A long thread but with small bytes.
1/n Cancer is basically when normal body cells go rogue—dividing endlessly instead of following the body’s disciplined checks and balances.
So, the more cells an animal has, and the longer it lives, the more chances for things to go wrong.
1/n Cancer is basically when normal body cells go rogue—dividing endlessly instead of following the body’s disciplined checks and balances.
So, the more cells an animal has, and the longer it lives, the more chances for things to go wrong.
2/n This is why taller humans and larger dogs are known to have higher cancer risks.
More body = more cell divisions = more chances for mutations.
So big animals like whales or elephants should have a lot more cancer.
But they don’t.
More body = more cell divisions = more chances for mutations.
So big animals like whales or elephants should have a lot more cancer.
But they don’t.
3/n This contradiction is known as Peto’s Paradox, named after epidemiologist Richard Peto, who noted that cancer rates don’t increase with body size across species.
Despite being enormous and long-lived, elephants and whales have surprisingly low cancer rates.
Despite being enormous and long-lived, elephants and whales have surprisingly low cancer rates.
4/n In 2025, researchers published cancer prevalence data from around 260 species.
Yes, cancer rates do rise slightly with size…
But certain large animals seem to have evolved advanced strategies to suppress cancer very effectively.
Yes, cancer rates do rise slightly with size…
But certain large animals seem to have evolved advanced strategies to suppress cancer very effectively.
5/n Elephants are a striking case.
They live 60–70 years, weigh several tons, and yet have an estimated cancer mortality of only 5%.
In humans, that number is around 25%.
They live 60–70 years, weigh several tons, and yet have an estimated cancer mortality of only 5%.
In humans, that number is around 25%.
6/n One key reason: Elephants have about 20 copies of the gene p53, which produces a protein that guards against cancer.
Humans have just one copy.
When DNA damage is detected, p53 steps in—to pause cell division, attempt repair, or trigger cell death(apoptosis).
Humans have just one copy.
When DNA damage is detected, p53 steps in—to pause cell division, attempt repair, or trigger cell death(apoptosis).
7/n If p53 fails, damaged cells can keep multiplying—and that’s how tumors grow.
It’s estimated that over half of all human cancers involve a failure of this p53 system.
It’s estimated that over half of all human cancers involve a failure of this p53 system.
8/n But elephants don’t rely on just one version of p53.
They have multiple-almost 20, slightly different versions—called isoforms—giving their cells more ways to catch and stop DNA errors early.
They have multiple-almost 20, slightly different versions—called isoforms—giving their cells more ways to catch and stop DNA errors early.
9/n Another key player is MDM2, a protein that normally inactivates p53 when the cell is healthy.
In humans, it doesn’t take much for MDM2 to shut down our single p53 gene.
That’s a problem.
In humans, it doesn’t take much for MDM2 to shut down our single p53 gene.
That’s a problem.
10/n In elephants, it’s different.
With many p53 variants floating around, some are resistant to being shut down by MDM2.
So even if one pathway is blocked, others stay active—keeping cancer in check.
With many p53 variants floating around, some are resistant to being shut down by MDM2.
So even if one pathway is blocked, others stay active—keeping cancer in check.
11/n This multi-layered protection gives elephants an incredible biological advantage.
They can detect and eliminate faulty cells long before they turn cancerous.
It’s an evolutionary firewall against cancer.
They can detect and eliminate faulty cells long before they turn cancerous.
It’s an evolutionary firewall against cancer.
12/n Researchers are now studying these p53 variants for clues to new cancer therapies.
If we can mimic or reactivate p53 behavior like in elephants, we might build better defenses in humans too.
If we can mimic or reactivate p53 behavior like in elephants, we might build better defenses in humans too.
13/n But here’s a deeper question:
Why did elephants evolve so many p53 copies in the first place—especially when cancer usually hits after reproductive age?
Why did elephants evolve so many p53 copies in the first place—especially when cancer usually hits after reproductive age?
14/n A 2023 hypothesis points to their testicles.
Unlike most mammals including humans(that’s why the newborn males are checked for testes by the paediatricians), elephant testicles don’t descend into a scrotum.
They remain inside the body, exposed to higher temperatures.
Unlike most mammals including humans(that’s why the newborn males are checked for testes by the paediatricians), elephant testicles don’t descend into a scrotum.
They remain inside the body, exposed to higher temperatures.
15/n Heat damages DNA in sperm-producing cells.
So these cells need extra protection.
p53 is perfect for that—detecting DNA damage and stopping flawed cells from dividing.
So these cells need extra protection.
p53 is perfect for that—detecting DNA damage and stopping flawed cells from dividing.
16/n So elephants may have evolved extra p53 genes not to prevent cancer per se, but to safeguard sperm quality.
Cancer resistance might just be a powerful side effect, a nice one.
Cancer resistance might just be a powerful side effect, a nice one.
17/n Either way, elephants have shown us that nature has already solved problems we’re still grappling with.
And studying them might help us write a new chapter in cancer prevention.
#PetoParadox
#CancerCure
And studying them might help us write a new chapter in cancer prevention.
#PetoParadox
#CancerCure
18/n Testicondy- Where the testes remain intra-abdominal (inside the body) throughout life.
True testicond mammals (naturally internal testes):
•Elephants
•Whales
•Dolphins
•Manatees
•Armadillos
•Hyraxes
•Sloths
These mammals have evolved special adaptations (e.g., internal cooling systems or specialized vascular networks) to maintain sperm viability without scrotal descent.
True testicond mammals (naturally internal testes):
•Elephants
•Whales
•Dolphins
•Manatees
•Armadillos
•Hyraxes
•Sloths
These mammals have evolved special adaptations (e.g., internal cooling systems or specialized vascular networks) to maintain sperm viability without scrotal descent.
19/n In humans, undescended testes is called cryptorchidism. If not corrected either spontaneously or surgically, it leads to damage to germ cells causing infertility/subfertility and testicular cancer.
20/20. Thank you for reading this. I hope it was worth your time.
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