The Grandmother Hypothesis and the Cognitive Reserve Hypothesis: An Argument for Co-Evolution
(CSU, Sacramento)
Homo sapiens is one of the few species with a post-reproductive life stage. This paper compares two of the major theories about the evolution of longevity and the function of the post-reproductive life stage. Longevity is a trait that is difficult to find proof of selection for because natural selection becomes less of a factor past prime reproductive years. The grandmother hypothesis suggests that women live past their reproductive years so that they may help care for their children’s children rather than channel resources towards producing more offspring of their own. Studies have shown that women whose mother’s contribute to the provisioning of their offspring have higher survival rates of their first-born than women whose mother’s are not present. The cognitive reserve hypothesis has two parts, the passive and the active. The passive is simply that having a larger brain size confers some protection against dementia as well as assisting in healing faster after trauma. The active model considers how increased intelligence and education may stave off cognitive decline related to aging, disease or trauma. This paper examines the possibility that these traits may have co-evolved. If it is advantageous for a woman to stop producing offspring and contribute to the provisioning of her grandchildren, then it would be more to her advantage to maintain high cognitive functioning late in life. With people living longer, research related to aging is highly relevant in the world today.