Evolutionary perpective in modern medicine

Evolutionary biology has provided us with a much better understanding of the development of organisms and how they have evolved. Among these organisms are bacteria of which we know the structure, adaptations, and limits of several of them. We also have a better understanding of the structural evolution of the human body and how we evolved to walk upright (especially with the new discovery of Ardi). Thus it seems logical that an evolutionary perspective in modern medicine would have a positive impact.
If doctors have a better understanding of how certain bacteria evolved and what are their limitations, they can better treat diseases caused by such organism. Furthermore, if doctors have an evolutionary perspective with regard to the development and evolution of the human body, they can perhaps find better treatments for people with physical disabilities. Just as mechanics have to learn the components of an engine and how it transitioned from a small engine with a few cylinders to a large engine with several cylinders, doctors need to also know the components of the body and how specific structures developed and evolved in order to be able to provide care to it.

Evolution of Bipedalism and an Enlarged Brain

There are several forces or adaptations that led to the evolution of bipedalism, such as physical changes on the environment that leading to a longer search time of food across longer distances. Also, the ability to move faster and carry objects such as food or tools. Furthermore, it is believed that bipedalism evolved for a better reproductive success and because less surface area of the body is indirect contact with the sun, thus allows cooling more rapidly and efficiently.
The forces that lead to the evolution of a larger brain are believed to be linked to interactions between our ancestors in complex groups. These interactions include communication among them which lead to the development of language. Moreover, their ability of free hand movement lead to the ability to performed many different more complex activities and some of them at the same time. In order for this to be able to be achieved an enlarged brain must have evolved.

The Ancestor's Tale

In the The Ancestor’s Tale, Dawkins describes two misconceptions (which he refers to them as temptations) of the history of evolution. The first temptation is that historians tend to search for patterns in the history of evolution that tend to repeat themselves. The second temptation deals with the conceit of hindsight and with what Dawkins calls the “vanity of the present.” The misconception is that historians/individuals tend to believe that the past works to deliver the present and that evolution has reached a “perfect” state and evolution is finished. I personally believe that evolution will most likely never end, but if there is an end point I believe that there is a long way to go before evolution finally reaches an end point. We must avoid such temptations and remain objective when recording the history of evolution.
Moreover, Dawkins describes the Templeton’s method in determining the timing and history of migration from Africa which was based in the concept of tracing conserved segments of a genome referred to as haplotypes. Furthermore the Y-Chromosome Adam (all male lineage) and mtDNA eve (all female lineage), which are part of the same MCRA, where also used by scientist to determine the timing and history of human migration. From this, the idea of three migrations arose, and idea which Dawkins supports. However, Dawkins also believes that the entire story of the evolution of human is not known and that many more recent ancestors may still be found.

Altruism

Altruism is the opposite of selfishness, it is the selflessness concern for the well being of others. How or why did such behavior evolve? Let’s consider reciprocal altruism, it is the idea of helping someone else at a cost to the individual or organism performing the act. Such behavior most likely evolved because the benefits from helping someone else outweighed the cost, for example, the individual or organism that was helped could have performed an altruistic act towards the individual whom helped him earlier. There are several examples of organism that perform reciprocal altruistic acts such as vampire bats who will shared some of the blood they obtain with another bat that was unsuccessful at finding food. Another example can be found in meercats, they perform altruistic acts by taking care of unrelated young meercats while the parents and the rest of the pack goes out to look for food or by staying on the look-out for predators while the rest look for food. With the previous examples in mind, let us change gears and think about the prisoner’s dilemma.

The prisoner’s dilemma deals with the interaction between two individuals and whether they choose to cooperate or defect. If both individuals cooperate, they both obtain a reasonable benefit or payoff. If one of them cooperates and the other defects, one of them gets a better payoff than the previous mutualistic act but the other gets a very low payoff or benefit. If both individuals defect, they both received a fairly bad payoff. Can it be solved? As Dawkins explained on chapter 12 of the selfish gene, the best move is always to defect. If two rational individuals are involved in such interaction, it is more logical to defect (due to lack of trust on the other individual) and received the less harsher payoff or punishment, even when they both could get a reasonable payoff if only both would cooperate. There lies the idea of the prisoner’s dilemma.

What's in it for them? Queen VS workers

In the Selfish Gene, Dawkins introduces the idea of social insect individuals being divided into two main classes: the bearers and the carers. The bearers are those who reproduce and the carers/workers are those who perform work and are usually infertile. Both types carry out their jobs efficiently because they do not have to cope with each other.

If the workers are unable to reproduce, why aid the queen? What’s in it for them? Dawkins states that the workers “farm” the reproductive individuals, meaning that the workers manipulate the queen to propagate the worker’s genes. The conflict in this system lies in the sex ratio. The queen favors a 1:1 females to males sex ratio whereas the workers favor a 3:1 females to males ratio.

It makes sense that the queen benefits by investing equally in both sexes, but why do workers favor females over males? A simplified answers is that males contain just a single set of chromosomes (all passed on from the mother) whereas the females contain a double set of chromosomes (obtained from the mother and father). Among the females, full sisters are identical twins as far as their parental genes, thus females benefit by “farming” their own mother into a “sister-making” machine.

Is there a winner? Trivers and Hare found that among 20 species of ants, the workers bias the sex ratio in favor of females (The Selfish Gene, pp. 176-178). However some species of ants, after defeating another colony of ants, take the unhatched ants who become slaves. These slaves, not knowing that their not related to the queen, performed as workers yet do not affect the queen’s preferences.

Upgrating Generations: Natural vs. Sexual Selection

“Man selects only for his own good; Nature only for that of the being which she tends.” – Charles Darwin

Darwin explained the principle by which slight variations of traits, if useful, were preserved. Such preservation of favorable variations, and the rejection of those variations which were not beneficial, is what he referred to as Natural Selection. Moreover, Darwin explains that natural selection is dependent on a “state of nature” which enables the modifications of “organic beings” through the accumulation of “profitable” variations. Furthermore, Darwin argues that natural selection cannot modify the structure of a species without providing a certain advantage, hitting towards the role of sexual selection. Darwin defined sexual selection not as a struggle for existence but as the effects of the "struggle between the males for possession of the females,” the result not being death to the unsuccessful but lower production of progeny.

Natural selection is dependent on interactions with the environment. Dawkins argued that the gene’s survival is dependent on their interaction with the environment. Moreover, Dawkins argued that the environment also consisted of genes, which cooperate and compete with each other. Those who are better at cooperating and better in competing will persist. Sexual production is mainly shifted towards the greater production of quality progeny. In the “selfish” view, females look for the most fit male to mate with and better enhance her genes while passing them onto future generations.

Evolutionary Stable Strategy

In the Selfish Gene, Dawkins describes the concept of the evolutionary stable strategy (ESS) as a strategy that depends on the actions of the majority of individuals in a given population in an attempt to maximize their own success. As the strategy continues, it evolves and it cannot be bettered by an altering strategy, “selection will penalize deviation from it.” (Dawkins, 69) Fisher applied this concept to sex ratios, arguing that an equal sex ratio (50:50) is an ESS. We can imagine a scenario in which males could bias sperm production or females bias the rate of fertilization as to favor the generation of one. Both Dawkins and Fisher counter such scenario by stating that following an environmental change or instability, an ESS will be achieved again. I believe that sex chromosomes favor an equal sex ratio as an ESS. Fisher supported this by explaining what the outcome would be if a specific gender persisted, reproduction would decrease and the opposite gender will bias its generation, thus equalizing the ratio. One could think that cytoplasmic elements are an ESS, however this cannot be true because all elements are not used equally and tend to favor one sex over the other.