Thrifty Phenotype: Adaptive Reasoning for Adult Onset Type 2 Diabetes
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Thrifty Phenotype: Adaptive Reasoning for Adult Onset Type 2 Diabetes

This is a discussion about modern traits being either adaptive in an evolutionary sense or pathological based on environmental change out pacing evolution. Modern diets and Diabetes

The question is whether a trait is adaptive or pathological, but for this we have to understand what a trait is, and what is not. There is a great deal of debate on this issue. The dictionary describes a trait as a distinguishing characteristic, which is a bit vague for our purposes. A much more precise definition is “…structures optimally designed by natural selection for their functions” (Gould, Lewontin 1984). Gould goes on to argue that not all traits are necessarily functional or adaptive. A good example of this how we regard the chin. If we think of the chin as an entity all its own instead of just a symphasis between the alveolar and mandibular bones then we begin to ascribe functionality in a panglossian sense to something that does not exist in the first place. The chin is not however pathological, it is just not a trait per say. This paper is to explore the difference between what traits are adaptive and which are pathological.

One major contention on the issue of adaptedness verses pathology is that traits seem to be environmentally contingent. I read this as meaning that traits developed in the environment of evolutionary adaptedness or the EEA are no longer advantageous or adaptive in the new urban environment we have created for ourselves in just the last few thousand years. The rise of civilization as we know it has come at a rate that is greater than the speed of evolution. Add to the new environment the revelation of industrialization and we suddenly, in just a few decades, live in a very different environment. But does this mean that once useful adaptations become pathology. The clumsy and embarrassing example put forth by Satoshi Kanazawa of male erection in response to sexually suggestive women (Kanazawa, 2001) does not seem to be pathological or maladaptive in any way but there is a certain logic to physiological and mental responses based on four million years of evolution that would be out of place in our day and age. I do not think of the crew of the starship enterprise as my personal friends but Kanazawa’s socialization argument still has merit. However, it does not account for feelings that are maintained for old friends infrequently seen or strong feelings for a new friend. This idea of pornography and television driving socialization seems a bit weak and obscure.

An example of adaptation come pathology that has gotten a great deal of attention and study is the onset of type 2 diabetes based on prenatal environments. The idea is that our diet today is so radically different from the EEA diet that our bodies are adapted to, causes insulin imbalances based on the quick trigger idea of usage. This is to say that dietary glucose was rare in our diets as hunter gatherers and that our bodies adapted to processing and using it quickly when it was encountered. This idea is at least congruent with the patchy resource model of most frugivorous primate groups. Now that dietary glucose is not only common but abundant in our fast food, MTV society our bodies have retained that quick trigger mechanism resulting in adult onset diabetes rates that are well above normal. This supposition is supported by the comparison that Neel and company make with Amerindian groups who are non- acculturated and those that are. They found that the non-acculturated Indians who are subsisting on what is, for lack of a better term, a primitive diet show far fewer instances of type 2 diabetes than the groups of native Americas who have assimilated into the mainstream culture and eat diets high in processed food amounts. (Neel et al. 1998).

Gould, SJ, Lewontin RC. 1984. The Spandrels of San Marco and the Panglossian paradigm: acritique of the adaptationist programme. Proc. of the Royal Society of London B, 205:581-598.

Kanazawa, S. 2001. Bowling with our Imaginary Friends Evolution and Human Behavior 23 (2002) 167 – 171 Pennsylvania In. PA

Neel JV., Weder AD., Julius S., 1998 Type II Diabetes, Essential Hypertension, and Obesity as “Syndromes of Impaired Genetic Homeostasis”:The “Thrifty Genotype” Hypothosis Enters the 21st Century. Perspectives in Biology and Medicine, v42 I1 p44(1)

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