The Environment of Evolutionary Adaptation

[Gil]

Firstly is presented the theory itself and then my personal analysis.

This term (EEA) was coined by John Bowlby, and refers to the conditions present in the environment when species adaptations were naturally selected for. According to Babcock, 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
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, a British Biologist, summarizes 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 individual’s 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. When the expression of a gene is influenced by environmental factors, as it is in the above case, it is called a facultative gene.


My Analysis

I believe that the Environment of Evolutionary Adaptation (EEA) is indeed a more accurate way of looking into human (and non-human) evolution. EEA is more complex than the above explanation but the main core of it’s principles is expressed in the belief that human development as a species is not based simply on outside factors but on “try-fail-try again-success” strategies which can have two results: a) massive failure and either extinction or clustering and b) success and development of variation.

The occurrence of a) could be the explanation for rare, specific-geographical diseases, phenotypes, etc.
Example: A certain population remains cut off from outside gene exchange and therefore develops specific gene-related diseases which in turn could lead to severe congenital problems. EEA kicks in when their genes try to develop a disease-resistant factor which would prevent their extinction. Two cases could emerge: either only those possessing disease-resistant genes remain (and b) occurs) and though the population numbers lower they remain existent or the entire population fails to develop the necessary adaptation and is extinct.
The occurrence of a) also explains the prevalence of specific phenotypes within the population (cluster effect) but I’ll get back to that later.

As for b), that would explain evolutionary/adaptive traits which enabled humans to survive within specific environments which both shaped them and forced evolution.

Hope you enjoyed my analysis and please comment.

Cheers