Cross Dressing: All the cool kids are doing it!
Image copyright Carin Bondar 'The Nature of Human Nature'
I know several men who like to dress up like women; however, it’s not a phenomenon that is restricted to just one kind of sexual orientation or demographic. The truth is that cross dressing in the human species is widespread and extremely common. Having grown up in a pretty liberal city (Vancouver), I’ve seen many a drag queen that has got my butt kicked when it comes to being the most stunning woman in the room. Homo sapiens males who dress up as females are definitely not alone in the animal kingdom; it turns out that males of several diverse animal taxa like to appear in drag during certain stages of their lives. From insects to fish, birds and mammals we see various examples of cross dressing. Several hypotheses exist to explain why males have evolved to appear as females (a phenomenon termed ‘female mimicry’), most of which involve subordinate males’ interactions with dominant males. How could it possibly be advantageous to appear as a female? Cross-dressing has several potential functions for an inferior male: it could fool dominant males into allowing them close contact with females, it could serve to allow them access to high quality territories that they may not be able to secure on their own, or it may serve to reduce overall aggression within a group1. Any or all of the aforementioned reasons may apply depending on the kind of organism doing the cross-dressing and the social structure to which it adheres.
Individuals of the parasitoid wasp (Lariophagus distinguendus) undergo their developmental process in stored grain (much to the chagrin of the humans that are storing the grain…but I digress). Females oviposit into a single grain, where each individual wasp develops. Although each developing wasp is protected inside its own grain, entire developing populations are clustered in a similar area. Before each female wasp emerges from her developmental home, she produces a pheromonal (smelly) signal. This signal helps males find her, which is extremely important because each female mates only once. A male wasp that has detected her signal will wait nearby for her to emerge from her grain in order to inseminate her before any other male gets the chance (can you imagine mating just as soon as you’ve hatched?!). Now, this is all well and good for males that emerge early from their own grains, but what about those that emerge later? The late-bloomers need a fair crack at the female market as well, so they have evolved a special technique to enable them to be more successful…appearing as females! Male wasps mimic the female pheromonal signal while they are still within their grains, effectively causing other males to sit and wait for someone of the wrong sex2. The fact that some early-hatching males have been distracted by the ‘fake female’ pheromone means that the cross-dressing males have a greater chance of spreading their seed to the next generation. This is an example of cross dressing in an olfactory (rather than a visual) sense, and that’s the one that matters if you are a parasitic wasp.
Capuchinbirds (Perissocephalus tricolor) take cross dressing to the next level. Behavioral observations on this South American rainforest species have demonstrated a great deal of sexual mimicry. Males appear as females, but females also appear as males3. In this extreme form of cross-dressing subordinate males benefit by obtaining closer contact with true females (who are normally under the protection of a dominant male). Copulation in this species is extremely fast (1-2 seconds), so a male stands a pretty good chance at successfully copulating if he can make his way to a sexually mature female without being detected. Females benefit from appearing as males because they are not bothered by subordinate males whilst on their quest to copulate with the dominant male. Generally, sub-dominant males continually chase females and she can therefore get a ‘break’ from this chasing by appearing as a male (ahhhh the irony of evolution!). It might just be me, but it seems that actually finding a compatible sexual partner in this species is no small task!
By appearing as a member of the opposite sex, individuals of the species in the examples above have evolved ways to make themselves more successful in the reproductive sense. Can this same logic be applied to sexual mimicry in the human species? Do cross dressing men increase their chances of offspring production by using their disguise to invade another man’s home? It seems to me that this is an example of human behavior without any biological basis whatsoever. Reasons for cross dressing in our species have little to do with reproductive success or increased survival….it may simply be that the elaborate garmets generally worn by the female gender of our species are too lovely for some males to pass up…after all, who doesn’t want to feel pretty now and then? I know that I’d certainly prefer a fabulous dress over a boring old suit any day.
1Rainey, M.M. and G.F. Graether. 2007. Competitive mimicry: synthesis of a neglected class of mimetic relationships. Ecology 88(10): 2440-2448.
2Steiner, S., J.L.M. Steidle and J. Ruthner. 2005. Female sex pheromone in immature insect males- a case of pre-emergence chemical mimicry? Behavioral Ecology and Sociobiology 55:111-120.
The graceful group dance of the pink flamingo – and other dance routines from the animal kingdom…
I happened upon a few GREAT videos a while back that showcase the lovely mating dances performed by males of several different animal species. My favorite of these happens to be the group number of the Andean pink flamingo:
Enamored? Check out the amazing dances of some of the other boys I profiled in my latest post at Scientific American. There’s even a lowly Homo sapiens in the mix 
Happy Weekend Everyone!
Missed the link? HERE it is again!
No eggs? No problem!
Copyright Carin Bondar 'The Nature of Human Nature'
According to our biological mantra, any energy spent either finding, courting and or fornicating with a member of the opposite sex is only justified if such an act is a bona fide attempt at spreading one’s genetic blueprints. Where’s the fun in that? Homo sapien males engage in copious amounts of sex without the thought of reproduction, and actively seek out partners that are sexually sterilized (see ‘Yes I’m on the pill’) in order to engage in it without the ‘worry’ of the potential side-effects (i.e. offspring). Biologists generally assume that most other boys in the animal kingdom are much more asute than this when it comes to leaving your share of genes in the pool for subsequent generations. Indiscriminate sex should be a rare occurrence due to the fact that energy is wasted on dead-end sex as opposed to being used for other forms of survival (e.g. food gathering or avoiding predators) or reproduction (e.g. courting a viable mate or creating a favorable environment in order to attract one). However, there are always exceptions…and like the human male, there are others who do not necessarily wait for Ms. Right to come along before attempting sexual relations. Animal species that live in both sexual and asexual forms present an interesting conundrum when it comes to mate selection. Females are generally the gender with both sexual and asexual morphs, leaving the males to determine where his sperm will be most usefully spent. However, many are incapable of discriminating between sexually competent or sterile females, meaning that human males aren’t the only ones to discard sperm without regard for its future…
The New Zealand mud snail (Potamopyrgus antipodarum) is a lake-dwelling mollusc whose females can be either sexually reproducing (requiring male ‘input’ for successful embryo production), or asexually reproducing (clonally reproducing without sexual activity). Further, many native populations of this organism are infected with a parasitic trematode that causes castration (sterilization) in females. Hence, males in these populations have several factors acting against their sexual success, leaving them in quite a conundrum when it comes to allocating energy to reproduction. One might imagine that the powers of evolution would have dealt these poor fellas a little help in the mate-discrimination department; however, that doesn’t seem to be the case. Mate choice experiments in which males were given a choice of either a) sexual vs asexual females OR b) healthy vs castrated females revealed that they don’t do a whole lot of discriminating1. Males showed no preferance for viable over non-viable females, appearing instead to simply attempt copulation with whichever females they could find. In this species the average copulation event lasts approximately 2 hours, during which both the male and the female involved in the act are relatively immobilized…leaving them more susceptible to predation. Conclusion: a copulation event represents a fairly large cost to a male if he is mating with an asexual or a sterilized female. So would he do it? Although the possibility exists that there may be an even larger cost to a male (in terms of time and energy lost) if he were to attempt to discriminate between fertile and sterile females, the scientists conducing this study surmise that at some level the male mud snails are engaging in behavior that is simply not contributing positively to their biological fitness in any way1.
Rotifers are tiny freshwater-dwelling organisms that also have two distinct female forms: sexual and asexual. Akin to the mud snail and the human, there are no clear physical differences between sexual and asexual females; although those females that are sexual must be fertilized when they are at a very early age (they are no longer fertile after 9-20 hours of life2). Male rotifers show a distinct preference for fertilizing very young females (2-3 hours old) which slightly improves the liklihood of fertilizing a sexual female, although they do not specifically discriminate between sexual and asexual individuals3. Why don’t the males preferentially select females with the capability to propagate their genetic lineages? They have a short lifespan (approximately 48 hours) and a large-enough supply of sperm so as not to become completely tapped out during this short time (it takes a total of about 13 copulations for him to be spent), drastically decreasing the need to discern between sexual and asexual females. If he had a lower amount of sperm to work with, it may lead to increased selection pressure to find the right girl rather than any girl.
As these examples show, if males cannot distinguish between fertile and sterile females, several of his sexual conquests may be in vain. This could mean big trouble if you are a rotifer or a mud snail: reproduction is as important as survival to any particular individual, and if the chances to do so are impaired then biological fitness is automatically lowered. So where does that leave the Homo sapien? Far from the priorities of our cousins in the animal kingdom, many of ours (with respect to reproduction anyway) have been altered in order to minimize biological fitness. Human males, unlike their snail and rotifer counterparts, actually seek out sterility in a potential partner….and for good reason: could you imagine if each of your own sexual conquests had resulted in offspring? You might have the highest biological fitness of all of your friends, but to the Homo sapien this situation would be far from optimal.
1Neiman, M. and Lively, C.M. 2005. Male New Zealand mud snails (Potamopyrgus antipodarum) persist in copulating with asexual and parasitically castrated females. American Midland Naturalist 154: 88-96.
2Snell, T.W. and Childress, M. 1987. Aging and loss of fertility in male and female Brachionus plicatilis (Rotifera). International Journal of Invertebrate Reproduction and Development 12: 103-110.
3Gomez, A. and Serra, M. 1996. Mate choice in male Brachionus pllicatilis Rotifers. Functional Ecology 10: 681-687.