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5 The Behavioral Inheritance Systems Nonbiologists will probably sigh with relief when they see the title of this chapter. After discussing genes, biochemistry, and molecular biology, about which nonbiologists do not have ready intuitions, we turn to behavior. Here, the layperson usually feels a lot more at home. We are all sharp-eyed observers of behavior, and feel that our personal experiences qualify us to understand many of the complex processes that are related to behavioral change. We know that there are many ways of learning, and that we learn from each other as well as on our own. As nature lovers and pet owners, we are well aware that animals can learn a great deal too. Mammals and birds, the animals with which we are most familiar, learn from their personal experiences, from their owners, and from each other, often displaying remarkable abilities as they do so. But how important is such learning in evolution? Of course, all biologists agree that in many circumstances learning is enormously beneficial, and that the capacity to learn has evolved genetically, but is learning also an agent of evolutionary change? For example , how does the fact that animals learn from each other affect the evolution of their behavior? The current fashion among evolutionists, seen particularly in the writings of those who study human behavior, is to stress the genetic basis of behavior, and especially that of best-selling, sex-related behavior.1 These evolutionists maintain that the behavioral strategies for things like finding a mate, or becoming socially dominant, or evading danger, or finding food, or caring for infants are to a large extent genetically determined and evolutionarily independent of each other. Each has been shaped through the natural selection of genes that led to the construction of a specific behavioral module in the brain, which tackles that particular “problem.” This is an interesting point of view, and we are going to examine it in some detail in later chapters, but in this chapter we want to look at something very different . As far as we can, we want to deal with the third dimension of heredity 154 Chapter 5 and evolution, the behavioral dimension, in isolation from the first, genetic, dimension. This means that we are going to be looking at behavioral evolution that does not depend on selection between genetic variants. Evolution among the Tarbutniks It is not easy for biologists to think about behavioral evolution without automatically resorting to ideas about selection among variant genes, so to help overcome this we will again use a thought experiment. This one is about tarbutniks, who evolved in the minds of Eytan Avital and Eva Jablonka in 1995, and are described more fully in their book Animal Traditions .2 What follows is an abridged and slightly modified version of what they wrote there. Tarbutniks are small rodentlike animals, which got their name from the Hebrew word tarbut, which means “culture.” One of the interesting things about them is that they are all genetically identical. They have perfect DNA maintenance systems, so their genes never change. In this they resemble the Jaynus creatures of the previous chapter, but unlike Jaynus creatures, they also have mechanisms that completely prevent any transgenerational transmission of epigenetic variations. Tarbutniks can therefore inherit neither genetic nor epigenetic variations from their parents. This does not mean that they are all identical, of course. Chance events during their development result in small differences in their size, fur color, the proportions of their body parts, and also in their calls and various aspects of their learned behavior. In fact, there is quite a lot of variation among tarbutniks, but—and this is the important point—there is no correlation in appearance or behavior between parents and offspring, because the differences between individuals are not inherited. And since the variation is not hereditary, these tarbutnik populations cannot evolve. Tarbutniks live in small family groups consisting of a pair of parents and several different-aged offspring. They begin life as rather helpless creatures , relying on their mother’s milk for food, but they grow rapidly, and soon begin to accompany their parents on foraging expeditions. As they do so, they learn about their environment. They discover how to open nuts and get at the seeds inside by trial and error, but it takes a lot of attempts before they hit on the right way of doing it. They also learn the hard way that black-and-red striped beetles have a nasty taste and...


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