Longevity Briefs: How Do Some Species Live Longer Than Others?

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

The problem: The lifespans of different species is a puzzle that science still hasn’t really solved. Blue whales are more closely related to mice than they are to tortoises, but live far longer than the former while being outlived by the latter. Animal size correlates quite well with longevity, although there are many outliers (including humans and the aforementioned tortoises). To understand why some species live longer than others, we need to delve into the molecular biology of ageing. Hopefully, this will teach us how we can modify our own biology to live far longer than currently possible.

The discovery: In this preprint study, researchers developed a model that was able to accurately predict the lifespan of a species by looking at a process called DNA methylation. DNA methylation is a type of modification to the DNA molecule that does not change the genetic code itself, but rather the way in which it is read. It can be likened to bookmarking a page in a book. 

Certain sites within the DNA undergo methylation in a predictable way throughout life, and so DNA methylation is commonly used in research to estimate how quickly an individual organism is ageing. This study, however, shows that DNA methylation data can also be used to predict how long a species is expected to live. This only worked when researchers averaged the methylation data from various tissues, since different tissues undergo methylation at different rates. Using data only from stem cells, for example, tended to result in lifespan being underestimated.

While the model could accurately predict the average lifespan of a species, it did not seem to predict lifespan differences between individuals of the same species. When applied to human data, its predictions were unaffected by factors known to affect lifespan, such as smoking and obesity.

The implications: Previous studies using methylation data suggest that lifestyle factors can slow or hasten DNA methylation, and perhaps alter the rate at which an individual person ages. This study, however, suggests that there are some elements of DNA methylation that are intrinsic to a species and separate from the factors that influence individual lifespan. Understanding these fundamental epigenetic differences could be key to one day unlocking the leaps in maximum lifespan seen between different species.