Washington, December 11 : A new study suggests that the smaller life spans of pygmies across the world might be a reason as to why they are smaller in size than average humans.
A new study suggests that the smaller life spans of pygmies across the world might be a reason as to why they are smaller in size than average humans.
The research suggests that brief life spans put evolutionary pressure on pygmy women to stop growing and to start giving birth sooner. As a result of this, the energy that should normally be expended on growth gets spent on reproduction at a younger age.
"The idea is that (pygmies) have to stop growing earlier, because when you start reproducing-at least for women-all the energy you would put in growth is put into reproduction," the National Geographic quoted Andrea Migliano, the lead author of the study and a postdoctoral fellow at Clare College, Cambridge, in the United Kingdom, as saying.
"You have to choose-either you grow or you reproduce," she added.
Reported online in the Proceedings of the National Academy of Sciences, Migliano's study contradicts the age-old belief that pygmies' small stature is due to environmental factors like poor nutrition.
Migliano said that she could not agree with the suggestion of malnutrition because some of the world's tallest people-such as Kenya's Maasai and Samburu-also typically suffer from poor nutrition.
She instead proposed that an evolutionary process woven into pygmies' genetic structure was the reason behind their stature. She also said that pygmies' stature would not change even if they were subjected to less stressful environment.
Migliano and her colleagues studied two populations of pygmies in the Philippines, the Aeta and the Batak.
The communities studied have high mortality because the populations are ravaged by easily preventable diseases like measles and chicken pox.
Migliano revealed that poor diets make them more vulnerable to illness.
So far, theories similar to her hypothesis have been used to explain the difference between other kinds of mammals like elephants and mice.
"The broad variation in size across mammals goes with extreme variation in the pace of life histories-little-bitty ones live fast and die young, and big ones live slowly and die old," said Kristen Hawkes, an anthropologist at the University of Utah in Salt Lake City who edited Migliano's paper.
"Links between body size and life history have been applied to species changes over time within our lineage, but (Migliano) is the one who's taken this theory to look at within-species variation among living people," Hawkes added.
Since Migliano's theory proposes that pygmies are proof of how Homo sapiens continue to evolve, it is unlikely to go down well with creationists and proponents of intelligent design.
Migliano, who said she had already gotten some criticism for putting her theory forward, said: "There is this idea that evolution should not apply for humans."
She also revealed that she was working with the Government of the Philippines to improve pygmies' living conditions.
"I am sure we are still adapting to our environment. But saying we are adapting to our environment doesn't say that the pygmies are fine. They are adapting to the worst situation in the world," she said. (ANI)
© 2007 ANI
