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.
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.
- 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.
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.