How far do you live from your mother? In 2015, the New York Times reported that the “typical [US] adult lives only 18 miles from his or her mother.”
The data reveal a country of close-knit families, with members of multiple generations leaning on one another for financial and practical support. The trend will continue, social scientists say, as baby boomers need more care in old age, and the growing number of two-income families seek help with child care.
In this stick-to-home behavior, Americans carry on a tradition that may have appeared in Africa 200 centuries ago.
“As the African tropics came out of the last ice age” about 20,000 years ago, people began finding mates closer to home rather than traveling long distances, according to a report in Nature this week.
Researchers reported that central, eastern and southern regions of sub-Saharan Africa became a “genetic melting pot, in which hunter-gatherers migrated between the three regions, mating with each other along the way” beginning about 50,000 years ago.
“Culturally distinct groups tended to seek mates from neighboring groups with whom they had more in common than migrants from distant regions,” Yale University bioarchaeologist and study coauthor Jessica Thompson “suspects.”
People may have stayed closer to home at least partly because the last ice age peaked around that time, reducing the number of areas harboring enough edible plants, animals and other resources needed to survive…
A big boost to the new investigation came from the inclusion of several examples of the oldest known human DNA from Africa. Even older examples of DNA from Homo sapiens and closely related populations, including Neandertals from around 430,000 years ago (SN: 3/14/16), have been found in Europe and Asia where cold conditions preserve genetic material better than the African tropics do. Only H. sapiens is known to have inhabited Africa during the Stone Age stretch covered in the new study.