Human X (left) and Y (right) chromosomes
Did the internet get stupider while I was away this past week? I mean, it’s gratifying to my ego to imagine the average IQ of the virtual collective plummeting when I take some time off, but I really can’t believe I personally have this much influence. Maybe the kooks crept out in my absence, or maybe it was just the accumulation of a week’s worth of insanity that I saw in one painful blort when I was catching up.
What triggers such cynicism is the combination of Deepak Chopra, Oliver Curry, and now,
William Tucker. Tucker wrote a remarkably silly piece in the American Spectator in which he drew deeply faulty conclusions from human genetics to support a thesis rife with misogyny and foolish chauvinism on human evolution. It was like a piece on evolutionary psychology written by someone who didn’t know any genetics at all.
Hang on to your hats—we’re going to see a factoid from one magazine article balloon up into a declaration of the superiority of the male species (I use “species” here both ironically and mockingly).
Time magazine did one of those Evolution updates last week, “How We Became Human,” on its cover. There wasn’t too much new — just how little we differ genetically from chimpanzees.
Yet there was one sentence that stood out like a lightning bolt. It has enormous implications for understanding how human societies evolved and why they sometimes find it difficult to get along with each other. Here it is:
[T]he principle of gene-by-gene comparison [between species] remains a powerful one, and just a year ago geneticists got hold of a long-awaited tool for making those comparisons in bulk. Although the news was largely overshadowed by the impact of Hurricane Katrina…the publication of a rough draft of the chimp genome in the journal Nature immediately told scientists several important things. First they learned that overall, the sequences of base pairs that make up both species’ [i.e., humans and chimps] genomes differ by 1.23% — a ringing confirmation of the 1970 estimates — and that the most striking divergence between them occurs, intriguingly, in the Y chromosome, present only in males.
Did you see that? It deserves much more attention than Time was willing to give it. Basically, the point is that, in crossing the little evolutionary distance that exists between chimps and humans, most of the changes occurred in males. In other words, what differentiates us from our mammalian relatives is changes that have occurred in the male of the species.
Now I haven’t seen the Time article he’s talking about, but I suspect it is partly to blame for inflating the significance of the differences in the Y chromosome. The human Y chromosome does have more variation in it, compared to the Y chromosome of chimpanzees, than do similar comparisons of other chromosomes, but the intriguing aspects are left hanging in the quote…and Mr Tucker charges off into some very strange interpretations.
Before I explain what those Y chromosome differences are, though, let’s see what stories Tucker spins from it.
What has changed is the role of males. Among chimps, males hang out in groups, form alliances, forage together, and do a lot of bickering over status. They do not participate at all in child rearing. By the time hunting-and-gathering tribes arrive, however, men have been folded into the family. Monogamy predominates and both parents participate in child rearing. The extraordinary innovation is “fatherhood,” a role that doesn’t really exist elsewhere in nature.
Apparently, “fatherhood” is a special attribute embedded in the Y chromosome. Monogamy and shared parenting is certainly found in many vertebrates—sea horses and sticklebacks, voles and penguins come to mind—so I’m afraid that his claim of a special status for human fathers is complete nonsense.
He fine tunes his argument, though: paternal investment is a strategy that distinguishes humans from their nearest primate relatives, and is the reason for our success.
In fact, the discovery of bonobo society proves just the opposite. It is precisely because females play a dominant role and males are so passive and unambitious that bonobos did not produce an evolutionary line that led to human beings. Instead, they remain a relatively minor, underpopulated species holding their orgies deep in the jungle. The larger East African chimp, where males predominate, produced the line that led to humanity.
Well, having males “predominate” might not be the best strategy for increasing a population—I think he is referring to male dominance. He really seems to think that letting females have a dominant role in society would mean we’d just be having jungle orgies, and that patriarchalism leads to human ambition and progress (umm, can I just say…the jungle orgies don’t sound all that bad.)
It sounds unbelievable, but he credits males with all the evolutionary advantages because the key changes have all occurred on the Y chromosome. The male chromosome. The chest-thumping, macho, super-duper chromosome.
Really.
The evolution of human intelligence would have been impossible without the change in male role and the adoption of monogamy. For that reason, it is not at all surprising to find that the key genetic changes have occurred on the male chromosome.
It’s seductively easy to jump from the fact that the Y chromosome is only present in males to the conclusion that it is responsible for encoding all male attributes, including as Tucker does male monogamy and various features of behavior associated with masculinity. It isn’t true.
The Y chromosome only contains about 90 different genes, and here’s a list of a few of them:
- AMELY (amelogenin,Y-chromosomal)
- ANT3Y (adenine nucleotide translocator-3 on the Y)
- ASMTY (which stands for acetylserotonin methyltransferase)
- AZF1 (azoospermia factor 1)
- AZF2 (azoospermia factor 2)
- BPY2 (basic protein on the Y chromosome)
- CSF2RY (granulocyte-macrophage colony-stimulating factor receptor, alpha subunit on the Y chromosome)
- DAZ (deleted in azoospermia)
- IL3RAY (interleukin-3 receptor)
- PRKY (protein kinase, Y-linked)
- RBM1 (RNA binding motif protein, Y chromosome, family 1, member A1)
- RBM2 (RNA binding motif protein 2)
- SRY (sex-determining region)
- TDF (testis determining factor)
- TSPY (testis-specific protein)
- UTY (ubiquitously transcribed TPR gene on Y chromosome)
- ZFY (zinc finger protein)
Hmmm. No monogamy gene. No sports fan gene. No hyperactive remote control button pressing gene. Why, there isn’t any simple correspondence between any gene and stereotypical behaviors anywhere—it’s as if behavior is an emergent property of the interactions of many genes throughout the genome and the environment, rather than a facile mapping of a complex phenotype to a short stretch of nucleotides.
For example, if monogamy is attributable to some array of different genes, those genes aren’t going to be on just the Y chromosome: they’re going to be scattered throughout the genome, including on chromosomes that we share with <gasp> females. Genes like SRY on the Y chromosome may trigger epigenetic changes that modify the expression of genes located anywhere in the genome. It might blow poor Mr Tucker’s feeble mind to learn that the gene for the androgen receptor, a protein absolutely essential to the development of his masculinity, is located on the X chromosome—you know, that female thing.
The idea that we can credit the “male” Y chromosome with encoding a constellation of attributes that are exclusive properties of the male phenotype is nonsense. What about the observation that “the most striking divergence between [humans and chimps] occurs, intriguingly, in the Y chromosome”? If the human Y chromosome has accumulated all these differences, they must be important changes in human evolution, right?
Nope. If Mr Tucker had actually read the Nature paper on the human-chimpanzee comparisons or an earlier work by Skaletsky et al., he would have discovered that they had an explanation, and it wasn’t the selective preservation of advantageous masculine mutations. The Y chromosome diverged between the two species entirely by chance.
There are 5-6-fold more cell divisions involved in the production of sperm than ova, which means that male germ cells have many more opportunities for replication errors—this increases the frequency of mutations in chromosomes from the male parent. In addition, recombination is mostly eliminated in the Y chromosome, and recombination is a process that allows deleterious alleles to be purged by shuffling ‘bad’ combinations away.
The actual reason human and chimpanzee chromosomes are more different than others is not quite as dignified or wonderful as Tucker thinks. It’s because the Y chromosomes accumulate more random garbage over time, and lack a mechanism to clean themselves up. I suppose one could argue that perhaps that does map onto some male properties, but they aren’t the ones Tucker dreams of as the source of human progress!
This is plainly stated in the Nature papers. It’s important and interesting that simple chance leads to variation, but it is a far cry from the overreaching selective advantages Tucker wants to see in the differences. It is definitely remote from the weird and unbelievable conclusions he wants to draw:
So what does all this suggest for the present? First, it says that feminism, in its most obviously primitive forms, is undermining human evolution. Everywhere in the Western world, the emancipation of women has initially led to rising divorce rates and plummeting births. After intelligent consideration, however, many “second-generation” feminists have been able to handle both careers and families, which means the human family may be able to reconstitute itself on a more equitable basis.
I guess feminism oppresses his mighty male chromosome, seat of all of his superiority. Poor man—he needs to learn that he is not his Y chromosome, which is little more than a trigger (plus a few other genes) to modulate expression of genes on all of his other chromosomes.
Chimpanzee Sequencing and Analysis Consortium (2005) Initial sequence of the chimpanzee genome and comparison with the human genome.
Nature 437(7055):69-87.
Skaletsky H, Kuroda-Kawaguchi T, Minx PJ, Cordum HS, Hillier L, Brown LG, Repping S, Pyntikova T, Ali J, Bieri T, Chinwalla A, Delehaunty A, Delehaunty K, Du H, Fewell G, Fulton L, Fulton R, Graves T, Hou SF, Latrielle P, Leonard S, Mardis E, Maupin R, McPherson J, Miner T, Nash W, Nguyen C, Ozersky P, Pepin K, Rock S, Rohlfing T, Scott K, Schultz B, Strong C, Tin-Wollam A, Yang SP, Waterston RH, Wilson RK, Rozen S, Page DC (2003) The male-specific region of the human Y chromosome is a mosaic of discrete sequence classes. Nature 423(6942):825-37.
Um, I’d like to know more about that zinc finger protein.
It might explain a few things.
ej
Everywhere in the Western world, the emancipation of women has initially led to rising divorce rates and plummeting births. After intelligent consideration, however, many “second-generation” feminists have been able to handle both careers and families…
Is he seriously suggesting that the emancipation of women is a bad thing? I just can’t really see any other way to reasonably interpret that.
By his reckoning our evolution should of stopped with early humans before marriage and before monogamy. He’s suggesting that marriage and a servile woman is what promotes evolution.
Uhg the stupidity.
I thought I remember that bonobos and chimps are in the same lineage that split after it had already seperated from humans. Anyone know if I’m mistaken about this.
Also based on PZ’s explanation it seems like we should expect the y chromosome to show more divergence in different species in general. Has this been observed at all?
Steve_C: The larger East African chimp, where males predominate, produced the line that led to humanity.
I thought I remember that bonobos and chimps are in the same lineage that split after it had already seperated from humans. Anyone know if I’m mistaken about this.
That’s what I’ve read as well. Indeed, this man has some pretty convoluted ideas about human history.
The change in male genetics here fits in with the idea that what has happened with humans is self-domestication, or, more to this info’s point, a sort of domestication of males by females. I can’t see Tucker embracing this idea, since it’s exactly counter to his, but it makes far more sense. For instance: Which species underwent more change in any of the various bouts of domestication by humans, the humans? or the dogs, cows, horses, chickens, etc.?
Pedantic note: “monogamy” as applied to humans is not a good fit, as witness the various ways its definition has been butchered by those who try fitting it: “serial monogamy” or even multiple partners as being “monogamous. Some examples from one of my old newsgroup posts (1995):
Keep in mind that, although there are many claims that humans are “pair-bonded” (“imperfectly so” according to Melvin Konner), or “monogamous” (according to Helen Fisher “This does not suggest that partners are sexually faithful to one another”), these claims rely on equating sex with marriage (when a casual knowledge of human relations demonstrates that the two are only coincidentally related) and the type of semantic gymnastics seen in the quotes above. These quotes often come just before or after statistics that contradict them, as per this Sarah Blaffer Hrdy quote: “Humans, of course, provide another example of facultative monogamy. Approximately 20 percent of human societies are monogamous, 80 percent polygynous.”
I believe it is accepted that Chimps and Bonobos are more closely related to eachother than either is to humans, though I can’t recall any specific citation.
I have a huge zinc finger.
I’m not so sure about the chimpanzee/bonobo thing…
Take a look at the Wikipedia description of bonobo sexual behavior, then do a Google search for “sex”, and tell me we’re not closely related.
Humans show various characteristics that in other primates are associated with relatively monogamous pair-bonding and relative lack of male dominance (eg, less sexual dimorphism, larger penises). There is an interesting argument to be made that this female “empowerment” was one of the driving forces in human evolution.
For all Tucker’s tenuous arguments about fatherhood in humans, human fathers apparently cannot lay a claim to being the best fathers in the kingdom animalia. Among primates, marmosets – small arboreal monkeys – may qualify as the best, since their males spend about 70% of their time caring for neonates and infants. This quality time spent with the baby marmoset apparently makes up for more than just a sensitive, new-age monkey; it makes the marmoset dad smart; the nurturing actually boosts mental activity.
In last month’s Nature Neuroscience, Yevgenia Kozorovitskiy and her colleagues from Princeton U Dept of Psychology publised a study on the effects of fatherhood on the brainstem axis (Nat Neurosci. 2006, 9(9):1094-5).
They found that other areas such as hypothalamic paraventricular and supraoptic nuclei, with no known projections to the PFC, as well as PFC pyramidal cell bodies were the source of the vasopressin that flooded the PFC and enhanced the expression of the vasopressin receptor V1a. V1a receptor binding excites cortical neurons, and excitation can induce spine growth; therefore, they concluded that fatherhood in marmosets resulted in enhanced dendritic spine density.
For the uninitiated, the dendritic spines are projections from cortical neurons and form a part of the synapse. More dense these projections are, higher is the number of neurons a given neuron can communicate with. Changes in dendritic spine density have been implicated in many brain functions, including motivation, learning, and memory.
References can be found here.
Yeah, of the many moronic claims made by this gobbler, I was also struck by this particularly appalling one:
This one is a true howler, on the level of DWARFS + PYGMIES. The larger East African chimp is NOT on our ancestral line–we (and a whole host of other human ancestors in the “homo,” “australo,” and still-earlier groups) AND (chimps + bonobos) are descended from a common ancestor. That, um, hasn’t existed for seven million years. Can we count to SEVEN MILLION, class! Argghh!
I mean, even drew hempel–who is convinced by Schwartz’s arguments that our closest ape relatives are orangutangs, rather than chimps/bonobos–knows better than to claim something like “the longer-limbed Indonesian orangutang, where only successful males who have access to females develop ‘full’ masculine characteristics, produced the line that led to humanity.”
Once your eyes cruise across something this execrable, the rest of PZ’s excoriation becomes superfluous (although still entertaining).
Maybe what we need is a Genetics or Human Evolution 101 web-pamphlet–with big easy-to-follow Jack Chick-oid graphics–that lays out the most very basic info in terms that even wingnuts this loose can grasp. The series could be called something snappy like “Really Hard Stuff Made So Simple That Even Maroons Can Follow It, Duh, Mostly.”
Is this plagary? “The longer-limbed Indonesian orangutang, where only successful males who have access to females develop ‘full’ masculine characteristics, produced the line that led to humanity.” — drew hempel, MA
haha
Seriously though — isn’t the Y Chromosome headed for extinction? What do the Genetic Geeks on Pharyngula say about that “Male Human going extinct” book that was published a few years ago?
I think the timeline was 1000 years as a conservative estimate. Well we have 25 years left of freshwater so maybe all that atrazine in the water will change our perception of time to a more Lunar-dialectic?
Indeed? And where are all the spitoons of yesterday now that we could really use them?
While you’re right in your analysis, and Tucker is wrong, he could have been right in principle. That is, one can propose a model by which mutations in the Y chromosome alone change male aggression and dominance. We know, for example, that extra copies of the Y chromosome produce high testosterone levels (and attendant low intelligence, hyperaggression, etc.), so obviously amplifying the signal from SRY to differentiate testes could cause the testes to produce extra testosterone.
I’m just saying the model he proposes is plausible, although not for the simplistic reasons he cites.
The idea that we can credit the “male” Y chromosome with encoding a constellation of attributes that are exclusive properties of the male phenotype is nonsense.
That’s not really true, because, one gene can control many others. The entire physiological and behavioral differentiation between men and women is controlled initially by a single gene. It’s not impossible that another gene just downstream, which controls only a subset of the differences, could be altered between humans and chimps.
Again, I’m not saying it’s true, I’m just providing a plausible model.
In fact, the discovery of bonobo society proves just the opposite. It is precisely because females play a dominant role and males are so passive and unambitious that bonobos did not produce an evolutionary line that led to human beings. Instead, they remain a relatively minor, underpopulated species holding their orgies deep in the jungle. The larger East African chimp, where males predominate, produced the line that led to humanity.
The fact that he wrote this paragraph should disqualify hime from EVER writing about evolutionary biology again.
“Among chimps, males hang out in groups, form alliances, forage together, and do a lot of bickering over status.”
That is not true of humans?
This thing is really dreadful, but is it worth criticising? I have never heard of Tucker or the American Spectator before
I think human monogamy, such as it is, is at least partly just a function of money.
Once you decide that women have to prioritize taking care of the kids and that therefore men have to provide economic support to them, you then get the situation where it’s too expensive for most men to support more than one woman, and eventually too much a matter of pride for most men to want to share the economic support (and loyalty) of one woman (and her children – who might be another man’s children), with one or more other men.
However, some cultures obviously permit and even promote polygyny among wealthy men, and some cultures certainly permit polyandry where men are poorer. And then there is our culture, where we have the wink at wealthy men with mistresses who we don’t publicly sanction but who gain the admiration or envy of a lot of other men.
And the rich men’s wives make it with the pool boy.
I always had the impression the Y chromosome was the incomplete one, anyway.
[From the author bio] WILLIAM TUCKER is a writer in Brooklyn, New York, and a frequent contributor to http://www.spectator.org.
A writer? And he lives in Brooklyn?
That’s it? Not “Tucker studied paleoanthropology at Humpsnout University” or “Tucker is the author of What to Expect When Your Snotty Feminist Soon-to-Be-Ex-Wife Is Expecting” or anything else to distinguish him from the hoards of (I’m guessing) other office temps (1) who identify themselves as writers?
Look, I concede that you don’t need some fancy-shmancy science degree to have the chops to write about science. But you have to make some effort; this guy clearly doesn’t have the chops.
Moreover, the Sun editors obviously didn’t bother to ask themselves whether the guy knew what he was talking about. It’s a ‘winger rag; the piece probably qualified on the basis of He-Man Women Haters’ tone.
(1) I’ve temped. It’s not a moral failing, it just doesn’t qualify you for anything.
To see how utterly wrong Tucker is about chimpanzees and bonobos, check out figure 2 from this paper (pdf): http://email.eva.mpg.de/~paabo/pdf1/KaessmannGreatApeNatGen2000.pdf
I think PZ’s postulation is correct – it has been ‘stupid week’ on the ‘net. I think we need a poll on who is stupider: Tucker or Curry. Maybe they could get together and talk about the what will happen over the next 1000 years in the evolution of feminists? Would these be Curry’s squat hairy goblins (ouch)? But how are we supposed to get all that homogeneity if the straight-jawed, big willy, ultra-males are all monoganous? These ramblings are off the stupid scale, why are these guys getting any coverage???
As an aside, I do remember a bit of resaerch from a few years ago that found a correlation among primates between testicle size and monogamy. Gorillas are mister faithful and have small ones. The promiscuous primates ‘hang low’, as they may need to call on reserves. On this scale human males were not strongly either way, and were predicted to mostly ‘walk the line’ with lady No. 1, but also to be opportunist at times. Bear in relation to observed (collective) behaviour of human males?
Whip it out people. Oct 16, 06, New Scientist:
According to new study, male beetles with the most dramatic and ostentatious sets of horns apparently pay for that with smaller testicles.
… that “Male Human going extinct” book that was published a few years ago?
I think the timeline was 1000 years as a conservative estimate.
The book you’re thinking of is probably Bryan Sykes’ Adam’s Curse, but he projects it’ll happen in 125,000 yrs, not 1000. He proposes the Y-chromosome’s “ruin” for exactly the reason PZ notes the human Y diverged from (and is now longer than) the chimp Y: an accumulation of too many deleterious mutations without the means to repair itself. He projects a gradual, longterm decline in male fertility by 0.1% per generation, meaning it’ll drop effectively to zero in around 5000 generations (barring a mutation elsewhere in the genome that enables some other gene to turn on the process that produces males).
Now, I’m not claiming I agree with him — as a layman, I don’t have the genetics background to prove or disprove him. What do those of you HAVE such backgrounds think?
Well, your impression is right. The Y chromosome has been degenerating since its inception, because of the lack of recombination. Just like mitochondrial DNA is very primitive because it accumulates deleterious mutations, so does the Y chromosome degrade over time.
Thanks for the “heads up” — it seems Tucker “protesteth too much” — the Napoleon Effect.
“Did the internet get stupider while I was away this past week?” Yes. Of course.
As a laywoman myself, all I can say is it just stuns me that these goons appeal to “nature” whenever it suits them to contradict inconvenient facts, then whip out the so-called supernatural “soul” argument whenever it suits them to contradict inconvenient facts about “nature.”
Sigh. The sooner we get rid of those pesky y chromosones, the better.
;^)
Wow. William Tucker–you got owned.
Brilliant takedown, PZ.
No, I’m guessing if he had read the paper he would have discovered that actual science is too hard for him to understand, and would have quickly gone back to spewing his article.
oh and Jeff, you win the thread.
Pete and Jeff have now reaffirmed Tucker’s results:
What is it about this “male brotherhood” that points the way to human evolution? First of all, male chimps have learned to work with each other in co-operative effort — something nearly all other species don’t do.
If feminism wasn’t underming evolution then why are there PYGMIES and DWARVES?
I actually did a spit take when I read the part about fatherhood being a unique human trait. I wasn’t drinking anything, thankfully.
I am constantly smacking myself in the head for thinking, back in my school days, that I had to actually know about stuff in order to be a paid writer. It’s not too late, I can get onto a publication and write whole articles where I invent bogus theories based solely on pulled quotes from popular magazines and my own crusty biases. Research? Who needs it?
Hmmm. Midway through the article, I wasn’t quite sure what you were going to say about this, PZ. I wasn’t expecting the “increases the frequency of mutations in chromosomes from the male parent” explanation. My guess was this: we already know that the Y-chromosome has a large number of psuedogenes and many genes have been copied off to reside elsewhere in the human genome. This makes the Y-chromosome a bit of a graveyard for old genes. Since much of the Y-chromosome isn’t under selective pressure (because it’s largely “junk DNA”), mutations have been accumulating more quickly in that part of the genome (both in chimps and humans). Absent of selection pressure, we’ve ended up with more mutations there. The interpretation that “what differentiates us from our mammalian relatives is changes that have occurred in the male of the species” is false under my explanation, because the extra mutations are just junk mutations anyway.
I am so far out of my league here, and I am working from a physical anthro class taken back in 1983…but I’m all over PBS, and the following is news to me.
“First of all, male chimps have learned to work with each other in co-operative effort — something nearly all other species don’t do.”
Details please. The last time I checked, species ranging from hyena to porpoise to lion to whale to wolf to geese “cooperate.”
Everywhere in the Western world, the emancipation of women has initially led to rising divorce rates and plummeting births.
That’s so sad. Everybody, bow your heads and mourn the fact that now there’s a mere 6.5 goddamn billion people on the planet.
Well I had a “whale” of a grandmother so I appreciate Tucker’s insights:
Grandmother hypothesis
From Wikipedia, the free encyclopedia
The grandmother hypothesis is meant to explain why menopause, rare in mammal species, arose in human evolution, and how late life infertility could actually confer an evolutionary advantage. The hypothesis suggests that this is because of risks associated with pregnancy and childbirth and the relative importance of parental investment to the human species. Grandmotherly investment may also be important in the few other animals which experience menopause, such as whales. Kristen Hawkes originated the hypothesis, and C.G. Williams was the first to posit that menopause may be protective
http://www.politicalgateway.com/news/read/42681
Big new (level of quality) fossil find? The article doesn’t state what the species is, but claims that it’s revolutionary since they’ve never had anything more than squished slices of it before, and this is the real 3d deal.
steviepinhead wrote:
‘Maybe what we need is a Genetics or Human Evolution 101 web-pamphlet–with big easy-to-follow Jack Chick-oid graphics–that lays out the most very basic info in terms that even wingnuts this loose can grasp. The series could be called something snappy like “Really Hard Stuff Made So Simple That Even Maroons Can Follow It, Duh, Mostly.’
It really isn’t such a bad idea, even though you were being facetious. The title might not attract too many people, but if the graphics are good it would be just the thing to leave at tables outside of “evo-ID” debates.
What’s the state of play with the Y chromosomes of other mammalian species? If the date of expiration on the human Y is 100,000 years away, does that mean that other mammals’ Ys will also spontaneously combust 100,000 years from now?
And is the same thing happening with the bird’s corresponding chromosome (W or V, I forget which is which)?
BRING FORTH THE BURKA’S TO CURB THE OPRESSION OF MY Y CHROMOSOME!!!!1
gee, now that was a great article yet again. I really dig ur sarcasm at times.
It`s not gonna change Tucker`s picture of the world, but at least it stirs up some attention and let`s others share Tucker`s insight in a scorning and gleeful fashion.
I suspect however that Tucker does not read nature given that he knows so little about it. But he might be a proud owner of creationystpedia – a detailed creationist`s guide to underdumbing the universe.
If you read old Edgar Rice Burroughs novels, then it is seen that this idea that male dominance is required for progress and societies with women equal or dominant remain stagnant is an old one.
Anything published in the American Spectator is virtually guaranteed to be “remarkably silly” so no surprise there. Which is not to say that, even considering the fringiness of the source, it isn’t still a good idea for biologists to speak out about such asinine distortions of science.
The Y chromosome story is a bit more complicated than “disappearance in 100,000 years”. For one thing some countervailing mechanisms that tend to preserve Y-cromosome genes are being discovered. For another,even if it does disappear there’s no reason to fear for (or hope for, depending on your point of view!) the demise of males. There is at least one mammalian species, the mole vole, which has lost the Y chromosome completely, including the SRY locus (or whatever its vole functional equivalent is). Yet there are still male mole voles- they simply came up with an alternative regulatory scheme (not yet well-studied AFAIK) for activating all the downstream pathways that lead to male development in the absence of a master regulatory locus on the Y.
Clearly, these are the genes for man’s massive penis (as compared to other primates, by weight).
“Now, I’m not claiming I agree with him — as a layman, I don’t have the genetics background to prove or disprove him. What do those of you HAVE such backgrounds think?”
I don’t have that background either, but the “list” link PZ has ( http://en.wikipedia.org/wiki/Y_chromosome ) happen to discuss the 300 million year history of the Y chromosome, some possible repair mechanisms and some possible futures. For example, latest at the kangaroo state (only sexdetermining SRY remaining) we can go the vole way and start over with a new Y chromosome by combining it with another one. Syke’s scenario isn’t even mentioned.
Uhm, in other words, what Steve said.
I’m not the expert here, but I always assumed that if the Y chromosome had an expected life of a hundred thousand years or so, humans will not be standing around all like, “OK, so what now?” – we will probably have invented or evolved something to compensate. (If we can even tell the difference between our evolution and our engineering by then.)
Funny, seeing how according to a recent Nature Genetics article — Parma P, et al. R-spondin1 is essential in sex determination, skin differentiation and malignancy.Nat Genet. 2006 Oct 15. — the Y-chromosome isn’t even necessary for an individual to develop into a male! It is necessary to develop into a fertile male! A point mutation in human R-spondin 1 is apparantly the cause of full sex-reversal in XX-individuals, even in absence of SRY, a testis-determining gene.
I wonder how important the Y-chromosome really is.
If the Y has an expiration date, and there is no repair…
Then we end up another footnote in history. That’s evolution.
Until then, bring on the jungle orgies!
Gee, if species could go extinct due to Y-chromosome loss, you’d think mice would be long gone from the planet.
Geez. This seems to be the modern-day “Irish elk went extinct under the crushing weight of their antlers.”
If I read the Wikipedia article correctly, in our system it’s a single gene which triggers the maleness cascade. Male genes accumulated near SRY; Y became harmful in recombination, so stopped recombining; as a result, non-male genes jumped ship. The “degeneration” of the Y-chromosome is simply the movement of general genes to safer (error-corrected) chromosomes, in fact a genetic improvement, if one must think in such terms. SRY itself is under tight selection pressure and will be preserved directly, absent some other male-determining mechanism.
Um… isn’t it fairly obvious that if *some* people’s Y chromosome gets a mutation that causes it to break down completely, and *other* people’s don’t, that the next generation will be descended from the men with the working Y chromosomes?
You’d need some kind of magical “now every Y chromosome in the world breaks simultaneously!” to have the kind of doom of the species some people seem to be predicting. That could *maybe* be done by some kind of genetically engineered retrovirus, if you want to make a science fiction story out of it (getting 100% exposure would be a bitch, but it’s a more interesting story if there are a few fertile men left anyway). It’s not going to happen by chance.
Nonfunctional Y chromosomes, by definition, can’t spread through the gene pool (unless their owners have an alternative mechanism for regulating sex, like the mole voles, which makes the Y unnecessary; but I’m pretty sure that in humans, a zygote with X and no Y doesn’t develop at all, let alone into a functional male).
Assuming that deleterious mutations are going to keep accumulating until the species goes extinct betrays a deep misunderstanding of evolution. Deleterious mutations don’t accumulate in a large population. They get selected out. The more deleterious they are, the faster they get selected out. Total sterility is about as deleterious as it gets.
Removing recombination may weaken this process, but it doesn’t destroy it; ask any asexual species. They have to be at least good enough to leave offspring or their genes, mutant or otherwise, go exactly nowhere.
Chris wrote:
In other words, you’d need the episode “Love Gods” of Sliders, wherein our heroes find a parallel Earth on which almost all the males have died, thanks to a genegeneered Iraqi virus which attacks the Y chromosome. It makes Australia a world superpower, I seem to recall.
Oh cruel and vengeful Lord, why is my brain filled with Sliders trivia from eight years ago instead of anything useful?
Chris, you’d think it would be obvious, so why does Brian Sykes of “Adam’s Curse” infamy- a professor of human genetics!- fail to get it? That’s baffling. And embarrassing (for him- though I suspect he’s laughing all the way to the bank and doesn’t care.)
Chris also wrote:
See Turner’s syndrome. An individual with one X chromosome and neither a Y or another X grows up female, with various possible developmental problems.
I am trying to imagine how a gene for monogamy, taken by itself, could ever invade and take over a reproductive population. I suppose it could be assumed that monogamy contributes to reproductive success because pair-bonded parents could contribute more to offspring survival than single mothers can, but that involves a constellation of behavioral changes, not some binary monogamy/polygamy switch. It’s like wondering about the heritability of a “gay gene.” Practically by definition, something more subtle than a single gene spreading throughout a populatoin has to be at work. Oversimplification is a shortcut to stupidity.
This is a nice paper describing why we can kiss our Y chromosomes goodbye, boys.
JA Graves. 2006. Sex chromosome specialization and degeneration in mammals. Cell 124(5):901-14.
Throughout evolution the biology of fe/male is labile and is not intuitive – and is far from focused on the existance of “Y . Birds and some insects use a ZW sex-determination – and there the male is ZZ, while the female is ZW. (Which I happen to remember because those are my wife’s initials, and she’s named after a bird – and, funny thing, is a volunteer bird bander.)
In addition to the wikipedia article on “y_chromosome” I recommend their entry for “male”. Both are pretty good.
Upshot: what Torbjörn said. If our Y degenerates totally, the human species will still have males, determined by some other genetic mechanism. Altho speedwell’s scenario of a bioengineered intervention is unfortunately plausible. (Unfortunately? Just look at what we do to the sex ratio now in India and China using only pre-natal sex determination.)
Greg, spot on. Here‘s a lecture outline which hints at the many factors which shape various species’ dominant mating system including monogamy. (Sinervo’s site is of general interest for behavioral and evolutionary biology- check out his lizard-land and its rock/scissors/paper game.)
What has changed is the role of males. Among chimps, males hang out in groups, form alliances, forage together, and do a lot of bickering over status. They do not participate at all in child rearing.
So this differs from a sports bar during football season…how precisely?
We know, for example, that extra copies of the Y chromosome produce high testosterone levels (and attendant low intelligence, hyperaggression, etc.), so obviously amplifying the signal from SRY to differentiate testes could cause the testes to produce extra testosterone.
I’d like to see a reference for that, Eddie. “We know” needs some backing up.
My understanding of extra-Y in humans was that statistical noise swallows any potential signal of “increased nasty male”. I thought this misunderstanding was based on the observation that the proportion of double-Y males (XYY genotype) in prisons was higher than the proportion in the rest of the population – but that this difference is small, and the fact remains that the overwelming majority of double-Y males are NOT criminals, Aliens-3 notwithstanding.
Doubling a chromosome does not necessarily mean a doubling of expression of any (or all) genes on that chromosome – witness the X-inactivation in normal XX female mammals, a mechanism that is active in XXY males, leading (most visibly) to the very rare male calico cat. Besides, what evidence is there that doubling expression of SRY specifically leads to higher circulating testosterone levels? SRY is not a gene “for” testosterone – it’s a switch at the top of a long and complicated cascade of gene activation and inactivation.
Furthermore, there are many other ways of determining sex as alternatives to the mammalian SRY system. Birds and butterflies, as noted above, use the WZ system, in which females are the heterogametic sex. Across fish taxa, almost every imaginable sex determination system can be found – XX/XY, WZ/ZZ, Hermaphrodites, Environmental (eg. temperature-dependent), “Super-Y”, “Super-X”, weird rock-paper-scissors three-way dominance interactions (I’m thinking of Xiphophorus fishes here), and more.
Well, the Y chromosome *does* have that weird palindromic-folding thing to try to keep mutations down. (Do we know how much of the chromosome that actually covers?)
Anyone who thinks the concept of “fatherhood” doesn’t exist in nature outside our own species should raise a few families of gerbils. Gerbil fathers are equal parents–up to and including the rather icky gerbil version of changing diapers. I’ve never yet met any human male willing to undergo *that* task ;^)
Lynn
I’m fine with changing diapers, excepting some of the times when I’m eating or have a fresh cut on one or more fingers. I don’t know how well this corresponds to gerbils, and whether you meant cleaning up infants specifically, or their particular method (I can imagine well enough, I think).
Yet another good reason to spread the word:
End A War! Save A Gerbil!
Sorry the bumper stickers are taking so long…
In gerbils, the “changing diapers” task involves intimate contact between the tongue of the parent and the dirty little behind of the infant ;^)
Lynn
Azkyroth – so if both parents have fresh cuts on their fingers, the diapers go unchanged?
Did I say that?
I said I didn’t object to changing diapers except when I’m either eating or have concerns about contributing to possible infection of wounds. That doesn’t mean I wouldn’t do it if necessary, just that under those circumstances I would prefer to avoid it if possible.
We already have Mike here to confront me with bizarre distortions of my statements, so your contribution in that regard is redundant…
Zincfinger
He’s the man, the man with the zidas touch
A spider’s touch,
Such a cold finger
Beckons you to enter his web of sin,
But don’t go in
Zincen words he will pour in your ear,
But his lies can’t disguise what you fear,
For a galvenized girl knows when he’s kissed her,
It’s the kiss of death from
Mister Zincfinger.
Pretty girl, beware of this heart of zinc
This heart is cold
Zincen words he will pour in your ear,
But his lies can’t disguise what you fear,
For a golden girl knows when he’s kissed her,
It’s the kiss of death from
Mister Zincfinger
Pretty girl, beware of this heart of zinc
This heart is cold
He loves only zinc
Only zinc
He loves zinc
PS: Lynn: I figured it was something like that. And yeah…between the gross-out factor, the potential for gastrointestinal infections, and the fact that putting one’s tongue on an infant’s behind in any case pretty much guarantees a substantial prison sentence and lifetime probation, I doubt you’ll find many human males willing to do that.
If both parents have fresh cuts on their fingers, each parent contributes the uninjured hand to a joint venture.
For those babies lucky enough to have two parents…
It takes a village?
I really can’t believe I personally have this much influence. Why not? You believe all kinds of other nonsense. Why not the proof of your towering arrogance?
(Yes, echo chamber sycophants, I recognize he is being ironic. . .)
Yes, his influence is minimal, which is why self-righteous little brats like yourself feel the need to come here and lob feeble potshots at him and everyone else who can trounce you in an actual argument without breaking a sweat, even if you’re too dense to admit defeat.
“…[bonobos] remain a relatively minor, underpopulated species holding their orgies deep in the jungle.”
This slam of the helpless bonobo is 100% justified — provided one defines success as a species in terms of sheer population and geographical distribution. But if we’re going to set the goalposts as being who builds skyscrapers & lunar landers, humans would be wise to be humble. After all, Homo sapiens aren’t the only species to visit the Moon — so did the arthropods swimming in the Apollo astronauts’ eyelashes, and the bacteria in their guts. Those modes of living have spread them just as far & wide as humans — perhaps farther. Maybe we should be taking lessons from them.
Wait a minute – if the Y chromosome is responsible for human superiority, this would surely imply that women, with nary a Y chromosome in them, would:
– Grunt in monosyllables and refuse to introspect about their feelings
– Happily live in animalistic squalour if left to their own devices
– Be routinely distracted by sexual signals sent by the physical characteristics of the opposite sex AND
– Have an inordinate interest in ritual displays of violence and territoriality.
I’m not sure this is the case, but as soon as I dump these pizzas on the floor and watch the football and this new porno I rented, I’ll be sure to get to researching it.
Everyone pretty much has this covered, but I had to add.
Monogamy predominates and both parents participate in child rearing. The extraordinary innovation is “fatherhood,” a role that doesn’t really exist elsewhere in nature.
Yeah, except for, just to give primate examples, Callithrix (marmosets) and Hylobatids (gibbons).
In fact, the discovery of bonobo society proves just the opposite. It is precisely because females play a dominant role and males are so passive and unambitious that bonobos did not produce an evolutionary line that led to human beings. Instead, they remain a relatively minor, underpopulated species holding their orgies deep in the jungle. The larger East African chimp, where males predominate, produced the line that led to humanity.
Forgetting that neither species of chimp “produced” the line that led to humanity…grr…DNA hybridization shows that the gracile, jungle-orgy bonobos shared a common ancestor with humans much more recently than the other kind of chimp.
(I just had to demonstrate that I am actually learning something in my primatology class)
Forgetting that neither species of chimp “produced” the line that led to humanity…grr…DNA hybridization shows that the gracile, jungle-orgy bonobos shared a common ancestor with humans much more recently than the other kind of chimp.
Not exactly, since genetic studies also show that bonobos and chimps shared a common ancestor much, much, much more recently than either does with humans (see article Carl Zimmer links to above).
It’s true that bonobos show slightly lower distances than chimps in DNA hybridisation studies. But it is a very rough method to estimate genetic divergence – hopefully the bonobo genome gets sequenced one day.
Heh, I thought I knew the name American Spectator from somewhere; it turned out they’re the outfit that thought it would be cool to have a blackface cover when talking about multiculteralism.
They’re know nothings and proud of it.
Someone please tell me that the coloration in the above picture is an artifact of photomicrography or my aging Trinitron: is the X chromosome really predominately pink, and is the Y chromosome actually tinted blue?
Actually, there is no color whatsoever in electron photomicroscopy: the picture was colored long after it was taken.
I just happened upon your post. Thanks for taking the time to lay it out – I had no idea.
“In addition, recombination is mostly eliminated in the Y chromosome, and recombination is a process that allows deleterious alleles to be purged by shuffling ‘bad’ combinations away.”
Hi folks,
For a non geneticist such as myself, the mention that “recombination is mostly eliminated in the Y chromosome” implies it has not been in the X chromosome. If some of the alleles that are not being purged on the Y chromosome express as positive characteristics and some as negative ones, this further implies that we should see a greater std dev of expressed characteristics in men with their XY than in women, whose two X chromosomes are more homogenous across the population, at least for those characteristics coded for by the Y chromosome. Is that correct? Do we see greater variability between men than between women? What’s the deal? Do tell.
Thanks.
Stanton –
Thanks for clarifying that. Would you know if the coloring is intended to mean anything significant, or just represents someone’s whimsy?
Wait… so feminism as in women taking men’s roles is bad, but second-generation feminism in which women take men’s roles (work outside the home) and also kkeep the home fires burning and babies changed and so forth is ok? So what’s the x good for again? Oh, orgies in the jungle.
Wait… so feminism as in women taking men’s roles is bad, but second-generation feminism in which women take men’s roles (work outside the home) and also kkeep the home fires burning and babies changed and so forth is ok? So what’s the x good for again? Oh, orgies in the jungle.
Chris: men’s X chromosomes always come from their mothers, where they are the product of recombination between her father’s X chromosome and her mother’s, so no.
Pull my zinc finger protein! Badoom-sha!
And I don’t know why I never thought this before, but it just occurred to me that I have all of the genes necessary for building ovaries. Kinda cool, actually.
Ummm, Steve C, I’m not sure you should be slinging the word “stupidity” around, when you used “should of” in place of the contraction, “should’ve,” which of course is short for “should have.”