And that includes crafting a title that can entice people to learn about a subject that can be technical.

Sometimes, though, science does all the hard work for you.

Elephants' giant hot testicles might be the reason they get less cancer.

And yes, that is a real headline based on a real scientific idea called the hot testicle hypothesis.

Thanks to some super protective genes, elephants are really good at not getting cancer.

In fact, research suggests that elephants are up to five times less likely to die of cancer than humans.

But this hypothesis posits that these genes didn't originally evolve to fight cancer at all.

Elephants may be special in this way for another reason.

And it has to do with their giant hot testicles.

[♪ INTRO ♪

Our story begins in the genome of an elephant.

Specifically, a gene called TP53, which controls the development of molecules called p53 proteins.

Super original, I know.

But these proteins are also called the guardians of the genome, because they protect against harmful mutations that pop up during a cell's life cycle.

In order to replicate, a cell also needs to duplicate the DNA inside of it.

But that duplication process is never 100% perfect.

You basically get a few typos in the new DNA.

Or, in other words, a few mutations.

So p53 proteins have the very important job of kicking off the process of DNA repair, to edit as many of those mutations as possible.

And if that process fails, the p53 proteins can also activate a cell's self-destruct mechanism, stopping the mutation from spreading any further, and preventing the cell from harming the rest of your body.

This makes p53 proteins excellent at fighting cancers.

But not just in elephants.

Lots of other animals have these proteins, as well as the TP53 gene that codes for them.

Including you!

In fact, humans with a mutated version of TP53, a condition called Li-Ferromani syndrome, have a 70% chance of getting some kind of cancer over the course of their lives.

But here's where we're different from elephants.

The human genome has a single copy of the TP53 gene, like nearly every other species.

But elephants have 20 copies, and they're all slightly different.

Which means they can make a bunch of different versions of p53 proteins with various different effects.

It's this suite of tumor-fighting proteins that gives elephants extraordinary defenses against cancer.

But exactly why elephants evolved to have such a suite isn't totally clear.

Part of the answer might be their size.

Elephants are really big, and a bigger body has more cells.

And more cells means more cell division.

And every time a cell divides, it's an opportunity for something to go cancerously wrong.

Elephants are also long-lived, which means more cell divisions during their lifetime.

This means they might naturally be at higher risk for developing cancer.

So over time, evolution found a way to compensate by giving them extra copies of a cancer-fighting gene.

But whales are also gigantic and long-lived.

And they don't have multitudes of p53 proteins.

Instead, there's some evidence that they evolved their own unique adaptations for fending off cancer, which means they don't have to rely as much on p53.

So maybe elephants evolved these cancer defenses simply because their size and longevity put them at risk.

But there's another hypothesis.

Maybe elephants originally evolved these proteins for a completely different purpose— to protect their extremely hot testicles.

But before I explain that sentence, we're gonna do an ad.

So, real quick.

Thanks to Incogni for supporting this SciShow video.

Incogni's mission is to help you avoid cybercrime and personal privacy breaches.

Data brokers collect and sell personal information, like social security numbers and login credentials, putting you at higher risk of identity theft.

So Incogni reaches out to data brokers on your behalf and requests that they remove your personal data.

With their Family and Friends plan, you can let four additional members benefit from the exact same service you do.

You can try it for 30 days and get a full refund if you aren't happy with the service.

To take your personal data back and get 60% off an annual Incogni plan, use the code SciShow at incogni.com slash SciShow, or click the link in the description.

Testicles, obviously, are where the body produces sperm cells.

And this process requires temperatures to be just right.

If things get too hot, the sperm could end up with damaged DNA.

And damaged DNA makes it really hard for sperm to do its job of helping to create a fully functional animal.

Most mammals have an internal body temperature that's kind of too high for sperm production, and they get around that by dangling the testicles in a scrotum.

Down there, the testicles don't just get a little bit of cooling airflow.

The scrotum also has a special network of blood vessels where one half of them, the veins, can siphon away heat from the other, the arteries.

It's a process known as countercurrent exchange.

And it's happening in some of you right now.

So altogether, a typical human body has an internal temperature around 37 degrees Celsius.

Meanwhile, if it's also got some scrotum-based sperm factories, they're hovering around a cool 34 degrees Celsius.

But elephants don't have a scrotum.

Their testicles are located deep inside of their bodies, near their kidneys.

So they can't just hang them out to cool like humans do.

But also, elephants can run even hotter than we do.

Their body temperature tends to hover around 36 to 37 degrees.

But on a hot day, which is most days in their tropical homes, they can get into the 40s.

This means their testicles are constantly in danger of overheating.

Now, elephants are not the only mammals with internal testicles, and therefore in need of some way to handle this problem.

For example, whales have a network of heat-shedding blood vessels that operates similar to our own scrotal cooling systems.

And hyraxes, which are close cousins of elephants, despite not looking like them at all, have simple physics on their side.

It's the inside of a mammal's body that generates heat.

And the skin dumps all of that heat into the outside world.

A small animal, like a hyrax, has lots of skin area compared to their size, so they shed heat pretty quickly.

Meanwhile, an elephant is not small.

It's huge.

It has way more internal volume compared to its surface area.

So they are much better at generating heat than they are at shedding it.

Which brings us back to the hot testicles problem.

What are they going to do?

Enter the guardians of the genome.

Those p53 proteins which repair genetic mutations and destroy malfunctioning cells during cell division.

They might be excellent tools for safeguarding sperm production in an environment where the temperature is too high.

And with this in mind, back in 2023, one researcher proposed the hot testicle hypothesis.

The elephant's incredible array of TP53 genes originally evolved in response to their endangered sperm.

In which case, their decreased risk of getting cancer would just be a happy side effect of increased protection for their hot testicles.

Now, of course, the reason could ultimately be a mix of both of these things.

It doesn't have to just be the fact that elephants have a lot of cells that divide over the course of their very long lives, or just the fact that they need a way to keep their sperm in working order.

Research into elephant evolution suggests that the number of TP53 genes in their DNA expanded around the same time as other genetic changes that are associated with having a larger body size.

Bigger bodies present both a higher potential risk for cancer and make it harder to shed excess heat.

So becoming elephant-sized might have created problems in the cancer department and the sperm department at the same time.

And the evolution of a fleet of tumor-suppressing proteins might have been a solution for both problems.

Two birds, one stone.

Or two birds, many copies of TP53.

But what does this mean for me?

For us?

Some research has already found that the elephant versions of P53 proteins are capable of combating cancerous cells in the tissues of other species, including dogs and humans.

So who knows?

Someday, we might be a step closer to living cancer-free, thanks to a protein cooked up inside of an elephant's toasty testes.

[♪ OUTRO ♪)]