The Most Controversial Idea in Biology

If you want to know if someone really understands evolution, just ask them this one weird question. >> Why does poop smell bad? >> Wow. >> Oh gosh.

>> Because that's bacteria in it. I guess >> microbiome. Probably trash. >> Yeah, trash the body.

The food we eat because of the chemicals. >> Arts don't always smell bad. >> So, >> yeah. Well, that's that's a different question entirely.

>> Do you think it objectively smells bad? >> M. Yes, I think so. >> Yes.

>> How do you think it smells to flies? Like [laughter] the >> They like it. They like it. >> Animals love stinky things.

>> Yeah, >> they're attracted to it. >> Poop smells good to flies because poop is full of nutrients. They use it as food. But it's also full of bacteria that can be life-threatening to humans.

So, the real reason poop smelled bad to us is because if anyone ever thought it smelled good, they would probably get really sick, die, and not pass on their genes. After all, it's about survival of the fittest. But survival of the fittest? What?

I mean, most people think of natural selection as being about the survival of the fittest individual animal. >> Individual. >> Individuals. >> Animal.

>> Animal. Okay. So, it's like an individual. >> Yeah.

>> Which makes sense. [music] I mean, individuals best adapted to their environment have increased odds of survival and therefore a higher likelihood of passing on their genes. So, it follows that each individual should do everything it can to survive and reproduce. That is, it should be selfish.

But if that's true, then how do you explain this? I mean, worker bees will sting predators to protect the hive, even though it might kill them in the process. Female worker ants are sterile, so they can't reproduce. But regardless, they work for the colony for their entire lives until they die.

Monkeys adopt orphans. Wolves bring meat to non-hunting members of the pack. And squirrels can let out alarm calls to warn others about nearby predators. >> So if natural selection is all about selfish individuals, why do we observe so much altruism [music] in nature?

>> The survival is of the species that can adapt. >> It's generally the species >> for the survival of the species. >> So it's the survival of ...