How dinosaurs may have influenced human aging

Have you ever wondered why animals, especially birds and some reptiles, especially turtles, live such long lives compared to mammals with the same body masses? According to molecular biogerontologist João Pedro de Magalhães, professor at the Institute of Aging at the University of Birmingham, this could be an evolutionary vestige that dates back to the era of the dinosaurs — which ended with their mass extinction around 66 million years ago.

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João Pedro de Magalhães, a renowned expert on aging, who dedicated his entire professional life to understanding the genetic, cellular and molecular mechanisms of this characteristic of human evolution, has just published his fascinating hypothesis, “the longevity bottleneck” (ref.). This hypothesis connects the long-term ecological and evolutionary effects that predatory dinosaurs had on the aging process in mammals, up to the present day.

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Some groups of animals escaped these effects. Why?

It has long been observed that most birds and some reptiles and amphibians show few or no signs of aging, while all mammals, including humans, show an obvious aging process. This is probably a result of the dinosaurs’ eating habits, according to the expert.

“Some of the earliest mammals were forced to live at the bottom of the food chain and probably spent 100 million years during the age of dinosaurs evolving to survive through rapid reproduction,” Magalhães said. “This long period of evolutionary pressure has, I propose, an impact on how humans age.”

The hypothesis proposes that during the Mesozoic Era, when dinosaurs reigned supreme in the wild, mammals faced persistent pressure to mature and reproduce quickly before being eaten. This pressure has led to the loss or inactivation of genes associated with longevity, especially those associated with tissue regeneration and DNA repair.

“The ‘longevity bottleneck hypothesis’ can shed light on science about the evolutionary forces that shaped mammalian aging over millions of years,” explained the professor. “Although humans are among the longest-lived animals, there are many reptiles and other animals that have a much slower aging process and show minimal signs of senescence throughout their lives.”

Adding to more information about the aging of modern mammals, an interesting discovery from a different group suggests that early mammals from the Jurassic period may have aged in a similar way to reptiles (ref.) — that is, slowly. (Dinosaurs came to dominate during the middle and late Jurassic.)

These studies suggest that many birds (which are, after all, dinosaurs) and some reptiles, especially turtles, possess the genes needed to deal with oxidative stress and the resulting tissue damage.

“We see examples in the animal world of truly remarkable repair and regeneration. This genetic information would have been unnecessary for the first mammals that were lucky enough not to end up as food for T. rex”, explained Magalhães. “Although we now have a multitude of mammals—including humans, whales, and elephants—that grow and live long, we and these mammals live with the genetic constraints of the Mesozoic era, and we age surprisingly faster than many reptiles.”

These genetic losses may also explain why mammals are more likely to develop cancer as they age.

“Although it is just a hypothesis at this time, there are many interesting angles to explore, including the prospect that cancer is more frequent in mammals than in other species due to our evolutionary history.”

Source:
João Pedro de Magalhães (2023). The longevity bottleneck hypothesis: Could dinosaurs have shaped aging in modern mammals? BioEssays | doi:10.1002/bies.202300098

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