With the gene drive technology, the modified gene is always inherited.

the 750 million number is there to speed up the process.

(This my understanding from reading the first few paragraphs from https://en.wikipedia.org/wiki/Gene_drive)

A harmful modification that doesn't cause sterility will propagate across generations if the indivuals are able to reproduce.

For example a scenario where we see the symptoms but we don't know that they are caused by a gene modification. And where individuals are still able to live and have children.

And I'm not saying that the tech is bad. I'm sure that people can come up with a lot of good use cases.

If it's harmful, it will get selected against, and will disappear rather rapidly.

There's a reason why they need to release 750 million genetically modified mosquitos, and not just 1.

With 6 billion people in the world today, even if our nefarious post-doc somehow gene-spliced 100 people with a 100% probability transmit of a "bad" recessive gene, it would take so many generations for any effect to be felt.

By then, we can assume, it would be trivial to reverse the "damage" caused. Hence the eye-rolling at the idea that one post-doc could be any serious threat.

You could always have a tick box for it on the Tinder profile.

Mad geneticist injects 1000 people with a gene.

50 years later, 7500 people have to pay for the fix! The profits!

And that's ignoring the failure rate of the initial shot.

This is a worse return on investment than a maniacal scheme to infect people directly, and then 1:1 charge them for a cure.

You're right of course, and unfortunately sooner or later what you say will come to pass (tragically, I see it as inevitable).

My take is slightly different: as the technology is here now, and given that we cannot stop it (certainly not in the long term - as eventually the tech will get so easy that it'll done in backyard sheds), then it's better to run with something like this mosquito eradication which hopefully may do some good.

With luck - and we'll need lots of it - intelligent regulation may follow. Ban it outright and it'll definitely go underground. Backyard sheds will then become labs that are centers of research. Heaven knows where that would lead us.

For example, there was a story in the UK press (it may be fictional, but I think it will still serve the argument) that there is a gene which causes extremely strong male-directed sexual attraction in both men and women [0] — all men with it are gay, all women with it are hyperfertile, and the hyperfertility is strong enough that positive evolutionary pressure from the women counterbalances the negative pressure from the men.

I think that this sort of thing could count as a toy model of gene-drive, but do correct me if I’m misusing terms or generally failing to understand.

But, even in this toy example probably based on a journalist failing to understand the science, we can not only genetically modify ourselves, but also we have in-vitro fertilisation so we don’t even need to GM ourselves.

[0] don’t worry, I’m bi, this isn’t a hopeless pearl-clutching story about gay genes

It might not be practically possible. Genetic modification has side effects, where typos are introduced in other areas than the target.

This means that the first generation of a hypothetical new gene drive is less likely to survive long. But once the gene drive got established subsequent generations would become more and more normal (as typos were lost by interbreeding and natural selection).

Now imagine that we discover a rogue gene drive introduced in humans after, say, it has affected 1000 individuals. There isn't any way of ethically fixing it in their children. You can't go to a person and tell them that they are not allowed to have children. Nor can you tell them that they need to undergo an experiment that makes their children 100x more likely to die young, for example.