Why do some animals live longer than others?
Plants that remember hot summers, why humans sleep less than other primates, bird flu in humans, and muons
A giraffe is much larger than a human but lives 20-30 years. A mouse typically lives 2-3 years, but a naked-mole rat (which is slightly bigger than a mouse) lives as long as a giraffe.
This is the subject of my most recent Hindustan Times column.
New research published in Nature last month found that animal lifespans are highly correlated to the number of somatic mutations in similar cells that each possesses. Somatic mutations are changes to DNA that occur over time in cells of the body. Some of these mutations cause cancer, but the vast majority are harmless or have no known function.
As I write in my column —
What is perhaps most astonishing is that despite vastly different sizes of animals and differing lifespans, the total number of mutations that can accrue in different animals falls in a narrow range.
Simply put, what this means is that as a general rule shorter-lived animals accrue mutations at a faster rate than longer-lived ones. This is an incredible correlation that immediately suggests that there’s a mutational clock ticking away at different speeds in different animals but getting to roughly the same “stroke of midnight” signalling end of life.
The new research shows that mutations accumulate like clockwork over time in different cells of different animals. In the case of the naked mole-rat and the giraffe, they both have similar lifespans and as predicted roughly the same rate of accumulating somatic mutations…
Nature summed it up brilliantly in a graphic.
Also, as I mention —
Many factors influence ageing and lifespan, but if there is a biological limit to the number of mutations cells can accumulate before malfunctioning that is preserved across different animals, that would mean that humans are not exceptional animals. It also opens up the intriguing possibility of lifespan extension by enhancing DNA repair mechanisms that fix mutations.
But as any scientist studying ageing will tell you, there isn’t usually one factor that can extend lifespan in humans. In laboratory mice which live much shorter lives, and even in non-human primates, lifespan extension is possible through calorie-restricted feeding and fasting, but this remains a holy grail for human health.
What I’ve read
Why humans sleep less than our primate relatives. This is a great read.
Plants remember hot days gone by. They’ll certainly remember this summer in India.
There’s a bird flu outbreak in birds in North America and now a man in Colorado tested positive for bird flu.
Looking at jellyfish in a new light.
How muons can be used to reveal the secrets of pyramids and volcanoes.
What I’m reading
Ainissa Ramirez has written an engaging book on how eight inventions - clocks, train rails, copper cables, photo film, light bulbs, hard disks, glass labware, and silicon chips have influenced modern human experience. Ramirez’s book expands beyond the known stories to reflect on some of the unintended consequences. I’m about three-quarters of the way done.
What I’ve watched
The promise and peril of hydrogen energy
Endnotes
My favorite city in China, Shanghai, is in the midst of a protracted lockdown right now. Here’s a virtual postcard from my first visit in 2017. I visited in 2018 and 2019 again and have many fond memories (and I would’ve been in Shanghai exactly two years ago had it not been for the pandemic).
Bloomberg Odd Lots has a fantastic interview with someone who is in the middle of the lockdown in Shanghai right now. It’s worth a listen.
That’s it for now. Stay cool everyone.
Is there any correlation between lifespan and age of maturity?