Physiology is about Summation: 1

Delusions come in many shapes, sizes and forms. The delusion of knowledge is one of the more popular, and I will say more that in another post. However the end effect of all delusions is the neglect of reality to the detriment of the deluded.

One of the most popular delusions in the blogosphere seems to the deterministic belief that genes are destiny. Now I should mention upfront that this secondary delusion require the primary delusion of knowledge. Essentially, only a completely characterized and understood complex system is even close to deterministic. Our current understanding of biological systems is pathetic at best, and we are therefore so far from determinism that it is not even funny.

The ‘genes are destiny’ meme arises from a misunderstood belief that one gene = one physiologically active protein. While one open reading frame of DNA (with or without interruptions) does indeed correspond to one expressed protein, the rest is far more complicated.

Evolution never designs or optimizes. It merely lets what is not successful, under the given conditions, to die.

Evolution by definition cannot converge on an optimal solution to a problem. It can stumble upon many almost optimal solutions. However since the conditions under which natural selection operates are themselves not constant, the genetic algorithm (evolution) cannot ever converge into one optimal solution.

This lack of optimization leads to one rather peculiar feature of biological systems. Almost all biological processes are driven by summation of multiple pathways.

Let me explain.. Imagine if a important process such as control of cell division, electrolyte regulation, nutrient handling, sexual reproduction was driven by a series of simple linear biochemical pathways where disruption of one part of a pathway would cause the output to collapse.

Given the number of DNA base pairs and rates of mutations, even one mutation in an obscure pathway could kill the organism. Given that mutations are a function of genome size (and DNA repair efficacy), only the simplest and most fecund organisms (bacteria) could ever use such simple point-to-point biochemical pathways. The rest (and even many bacteria) do things differently.

They use pathway summation.

Let me start with an easy example: Food intake and handling by humans.

Hunger in humans is controlled by a number of overlapping and cross-talking biochemical pathways. These include insulin, serotonin, dopamine and a host of other hormones and pathways. None of them by itself is important enough to kill if it malfunctions.

Insulin increases hunger mainly by causing hypoglycemia, but it has other more indirect effects on human biochemistry that make one crave more starchy and sugary foods. However two people do not gain the same amount of weight on a high-carb diet even if they are fairly similar to each other. Other systems such as brain serotonin and dopamine levels modulate the insulin hunger and craving signal.

It is well known that SSRI antidepressants cause weight gain by increasing serotonin levels, as do anti-psychotics by blocking dopamine (both in the brain). However neither have identical effects in a group of similar people, and it is well known that some people are far more sensitive to the weight gain caused by these medications.

The net result is that food intake and fat storage is the sum of a number of pathways that often interact with each other. The whole system is influenced by a number of hormones from insulin, serotonin, dopamine, testosterone, estrogen to even the availability of certain types of food and recreation facilities. There is therefore no magical gene or factor that is responsible for most of the obesity around you. Researchers can play all the statistical games they want, but the very organization of living systems works against such simplistic and religious beliefs.

The end result is that crucial biochemical systems are far more stable than would be otherwise possible. Such dynamic stability makes evolution possible, otherwise even one wrong turn could kill the mutation containing organism.

Think about it: Cystic fibrosis (not a very common disease) is the most common single gene linked disease and even it has some survival value in its sub-clinical forms.

Another example would be sexual functioning in human males.

To get a usable erection and achieve orgasm, many systems in the body have to work in synchrony. You require enough testosterone, enough dopamine, enough serotonin, increase in parasympathetic nervous system activity, decrease in sympathetic activity and a host of other things to work within the normal range. Frequently inadequate settings on one component can be functionally bypassed by increased activity of other components of the system, and most of such equilibration without your conscious knowledge.

The very fact that most men can get an erection and ejaculate when presented with an opportunity to be stimulated properly by a half-decent looking woman says volumes about the systems functional robustness.

Even significant physiological malfunction can be overcome by simple interventions. Low testosterone could be boosted by frequent exposure to receptive hot women (or you could just buy testosterone gel). While anxiety can cause both erectile problems and premature ejaculation, moderate amounts of alcohol and a degree of familiarity with the woman can alleviate them (as can PDE5 inhibitors). The adverse effects of SSRIs on sexual function can be reversed by not taking them (or taking dopaminergic antidepressants) and so on.. The reality is that unless you live in a hostile society which is full of all sorts of deprivations, you will do OK.

The hard-to-accept reality is that there are no perfect solutions or optimized physiologies, merely different types and degrees of malfunctions. However most malfunctions allow the overall system to work well enough to perform its function.

However the whole myth of human hierarchy is based on make-believe BS about innate superiority of some over the rest. Keep buying into that crap.. they require more suckers like you.

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