We humans are unusually long-lived in comparison to our near primate cousins, and also compared to other mammals of similar body mass. We also exhibit menopause, an end to reproductive capability well before the end of life, which occurs in only a small number of other mammalian species. With a few noteworthy exceptions, such as naked mole-rats, some bats, and we humans, mammalian lifespan correlates quite well with some combination of body mass and resting metabolic rate. So why are the outliers long-lived?

Evolutionary theorists consider longer human life spans to be a consequence of our intelligence and culture. Once it became possible for grandparents to meaningfully contribute to the fitness of their grandchildren, a selection pressure for longer lives came into being. Unfortunately that selection pressure was not necessarily for anything other than an extended decline, given that the role of grandparents in the success of grandchildren is more intellectual and cultural than physical. At that point, we diverge from other primate species over time by gaining a much longer life span.

Today's research materials are an interesting look at some of the differences between humans and chimpanzees, the latter living a little more than half as long as we do. The effects of a sedentary lifestyle are clearly quite similar at the end of the day, despite the faster process of aging that occurs in our primate relatives. The pace of aging can be measured by an epigenetic clock that assesses characteristic changes in DNA methylation that take place with age, and researchers have recently extended that line of work into a number of species, chimpanzees the latest addition.

Evolution of the primate ageing process

The world's population is ageing rapidly, presenting an urgency to address the health problems of the aged. Critical insights on these problems can be gained by examining how the ageing process has been shaped over evolutionary time, and how it is influenced by different environments and lifestyles. In this issue, we feature research conducted on humans in small-scale societies and on our closest primate relatives to ask how bodies, minds, and behaviour age outside of the usual research settings. These contributions shed light on the complex relationship between ageing and disease and offer clues to the social and ecological predictors of successful ageing.

Researchers find cardiovascular health similarities between chimpanzees, humans

Researchers examined cardiovascular profiles in chimpanzees living in African sanctuaries. These chimpanzees occupy large rainforest enclosures, consume a diet of fruits and vegetables, and generally experience conditions more similar to a wild chimpanzee lifestyle. They measured blood lipids, body weight and body fat in 75 sanctuary chimpanzees during annual veterinary health check-ups, and then compared them to published data from laboratory-living chimpanzees. Free-ranging chimpanzees in sanctuaries exhibited lower body weight and lower levels of lipids, both risk factors for human cardiovascular disease. Some of these disparities increased with age, indicating that the free-ranging chimpanzees stayed healthy as they got older. Prior work suggested that chimpanzees have very high levels of blood lipids that are cardiovascular risk factors - higher than humans in post-industrial societies in some cases. The work also showed that chimpanzees living a naturalistic life have much lower levels even as they age, providing a new reference for understanding human health. In biomedical research labs, chimpanzees have more limited space and often consume a processed diet (food such as primate chow), unlike wild chimpanzees.

Your Cells Look Young for Their Age, Compared to a Chimp's