Jacob Kimmel

bacteria and other types of microorganisms are very well adapted to building these complex metabolic cascades that are necessary to make something like antibiotics.

And it's necessary to maintain that same mutation rate and population size in order to maintain the competition.

Even if our human genome stumbled into making an antibiotic, most pathogens probably would have mutated around it pretty quickly.

I'm going a bit beyond my own knowledge here.

So I want to say my strong hypothesis would be yes, I can't point to direct evidence today.

There are some examples of this where, for instance, bacteria that fight off viruses that infect them, bacteriophages, have things like CRISPR systems.

And you can actually go and look at the spacers, the individual guide sequences that tell the CRISPR system which genome do you go, where do you cut.

And you find some of these guides that are very ancient.

It seems like this bacterial genome might not have encountered that particular pathogen for quite a while.

And so you can actually get sort of an evolutionary history of what was the warfare like, what were the various conflicts throughout this genomic history just by looking at those sequences.

In mammals, where I do know a bit better, we do have examples of this, where there is this coevolution of pathogen and host.

Imagine you have some antipathogen gene A fighting off some virus X. Well, you then actually update, so now you have virus X prime and antipathogen gene A prime.

Now virus X prime goes away, but actually virus X still exists and we've lost our ability to fight it.

Those examples really do happen.

And so there's a prominent one in the human genome.

So we have a gene called Trim5-alpha.

And it actually binds a endogenous retrovirus that is no longer present, but was at one point actually resurrected by a bunch of researchers.

And it was demonstrated that it is the case.

We have this endogenous gene, which basically fits around the capsid of the virus like a baseball and a glove and prevents it from infecting.

And it turns out, if you look at the evolutionary history of that gene, and you trace it back through monkeys, you can actually find that a previous iteration inhibited SIV, which is the cousin of HIV in humans.