![]() This is a problem for the classical theories of aging that assume that mortality increases with age, notes Alan Cohen, an evolutionary biologist at the University of Sherbrooke in Quebec. In contrast, Hydra, a microscopic freshwater animal, has constant mortality and lives a whopping 1,400 years. Oarweed, for example, has a near-constant level of mortality over its life and lives about eight years. Same goes for the species that don’t age at all. It turns out that some species with pronounced aging (meaning those with mortality rates that increase sharply over time) live a long time, whereas others don’t. What the new study didn’t find, notably, is an association between lifespan and aging. “It’s crazy to think that we’ve been working on aging for so long and something as fundamental as this hasn’t been seen before.” “Some patterns have emerged in this paper that none of us knew were there,” says Reznick, who has studied aging patterns among different populations of guppies. But others are weird, at least from a human-centric view. elegans and Drosophila, have shapes like ours. The study shows, for example, that most mammals and, importantly, the species that scientists tend to use in the laboratory, such as C. “They’ve come up with a way of putting everything on the same scale, so you can perceive patterns that have never been looked at before.” “That’s what’s so disarming about it,” says David Reznick, a distinguished professor of biology at the University of California, Riverside, who was not involved in the new study. This allows for easy comparison across species, just by looking at the shapes of the curves. Jones got around these obstacles by defining “relative mortality” and “relative fertility” numbers for each species, calculated by dividing fertility or mortality rate at a particular age by the average rate across the organism’s entire lifespan. What’s more, for some species - like the white mangrove, red-legged frog, and hermit crab - this data comes from defined stages of development rather than across the entire lifespan. Mortality and fertility rates of various organisms can differ by orders of magnitude. One challenge is that it required a deep dive into the published literature to a) find the raw data on all of these species, and to b) get in touch with the researchers who conducted the field work to see if they’d be willing to share it.Īfter rounding up all of that data there was then the problem of standardizing it. This sweeping comparison didn’t require particularly high-tech equipment it could probably have been done a decade ago, if not before. “This article is probably asking more questions than it’s answering.” “You have to then begin to ask yourself, why are these patterns like they are?” he says. His study found, for example, that most vertebrates show similar patterns, whereas plants are far more variable. What’s most interesting to Jones is not only the great diversity across the tree of life, but the patterns hidden within it. “But if you go and speak to someone who works on fish or crocodiles, you’d find that they probably wouldn’t be that surprised.” We think everything must behave in the same way that we do,” says Jones, an assistant professor of biology at the University of Southern Denmark. That diversity will be surprising to most people who work on human demography. Still others show no change in fertility or mortality over their entire lifespan. Others show a spike in both fertility and mortality in old age. Some organisms are the opposite of humans, becoming more likely to reproduce and less likely to die with each passing year. But lots of species show different patterns - bizarrely different. Sure, some species are like us, with fertility waning and mortality skyrocketing over time. ![]() For folks (myself included) who tend to have a people-centric view of biology, the paper is a crazy, fun ride. Today in Nature, evolutionary biologist Owen Jones and his colleagues have published a first-of-its-kind comparison of the aging patterns of humans and 45 other species. Hamilton wrote in 1966, “is an inevitable outcome of evolution.” To use the lingo of evolutionary biology, they’re not subject to selective pressure. That combination means that the genetic underpinnings of aging, whatever they are, don’t reveal themselves until after we reproduce. Since the early 1950s, evolutionary biologists have come up with a few explanations, all of which boil down to this: As we get older, our fertility declines and our probability of dying - by bus collision, sword fight, disease, whatever - increases. Why don’t all tissues regenerate forever? Wouldn’t that be evolutionarily advantageous? A full set of DNA resides in each of our cells, after all, allowing most of them to replicate again and again and again. Why we age is a tricky evolutionary question.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |