Wednesday, January 25, 2012

Why haven't cockroaches shells evolved so they can withstand being stepped on?

Since they've been around for millions of years you'd think thats where they would start.

Why haven't cockroaches shells evolved so they can withstand being stepped on?
Because, unless there is a genetic ability there in the first place to be acted upon, natural selection cannot select for it.



Evolution is non-directional, it only acts on what's available in the population. If it's not available in the population (either by mutation or recombination) then it can't happen.



The only reason people tend to see evolution is directional, is that they look at the past and apply a selection theory to the results (what was the selection pressure that gave rise to a trait). That doesn't mean we are able to predict what the present or future selection pressures are. And since I haven't heard cockaroaches performing self gene-splicing experiments, the potential isn't there either.
Reply:To avoid death by someone stepping on them, they have evolved high running speed and wings to fly. Those defenses are better than a hard shell and take less energy to create.
Reply:Shhhhhhh....don't give them any ideas!
Reply:Give them time....
Reply:Actually, they HAVE evolved to the point where they can live for three WEEKS without a head, not to mentio the fact that, in the occurence of a nuclear war, they will be the only survivors.
Reply:because you cant pass on the "stepped on" to their offspring. Unlike bug spray in which they inhale and survive/ evolve and then reprodoce passing that survival aspect to the little roaches.
Reply:The correct answer is that natural selection operates on a population and not on an individual...Stepping on cockroaches at home is only 1 part of population. Other organisms live in jungles and donot suffer this.
Reply:Probably for the same reason that we haven't.............they have other defense mechanisms


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