Dinosaurs could be to blame for the human aging process being faster than that of some other creatures, scientists have suggested.
Did human ancestors lose or deactivate “long life genes”?
Seeking to explain why some reptiles and other vertebrates age more slowly than humans, show few signs of aging before they die, and even possess “truly remarkable” regenerative traits, Doctor João Pedro de Magalhães from the University of Birmingham has proposed that reptiles and other vertebrates that were around on Earth before “the rule of the dinosaurs” therefore had the time and environments to be able to evolve “genes and pathways associated with long life”.
In contrast, mammals like our ancestors, that evolved during the 100 million years when dinosaurs were the dominant predators on the planet, evolved to favour rapid reproduction and so, over time, lost or failed to develop unneeded anti-aging or regenerative traits. Those early human ancestors and “that long period of evolutionary pressure has, I propose, an impact on the way that we humans age,” Dr Magalhães commented.
Longevity bottleneck
The so-called “longevity bottleneck hypothesis” suggests that, as potential prey for dinosaurs all the time, it was more important for our small, short-lived mammalian ancestors to reproduce quickly than to live to be over 100. Under constant reproductive pressure, genes that promote healthy reproduction and survival at younger ages were favoured instead of the genes that lie behind a healthy old age such as tissue regeneration and DNA repair.
Genes ruled by Mesozoic era constraints
“While we now have a plethora of mammals – including humans, whales, and elephants – that grow big and live long, we and these mammals live with the genetic constraints from the Mesozoic era, and we age surprisingly faster than many reptiles,” Magalhães explains.
The study acknowledges other potential factors that could influence gene selection such as temperature. As creatures that can adapt to different temperatures, mammals are so-called “poikilotherms”. Higher body temperatures are associated with shorter lifespans, but, as the study’s author notes, “whether the higher body temperature of mammals might contribute to their faster ageing when compared to reptiles and amphibians remains unknown.”
Resistance to cancer
The study was undertaken with support by the Wellcome Trust, Longevity Impetus Grants, LongeCity and the Biotechnology and Biological Sciences Research Council.
Potential further pistes for the research include whether the ability to self-heal or greater resistance to cancer were lost or inactivated in mammals. The advent of genomic sequencing has “opened the door for large-scale comparative analyses of longevity evolution” the study’s authors say.
