The sparrow with four sexes
nature.com
nature.com
I wonder if the birds instinctively "know" that they have 4 sexes
The "almost" hints at the origins of homosexuality.
There's no "origin" to homosexuality. If anything having differentiated sexes is an aberration, the majority of plant species have both as well as many of the precursor species to modern mammals like snails and flatworms. In situations where the separation of the sexes provided some kind of evolutionary advantage it took hold. In others it never happened.
Also our preconceptions about gender goes out the window when there's four possible expressions as in the case with these birds.
Did I use the word "origin" incorrectly? Because evolution of a second sexual system in these birds results in white-striped birds and tan-striped ones mating only with the other almost all the time instead of always all the time, homosexuality is being built into the differentiation of a species into 2 sexes, I presume because DNA processing can never be error-free. I didn't imply it starts happening after the differentiation.
white/male + white/female is not "homosexual" by any conventional definition. If anything it's "homomorphic".
Birds, like any creature, don't do anything all the time. I think you're reading way too much into these observations.
Did I use the term "homosexual" incorrectly? Perhaps "origins of homosexuality" would be more accurate. That's what I said in the first place.
The article says "the researchers had come up with the concept that the birds were evolving a second set of sex chromosomes" and "the inversion on chromosome 2 doesn't include genes that determine sexual development — but it does contain some that affect the birds' reproductive behaviour". The tan-striped "swingers" are monogamous and fiercely protect their hatchlings from predators, whereas the white-striped "singers" are aggressive, promiscuous, and more cavalier about their offspring. The tan stripe birds almost always mate with the white stripes, but there are exceptions. We're seeing here firsthand (on a genetic time scale) the origins of homosexual behavior.
I appreciate your comment because when I first got the 5+ downvotes without any comments, I thought it was homophobic attitudes from HN readers. But now I know they could also be anyone with an overly pedantic reaction to the use of certain words.
Again, nope. I think you're taking a lot of flack here for implying that homosexuality, or homosexual behaviour is somehow unnatural and needed to evolve. That it's an aberration of some sort.
I'm asserting it has always been there, that it pre-dates the very concept of genders. There's an evolutionary bias in some species towards heterosexual relationships, but in others there's no such pressure. Aphids don't need to reproduce sexually, but they do if they feel it's a better deal. Snails possess both genders and breeding gets complicated.
The only thing we're witnessing the start of here is the introduction of new arrangements of genes that behave in a sex-like way. If there was a species where a sex gene was being evolved away there would be just as much scientific interest.
First you dispute my use of "origin", then you dispute my use of "homosexual". Now are you saying my use of "origin of homosexuality" to explain the almost in "A almost always mates with B" implies I think homosexuality is "unnatural"? You have an overly pedantic reaction to my use of certain words if you're inferring the opinion words "unnatural" and "aberration" from my first one-line comment.
There's nothing even remotely "homosexual" about your "A mates with B" statement. Horses almost always mate with other horses. Sometimes they mate with donkeys. That does not make the act homosexual in the least.
There's no origin, genesis, beginning, or start of anything homosexual with this addition of new sex genes. It just broadens the spectrum of what gender actually is.
I think my clarifying comments above are clear enough, certainly not "the most confusing way possible". Your comments each argue against something I'm not saying or implying.
If you have no idea how my original comment couldn't be construed as anything other than implying "homosexuality is somehow unnatural and an aberration", then I suggest perhaps you're bringing something from your personal situation into your reading process. I wrote the comment immediately after reading the entire article.
You can either put down the shovel or keep digging.
EDIT: gotta make you wonder if there were a large forest fire, volcano, human hunters or other event that almost wipe them out, and that the survivors went through a population bottleneck, perhaps picking up the mutation along the way.
The species has two chromosomes that act like sex chromosomes. That is to say, our Y chromosome never get's to mingle with other Y chromosomes, and so it accumulates mutations fairly quick, and thus a sex chromosome. In the bird species, there are 2 such chromosomes, and thus 4 unique states with regards to those unique chromosomes, as opposed to our 2 states.
They are defining sex not through sexual organs, but through the chromosomal state.
Sexual genetics are actually a lot more complicated than people think. There are YY "supermale" people, though it's more common in fish which gender-flip depending on population balance leading to XY males breeding with XY females. A YY male will always produce male children.
There's also XXY, XXXY and so on which is where things get even more complicated.
[1] http://www.bbc.com/earth/story/20150916-these-animals-are-ma...
Interesting to see that one phrase was changed to make the title more interesting, by nature.com.
Regardless, I wanted to point out that the title, while interesting, is hardly "click bait and switch." These birds DO have four sexes, from the point of view of their chromosomes, which results in behavioral differences between the four sexes, and produces birds that can only mate with a quarter of the entire population.
The biologist that said the "these birds act like..." quote was not the author of the paper being discussed. Also, later on he says "...in a four-sex system, each bird must work that much harder to find a mate — a white female is not just looking for a male, she needs a tan one — so selection will favour a more advantageous two-sex system instead."
So which is it? "A four-sex system" or something that "looks like a four sex system"? I think the article makes it pretty clear that it's the former.
Also, from the article: "Some animals, such as reptiles, have two sexes and no sex chromosomes, whereas the freshwater protozoan Tetrahymena thermophila has seven sexes, each of which can mate with any type except its own. Two sexes with one set of sex chromosomes is the most common arrangement, and has evolved independently many times. But there's no reason a species can't have more sex chromosomes, Wilson Sayres says. “If you've got two genes linked together that can't cross over during meiosis, and one of them plays a role in sex determination, suddenly you can have a new sex chromosome.”"
How is the title incorrect?
Still, I do think there's an unfortunate amount of truth in my comment, even in the likely case that the parent is incorrect that it applies to this article.
But what I got is that there males and females. But some of them have a different chromosome, to that it's transmitted for their little cute birdies. Let's call it n and m versions, and keep the males (Y) and females (X)
So you have Ym, Yn, Xm and Xn. You just have Ym x Xm or Ym x Xn. OR Yn x Xm or Yn x Xn. You don't have Ym x Yn. Nor Xm x Xn. You just have 4 possible combinations, not the whole 6 combinations if there really were 4 different sex.
Perhaps I'm missing something from the article, from the paper, or from biology, but since those special mutation from the chromosome 2 doesn't generate infertile offspring, I simply understand it as "birds with a white hair prefer those with red hair, instead of opposite-sex with the same hair color, generating a offspring that will have white or red hair with the same probability."
Those "special mutations" on chromosome 2 result in a chromosome that cannot recombine like a normal chromosome -- a new separate sex chromosome.
Can someone explain to me what prevents a tan-striped male mating with a tan-striped female?
Think about humans. For Chinese males, it is very likely to mate up with Chinese girls. That's not just a matter of availability (in China, there live mostly Chinese-looking people o_o), but also a phenomenon overseas, I believe. You have a lot more in common, similar values and similar cultural perceptions.
PS: This case shall not be construed to address Chinese especially, I'm convinced it works the same with all the similar ethnic groups and even subgroups.