Dinosaurs may be the reason we don’t live to be 200 years old: ScienceAlert
There is a distinct difference between how quickly mammals (including us) age and how quickly many species of reptiles and amphibians age.
One scientist suggests that this discrepancy may be due to the dominance of dinosaurs millions of years ago, during a critical period in mammalian history.
Microbiologist João Pedro de Magalhães of the University of Birmingham in the UK describes his “longevity bottleneck” hypothesis in a newly published paper.
Here’s the thinking: When dinosaurs ruled the Earth, it was necessary for smaller mammals to be able to reproduce quickly in order to survive, which means that genes for longer lifespans may have been eliminated as evolution progressed.
“Some of the first mammals were forced to live at the bottom of the food chain, and they likely spent 100 million years during the age of dinosaurs evolving to survive through rapid reproduction,” de Magalhaes says.
“I think that long period of evolutionary pressure has had an impact on the way we humans age.”
Published research suggests that our ancient ancestors in the eutherian mammalian lineage appear to have lost some enzymes around the time of dinosaurs, enzymes that repair damage caused by ultraviolet radiation.
Interestingly, even marsupials and monotremes lack at least one of the three UV repair enzymes, known as photolyases. It is difficult to determine whether this is related to their relatively short lifespans in any way.
One possibility is that the loss was because mammals became more active at night to stay safer, and after millions of years, we compensated by using sun cream. It is an example of the repair and restoration mechanism we could have had.
There are other signs too. Take teeth, for example: Some reptiles, including crocodiles, can continue to grow teeth throughout their lives. Humans clearly cannot – again, perhaps as a result of genetic selection dating back hundreds of thousands of years.
“We see examples in the animal world of really remarkable repair and regeneration,” says de Magalhaes. “This genetic information was so unnecessary to early mammals that they were lucky not to become so T-Rex food.”
Of course, a number of mammals celebrate triple-digit birthdays, including whales and us humans. Whether we did so under the constraints imposed by our shorter-lived ancestors, or somehow evolved to be unaffected by them, may be the goal of future research.
Understanding more about the factors behind aging is always helpful in the fight against age-related diseases, including dementia and stroke, and the genetics behind the “longevity bottleneck” may have a lot to teach us here.
“Although it’s just a hypothesis at the moment, there are a lot of interesting angles to look at this, including the possibility that cancer is more common in mammals than in other species due to the rapid aging process,” de Magalhaes says.
The research was published in Bio articles.