Kin Selection

The concept of kin selection is closely related to the concept of replicators trying to maximize their reproduction. Kin selection is behavior that favors or demonstrates "altruism" toward a family member. This type of behavior has long baffled evolutionary theorists because, if natural selection is always at work, each organism should be concerned only with its own survival. However, with the advent of replicators as the primary unit of selection, this dilemma was easily solved. Genes that favor altruistic behavior toward a family member are genes that favor their own success, since family members have a good chance of sharing genes. Therefore, altruistic behavior toward family members can be explained by the selective advantages to genes of taking measures to propagate copies of themselves.

Moreover, such altruistic behavior seems to correspond, as nearly as an organism can measure, to the degree of relatedness of a family member. For example, an organism is on average about 1/2 related to a sibling or a parent. In other words, the organism shares about 1/2 of its genome with its sibling or parent. Therefore, on average, an organism's parent or sibling will receive about 1/2 of the consideration it gives to itself - the organism would be willing to expend on the life of its parent or sibling about 1/2 the effort it would expend on the preservation of its own life. Similarly, cousins and grandparents are 1/8 related and merit 1/8 the effort, and so on.

Of course, this is a strictly mathematical model. Organisms cannot directly measure its degree of relatedness with every other organism it meets. It generally uses some proxy measure to determine degrees of altruistic behavior. This choice might be very simple, such as: "I will behave altruistically toward every fellow member of my species that I find inside my nest." Or it might be based on more complicated criteria, such as: "I will behave altruistically toward those who I recognize as living in my nest, slightly altruistically toward all those resembling those in my nest, and I will make other decisions based on circumstances." (Of course, the organism does not actually say these things; they are only demonstrations.)

There are also other considerations that genes adapted to such behavior may involve. For example, it may be more beneficial for older parents to behave altruistically toward their offspring than for the reciprocal behavior to take place. This is because the young offspring still have reproductive years ahead of them, and will probably be able to propagate more copies of the genes in question than the parents. On the other hand, if the offspring is very young, it may be more beneficial for the parents to first evaluate its likelihood of survival to reproductive age; if it did not, the parents' efforts would be wasted.

Such theories of altruistic behavior arising through kin selection also help to explain the anomaly of insect colonies with sterile workers. Such workers obviously cannot work to maximize their own reproductive fitness or pass along their genes, which are now dead-end replicators. These workers instead care for the young of the colony's queen, thus exhibiting altruistic behavior in proportion to their relatedness.

It is worth mentioning that these discussions of altruistic behavior apply predominantly to instinctual organisms, not to volitional ones (i.e., humans). While humans may very well possess genes that favor such distributions of favor as described above, humans have the benefit of consciousness to guide such decisions. While lower organisms can only make "decisions" based on instinctual proxy criteria, humans can evaluate individual cases and decide on each individual's merit whether to behave charitably toward that person and how much charity is deserved. Typically decisions to behave charitably toward individuals are made on the basis of memes, not genes, in humans.

The Theory of Punctuated Equilibrium

Scientists Stephen Jay Gould and Niles Eldredge published an alternative to traditional Darwinian "gradualism" based on natural selection. Their theory, called punctuated equilibrium, states that populations remain in a state of stability or stasis for long periods of time. These equilibrium periods are then punctuated by various major events that induce relatively rapid periods of evolutionary change. These speciation events then die back down, giving way to new periods of stasis without much evolutionary change.

This theory states that most evolution or speciation takes place within reproductively isolated subsects of larger populations. Thus, speciation is a branching event, not a transformation of one species into another. This would lead to a large number of new species coming into existence under the theory, which is supposedly eliminated by species selection. Doubt has been cast on whether or not species selection occurs (Richard Dawkins' work has been especially informative) and, by extension, on punctuated equilibrium as a whole.

Punctuated equilibrium was originally presented as a revolution in evolutionary theory. Often confused with - but radically different from - saltationism, punctuated equilibrium was hailed as a major departure from basic Darwinian gradualism. However, as Dawkins showed in his book The Blind Watchmaker, punctuated equilibrium is really only a modification of Darwin's ideas and an extension of natural selection, not a radical opposition to the established theories. Therefore, the debate often touted by sensationalists as a "break" in Darwinism is in reality only a difference in the specific mechanisms by which gradual evolutionary change takes place.

Looking Further: Links and References

The following links and references discuss the topics of artificial selection, kin selection, sexual selection, and punctuated equilibrium.

• Books
  • The Origin of Species by Charles Darwin
  • The Variation of Animals and Plants under Domestication by Charles Darwin
  • The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe Without Design by Richard Dawkins
  • The Extended Phenotype by Richard Dawkins
  • The Selfish Gene by Richard Dawkins
  • The Pattern of Evolution by Niles Eldredge

• Websites
  • The World of Dawkins (unofficial)
  • Punctuated Equilibrium
  • Gould: The Evolution of Life on Earth
  • Levels of Selection by Barry Sinervo
  • The Phyletic Gradualism - Punctuated Equilibrium Debate

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