The title for World’s Oldest Dog goes to Bluey, the Australian cattle dog, who reportedly lived to the grand old age of 29. However, the average life expectancy for most canines is a relatively meagre 10 to 13 years. So, why is it that the lifespan of a dog is so much lower than that of species like the rhino, which can live up to 50 years?
The lifespans of mammals vary dramatically, from species of shrew that don’t make it to their first birthday to the bowhead whale, which celebrates two centenaries. Previous studies have suggested that a larger brain size in comparison to body weight could be indicative of a longer lifespan.
Now, researchers writing in Scientific Reports have found longer lifespans linked to an expansion of gene families responsible for boosting the immune system.
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Dog and Mammal Lifespans
To determine the impact of certain genes on longevity, researchers compared the maximum lifespan potential (MLSP) of different mammals. This refers to the age of death of the longest-lived individual on record for that particular species, which, in humans, would equate to 122 years – a record set by Jeanne Louise Calment.
Average lifespan may be influenced by factors such as the availability of different resources or the chance of winding up as someone else’s prey. MLSP can instead be considered a built-in biological limit on how long a particular animal can live, reflecting the body’s ability to manage the aging process, stave off physical and mental decline, and ward off infection.
All in the Canine Genes
Scientists consider the expansion and contraction of gene families to be an important factor in the evolution of physical traits. For example, when a gene is duplicated, it may be defunct and eventually cease to exist, or it may impact the functioning of the body, either by increasing the amount of protein that the gene produces or by creating new versions of the proteins.
In the notoriously long-lived bowhead whale, for example, biologists have identified gene changes that promote DNA repair, improve cell-cycle regulation, help prevent cancer, and protect against aging. Elephants, another mammal known for their long lifespan, possess genes that support DNA repair and suppress tumors.
For this study, researchers analyzed over 4,000 gene families from 46 mammalian species to investigate how changes in gene family size affect longevity, identifying 236 families that had a statistically significant bearing of MLSP. The findings suggest that those associated with a longer MLSP often played a role in the functioning of the immune system, increasing the organism’s ability to repair old or damaged cells, counter inflammation, and fight infection.
Interestingly, the study’s authors observed an overlap between gene families linked to brain size and those linked to lifespan. Of the 184 gene families associated with a larger brain size (in comparison to body mass), 161 were also associated with a longer MLSP – evidence that a bigger brain and a longer life may have evolved together. The same did not hold true for longer gestation periods (i.e., the length of pregnancy) or the age of sexual maturity, both of which have also been positively associated with a longer lifespan.
“Extended lifespan is associated with expanding gene families enriched in immune system functions,” the authors write. “Our results suggest an association between gene duplication in immune-related gene families and the evolution of longer lifespans in mammals.”
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
ABC Australia. Rochester's Bluey reclaims title of world's oldest dog after Guinness World Records reviews Bobi's credentials
Scientific Reports. Maximum lifespan and brain size in mammals are associated with gene family size expansion related to immune system functions
Guinness World Records. Oldest person ever
Rosie McCall is a freelance writer living in London. She has covered science and health topics for publications, including IFLScience, Newsweek, and Health.
