Jacob Kimmel

One of the main mechanisms that just makes it difficult for evolution to solve a problem is that if a mutation breaks a gene or somewhere along the path of edits, imagine there are three edits that take a host defense gene from restricting SIV to restricting this new nasty PT endogenous retrovirus.

Well, if one edit just breaks the gene, two edits just breaks the gene, three edits fixes it, it's really hard for evolution to find a path whereby you're actually able to make those first two edits because they're net negative and that net negative for fitness.

You need some really weird contingent circumstances.

Through duplication, you can create a scenario where those first two edits are totally tolerated.

They have no effect on fitness, you've got your backup copy, it's doing its job.

And so even though the mutation rate is low, some of these edits actually aren't that large.

I'm going to forget the number of edits, for instance, in TRIM5-alpha for this particular phenomenon we're talking about for memory.

But it's in, like, the tens.

It's not that you need massive kilobase scale rearrangements.

It's actually a fairly small number of edits.

And basically, you can just align the sequence of this gene in new world versus old world monkeys and then for humans.

And you find there's a very high degree of conservation.

You can arrange genes in the human genome by homology to one another.

And what you find is even in our current genome, even without having the full historical record, there are many, many genes which are likely resulting from duplication events.

One like trivial way that you can check this for yourself is like just go look at the names of genes.

And very often you'll see something where it's like gene one, gene two, gene three, or, you know, type one, type two, type three.

And if you then go look at the sequences...

Sometimes those names arise from like they were discovered in a common pathway and they have nothing to do with each other.

A lot of the time it's because the sequences are actually quite darn similar.

And really what probably happened is they evolved through a duplication event and then maybe did some swapping with some other genes.