What Can Orangutans and Other Great Apes Teach Us About the Menopause?

Until recently, humans were thought to be the only mammals to experience menopause. However, recent studies have revealed that our closest relatives, chimpanzees, and gorillas, also undergo this biological transition. Menopause, the permanent cessation of menstrual cycles, has long puzzled evolutionary biologists. Why would a species evolve to outlive its reproductive years? As it turns out, menopause is a crucial factor in our evolutionary success.

The Hadza, a modern-day foraging tribe, offers a fascinating glimpse into the role of postmenopausal women in human evolution. In this society, postmenopausal women consistently contribute more food to the community than any other age or sex group. Years of experience have honed their foraging skills, ensuring the tribe’s survival.

The “grandmother hypothesis” also proposes that menopause evolved as an adaptation to boost infant survival. By shifting their focus from direct reproduction to caring for grandchildren, older women enable their daughters to have more children, ultimately increasing the group’s reproductive success. This unique strategy may have given early humans a significant advantage over other hominids like Neanderthals. So… what does this have to do with orangutans?

Orangutans have the slowest known life histories of any mammal. They take the longest time to grow up and they are the slowest to reproduce. For the first two years of a young orangutan’s life, they are completely dependent on their mothers for food and transportation. Even when they are too old to be carried, young orangutans remain close to their mothers until they are about 10 years old – and they visit their mothers for years afterwards!

Now, new research suggests that Sumatran orangutans also experience menopause. Scientists have uncovered multiple lines of evidence, including ultrasound, hormone analysis, and tissue examination, confirming a case of menopause in a female Sumatran orangutan. This groundbreaking discovery adds another layer of complexity to our understanding of these intelligent primates and their unique life history. 🦧💚