Katie Wu

So if you sort of spin this story the other way, it's not why are there so many people with this broken gene walking around?

It's what might have made that version of this gene super useful to our ancestors in the past?

And one possible answer to that is it might have helped us fight off a bunch of different infectious diseases.

Right.

And I kind of love the logic here, right?

We know that there is a kind of poison component to this story.

Having this buildup of aldehydes in our body is bad for our tissues.

But aldehydes are such a kind of...

all-purpose toxin, that the idea is they could be harming microorganisms that wanted to hurt us as well.

And so maybe our bodies just kind of wised up to the system and they were like, okay, we're making all of this toxic trash.

Maybe that can actually be useful for defending ourselves, which has to come into play really often.

Yeah, so one of the most intriguing possibilities is that this could have been useful against ancient outbreaks of tuberculosis.

And that's actually a really compelling idea because we know that tuberculosis or TB has been one of the greatest infectious killers in history.

If there was even a slight advantage to carrying this mutation, if it meant that people were even slightly better at suppressing bacterial growth or spreading fewer of the bacteria to others, then that might have been enough to help this mutation sort of build up in the population and reach some of the numbers that it did today.

I think that's absolutely right.

You know, the TB idea, I think, is a really compelling possible example of

It is tricky to prove, though, right?

And we know that, for instance, aldehydes can kill TB in the laboratory.

That is super compelling, but it doesn't necessarily mean that TB is what drove this mutation to prominence thousands of years ago.

A lot of experts who weren't involved with the work told me infectious disease writ large probably was a huge influence here because there's evidence that aldehydes are bad, again, not just for our tissues, but a ton of bacterial cells.