Diversity Is Strength (part 2)
Although diversity is strength, that doesn't mean it will benefit you, specifically. In a general sense, the species is made up of individuals, and the species wants to survive, so yes, it wants individuals to survive, too. But if sacrificing the well-being of some will serve the greater good, then the trade will be made.
Consider sickle-cell anemia:
It occurs due to a fairly simple recessive genetic trait. Your parents each contribute half, and as long as they don't both give you a recessive gene, you'll be okay. The Punnet square looks something like this:
| R | r | |
| R | RR | Rr |
| r | rR | rr |
As you can see, 1/4 of the population ends up with "rr", which means they have the disease. Unlucky them.
Why would the species permit a quarter of its individuals to suffer a shortened lifespan and chronic pain and organ damage? Because the benefits outweigh the costs.
Carrying the recessive gene gives you increased resistance to Malaria. So 1/2 the population (the "Rr" and "rR" folks) have this extra protection. The "rr" people don't even get that benefit, alas.
In an environment with prevalent Malaria, this trade works out to benefit the species. This may be small consolation for people suffering from sickle-cell anemia, though.
Now let's talk about bedbug sex!
Female bedbugs have perfectly functional reproductive tracts, but they don't get used by males. Instead, a male performs what is pleasantly called "traumatic insemination" — they jab their penis into their partner's abdomen and inject the sperm directly into the body cavity.
Why would this trait evolve? It certainly harms the females, putting them at risk of infection, etc. Arguably, this behavior hurts species as a whole, since it makes reproduction more dangerous.
Sometimes behaviors take hold simply because they can. The males that reproduced in this way passed on their genes more effectively than others did, thanks to their short-circuiting of normal mechanisms. The stabby-sex trait proliferated and dominated until eventually that's the only way it happens any more. It became dominant because it was not harmful enough to be selected against.
And so, while we might say "diversity is strength" and emphasize the value of mutants and oddities, make no mistake: it's not as though these individuals have received some special blessing. The process that produces and takes advantage of them can be a cruel meat grinder, no friend of yours.
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