WWhy aren't more animals hermaphrodites? Snails and worms appear to have successfully used this method to exchange genes between any two individuals, but vertebrates have moved away from it. Why? Janet Leslie, Kent, UK
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Readers' response
Because it takes all the fun out of courtship. Richard Orlando
The question is based on a misperception. Large chunks of the phylogenetic tree of animals are hermaphrodites. There is a distinction between simultaneous hermaphroditism, where the same animal produces two different gonads at the same time, and other forms of hermaphroditism called sequential, where an animal can change from male to female or vice versa. If you put it all together, that's a lot of animals and most of the angiosperms. This shows you how narrow cultural and human perceptions are and how disconnected they are from facts. One of the beauties of science is that it allows these misconceptions to be corrected in a structured way. Who could it be
For life forms where finding a mate is relatively easy, it is much more beneficial to specialize in dimorphism to optimize traits, both female and male. For a life form with access to limited resources, investing in both systems is expensive and does not provide as many benefits. Niklas Uhlfeldt
Common garden snails are hermaphrodites, but not all molluscs are. Some are sequential hermaphrodites, but many have separate sexes and exhibit extreme sexual dimorphism, such as the paper nautilus. [a species of octopus]. Investment in eggs often requires larger body size, or at least larger female cells. If the female has to care for eggs or young, this also requires more investment in growth. I suspect there is a connection between hermaphroditism and lifespan, and whether the animal is viviparous or ovoparous. JaneSnail
Wait. Are you telling me that Brian from The Magic Carousel wasn't a guy? Eddie Chorepost
No. He was both! Brutus
It seems to me that much of biology is based on opportunistic evolutionary chances, mutations and the conditions that the organism is exposed to. Nature is not picky – it goes to the limit of possibilities in all spheres of life, hence the appearance, for example, of the most extraordinary deep-sea creatures. But he doesn’t “care” about the consequences either. This is illogical in every sense that the human brain can imagine. While “why” is my favorite question, I don’t believe there is a single answer in this case. LorLala
Gonochorism [a system where there are two sexes and each individual organism is either male or female] more fun 🙂 SilDaiPow
As expected, this question elicited some mildly humorous responses. The possibility that this is a pure evolutionary accident may seem a little threatening to our sense of sexual identity. However, the good news is that there is a good scientific reason why more advanced animals will be either one sex or the other. The presence of reproductive organs of any type leads to metabolic exhaustion of a person. Any person having both types at the same time doubles this burden and thus puts the person at a disadvantage for survival. Thus the force of evolution will, however slightly, favor a form that is sexually dimorphic rather than hermaphroditic. Updated
