A new research paper finds that naked mole-rats (Heterocephalus glaber) don’t have biological age like most other other organisms do! Could they be biologically immortal?

The Naked mole-rats (Heterocephalus glaber) are one of the most interesting mammals that we have in the entire world, because these little guys have some extreme features that has not been seen in any other organism, especially not in any other mammal species!

Aren’t they cute? Image by Roman Klementschitz, posted with the Creative Commons Attribution-Share Alike 3.0 Unported license.

About nine months ago I did a post about how the naked mole-rats can survive for several hours at extremely low oxygen concentration. These oxygen concentrations would kill humans and most other mammals within minutes, but the naked mole-rats would stay there for hours without getting harmed. The experiment was even stopped after a while because the rats seemed unaffected, not because they had a limit at a few hours!

Not only can they survive extreme temperature conditions, they also cannot feel certain types of pain, are naturally resistant to cancer, and are cold-blooded (like a reptile). And just like you would expect from the picture above, it is mostly naked except for a few scattered hairs. It is indeed a strange, but wonderful little creature, and a new research paper published eLife suggest that they don’t experience biological mortality like most of us do.

How we define biological age

We actually have a “Law of mortality” when we are describing biological age, and up until this point every single mammal has shown to follow the Gompertz–Makeham law of mortality. This is basically an exponential growth, and for humans the mortality rate is doubling every 8 years after we hit 40. While the exact equation might not be 100 % perfect, it has mostly been right when used to predict the mortality rate of mammals as they age, until a scientists decided to see how long a naked mole-rat would typically live.

Keep in mind that there are some other organisms that do not follow this law at all. The Immortal Jellyfish (Turritopsis dohrnii) will for instance revert back to a polyp stage at a certain point, essentially making it biologically immortal. We could also argue that organisms that give birth to clones of itself is essentially biologically immortal since their survival rate as well as their reproductive success will not decrease over time.

An image of the Immortal jellyfish. Image by Wikimedia Commons user Bachware, posted with the Creative Commons Attribution-Share Alike 4.0 International license.

The survival rate of the naked mole-rat stays the same during its entire life!

Comparative biologist Rochelle Buffenstein has been studying naked mole-rats for the most of her life, and has collected vast records of all the naked mole-rats that have been in her care. She recorded the date of birth, date of death, as well as cause of death. In total she ended up with over 3,000 data points, and tested these against the Gompertz–Makeham law of mortality. We would typically need at least 100 data points of life expectancy for this equation to be correct, but it did not manage to find the lifespan of the naked mole-rats even with over 3,000 points of data!

The naked mole-rats become sexually mature at 6 months old, and at this point each mole has a 1/10,000 chance of dying. Other mammals would have an increasing chance that exponentially increases, but the naked mole-rat’s keep staying at the same level for at least 30 years! At one point it even decreases at a certain age, and goes directly opposed everything we know about mammalian aging.

The females also stayed fertile during this entire time, so as far as we know they don’t even become infertile at one point. Even females who were over 30 years old has the same fertility as younger individuals.

Image is Public Domain.

Are they biological immortal, or just very slow-aging?

It is very important to keep the limitations of this study in mind, and not just assume that the naked mole-rats has achieved biological immortality just yet. One of the biggest problem with the study is that very few “old” rats were used. They had a few that were close to and around 30 years of age, which is very old for a rodent this size, but it would certainly be preferable if they had even more individuals at this age, or maybe even older. For all we know they could face a sharp decline in survival rate at age 50?

At this point it surely looks like the naked mole-rats could be a non-aging mammal, but just keep in mind that there are still many unanswered questions.

Why are the naked mole-rats so special?

So, what exactly makes the naked mole-rats able to be seemingly biologically immortal? The leading theory has to do with their unique genes. Basically the naked mole-rat has some very cool parts of DNA that is able to code for systems that keep all of its DNA healthy. All organisms have this (or else we would die a lot faster), but our system tend to get weaker as we get older. They also have high levels of chaperone proteins that help other proteins fold in the correct manner, which is also a huge problem for older individuals of other species.

Thanks for reading

Thank you for spending your Sunday by reading my post about one of the coolest animals that exist. I hope you enjoyed it. If you are curious to learn more, then just follow the links in the text, but be warned; some of the ones about genetics can be very heavy for those without much knowledge of this topic. And as always, leave a comment below if you got anything to share!

Make sure to follow @valth for more posts like this!