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Some Falsehoods about the Y chromosome and Male Brains

y chromosome

Note: Greg Laden has made a comment on this post saying that I misrepresented his position. I am open to the possibility and have therefore asked some follow-up questions, but at the time of writing this note (2012-07-26 22:23 GMT +1 DST), Laden has not clarified the situation for me. Keep this in mind while reading this post. Will update this again when he does.

Note: I just noticed (2012-07-28 22:08 GTM +1 DST) that Heina Dadabhoy did not mean what she actually said, but said it as a joke in response to a tweet by Zvan. There is an alternative explanation, namely as a post hoc rationalization when Heina discovered that she had been called on it, but it seems less likely. In essence, this means that we can probably consider both the claim made by Greg and Heina to be jokes or awkwardly expressed science. The only think left now is for Greg to finish writing up his follow-up and/or setting me straight by explaining more in detail in what way I misrepresented him.

Note: As a clarification (2012-07-28 23:06 GMT +1 DST) for Kelseigh Nieforth (‏@Nezchan), I reject this alternative explanation. It is possible, but relatively implausible. I did not intend to sound “mean-spirited & insulting”, quite the opposite. My intent was to rebuke what I felt was going to be the standard misogynist reply (i.e. claiming that Heina only said it was a joke when she noticed it had gotten a lot of attention and reflected badly upon her).

Note: Greg Laden has clarified his position over at his Scienceblogs blog. The general idea is that testosterone alters the male brain during different stages of development and “damaged” referred to the fact that androgens and other biosocial factors influence certain men to be more statistically likely to exhibit socially noxious and harmful behaviors that are incompatible with progressive, egalitarian and peaceful world. I have no general problems with this position (note added 2012-08-03 20:16 GTM +1 DST).

Note: This blog post has been linked by a men’s rights activist blog. All forms of discrimination is morally wrong, but most men’s rights activism I have come across seems to be equal parts pseudoscience and blanket anti-feminism. I therefore, in general, reject men’s rights activism. This post should not, and cannot, be interpreted as giving men’s rights activism any support, whatsoever (clarification added 2012-08-04 14:14 GMT +1 DST).

The background to this story is that Heina Dadabhoy and Greg Laden, at a panel discussion on gender differences at SkepchickCon/CONvergence, claimed that the Y chromosome was “broken” and that the male brain is a female brain damaged by testosterone. Amidst substantial criticism of these claims, the FtB blogger Stephanie Zvan decided to take upon herself to defend these flawed notions. As we shall see, her attempt is filled with incorrect characterizations and selective use of the scientific literature,

But first, let us make sure we have understood the claims being put forward in the video, so that we do not incorrectly characterize them as something they are not. A video of the panel discussion can be found here. I will post enough of the discussion for context, but readers are encouraged to check if I have gotten everything right. Laden was especially hard to take a transcript of, because he talks very fast and often changes mid-sentence, but hopefully I got the gist. It starts with a question from the audience at 35:41 about the gender differences in autism diagnosis and how males are supposedly more often autistic than females:

Heina Dadabhoy: That is an underdiagnosis issue, actually. They have been doing more and more research on women and autism. A lot of us women who fall on the spectrum only find out when we are adults, because a lot of the behaviors that manifest…the ways that girl tend to manifest it is slightly different and you know a girl who gets obsessed with something they are like “oh, well she is a girl and she has her little obsessions, how cute and when it is a boy it is like “oh, why isn’t he out beating up his peers?” so that is a big issue with autism.

Member in the audience: …inaudible… [probably something to do with differential disease susceptibility between genders e. g. red-green color blindness or hemophilia – E. K.]

Heina Dadabhoy: That is the Y chromosome. It’s broken [Dadabhoy smiles and laughs – E. K.]

Greg Laden: There is… there is … One thing that psychology does…There is some reasonable evidence that certain….There are gender differences.. [inaudible]. But there are gender differences. One of the most important gender differences.. in other words males versus females do not overlap that much at all… in certain areas and one of…one place they do not overlap at all, and you can’t change this… with culture… much..like you can change spatial orientation by giving everyone Tetris when they are born and will be the same. What we can’t change is that, for example, is the number of kids that cannot read until much later…the age at which you start to read and how you have dyslexia and so on that are boys is an order of magnitude higher in girls and you can do everything you want to fix that and you can only fix them a little bit. Most of those differences disappear and are not necessarily that significant, but is real. You know, the male brain is a female brain damaged by testosterone in various stages in it’s life. I think probably there are some very interesting adult difference…you cannot look at at a person and say that, but population differences between males and females that has to do with brain development because hormonal differences and…most of them are probably kind of trivial but there probably are some…yeah autism…I don’t think that is an example of one, but there probably are some things but if we where that different, it would be a hard time communicating…[inaudible].

So, right of the bat we can see that Zvan has incorrectly characterized both what Dadabhoy and Laden had stated. Dadabhoy stated that the Y chromosome was broken, not, as Zvan wants to have it that the Y chromosome is a broken X chromosome. Laden stated that male brain is a female brain damaged by testosterone in various stages in it’s life and did not use the term development. As we shall see, it is these false characterizations that Zvan’s bases her arguments on, but the bigger problem is that Zvan has no scientific foundation for her argument, leading the entire tortuous justification of the notion that men are genetically and neurologically “broken” to collapses onto itself.

The Y chromosome is not broken, but contains 86 unique and functioning genes

In her attempt to justify the absurd notion that men are genetically broken, Zvan appeals to the fact that the Y chromosome cannot recombine with the X chromosome to the same degree that the X chromosome can with another X chromosome. While this is true, this does not justify the original claim that the Y chromosome is a broken X chromosome, or the stronger claim that the Y chromosome is broken. In fact, the Y chromosome contains 86 fully functioning genes and this does not even count the genes that exists on both the X and Y chromosome. For the vast majority of individuals, the Y chromosome is fully functional and does not produce genetic defects or pathology. So nothing is actually “broken”.

X-linked recessive disorders signify a problem with the X chromosome, not the Y one

Zvan points out that males are more at risk for certain heritable disease because the related gene only occurs once, while in females it occurs twice (since they have two X chromosomes). This is also true, but the causative factor is the disabling mutation in the X chromosome that causes the disease, not something to do with the Y chromosome. So in other words, what is “broken” in these cases, is the X chromosome, not the Y.

Lack of large-scale recombination is sometimes a good thing

The loss of an ability for large-scale recombination is not something uniformly bad. In fact, if large-scale recombination between the Y chromosome and X chromosome was possible, it could result in males without the necessary sex-determining or sex-influencing regions in their Y chromosomes and females with harmful genes only found on the Y chromosomes, so the lack of large-scale recombination between X and Y is clearly adaptive. A loss does not need to be evolutionary or physiologically detrimental.

Ancestral does not mean “better” and modified does not mean “broken”

It is true that the X chromosome is probably more genetically similar to the shared ancestor between the X and Y chromosome, but this does not mean that the Y chromosome is “broken”. It only means that it differs more from the ancestral state than the X chromosome. There is nothing, absolutely nothing, that suggests that the original ancestral chromosome was “better” than what we have now. Newer modifications does not mean “broken”, even if it is associated with a reduction in the ability for recombination or a reduction in the number of genes. For instances, parasites usually lose parts under evolution to make them better adapted at exploiting their hosts.

Evolutionary “broken” does not mean physiologically “broken”

It is also a failed appreciation of the fact that what is seen as “bad” in an evolutionary context is not necessarily seen as “bad” in the physiological context of the individual. The classic example is birth control pills which are terrible news from an evolutionary standpoint (no babies), but great for the individual (strongly reduced risk of getting pregnant, and depending on the type, treatment for severe menstrual cramps). So even if the shrinking Y theory is accurate (the Y chromosome is losing genes and will soon be annihilated), this does not mean there is something genetically or physiologically wrong with the Y chromosome and certainly does not suggest that it is “broken”.

The Y chromosome has not lost any genes for 6 million years and only one gene in 25 million years

As it turns out, the shrinking Y theory has been challenged in recent years. A study by Hughes et. al. published in Nature in 2005 demonstrates that not a single gene has been lost since the split between humans and chimps some six million years ago due to purifying selection. This puts a dent into the notion that the Y chromosome has an “impeding demise”. A further attack occurred just earlier this year when Hughes and colleagues showed that the human Y chromosome has survived almost intact for 25 million years, losing only one gene (an estimated 3% of the total amount of DNA). David Page, a co-author of the 2012 paper, says that it is a checkmate for the shrinking Y hypothesis.

The Y chromosome can “recombine” with itself using gene conversion

As it turns out, it is not even true that the Y chromosome cannot recombine Y-chromosome specific genes. In reality, this can, for some many of the genes, occur by a mechanism called gene conversion. Rozen et. al. (2003) showed that the male-specific region of the Y chromosome have over 99% intra-palindromic sequence identity. The evidence shows that the Y chromosome has undergone repeated arm-to-arm gene conversion in humans.

With this, we can pretty much consider the claim that the Y chromosome is “broken” as falsified by the scientific evidence. What about the claim that males are neurologically damaged? As it turns out, the evidence for that is even more shaky.

So male brains are broken because they are specialized? Come on…

I kid you not, that is her argument.

If you have a complex system that is capable in a general sense, and you retool it to specialize, you lose some of that general capability. In other words, you have damaged the ability of that system to generalize.

This justification is so absurd that it probably does not merit a response, but for completeness, I will explain why it is wrong. You see, the word “damaged” has to do with harm. No harm, no damage. Since specialization does not cause harm, it does not make something damaged. Also, neuroplasticity shows that it is not as simple as saying that “specialized means you have damaged the ability to generalize”. Environment modifies the brain. Furthermore, specialization is not necessarily bad and certainly not a form of “damage”.

As the commentator tigzy wrote on the post by Zvan:

Yeah, but Greg’s assertion that testosterone damages the female brain in order to make it male implies an impairment to the functioning of the organ. This statement is only tenable if one assumes that a male brain has been functionally impaired in relation to its former state – i.e., that it is not as effective as a female brain.

A beak that is specialized by evolution to crush seed will be less able to draw out prey that is hiding in holes in the tree or drink nectar, but this is not harmful to the organism.

In fact, this kind of anatomy, given a constant environment with lots of hard seeds, is incredibly adaptive. We can take an example from development. Some cells in the body differentiates to become kidney cells. This means losing the ability to become neurons (except in the case of induced pluripotent stem cell technology), but this does not mean that the cell is “damaged”. On the contrary, the cell will in general, go on to be fully functional and help to perform vital functions in the kidney and people without kidneys do not really do that well. Again, “loss of ability to do X” does not necessarily equal “it is damaged!!1”. It is context-dependent, and in this case the context is the environment.

Conclusion:

It is clear that for some people, it is only sexist when it is directed towards females. But when the sexism is directed towards men, such as calling them genetically and neurologically “broken”, it falls under the radar and, in this situation, zealously defended as obviously true by substandard arguments. What is “broken” in this situation is not the Y chromosome or male brains, but rather certain forms of feminism that become subverted by pseudoscience in the hands of ideologues. Many forms of feminism are extremely, extremely valuable to and necessary for both individuals and society at large, but only as long as they conform to the evidence. When they do not, they should be abandoned and other forms of feminism that do conform to the evidence should be given more intellectual attention.

References and Further Reading

Fearer, Matt. (2012). Theory of the “rotting” Y chromosome dealt a fatal blow. Whitehead Institute, MIT. Accessed: 2012-07-22.

Hughes, J. F., Skaletsky, H., Brown, L. G., Pyntikova, T., Graves, T., Fulton, R. S., . . . Page, D. C. (2012). Strict evolutionary conservation followed rapid gene loss on human and rhesus Y chromosomes. Nature, 483(7387), 82-86. doi:

Hughes, J. F., Skaletsky, H., Pyntikova, T., Minx, P. J., Graves, T., Rozen, S., . . . Page, D. C. (2005). Conservation of Y-linked genes during human evolution revealed by comparative sequencing in chimpanzee. Nature, 437(7055), 100-103.

Rozen, S., Skaletsky, H., Marszalek, J. D., Minx, P. J., Cordum, H. S., Waterston, R. H., . . . Page, D. C. (2003). Abundant gene conversion between arms of palindromes in human and ape Y chromosomes. Nature, 423(6942), 873-876

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