on body size.

For the study, data was collected over a 55-year period (1956-2010) by the UK Medical Research Council on thousands of women from two rural villages in the West Kiang district of Gambia.
Over the time period, those communities experienced significant demographic shifts-from high mortality and fertility rates to rapidly declining ones. The researchers also had thorough data on the height and weight of the women.

Their analysis shows that the demographic transition influenced directional selection on women's height and body mass index (BMI).
Selection initially favoured short women with high BMI values but shifted over time to favour tall women with low BMI values.

"This is a reminder that declines in mortality rates do not necessarily mean that evolution stops, but that it changes," Dr Ian Rickard, Lecturer in the Department of Anthropology said.
"Our results are important because the majority of human populations have either recently undergone, or are currently undergoing, a demographic transition from high to low fertility and mortality rates.
"Therefore the temporal dynamics of the evolutionary processes revealed here may reflect the shifts in evolutionary pressures being experienced by human societies generally," Rickard said.
"Although we cannot tell directly, it may be due to health care improvements changing which women were more or less likely to reproduce," Alexandre Courtiol of the Leibniz Institute for Zoo and Wildlife Research in Germany, said.