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8 Genes and Behavior, Genes and Language One of the take-home messages of the previous chapter was that in evolution the role of “the environment” is quite subtle. Traditionally, it is seen as the agent of selection, determining which variants survive and reproduce. Yet, because it influences development, it also has a role in determining which variants are there to be selected. The consequences of this dual role are that environmental effects on development may guide the selection of genetic variants. In the previous chapter we looked at this in relation to environmentally induced developmental modification of an organism’s form, describing how, through natural selection, an induced change can eventually become a permanent part of the phenotype. We now want to extend the same idea, the idea of genetic assimilation, to behavior, and show how natural selection can convert what was originally a learned response to the environment into behavior that is innate. We will also be considering another factor that complicates the way in which we have to think about the role of the environment in evolution. It is that the organism itself is often responsible for selecting the environment in which it lives and for constructing some aspects of it. If you release English rabbits and hares into the countryside, the rabbits will head for the hedge and the hares will opt for the open field. They themselves decide where they will live and reproduce. Both types of animal will also modify their environment. This is very obvious with rabbits, whose feeding and burrowing habits often transform the landscape. Farmers have their own ways of describing such activity (“ruin” and “destroy” are two of the milder terms they use), but biologists call it “niche construction.”1 All organisms do a bit of niche construction (we gave some examples in chapter 5), but its effects on evolution are particularly significant for animals that inherit a niche in the form of the artifacts, behaviors, and cultures of their elders. Changes in habits and traditions can result in these animals creating a very different social and physical environment for themselves and their 280 Chapter 8 descendants. It is therefore wrong to think of them as just passive objects of environmental selection. This is especially true for humans, whose elaborate cultural constructions form such a large part of their environment. What we transmit through our behavioral and symbolic systems obviously has profound effects on the selection of the information that we transmit through our genes. We will leave the complexities of the effects of human culture on genetic evolution until later, and start this chapter with a relatively simple problem —the evolution of instincts. Instincts are complex behaviors that occur either without having to be learned at all, or with very little learning. They are clearly adaptive, and many would develop through learning even if they were not inborn, so how and why did they become permanent parts of the animal’s makeup? Was it simply a chance combination of rare and random mutations that made many small mammals show fear and avoidance responses upon first hearing hissing, snakelike noises? What type of selection resulted in hand-reared spotted hyenas, who have never had anything to do with lions or their mother’s responses to lions, reacting with fear when they first experience a lion’s smell?2 How did natural selection lead to newly hatched seagull chicks responding to a long object with a red dot (which vaguely resembles a parent’s beak) by pecking it? Genes, Learning, and Instincts The evolution of instincts fascinated and puzzled the early evolutionists. The Lamarckian explanation—that a learned behavior could gradually but directly become an inherited one—was obvious and satisfactory for many people, but it wouldn’t do for the neo-Darwinians. They had to explain the evolution of instincts in terms of natural selection. One of the earliest attempts to do so was made by the Scottish biologist Douglas Spalding. You will recall that in chapter 6 we used an adaptation of his story about Robinson Crusoe’s parrots to illustrate the differences between a symbolic and nonsymbolic communication system. In fact Spalding’s original story had a very different goal—it was intended to provide an evolutionary explanation of instincts. The original story reads as follows: Suppose a Robinson Crusoe to take, soon after his landing, a couple of parrots, and to teach them to say in very good English, “How do you do, sir?”—that the young...

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Additional Information

ISBN
9780262322676
Related ISBN
9780262525848
MARC Record
OCLC
878130644
Pages
576
Launched on MUSE
2014-04-24
Language
English
Open Access
No
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