At last, some recognition that evolution is not just random trial and error.
But how the whitefly managed to swipe a plant gene is unclear. One possibility, says Turlings, is that a virus served as an intermediate, shuttling genetic material from a plant into the whitefly genome.
> This study suggests that's not the only way these genetic changes happen
The study says nothing about the transfer mechanism, only that it took place.
That's really just a failure of imagination. Also, it ignores that the mechanisms of evolution have themselves evolved.
Sure, evolution seems unlikely if you assume discrete genes have to change in lockstep to adjust traits successfully (eg. if you assume that separate changes are needed to adjust bones, muscles, skin, nerves, etc. to lengthen a limb), but that isn't how our bodies wirk (if it was, it would be nearly impossible to heal from an injury), nor is it how genes control that development.
Instead, you have genes that control things in less direct ways, such as body to limb ratio, and other genes that direct development of things like muscles in relation to bones and joints don't have to change at the same time for everything to keep working.
Even that's an overly simplified model, but you should get the general idea. You might like to read the book "The Plausibility of Life", which goes into more detail.
From an evolutionary perspective, there are none. Both are but sources of variation (the actual cause does not matter) in the genome; which, depending on their impact, may or may not get fixated by natural selection.
The viral genes we have in our genome were acquired by chance.
This was a fluke that got amplified.
Evolution is hill climbing, but the gene introduction was random. Just as mutations themselves are.
To clarify for others: random gene mutation within an organism is not the same a random gene introduction from external source.
Take something like an Orchid Praying Mantis. If it were discovered that the Orchid Praying Mantis got some of its coloring from a gene transfer of orchid plants with which it cohabitated, that would remove an enormous amount of random mutations that needed to have occurred within its own genome to achieve that goal.
Nobody is saying that the mantis wouldn't be subject to all of the same forces of natural selection thereafter, or that the particular gene that was transferred wasn't itself a random selection from the orchid. It just makes the arrival at certain gene configurations immeasurably more likely than they would've been within the same time period, given an organism's lineage had only had its own random mutations available.
Horizontal gene transfer was actually discovered before we had any consensus that DNA was the biological mechanism of heredity, and the experiments showing evidence of HGT were used as evidence for that claim.
There is simply natural events or circumstance incidentally causing the death of individuals in environments for which they are unsuited before reproduction.