> This is no more likely than for other fish to get the same gene from the original jellyfish humans found it in. Unless there are close relatives of zebrafish in those streams which can cross-breed with the zebrafish, there is no chance of gene transfer.
I'm not sure that we know that yet. The science on horizontal gene transfer is in its nascent stages. Only last year did scientists first supply solid evidence of animal-to-animal horizontal gene transfer:
> [...] herrings and smelts, two groups of fish that commonly roam the northernmost reaches of the Atlantic and Pacific Oceans, both make [antifreezing proteins]. But it is very surprising, even weird, that both fish do so with the same AFP gene — particularly since their ancestors diverged more than 250 million years ago and the gene is absent from all the other fish species related to them.
> A March paper in Trends in Genetics holds the unorthodox explanation: The gene became part of the smelt genome through a direct horizontal transfer from a herring. It wasn’t through hybridization, because herring and smelt can’t crossbreed, as many failed attempts have shown. The herring gene made its way into the smelt genome outside the normal sexual channels.
The original article notes that the leading mechanistic hypothesis for this crossover involves genetic material hitching a ride during spawning:
> The remarkable gain of this advantageous gene was postulated to have occurred via HGT from foreign DNA attaching to sperm during spawning [2.], in a manner analogous to the technique of sperm-mediated gene transfer employed in laboratories to transfer genes to organisms, including fish [9.].
One might fairly extrapolate that the conditions necessary for such an unusual genetic exchange may be far more feasible for species in close proximity, rather than from a species of jellyfish limited to the west coast of North America.
It still seems extremely unlikely, however we lack a good sense of not only the frequency of such events (presumably quite low), but also the total number which have occurred over evolutionary history.
So I agree with you in broad strokes but I want to nit-pick some meanings here.
>It still seems extremely unlikely, however we lack a good sense of not only the frequency of such events (presumably quite low), but also the total number which have occurred over evolutionary history.
I think we have plentiful evidence for horizontal gene transfer, especially in bacteria (see "F-plasmids"). More relevant is all the endogenous retroviral sequences buried in our own DNA, all of which are effectively horizontal gene transfer between viruses and our ancestors. We know quite a bit about these random chunks of DNA so I am hesitant to call HGT either nascent or unlikely. Between seeing all the viral DNA and knowing roughly how fast mutations erase it, we can probably get a good estimate of how frequently it occurs.
But, I totally agree that this is all very unlikely. At least, HGT events are rare on human timescales. But they do seem to be somewhat common on evolutionary timescales! Sometimes I wish I could see our biosphere in 1000 years time. It would be a radically weird place.
I think that you missed my point. I was only speaking about animal-to-animal HGT, which was the essence of the :
> Only last year did scientists first supply solid evidence of animal-to-animal horizontal gene transfer
It was a response to your original statement:
> This is no more likely than for other fish to get the same gene from the original jellyfish humans found it in. Unless there are close relatives of zebrafish in those streams which can cross-breed with the zebrafish, there is no chance of gene transfer.
I am aware of HGT within bacteria and viral domains. Science has done more to study those domains in part because the genomes are much smaller and are more plentiful. Additionally, for species within Kingdom Animalia, biologists have turned toward DNA Barcoding as an identifier rather than whole genome sequencing, which functionally limits the data available for investigation of such anomalies. Hence we really don't have good data on HGT between animal species.
I'm not sure that we know that yet. The science on horizontal gene transfer is in its nascent stages. Only last year did scientists first supply solid evidence of animal-to-animal horizontal gene transfer:
> [...] herrings and smelts, two groups of fish that commonly roam the northernmost reaches of the Atlantic and Pacific Oceans, both make [antifreezing proteins]. But it is very surprising, even weird, that both fish do so with the same AFP gene — particularly since their ancestors diverged more than 250 million years ago and the gene is absent from all the other fish species related to them.
> A March paper in Trends in Genetics holds the unorthodox explanation: The gene became part of the smelt genome through a direct horizontal transfer from a herring. It wasn’t through hybridization, because herring and smelt can’t crossbreed, as many failed attempts have shown. The herring gene made its way into the smelt genome outside the normal sexual channels.
[0] https://www.quantamagazine.org/dna-jumps-between-animal-spec...
The original article notes that the leading mechanistic hypothesis for this crossover involves genetic material hitching a ride during spawning:
> The remarkable gain of this advantageous gene was postulated to have occurred via HGT from foreign DNA attaching to sperm during spawning [2.], in a manner analogous to the technique of sperm-mediated gene transfer employed in laboratories to transfer genes to organisms, including fish [9.].
[1] https://doi.org/10.1016/j.tig.2021.02.006
One might fairly extrapolate that the conditions necessary for such an unusual genetic exchange may be far more feasible for species in close proximity, rather than from a species of jellyfish limited to the west coast of North America.
[2] https://www.inaturalist.org/taxa/325995-Aequorea-victoria
It still seems extremely unlikely, however we lack a good sense of not only the frequency of such events (presumably quite low), but also the total number which have occurred over evolutionary history.