We humans get weaker as we age, and then finally we die.
That’s not normal across all species, and in fact some organisms don’t seem to age at all.
That’s what a new study has found this week, as published in Nature. It compares aging patterns of humans and more than 40 other species.
“We all have preconceived notions about aging and what it should be like,” says biologist Pedro F. Quintana-Ascencio, at the University of Central Florida. Quintana-Ascencio was one of the study’s contributors, under direction of evolutionary biologist Owen Jones at the Max-Planck Odense Center at the University of Southern Denmark. “But this study shows we really need to look at the aging process in more depth. All is not what it appears across species. Humans, especially modern humans, appear to be outliers.”
The group compared and contrasted how vertebrates, invertebrates, plants, and a green alga age, and included people, frogs, lions, lice and the native Florida plant Hypericum cumulicola.
What they found was that the mortality of some species, including humans and birds, goes up with age, while for others the increase is slower. For others still, including the desert tortoise and some trees, the likelihood of death goes down as they age.
The study found that there’s no strong correlation between aging patterns and the normal life spans of the species under study. Some can have increasing mortality and still live a long time, or declining mortality and still live a short time.
“It makes no sense to consider aging to be based on how old a species can become,” Jones said. “Instead, it is more interesting to define aging as being based on the shape of mortality trajectories: whether rates increase, decrease or remain constant with age.”