The Moral of the Gender-Fluid Flatworm: Hold the Hypodermic!

Being bisexual/hermaphroditic makes the battle of the sexes worse, not better.

Posted Mar 06, 2018

As I indicated in a recent post, it is now heresy in the eyes of many to claim that sex/gender and everything connected to it—notably behaviour and cognition—is biologically determined save for superficial, surgically-reversible details of anatomy. But heretical or not, Mother Nature has a lesson for us in some remarkable marine flat-worms where the issue of gender fluidity is concerned.

These worms are true hermaphrodites: being genetically male and female at the same time and having both ovaries and testes. Genitally though, they are all male to the extent that there is no female sex organ, only a sharply-pointed hypodermic-like penis (in fact a double-barrelled one in the species illustrated in the clip below). Indeed, to this extent, you could see these wonderful worms as ideally endowed: genuinely bisexual/hermaphroditic and fully gender-fluid, but not stigmatized by appearing to be either one sex or the other, nor discriminated against by being denied a penis and the active role in reproduction. If only everyone were like that, wouldn’t the world be a better place? At the very least, surely we would have seen the end of sexism, homophobia, and the ultimate triumph of feminism?As the video illustrates, because there is no female genital organ, the only way that this species can reproduce is by one hermaphrodite successfully injecting its sperm into another, where it finds its way to the recipient's ovaries and fertilizes the eggs. 

The problem though is that no one wants to be the mother. If you are impregnated, you have to pay the costs of healing the wound and incubating and laying the eggs which develop as a result. All this takes time and resources which you could have better spent impregnating some other worm. The result is epic penis-fencing battles in which each of a pair of worms fights to impregnate the other without being impregnated itself: a kind of rape contest, if you like, but with equally equipped contestants.

Alternatively, you could see these worrying worms as epitomizing the selfish-gene paradigm of evolution: organisms which evolved, not only to copy their DNA and transmit it to the future but to do so by injecting it into another such gene-copier which would save it the trouble of making more copies for itself. Not just selfish DNA, but selfish sex to go with it!

Yet however you look at it, the moral of this little bit of natural history is three-fold: First, it gives the lie to the belief that if everyone could be both male and female at the same time, the battle of the sexes would be over and all would be peace, love, and equality.

Second, it illustrates the fact that, hermaphroditic or not, the costs and benefits of being a father or a mother are not the same for the individual hermaphrodite.

Finally, the plight of the impregnated worm highlights the fact that being the mother is much more costly than being the father. And to the extent that all fathers are male and all mothers female, this is a generalization which applies universally throughout nature, given the objective, quantitative definition of the sexes in terms of cost and benefit, with female always being the more costly option—or at least, the one with the highest level of parental investment and largest gametes, (sex cells: ova, ovules) by comparison to the male (sperm, pollen).

Of course, we are not worms (although about 45 percent of our DNA is identical to that of worms whose genomes we have mapped). Nevertheless, internal fertilization and gestation in mammals mean that there is a valid biological parallel, with maternity being vastly more costly to the mother than paternity to the father. 

And this is just the start of it. In our species in particular the conflict has escalated to bizarre levels nowhere better epitomized than in imprinted genes, where paternal DNA exploits the mother’s resources for investment in the father’s offspring which she is forced to gestate internally, while the mother’s genes fight back, resisting the demands in the interests of her survival and future reproductive success.

Indeed, where human beings are concerned, the battle continues after birth, at least if the imprinted brain theory is to be believed, with paternal genes pushing a person’s cognitive configuration in a mechanistic direction away from mentalism, and maternal genes pushing oppositely, away from the mechanistic and towards the mentalistic. Taken too far, the outcome is autism caused by paternal predominance, or psychosis caused by maternal preponderance. Normality, according to this theory, is a precarious balance in between. But this parable of Mother Nature's suggests that a sane outcome is not likely to be achieved by imitating these flatworms as so many suggest we should in psychology today.

At the very least, and for reasons I explained in a post on a human form of pseudo-hermaphroditism, we should let Nature take her time and allow for the expression of all the genes concerned in a person's sexual development before other people start interfering. In fact, the implication of the imprinted brain theory is that this process is not complete until adulthood, thanks to the fact that maternal and X-chromosome genes implicated in psychosis have a notably late onset. 

The moral of the flatworms is hold the hypodermic!

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