Mystery of head shape on Amazon Tribe

Culture is likely to trigger the evolution of human physical characteristics. That's the conclusion of research on marriage practices conducted one tribe in the Brazilian jungle.

Midwife indigenous Xavantes, Elza Fiuza for Agência Brasil. (Picture from: http://blueline2011.wordpress.com/)

People often think evolution is triggered by various environmental factors, such as environmental and geographic conditions, such as rivers and mountains. It turned out that cultural factors, such as tradition and behaviors are passed on from one generation to the next, also affect behavior, even leading to evolutionary change.

To explore this, some researchers analyzed the physical characteristics, geographic, climate, and genetics of the 1203 people who are members of six South American tribe that lived in the Amazon region and the highlands of Brazil.

Father and son in the wai’a ceremony at the Xavánte village of Etéñitepa. In it men try to get in contact and receive the protection of spiritual powers. (Picture from: http://www.livescience.com/)

Their research found that the Xavante, one ethnic group, the morphology showed irregularities or physical form. They have larger heads, taller, and narrow-faced with a wider nose.

These characteristics developed over 1,500 years after they separated from the Kayapo, another group that has a close kinship with them. The rate of change of these features 3.8-fold faster than the rate of change of another tribe.

The main changes observed by the investigators is not expected to be affected by climatic or geographic conditions Xavante. Cultural factors strongly suspected was behind the special features.

For example, in one Xavante village in Sao Domingo, a quarter of the population were sons of chiefs, Apoena, who has five wives. Sexual practices of the tribe is allowing men in high places in the group to have many wives and children, who eventually special features they quickly dominate the population.

"We have been researching Xavante for nearly half a century, and since the beginning of their morphology shows differences from the classic pattern of American Indians," said Francisco Salzano, a geneticist at the Federal University of Rio Grande do Sul. He confirmed that the Xavante experienced very rapid morphological evolution. *** [LIVESCIENCE | KORAN TEMPO 3744]