Harmony and Conflict in the Living World - Alexander F. Skutch [14]
The discontinuities in the living world are closely related to biparental reproduction. To reproduce sexually, organisms must find partners whose genetic constitutions, called genomes, are compatible. This is the fundamental reason why plants and animals belong to species. In a world where asexual propagation predominated, instead of being subordinate to sexual reproduction as in our actual world, we might indeed find all transitions between the most extreme types, as on a small scale we do among cultivated plants. And how confusing this would be to everyone interested in nature, how frustrating to all attempts to classify and name! The biological definition of a species as a group of individuals any two adults of which, of opposite sex and normally developed, might together beget fertile progeny, recognizes the intimate connection between biparental reproduction and the segregation of organisms into species. By this definition, cultivated plants that can be propagated only vegetatively, such as certain varieties of bananas and sugarcane and many ornamentals, are clones that do not properly belong in any species, although for convenience they are classified in the species from which they were apparently derived. With these exceptions, individuals and species are mutually dependent; neither can persist without the other.
The publication two decades ago of Richard Dawkins's The Selfish Gene (1976) has helped to diffuse the idea, implicit in much contemporary thought about evolution, that the individual does nothing "for the good of its species." We need only to recall the interdependence of individual and species to recognize the logical
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absurdity of this perverse notion. If to exist is good, and if the existence of any composite entity, such as a species, depends upon its parts, then, simply by existing, individuals contribute to the good of their species. But living organisms commonly do more than contribute passively to the existence of their species, as parts of some lifeless object, a chair or a machine, contribute to its wholeness; by reproducing they perpetuate their species in a perilous world. Reproduction benefits not the reproductive individual but the progeny, few or many, that will continue to compose the species. Unless the parent finds satisfaction in rearing young, as apparently some do, or unless when grown the offspring promotes a parent's comfort or safety, as is rare in the animal kingdom, the individual gains nothing by reproducing. It squanders vital resources, exposes itself to dangers that it might avoid if careful only of its own safety, often exhausts itself, and shortens its life to perpetuate its species, as does the salmon when, after struggling upstream against foaming rapids, she lays her eggs and expires.
Modern evolutionary thought is preoccupied with the competition among organisms of the same species to increase their fitness, measured by the number of their living progeny. Successful individuals often deprive others of mates or opportunities to reproduce, sometimes of their lives. Responsibility for this selfishness is frequently attributed to the organisms' genes. However, if an individual's genes increase its fitness, their multiplication, even if this entails the exclusion of the less efficient genes of competing organisms, benefits the species, which thereby becomes more firmly established in the living world. In competing with others of their kind for the means of reproduction, individuals appear to vie with one another to contribute to their species. The great majority of organisms can serve their species only by producing offspring; but more social animals can otherwise benefit