Humans
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There’s no question that prehistoric hominins had it tougher than we do today, with the dangers of big-game hunting and a lack of modern healthcare stacking the odds of survival against them. It’s therefore unsurprising that we tend not to find any elderly Neanderthals or Denisovans in the fossil record, while for present-day Homo sapiens (that’s us), it’s really no big whoop to reach 80, 90 or even 100 years of age.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.One question that remains unresolved, though, is whether the genetic capacity for such longevity emerged before or after we split from our most recent common ancestor with these extinct lineages. In other words, with all things being equal, could a Neanderthal or Denisovan live as long as we do, or do they lack the super-ager genes?
To investigate, the authors of an as-yet unpublished study used epigenetic clocks to determine the maximum achievable lifespan of modern humans, Neanderthals, and Denisovans. Also known as DNA methylation clocks, these tools enable researchers to measure the biological age of human cells, giving an indication of how much life they have left.
Using 16 different methylation clocks, the study authors examined 15,283 methylation data samples from people of diverse ethnic backgrounds. These individuals varied in age from 0 to 114 years, with 219 samples coming from donors over the age of 90.
Employing a variety of approaches, the researchers attempted to find the theoretical upper boundary of the human lifespan. For instance, when splitting their sample up into different tissue types, they calculated that respiratory tissues have the lowest longevity and can’t live longer than 128.3 to 155.1 years.
Based on all the results obtained from the various epigenetic clocks used, the authors ultimately conclude that the absolute upper limit of the modern human lifespan lies somewhere between 128 and 202 years. However, they go on to state that achieving such an innings would likely rely on perfect environmental conditions, and that the “existing environment may not be sufficient to support the attainment of these age boundaries.”
Applying the same methods to Neanderthal and Denisovan genomes, the researchers calculate a maximum lifespan of 38.2 to 64.5 years for the former and 40 to 69.8 years for the latter. Despite this, they accept that reaching these ages was unlikely during the Pleistocene, as each day brought new survival challenges for these now-extinct hominins.
For instance, female Neanderthals are believed to have experienced high rates of pregnancy complications, resulting in elevated instances of maternal mortality. Males, meanwhile, often suffered serious hunting injuries, with infections posing a major obstacle to survival.
Moreover, while the results of this study are highly tentative and limited by the potential inaccuracy of epigenetic clocks, they do suggest that the capacity for extended longevity is a trait that evolved in modern humans after our split from the Neanderthals and Denisovans.
A preprint of the study, which at time of writing is currently undergoing review, can be found on Research Square.
