Females of some cetacean species extended their lives to take care of their grandchildren. 

It was once believed that menopause was unique to human females. However, 21st-century research has identified this phase in five distinct whale species, known as toothed whales or odontocetes, which live well beyond their reproductive years. Like humans, these species live in multigenerational social groups. Recent studies indicate these whales live longer to benefit their group and care for their grandchildren. Researcher Samuel Ellis from the University of Exeter revealed that these species live around 40 years longer than expected compared to species without menopause. This mirrors human females, who live over 40% of their lives post-reproduction. The phenomenon of menopause evolved independently in these species, which include orcas, false killer whales, pilot whales, narwhals, and belugas. Females of these species not only outlive females of similar-sized species but also the males of their own species. This study suggests that the evolutionary benefit of living longer, even without reproducing, could be to care for grandchildren rather than offspring. In species with menopause, grandmothers overlap their lives with their grandchildren, providing more time for intergenerational care. This mirrors the «grandmother hypothesis» in human evolution, suggesting that post-reproductive females play a vital role in the survival and well-being of their grandchildren.