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Another great biologist once recommended that to understand the actual we must contemplate the possible: ‘No practical biologist interested in sexual reproduction would be led to work out the detailed consequences experienced by organisms having three or more sexes; yet what else should he do if he wishes to understand why the sexes are, in fact, always two?’
genes do not control behaviour directly in the sense of interfering in its performance. They only control behaviour in the sense of programming the machine in advance of performance.
It is in general to be expected that, where there is strong selection in favour of some trait, the original variation on which selection acted to guide the evolution of the trait will have become used up.
there is variation in eye colour in the population; other things being equal, a fly with this gene is more likely to have red eyes than a fly without the gene.
black-headed gulls (Larus ridibundus), eggshell removal.
Rothenbuhler’s (1964) hygienic bees.
von Frisch (1967), in defiance of the prestigious orthodoxy of von Hess, conclusively demonstrated colour vision in fish and in honeybees by controlled experiments.
The jet engine superseded the propeller engine because, for most purposes, it was superior. The designers of the first jet engine started with a clean drawing board. Imagine what they would have produced if they had been constrained to ‘evolve’ the first jet engine from an existing propeller engine, changing one component at a time, nut by nut, screw by screw, rivet by rivet. A jet engine so assembled would be a weird contraption indeed. It is hard to imagine that an aeroplane designed in that evolutionary way would ever get off the ground. Yet in order to complete the biological analogy we
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When, in due course, the neck began to lengthen, the nerve lengthened its detour posterior to the aorta, but the marginal cost of each step in the lengthening of the detour was not great. A major mutation might have re-routed the nerve completely, but only at a cost of great upheaval in early embryonic processes. Perhaps a prophetic, God-like designer back in the Devonian could have foreseen the giraffe and designed the original embryonic routing of the nerve differently, but natural selection has no foresight.
The Picasso-like face of a flatfish such as a sole, grotesquely twisted to bring both eyes round to the same side of the head, is another striking demonstration of a historical constraint on perfection. The evolutionary history of these fish is so clearly written into their anatomy that the example is a good one to thrust down the throats of religious fundamentalists.
‘satisficing’ as an alternative to optimizing. If optimizing systems are concerned with maximizing something, satisficing systems get away with doing just enough. In this case, doing enough means doing enough to stay alive.
In the evolutionary design of animals and plants, judgement does not enter into it, nor does controversy except among the human spectators of the show.
‘Concorde Fallacy’ of valuing a resource according to how much they had already spent on it, rather than according to how much they could get out of it in the future.
In passing, the fundamentalist student might pause to wonder at a God who goes to great trouble to provide predators with beautiful adaptations to catch prey, while with the other hand giving prey beautiful adaptations to thwart them. Perhaps He enjoys the spectator sport.
Firstly, it is natural to assume that even if a manipulator gets away with it temporarily, it is only a matter of evolutionary time before the lineage of manipulated organisms comes up with a counter-adaptation.
In those cases where animal signals really are of mutual benefit, they will tend to sink to the level of a conspiratorial whisper: indeed
If signal strength increases over the generations this suggests, on the other hand, that there has been increasing sales resistance on the side of the receiver
Now suppose a male canary wanted to bring a female into reproductive condition, what could he do? He does not have a syringe to inject hormones. He cannot switch on artificial lights in the female’s environment. Of course what he does is sing. The particular pattern of sounds that he makes enters the female’s head through her ears, is translated into nerve impulses,
Bothriomyrmex regicidus and B. decapitans,
Monomorium santschii achieves
