The Environment of Evolutionary Adaptation

This term was coined by John Bowlby, and refers to the conditions present in the environment when a species adaptations were naturally selected for. According to Badcock (2000), the human species lived in small hunter-gatherer groups for over 99 percent of the time that our species has existed (estimated to be one million years). There is no evidence of humans living in large scale societies until ten thousand years ago. This is one major defining feature of our environment of evolutionary adaptation (EEA), as it means our adaptations are suited to small communities. However, this term is slightly misleading. The EEA is not a specific time or place - so really we should refer to our environments of change. For example, the ancestral environments that shaped the human species to move from quadrupedal locomotion to bipedal movement may have occurred hundreds of thousands of years before humans developed the structures that allow us to communicate using language - both of which are adaptations that developed due to the changing demands of the environment (Badcock, 2000).

As various phenotypes are preferentially selected in different environments, how does life maintain itself when it has no way of knowing what challenges the environment is going to throw at it next? C. H. Waddington (1975; quoted in Plotkin, 1994, p.138), a British Biologist, summarises this problem: "The main issue in evolution is how populations deal with unknown futures". Animals always face uncertain futures, and to cope with this, nature uses two heuristics to guide evolution. The primary heuristic is described by Henry Plotkin in Darwin machines and the nature of knowledge. This is the g-t-r heuristic, which stands for generate-test-regenerate. The g phase is the generation of variation, and has two functions: (1) Conserve selected essential information, (2) produce new variations. The t phase is testing and selection of those variants which are successful, thus allowing those genes to be put back into the gene pool. The r phase is the regeneration of further variations, conserving the genetic information that benefited the organism that was generated previously, and new variations from the ever present variation-generating mechanisms. Plotkin also describes the more rapidly adapting secondary heuristic. This heuristic enables organisms to track changes that are occurring too quickly for the primary heuristic to account for. This includes learning within the individuals lifetime, and is built to serve the interests of the primary problem solving heuristic through countering short term change. Learning can be classed as a 'tracking device' which is programmed by the primary heuristic, and therefore can only operate within genetically determined limits. But what the exact values within those limits that the values will settle to is not determined by genetics - this is where the genotype to phenotype translation is modulated by the environment. For example, male white crowned sparrows must hear, as nestlings, an adult male sing their species song if it is to be able to sing the song as an adult itself. The baby sparrows cannot learn another species song. The ability to learn allows the sparrow to, in effect, sing the correct dialectal song (Konishi, 1965; Marler, 1984; cited in Crawford, 1998). When the expression of a gene is influenced by environmental factors, as it is in the above case, it is called a facultative gene.

This is only a brief introduction to equip readers with enough of an understanding to think about and analyse the other topics discussed in this site. For a more detailed insight into the EEA, then click here.

Darwin's Theory of Evolution


Sexual Selection

The social function of intelligence

References and Bibliography

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