Fight Aging!

Sometimes I point out research not because it is relevant to the immediate cause of building therapies to control aging, but because it is interesting. That is definitely the case here: I doubt you can find a practical use for a paper on the modeling of aging and longevity in tyrannosaurs. That doesn't stop it from being a fascinating topic, of course.

Researchers follow their interests, and that is worth celebrating. If no-one was interested in deciphering and more importantly treating aging, we would still be in exactly the same position as all of our ancestors: doomed to short lives terminated by a period of pain, suffering, and debility. As things stand we are only maybe doomed, with the odds strongly depending on date of birth and progress in raising funding for research, but even that is an enormous improvement. Whether or not you and I personally make it into the age of radical life extension, by bootstrapping the use of one therapy at a time to incrementally repair our biochemistry and extend healthy life, it remains the case that by supporting this cause we help to create the means to save countless lives in the near future.

Aging is near universal trait among species, and has been for a very long time, all the way back to the murky origins of cellular life. You might look on the universality of aging as the result of an evolutionary race to the bottom, similar in a way to the human relationship with organized violence. War hurts the individual and diverts efforts from productive use, but the only way to survive as a collective when your competitors are proficient at violence is to follow the same path - and so everyone diverts resources into mutual destruction rather than growth. Aging may be such an effective evolutionary strategy because it enables better survival of a species in the face of environmental change. We age because the world changes, and ancestral species with aging replaced near all species without aging, right from the outset. Only in a few scattered niches do we find a tiny number of species where evolution has led to a move away from aging as a strategy. Thus when we look into the deep past and model the lives of species such as dinosaurs, those for which enough bones exist for decent models of life span, we should not be at all surprised to find the same patterns of aging as we see today.

Tyrannosaurs as long-lived species

Tyrannosaurs including Tyrannosaurus rex (shortly T. rex meaning tyrant lizard king) are very popular to the public as well as among paleontologists although they became extinct 66 million years ago. Many mysteries about population ecology and actual behavior of tyrannosaurs have been resolved thanks to modern technologies and collective data in paleobiology. In particular, rigorous anatomic methods have been developed and eventually reliable life tables for tyrannosaurs were estimated. Using their demographic data, tyrannosaur aging dynamics was carefully interpreted. Gompertz function or Weibull function was utilized to quantify tyrannosaur survival curves, but both might be insufficient to appropriately describe complicated biological survival curves. Suitable mathematical descriptions and statistical methods are still required to quantify survival and mortality curves of tyrannosaurs.

Here we address a methodology that enables us to appropriately quantify tyrannosaur survival and mortality curves by utilizing modified stretched exponential survival functions, which we have developed to precisely quantify human demographics. We find a demographic analogy between tyrannosaurs and 18th-century humans despite scale and ecological differences. Interestingly, mortality patterns for tyrannosaurs resemble those for 18th-century humans: probably tyrannosaurs would be able to live so long to undergo aging before maximum lifespans, while their longevity strategy would be more alike to big birds rather than 18th-century humans. We attribute longevity of tyrannosaurs to late sexual maturity, large body size, and rapid growth rate, which would be favorable for longevity.

Analyzing the stretched exponents helps evaluation of longevity strategy across species. Although survival and mortality curves look very similar between tyrannosaurs and 18th-century humans, their stretched exponent patterns are significantly different. The stretched exponents with respect to the normalized age show a clear difference in longevity strategy between 18th-century humans and tyrannosaurs. For 18th-century humans, the curves are similar to those of apes or crocodilians, whereas those of Albertosaurus sarcophagus show similar patterns with deer, cassoway, or raptors. This analysis suggests that tyrannosaurs would live longer than other species in terms of the normalized age. Tyrannosaurs would exhibit late sexual maturity, large body size, and rapid growth rate, which would be favorable for longevity. There would be benefits from predation relief by rapid growth for longevity of tyrannosaurs. Probably becoming giants through rapid growth or becoming apex predators would be favorable to acquire exceptional benefits for releases from predation in early life, which would be good for longevity, regardless of uncertainty on whether they were primarily predators or scavengers.