Natural Behavior. Burton A. Weiss
Читать онлайн книгу.
combinations at mating. Thus, for one pair of genes, the binomial expansion, (A + a)2, gives the frequency of possibilities (A2 + 2Aa + a2). A and a are the probability of occurrence of each gene allele (A + a = 1). With increasing numbers (n) of gene alleles, and estimates of the numbers of gene alleles in a population can be large, the frequency of possibilities (A + a)n approaches the normal distribution. For an imaginary, because all organisms have thousands of genes, single-gene organism with one dominant (A) and one recessive (a) gene allele, the mating possibilities of the population can be seen in Table 1-3.
Table 1-3 Gene Frequencies for Aa Type Parents.
The tabulated totals for Table 1-3 are: 1AA + 2Aa + 1aa. Graphically represented, the tabulated totals would look like Figure 1-2.
Figure 1-2 Graph of the Tabulated Frequencies of 1AA + 2Aa + 1aa.
For another imaginary, again, because all organisms have thousands of genes, dual-gene organism with two dominant (A, B) and two recessive (a, b) gene alleles, the mating possibilities of the population can be seen in Table 1-4.
Table 1-4 Gene Frequencies for AaBb Type Parents.
The tabulated totals for Table 1-4 are
1AABB + 1AAbb + 2AABb + 2AaBB + 4AaBb + 2Aabb + 2aaBb + 1aaBB + 1aabb.
Graphically represented, the tabulated totals would look like Figure 1-3.
Figure 1-3 Graph of the Tabulated Frequencies of 1AABB + 1AAbb + 2AABb + 2AaBB + 4AaBb + 2Aabb + 2aaBb + 1aaBB + 1aabb.
With just the two genes graphed in Figure 1-3, the shape is beginning to arrange into the familiar “bell curve” of the normal distribution. Increasing the number of genes determining a characteristic to a great many, as is typical, produces a normal distribution. Modern knowledge of genes is that they also interact and turn on and off, resulting in complex function. Thus, gene content results in the normal distribution of characteristics.
Life sciences typically employ structure to document the evolution of species, because structure leaves bodily or fossil records. Genes determine structure, which, in turn, determines behavior. Human genes mean we have arms, not wings, and that determines our behavior. But what most people, even many life scientists, fail to realize is that behavior determines the genes of the next generation through reproduction. Natural selection is the environment, which has no way of interacting with genes or structure. What natural selection actually selects is neither the genes that determine structure nor the structure that determines behavior, but the behavior itself. The behavior of an organism is what interacts with the environment. The behavior of the organism interacting with the environment selects which organism reproduces and, thus, establishes the genes, subsequent structure, and consequent behavior for the next generation, as illustrated in Figure 1-4. The evolution of any species is, therefore, as much an evolution of behavior as of structure. Behavior is, actually, the central feature of evolution because it is the focus of selection.
Figure 1-4 The cycle of the behavior of the organism interacting with the environment, selecting which organism reproduces and, thus, establishing the genes, subsequent structure, and consequent behavior for the next generation.
Therefore, behavioral characteristics, like aptitudes, also display a normal distribution. Behavior, structure and genes are inseparable in evolution. The evolution of a species could be traced by its behavior as well as by its genes or its structure. But, following the evolution of an organism by its behavior, using the fossil record is exceedingly difficult, because the behavior died with the organism. However, some behavior can be inferred from structure, like large canine teeth indicate a predator and extensive molars mean a grazing animal.
Courtship pattern is an excellent example of the evolution of behavior. Successful courtship leading to reproduction is extremely adaptive and highly favored by natural selection, because that behavior produces the next generation. Unsuccessful courtship, like mating across species, is selected against because such behavior creates, at most, sterile hybrids and does not contribute to the next generation. Any structure or behavior that leads to sexual attraction and subsequent successful courtship is favored. Repeated favoring of such advantages has led to very elaborate mate-attracting structures and extremely complicated courtship rituals in many species. The intricate courting “dances” of many birds are a dramatic example of the evolution of behavior.
Darwin (1871) was puzzled by mate choice because he thought that such behavior provided a direction in evolution separate from natural selection. Modern theorists also give a separate role to sexual selection (Daly and Wilson, 1978). Trivers (1972) felt that parental investment in offspring would influence sexual selection, even in humans. Thus, males would tend to be more polygamous, but females, with the heavier investment of pregnancy and infant care, would be more monogamous. Concluding that sexual selection is strictly genetic is impossible. Again, genes determine structure and structure influences behavior, which results in the genes of the subsequent generation. Mate choice is strongly influenced by behavior and the cultural consequences. In addition, choice of mates is part of the third condition of the previously discussed Hardy-Weinberg Law, in that, it violates the process of random reproduction. Without random reproduction, change in the population will occur and evolution accumulates through sexual selection.
Mate choice can also become out-of-phase with the environment, leading to conflict with natural selection. The Irish Elk (Megaloceros) is an example. Mate choice led to larger and larger male antlers, which had to be shed and regrown each year. The required energy expenditure produced extinction. Natural selection is the instrument of evolution.
Sexual selection, like any structural or behavioral feature, can be adaptive or not. Thus, sexual selection is not separate from evolution. Not only courtship patterns, but all behavior evolved. The process and phenomena of the evolution of behavior are the subjects for the remaining chapters.
The Non-conflict with Religion
One of the major reasons for difficulties in the trend away from the egocentric position noted early in this chapter is the supposed conflict with religion. If religion is ultimately the belief in God, rather than in human doctrine, there can be no conflict with science. Science can neither confirm nor disprove the existence of God. God is either believed in or not.
Difficulty stems from those who profess to believe, but whose personal faith requires proof, often from physical sources. The support for such fragile faith frequently comes under the scrutiny of science and the frail faith becomes threatened. The true believer knows that science, whose purview is phenomena, and religion, which deals with faith, do not even overlap and, therefore, cannot possibly conflict.
Clergy, however, repeatedly make ridiculous spectacles of faith by pronouncements about science. In 1650, Archbishop James Ussher of Armagh, Ireland, calculated from the ages of biblical figures that the world was created on Sunday, October 21, 4004 BCE, at 9:00 AM. Early in the 20th century, when several groups were struggling to develop “heavier-than-air” flying craft, clergy announced that such endeavors were folly because, if God meant