The sparrow with four sexes (2016)(nature.com) |
The sparrow with four sexes (2016)(nature.com) |
Discussion at the time: https://news.ycombinator.com/item?id=13027132
They are saying an individual can only mate with a quarter of the population, but it's obviously incorrect, as the pre-mutation birds can mate with both mutated and unmutated opposite sex.
The reason cross-morph pairs are observed more often as the mutated birds are more sexually aggressive and quickly round up unmutated opposite sex.
Even if the tan/tan is still physiologically possible it may be the case that they still won't mate even if there are no white present at all due to required mating signals being missing.
I.e., I would guess that plants that have easy seed propagation have less complicated sexes, but I don't know.
Or maybe it's just irrelevant for birds. Birds appear to break many laws of nature other animals have to abide by. They fly, they move where they want. They stay close to humans, observe them, and easily avoid them. They're amazingly energetic for how big they are. They migrate extremely far. They don't have to commit to anything except when rearing young.
Common ideas are commonly wrong. Non-useful ones only disappear reliably if they're selected against. Otherwise, you get goose bumps, or piloerection in humans: We don't have enough hair over most of our bodies for erecting it to do any good, but we still have all the structures to erect it anyway, because none of our ancestors lost any of them even as they became useless.
ie., evolution is starting with a bike and turning it into a car
it is not "starting with raw materials" and shaping them
So pretty much every life form is highly non-optimal wrt their environments.
By making procreation harder to achieve, you intensify the selection effect, since only the fittest individuals will be able to achieve it. So maybe it can be thought of as a kind of extra layer of "culling of the weakest" built into the genetics of the species?
Indeed it's one definition of a species that it's a population that can mate within it's group. So if they can no longer breed with each other, are they same species or not?
So it's not speciation, any more than sexes themselves are speciation.
This alone doesn't contradict the two-species theory. It could be that white-M + tan-F is species #1, and white-F + tan-M is species #2. Sure, it sounds weird, but not nearly as weird as the idea of 4 sexes, IMO.
> (And the offspring are about half white-striped and half tan-striped.)
Now, this is the important part. As I understand it, the offspring of "species #1" could be "species #2" or the other way round. This indicates that #1 and #2 are the same species after all.
So are females most strongly attracted to the tough, macho, white-striped males? Actually, no. Lab studies have found that females of either morph prefer the tan-striped males. White-striped females, more pushy than their tan-striped sisters, grab the tan-striped bachelors right away, so these pairs form more quickly than the opposite combination. Males of both morphs tend to prefer the white-striped females, but those females quickly hook up with tan-striped males if they can, so eventually the leftover birds will form pairs consisting of white-striped males and tan-striped females.
https://www.audubon.org/news/the-fascinating-and-complicated...
Granted, the question of homo-zygotic white offspring viability is not even touched.
Edit: yet another article tentatively says the double-white sparrows to exist, but in far lesser number than expected, they suspect some genetic disadvantage.
https://www.cell.com/current-biology/fulltext/S0960-9822(15)...
Also:
> ie., evolution is starting with a bike and turning it into a car
> it is not "starting with raw materials" and shaping them
I'm not sure if you're drawing a distinction between evolution and abiogenesis here. You're right, in that technically evolution doesn't come into play until you have self-replicators of some form, but in colloquial terminology "evolution" is used to encompass the entire process all the way back to whatever nonliving organic chemicals formed the basis for the first life.
I'd also add that it seems evolution isn't even turning bicycles to cars bolt by bolt, but is adding whole subsystems at a time. It's as if each bike was made of a set of standard ACME parts, and came with a set of blueprints for many other kinds of ACME parts - and evolution, at the large animal level, is just replacing one standardized part for another, or adding new ones where they didn't exist, or altering the manufacturing timings, etc.
I'm of course referring to the findings of evolutionary developmental biology - https://en.wikipedia.org/wiki/Evolutionary_developmental_bio....