Functional Is Not Optimal
If you look at what a random animal is doing at a random time, you will usually find a complex behavior, with many correlated parts. Similarly if you look at a random physical part of an animal, you will find a complex structure, with many correlated parts. The best way to make sense of such structures is usually to look for the functions they might perform, i.e., the way that they might contribute to survival and reproduction, now or in the past, of the animal or its parasites. Sure, some structures are "spandrel" side effects of other functional structures, but (at the aggregate level) most are not.
This, however, does not at all imply that most such structures are anything close to optimal, giving the best possible outcomes. Consider that when we transplant plants or animals to a new continent, they often handily out-compete existing species. This could not happen if the existing species were close to optimal. Often their structures worked in the past, but have not adapted enough to changing context.
It is similar for most human organizations. A good way to understand what a random organization is doing at a random time, or to understand a random part of its physical or communication structure, is to ask how such structures once functioned to help the organization or its parasites to survive or grow. But this hardly means that every organization is optimal; many are clearly dinosaurs losing to new rivals.
A lot of human behavior does not immediately make sense in terms of survival and reproduction. We sing, dance, joke, worship, collect, chatter, decorate, party, dribble, travel, argue, blog, and much more. With a little thought, we can come up with functional explanations, such as signaling theories, for most of this behavior. Many people, however, reject such explanations, saying functional explanations would imply human behavior is optimal, which it is clearly not. Thus, they argue, odd human behavior must instead be due to random mistakes, spandrels, or our changing environment.
This "head in sand" attitude is so contrary to what we know about animals and organizations that I have to conclude that not only is it seriously wrong, but that humans seem built to self-deceive about the functions of their behavior. While our behavior may be far from optimal, there is surely a detailed correspondence between our behavior and the functions they perform. But we prefer to be innocently unaware of the signals our behavior functions to send and receive.
From a lunch conversation with Mike Makowsky, Bryan Caplan, and Alex Tabarrok.
"humans seem built to self-deceive about thefunctions of their behavior."
That reminds me of what I added to Uncyclopedia's section about evolutionary psychology:
There is mounting evidence that evolutionary psychology may be an innate urge built-in to the brains of all human beings. It would have met the need, in our cave-dwelling ancestors, for an spurious position of authority to retreat to in the attempt to justify their most comfortable habits, thus imparting a genetic advantage of some kind yet to be made up.
I don't think I meant "around it" in a geographic sense, though I confess that I'm no longer sure, and I think my claim holds either way, if you'll grant reasonable assumptions about spatial autocorrelation of fitness in neighboring populations.
If we think about fitness landscapes (rather than geographic ones), evolution will push a population towards a local maximum, as Eliezer Yudkowsky said. My point is that that evolution is slow. I was not claiming that the minimum standard is static, and I don't think RBH was either. Because of the process you describe, the minimum standard will rise slowly (slowly because evolution is slow).
There was a time when ecology (my field) was focused on finding equilibrium rules for communities based on how natural selection would drive populations in a community in an unchanging environment. This generated a lot of fascinating math, and a lot of conundrums. Those challenges have largely been resolved by pointing out that environments do change. The organisms that survive and reproduce over the long run need not be the very best ones at each moment in time. The genetic lineages that persist are the ones that fail to perish under the full range of ecological conditions that the community experiences.
At any moment in time, the population is at a point which satisfices, a point at which the individuals that are not fit enough to survive and reproduce have little or no presence. The survivors were not (all) optimal, they are what was sufficient in that era. Predators, prey and other biological resources will adapt to that new population (Red Queen), but not instantly. The population will have to adapt to that new status quo, but it will not respond instantly, nor will its response be rapid. No doubt it has to keep running just to stay in one place, but that place will almost certainly not be optimal at any given point it time, and the population is not trying to stay in one place. It has to shift as the fitness landscape shifts.
A mutation that boosts fecundity (as in your example) means more infants competing with one another and with parents. In good years, that isn't a problem. In harsh years, it might mean that none of the offspring grow up and produce more than two offspring (depending on the details of the organism's life history). There is some optimal number of offspring in any given population and any given environment. When scientists measure fecundity in British great tits, they do not find it matching their modeled optimum, and environmental variability is the answer I recall them giving. I don't have the reference handy, but now I have to look it up and blog it.
With regard to your question about "spandrels" above: I don't see the word itself in the literature much, but the concept definitely comes up in conversation. I wasn't around before the spandrels paper, but I'm told that people are less apt to insist that every feature of an organism must be adaptive than they had been. I couldn't say how much of that results from the spandrels paper and how much reflects the greater appreciation for environmental stochasticity I described above, as well as the neutral (and nearly neutral) theory in population genetics. Those theories led to research which showed that a major fraction of genetic change is not due to selection, so the major advances in molecular biology all build on an understanding that adaptation is not the only way to explain biological data.