OK, here is something I have always wondered about, but lack an answer. So, I turn to the Teeming Millions (well, Teeming 30,025 at this point) for help.
Why don’t roaches evolve into creatures with human-level (or at least, say dog-level) intelligence?
Now, then, I know what you’re going to say: “But, Zev, the little buggers are doing just fine now. They’ve been around for millions of years, they infest practically every square inch of the earth and they’ll be around after a nuclear war.”
My response to that is, yes, the roachus disgustingus is doing quite well as a species. They breed like, well, like roaches and have survived quite nicely until now. However, if they evolved to a higher degree of intelligence, they would certainly do much better. They’d learn to avoid some predators, stay off the glue traps, not wait until the light comes on to run, etc.
Or, am I wrong, and they’re already evolving this, but it’s simply a few million years too soon?
Roaches have their niche in the world and seem to be happy in it. While they may not be intelligent, they certainly make up for it in ability to adapt and mutate.
I’m sure you’re familiar with the roach trap baits containing a poison in a glucose base? Supposedly the roaches cannot develop an immunity to the poison and for a couple years, the traps worked wonders. All of a sudden, they stopped working so well. Did they develop an immunity to the poison after all? Nope! Instead, they developed an aversion to the glucose base. They wouldn’t touch the stuff whether it contained poison or not.
It’s abilities like these that boost their survival ratio so high that they don’t have to develop petty things like intelligence.
It may be because they are doing well that they are not evolving much. One component of evolutionary theory is that environmental pressure accelerates it. Big die-offs the eliminate most individuals, and leave only those with the most advantageous gene set to multiply. If there aren’t big die-offs, a given mutation either never spreads through the species, or spreads much more slowly.
Also, I don’t see why intelligence would necessarily be a survival asset for small insects. Intelligence seems linked to a rather long gestation, and extended dependence on the parents after birth. Maybe not good things for teeny critters.
Of course, IANA scientist and this is only my WAG. But you could ask the same question about any species on earth, and the only general answer I can come up with is that there are plenty of ecological niches where not much brains are needed to sustain life.
In fact, I wouldn’t even say for sure that intelligence (in the sense of abstract reasoning and tool-use) turns out to be a positive survival for human. We’re very young compared to cockroaches, and probably more vulnerable. We might wipe ourselves out. The last few survivors might envy the lowly cockroach. :eek:
One often-overlooked aspect of evolution is internal constraint. Evolution is not “infinitely-adaptable organisms being molded by the environment”; the organism must also have to have the ability to produce a given mutation upon which selection can build. Just because Adaptation X may seem like a positive survival trait, there is no guarantee that it will appear in any given lineage. Even if it may be a “good idea” (from our homocentric, and erroneous, viewpoint), there are only so many possible variations that a given genome can produce. I’m sure birds would have been a lot happier if they had sprouted wings as two new limbs instead of having their forelimbs co-opted. But, six limbs is simply not part if the genetic make-up of vertebrates. So, it ain’t gonna happen.
In the case of roaches (and insects in general), they don’t possess anything near a complex enough nervous system to start evolving a brain capable of mammalian (or even cephalopodian) intelligence. And they don’t possess a near-complex enough nervous system because the current function of such probably doesn’t allow for a whole lot of variation. If too big a tweak is made in one area, the organism will likely die. Thus, there are limited safe pathways along which they can evolve.
And of course apes, wolves, lions and many other creatures do have a complex nervous system, a means of communicating, a social structure and other apparati (apparata?) needed so the same question could be asked about them.
What makes you think intelligence would be advantageous to a roach? It’s evolutionary advantages include being able to eat almost anything and breeding like crazy. So suppose you have intelligent roaches and they begin to develop fastidious tastes, complex mating rituals involving personal ads, birth control, and existential despair.
Imagine being an intelligent roach and waking up one day and thinking “Hey, I’m living in a sewer. This food tastes like crap. And that guy over there just likes me for my pheromones. Damned if I’m putting out.”
From a practical point of view, I’d imagine increased intelligence would require a bigger brain and more complicated neural circuitry. So you’d need to devote more energy to the brain and you’d need a bigger exoskeleton to hold it all. To take advantage of this intelligence, you’d probably need improved sensory apparatus and maybe better ways of manipulating the environment. So you’d have a bigger, slower, hungrier roach competing with the old, unmodified roaches. Would increased intelligence give enough of an advantage to allow them to prosper?
In which case, the answer may well be different. I was not implying that constraint is the reason in all cases, only that it is an aspect often neglected in these discussions. Form and function (or constraint and adpatation, if you prefer) are interlinked, and both contribute to the directions in which a population may evolve. The answer to the question, “Why didn’t this evolve?” is rarely as simple as “because it wasn’t advantageous”. One might look to arguments of advantage when discussing why a given trait did evolve, but such arguments don’t tend to hold up as well when asking why they didn’t.
Insects are segmented (that’s what insect means), but birds are not, so I don’t think a 6 limbed bird is possible.
Considering all the niches that primates occupy and the fact that only one evolutionary line led to intelligence (loosely speaking), it is not clear that increased intelligence is generally much of an advantage. Considering the last election,…
There are down sides to a brain (the most common method of evolving intelligence :)). Size and energy demands are two that come to mind. The larger the brain, the more demand and training it requires. Roaches use the survival through numbers approach- you kill a bunch and there’re always more who survive. Remember- evolution doen not act on individuals, but species. If the energy demands and training efforts are more efficiently put to use producing more offspring, that may give them a survival advantage (as a species).
One assumption among the answers above is intelligence = human. Lizards have more intelligence (I think) than roaches.
Also, roaches are pretty small. To develop intelligence may require larger bodies and head which would limit the numbers they could produce. It may be that they’ve reached the optimal compromise for their niche. OTOH, they’re niche has changed in the last few thousand years due to the introduction of humans, so maybe in another few million (or thousand- increased replication rates increase natural selection induced speciation rate) years they will be more intelligent. Or maybe they’ll have changed in other ways.