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What's wrong with the "cicada theory" 1. The most common cicadas come out every year or every other year. 2. The 17-year cicadas (for example) don't come out

What's wrong with the "cicada theory" 1. The most common cicadas come out every year or every other year. 2. The 17-year cicadas (for example) don't come out once every 17 years -- they come out every single year. Just in different broods (groups differing by phase). Some broods are much bigger than others of course, and broods are often located in different parts of the country, but many broods can and do overlap. So I dunno. I'm guessing they're 13 and 17 year cicadas because that's how long it takes to develop.

KirinDave 16y ago
Consider, though, that these groups of cicadas don't really "care" about one another from a genetic standpoint. If the broods don't interact, they're basically different sets of genes that only interact via mutations, so the principle still holds. What's interesting about that is how the broods might diverge to coprime emergence schedules to prevent competition.
- ars 16y ago
  Well, they do care. The idea is to starve out predators. If there is another set of cicadas feeding them, then it doesn't work for just you to avoid them.
  - scott_s 16y ago
    KirinDave's point is that there is no "idea." If the groups are disjoint, there's no conspiracy, no way for them to interact with each other. If you and your group avoid the predators, then you will thrive. It doesn't matter that another group does not. Evolution happens at the level of genes, not groups.
scott_s 16y ago
I'm guessing they're 13 and 17 year cicadas because that's how long it takes to develop. That's a tautology. "A baby takes 9 months to be born because that's how long it takes to develop." Well, yes, but the question becomes, why does it take that amount of time to develop? Were there direct selection pressures acting on that length of time, or is that length of time mostly a function of other variables which are acted on directly by selection pressure?

KirinDave 16y ago

Consider, though, that these groups of cicadas don't really "care" about one another from a genetic standpoint. If the broods don't interact, they're basically different sets of genes that only interact via mutations, so the principle still holds. What's interesting about that is how the broods might diverge to coprime emergence schedules to prevent competition.

ars 16y ago
Well, they do care. The idea is to starve out predators. If there is another set of cicadas feeding them, then it doesn't work for just you to avoid them.
- scott_s 16y ago
  KirinDave's point is that there is no "idea." If the groups are disjoint, there's no conspiracy, no way for them to interact with each other. If you and your group avoid the predators, then you will thrive. It doesn't matter that another group does not. Evolution happens at the level of genes, not groups.

scott_s 16y ago

I'm guessing they're 13 and 17 year cicadas because that's how long it takes to develop. That's a tautology. "A baby takes 9 months to be born because that's how long it takes to develop." Well, yes, but the question becomes, why does it take that amount of time to develop? Were there direct selection pressures acting on that length of time, or is that length of time mostly a function of other variables which are acted on directly by selection pressure?