Harmony and Conflict in the Living World - Alexander F. Skutch [70]
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I would not conclude from this that biologists should be concerned with teleology and give more attention to final causes: to elucidate the material and efficient causes that have shaped and preserve organisms should keep these scientists sufficiently busy. The investigation of final causes is more pertinent to philosophy than to science. But scientists should be more tolerant of philosophers' often groping efforts to throw light upon obscure aspects of reality that since people became thoughtful they have most ardently wished to illuminate; just as philosophers should be tolerant of the sometimes illogical pronouncements of scientists.
Intergroup Selection
The third of the most frequently condemned biological heresies is intergroup selection, often more briefly called "group selection." The orthodox view is that the natural selection of individuals, or their differential survival and reproduction, is adequate for the theory of evolution, or, more succinctly, that individuals rather than groups are selected by natural agents. This insistence upon the adequacy of interindividual selection has three weaknesses: it exaggerates the self-sufficiency of the individual, it neglects social interactions, and it underestimates the complexity of evolutionit is too simplistic.
Solitary animals, which associate with other adults only long enough to inseminate them or to be inseminated by them, are self-sufficient as to their survival but not as to their reproduction. Modern evolutionists assess the fitness of an organism by the number of its progeny; but no individual of a species that can reproduce only sexually is, in a strict logical sense, fit by this measure. It becomes fit only by choosing a partner in reproduction. Since each parent contributes an approximately equal number of genes to the progeny, the innate quality of the offspring, or their ability to survive and reproduce, will depend equally upon the genetic contributions of the parents, and their number will depend upon the adequacy of the parent contributing most to their production and
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nurtureusually the female, although in a number of species the male contributes substantially to the care of his offspring, and in certain birds, amphibians, and fish he is largely or wholly responsible for protecting and/or feeding them. This is the primary reason why insisting upon the adequacy of individual selection is an over-simplication of the problem of evolution. As though recognizing this, birds, more than most other animals, tend to be careful in the selection of their partners.
When we trace a lineage backward in time, we find that, in the absence of inbreeding, the number of ancestors increases geometrically with the number of generationsfour grandparents, eight great-grandparents, and so forth. Each of these forebears has contributed genes, which jointly determine the quality of the latest progeny; all are virtually involved in their birth. Likewise, when we project the transmission of an individual's genes forward through its descendants, we find that they tend to diffuse ever more widely through a population. The individual that succeeds in reproducing is but a link in a lengthening chain. Without the opportunity to mate with enough unrelated individuals to prevent deleterious inbreeding and to provide the genetic diversity that is the foundation of adaptability, a lineage may become extinct. When a dwindling species or race is tardily given protection from humans and encouraged to increase, as we might expect it to do rapidly because of reduced competition for resources, it sometimes fails to recover but continues to decline, as happened to the Heath Hen on Martha's Vineyard, an island off the coast of Massachusetts. Lack of genetic diversity was