As winner of the annual UCSB Harold J. Plous Award, anthropology assistant professor Michael Gurven will explain today why grandmothers help humans live longer and why people have such large brains.

Gurven will speak in the Humanities and Social Sciences Building’s McCune Conference Room at 4 p.m. He said the lecture is free and is designed for “an educated public,” and all who are interested are welcome to attend.

Gurven said he won the Plous Award last year for his research in Bolivia on human longevity. Named for its first recipient – economics assistant professor Harold J. Plous – in 1957, the award acknowledges the accomplishments of professors who have impacted the university through research, service and teaching. After each academic department chooses one nominee, a committee selects the winner.

In his lecture, Gurven said he will explain the “Grandmothering Hypothesis,” which examines the contributions grandmothers make to their families by helping to raise children and perform various domestic tasks. Gurven said he began research on the hypothesis through an investigation of hunter-gatherer societies.

“Certain levels of cooperation got me thinking of the impacts of grandparents helping grandkids and parents helping kids,” Gurven said.

He said he searched for explanations as to why humans live as long as they do.

“The existence of longer life defies any evolutionary logic,” Gurven said. “It doesn’t make sense [for women] to spend one-third of life after menopause if the purpose of natural selection is to reproduce … I’ve been trying to answer the question of why life spans are long, why our brains are so big, and why kids take so darn long to grow.”

Gurven said human life expectancy has increased by about four months per year for the last 160 years. The elderly indirectly contribute to this increase, as well as to reproduction in general, by helping their children and grandchildren survive longer. The tendency for humans to be social also partially accounts for why they live longer than any other primate.

To further examine human longevity, Gurven said he wanted to research societies lacking supermarkets, modern health care and sanitation. In his Tsimane Life History Project, Gurvin studied the economic production, trade and sharing of the Tsimane people in Bolivia. The Tsimane, who are hunter-gatherer horticulturalists, live similar lifestyles to those of human ancestors, he said.

Preliminary work on the project began in 1999 followed by official research initiated in 2002, Gurven said. He said he expects the research to continue until 2009.

The 10-year span of the project allows research teams to investigate changes within the Tsimane over time, Gurven said. Gurven’s research teams are fixed in various locations across Bolivia with a mobile team that visits 2,000 Tsimane people twice a year.

Besides being UCSB-affiliated, Gurven said the National Science Federation and the National Institute of Health granted funding for his project. The project is also affiliated with the University of New Mexico where Gurven holds a doctorate in anthropology. Gurven said he began teaching at UCSB in 2001.