Interesting study, but I hate the way they've framed it as if this is 'new' information. Of course urbanisation affects living things; you are literally changing the ground beneath their feet, the air they breath etc. Did people not expect adaptable organisms to.. adapt?
They're saying something more specific than "urbanisation affects living things" though. The paper tells us 1) that the adaptation has influenced our genetics 2) the approximate timeline (and speed) it took to see that adaptation and 3) that it can be seen across species and across urban centers (in other words, there's an "urbanize" pressure on evolution regardless of if you're in New York City or Delhi). I thought #2 and #3 were surprising, and not necessarily what you would expect.
People are always saying that humans can't be evolving because 'evolution doesn't work that fast'; by the same token, plants/animals can't be evolving that fast either because their generation times typically aren't more than a factor faster (and sometimes can be slower - think trees). So for me the interest is definitely, if all these plants and animals are so visibly evolving for urban environments which have only become predominant very recently even by human standards, how have humans been affected? We already know that humans have evolved smoke-tolerance to cope with the health effects of fire, but what else for cities? More intelligence, extraversion, parasite resistance?
I think the difference between plants/animals and humans might be tied to mortality rates. I would imagine that urbanization has a very adverse effect on most plant and animal species and that only a small minority of individuals survive the initial shock of urbanization. Those that do survive will pass on the traits that allowed them to flourish in their new environment and such traits will quickly dominate the post-urbanization populations of these plants and animals since they are necessary for their survival. Humans are different in that urbanization appears to make survival (and mating?) easier for a majority of the population and thus there are not such strong selective effects.
Note: I am not a genetic biologist, this is just conjecture
You've got the right idea. Think of any urban center as the site of a localized mass extinction, and you're even closer. Evolution doesn't always happen slowly. In a mass extinction event it happens quickly.
Now consider that in human history, about 40% of men were able to breed. So 30% of the population goes extinct every generation without passing on genes, assuming all women reproduce. So with a few hundred iterations of this kind of 70:30 split, you could see how evolution could happen quite quickly even under normal circumstances.
This has probably already been thought about in greater detail elsewhere, but I would think that there's a sense in which evolution is happening "quickly" even relative to a human perspective. Sure, big things don't change quickly, but thousands (millions? billions?) of little things are changing simultaneously, all the time.
