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Biologists Debunk the "Rotting Y Chromosome" Theory
An anonymous reader writes "Biologists have previously predicted that that the male sex-determining Y chromosome, which once carried around 800 genes, like the X, has lost hundreds of them over the past 300 million years, will mutate itself out of existence, leading to the eventual extinction of men. However, researchers of a study published in the latest issue of Nature found evidence to suggest that the Y chromosome will not shed any more of the 19 ancestral genes that it is left with."
Not like I love the Nature Publishing Group (NPG) very much, but let's link to the source to help give the original authors credit. (Which, as far as I can tell, the medical daily article doesn't even do!)
Here is a link to the original paper
For those who aren't molecular biologists or geneticists, here is a link to the Nature news article on the scientific paper
-Ryan
AUWYHSTOT (Acronyms are Useless When You Have to Spell Them Out Too)
If I search for "rotting y theory", all I get are variations of this article. Why would anyone who knows anything about evolution and genetics actually think that? And who were these people?
Autism is not the superpower that many people make it out to be. You only see the high functioning autistic people. There are a great many who cannot even communicate above an infantile level. Many also suffer from severe OCD. These people need constant care throughout their lives. The brilliance aspect is only found in a small percentage of autistic people, and I've never seen a conclusive study showing that brilliance is any more common among the autistic than it is among "normal" people. It may be that it is simply more noticeable when someone who's autistic has some great talent.
Another problem with the y chromesome is that it's not fully redundant with the x chromesome. There are plenty of important genes on the x chromesome that are not duplicated on the y chromesome. There are some diseases which mainly show up in men because females can be heterozygous for it, have one faulty copy but one good copy and be okay. Men on the other hand are hemizygous for genes on the x chromosome. If we get a faulty copy, that's it. We have the disease.
I think that is exactly why he stated "who get the right combination."
No, the XX/XY system of sex determination is just one of the many types used in nature, mostly by mammals. Some animals use the XX(female)/X0(male) system, like ants and bees, while reptiles, birds and some other use the ZZ(male)/ZW(female) system. As you can see, in birds and reptiles (not crocodilians or turtles those have a temperature based sex determination mechanism) the ZZ chromosome configuration (the default) is male, while the ZW configuration causes female development. However, back to the disappearing Y chromosome, it is the fastest mutating chromosome in the human genome (and in all mammalian genomes) because it does not recombine with an analogue chromosome, the way two X chromosomes would. However, just because genes are "lost" does not mean it is shrinking, and research stated here shows it to be the case.
I have yet to see any version of autism that confers any reproductive advantage. All of them I have met have been at a moderate to severe reproductive disadvantage.
It's worth noting that conditions apart from standard XX female and XY male do occur in humans:
Turner syndrome: usually, single X chromosome, no second X or Y. Creates females who are almost always infertile with varying physical problems. Incidence is around 1 in 2000 to 1 in 5000 (phenotypic) females.
Triple X syndrome: XXX chromosomes. Makes females with essentially no physical differences from XX females (including reproductively). Incidence: 1 in 1000 females.
Klinefelter's Syndrome: XXY chromosomes. Produces sometimes-infertile males, sometimes with developmental problems. 1 in between 500 and 1000 males affected.
XYY Syndrome: XYY chromosomes. Almost no physical differences with XY males (slightly taller). 1 in 1000 males.
XX Male Syndrome: XX chromosomes. Produces always-infertile males who usually appear to be XY males. 4 or 5 in 100,000 people.
Swyer Syndrome: XY chromosomes. Produces females without developed gonads, though a developed uterus may be able to carry another person's embryo.
The above is only a partial list. There are quite a few related conditions that fall under the general heading of "Intersex" (sometimes you see the acronym LGBTI; that's the I). They vary widely from producing (some type of) hermaphrodites to causing a large number of non-standard sex characteristics. From the article,
According to Fausto-Sterling's definition of intersex, on the other hand, 1.7 percent of human births are intersex.
and
Between 0.1% and 0.2% of live births are ambiguous enough to become the subject of specialist medical attention, including surgery to disguise their sexual ambiguity.
To give a very approximate comparison (these numbers vary a lot by region, time period, and definition), around 1% of the population is bisexual, and around 5% is gay. It's perhaps even more difficult to get an accurate transgender incidence number; I've seen between 0.2% and 0.003%. Those who get sex reassignment surgery are in the minority. (There's a lot more to gender than the type of gonads you have, and female-to-male surgery isn't terribly effective.)
It would appear, however, that Y chromosomes are a bit more robust than originally thought, and may be able to continue at their present level of basic function for tens of millions of years more. Just as my own thought, one reason for this may be the presence of genes on the Y which are necessary for sperm production. A transition to another form of sex determination would require those genes to be either moved or their functionality replaced elsewhere; otherwise any Y-less males would be azoospermic and therefore the new system wouldn't get passed on.
"FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
Evolutionists seem to think any non beneficial mutation results in a non reproducing/ non viable entity.
No we don't.
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
I think the article is an Amazonian plot. One designed to further degrade basic science education in the world. I mean, it gets some of the basic concepts wrong. I particularly enjoyed the part about the rhesus macaque being ancestral to both humans and chimps. It shows that the person writing the story doesn't have any clue at all about the subject.
Anyways, the source material is here:
http://www.nature.com/news/the-human-y-chromosome-is-here-to-stay-1.10082
Crossing over is normally a beneficial practice for chromosomes, and is a key advantage for sexual reproduction. See Muller's ratchet for the case of deleterious effects piling up in organisms who do not use recombination to shuffle around their genes. Therefore, it generally makes sense for chromosomes to pair up, so that at each generation, offspring get a mix of ancestral genes rather than a perfect (aside from mutation, of course) clone of a chromosome from parent's set. Being able to swap homologous genes dramatically increases the diversity of offspring. The X and Y pair is an exception because it would be a problem for recombination to occur. The genes on Y are supposed to be unique to males- if some regions of Y containing them recombined with X, those male-development specific genes could be traded away in exchange for nothing, likely leading to sterile offspring. Therefore, it has been to the advantage of XY-determination organisms to have X and Y as different as possible so that there is basically no recombination. The drawback is that Y doesn't get to recombine with anything (X can still crossover with another X), so a son's Y is essentially his father's Y and grandfather's Y, though with whatever errors have accumulated. This has led to a pruning of genes on Y over time- it appears from this paper that this deletion will not necessarily go to nothing, and that a "minimal Y" may be stable for many millions of years. It does however underline that the X/Y pair is a special case, that the endpoint of the asymmetric relationship that they have is for one chromosome to dwindle to a single purpose. The Y chromosome has 19 genes: X has around 2000.
"FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
Once again with the subject of genetics on Slashdot, we have a shocking level of confident ignorance on display (aided and abetted by the equally clueless moderators).
Please, evolution is not synonymous with natural selection. If all you know about genetics is what you learned in Biology 101, perhaps supplemented by a Dawkins book, you're missing out on most of the picture.
The degeneration of the Y chromosome was made possible by the lack of recombination along most of its length (Muller's ratchet/Hill-Robertson effect), which allowed the combined effects of mutation (including deletions) and genetic drift (which is much stronger on the Y due to there being 1/4 the number of Y chromosomes in a population than a given autosome) to very slowly truncate it. There's really no need to invent post-hoc selective stories to explain this; it's all pretty basic stuff.
Of course, you are correct that this doesn't mean that males would (or could) go extinct if the Y somehow did disappear. No competent scientist would ever claim this; most likely the sex-determining genes would move to other chromosomes.
Summary of this story in Nature
The origins of genome complexity
Since the info above was informative, here are a few other statistics that interest me and help put minority issues into perspective. They're at best tangentially related to TFA, though.
There are perhaps 100,000 furries in the US, or around 1 in 3000 people. [Furries at a glance: the majority are young white men; they're pretty much evenly split between hetero and homosexual, with many at varying degrees of bisexuality; very few own fursuits; to be clear, furries primarily have an interest in anthropomorphic characters, so "it's not about sex" (though as always it can be).]
30% of those over 24 in the US have a bachelor's degree. Only 3% have doctorates or professional degrees.
Around 25% of all people in Swaziland have HIV/AIDS. The number jumps to over 50% for women 25-29. [Yes, this is unbelievably tragic.] Around 0.4% of the US population has HIV/AIDS, though around 20% of men who have sex with men do (accounting for around half of all cases; receptive anal sex spreads it more quickly than any other common sex practice; interestingly, fellatio is almost entirely safe in this regard; condoms reduce transmission rates by only ~80%, depending on specifics).
Around 1% of the US population is some variety of Native American. Around 15% are poor.
If one defines free will as "the ability of the conscious mind to make long term plans and see them to fruition", then neuroscience has, as of yet, nothing concrete to say on the subject.
If you do that, what's the meaningful difference between "will" and "free will"? Nobody disputes the fact that the conscious mind can make decisions. That's just "will". The debate is over whether that will is "free" or not.
"Free" is usually defined as "free from causality" or "free from external influence", which is obviously nonsense to anyone who's familiar with "f=ma". Free will hasn't had a leg to stand on since Newton's time.
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