Blog 9: Evolutionary Medicine

Blog 9: Evolutionary Medicine
Firstly, I would like to state that any and all knowledge whether it be concerning evolution or not, can aid in the diagnosis and treatment a physician prescribes. However, speaking strictly in the context of evolution I believe that it awards many advantages that can be seen as highly beneficial in treating patients. A greater understanding of the body as well as how it evolved over the years, can enhance a physician’s ability to understand the conditions of their patients. Seeing the advantageous traits that evolution confers on select individuals, can allow doctors to use this substantial information for health care applications.

The well-known evolutionary theory of kin selection states how cooperation can evolve and lead to altruistic behaviors geared towards closely related individuals versus non-relatives. An example of these cooperative efforts is present in colonies of bacteria residing in oral cavities. Different unrelated colonies live on human teeth and the act of brushing ones teeth can be used to “mix” unrelated adjacent colonies which results in a decreased rate of bacterial growth, as well as of lessening plaque, and indirectly decreasing the rate of tooth decay. By simply understanding the evolutionary theory of kin selection, doctors, dentists and scientists, can create more effective products and treatments that seek to exploit this evolutionary fact for beneficial purposes.

Within the field of medicine nothing is more important than understanding the complex mechanisms of viruses. This area is so fundamental to the purpose of medicine since viruses are non-discriminatory against humans and seek to exploit their hosts’ defenses as well their biological machinery for their own survival, at the cost of the hosts'. Understanding the diverse pathways in which viruses are formed can allow us to formulate better mechanisms and tactics that inhibit viral production. Doing so will encourage a greater survival rate of the infected individual as well as diminish the effects of the pathogen. The evolution of viruses is so crucial to the study and practice of medicine that the two should never be polarized.
Another point that should be made, is the importance of understanding Darwin’s statement, “I have called this principle, by which each slight variation, if useful, is preserved, by the term of Natural Selection” By simply understanding that natural selection is a process that continuly seeks to perpetuate useful traits, then according to Darwin, in cases that may be perceived as potentially harmful toward and individual need to be further reexamined, as they may have been maintained throughout evolutionary time due to their unapparent advantages.. Such an example is morning sickness of pregnant women. The morning sickness serves a purpose, and that purpose is to protect the fetus from outside toxins consumed by the mother. Insuring that no toxins are ingested during this vulnerable time at this time will help ensure the safety of the fetus. Certain foods trigger nausea--the biological equivalent of a caution sign to the mother to not ingest certain foods so as to not harm her growing child. Many medications today are prescribed to relieve women of their morning sickness, however by doing so—rather than educating the women about certain diets that can diminish or completely rid them of their morning sickness all together---- may alleviate the mother’s symptoms but at the cost of harm to the fetus.

So it can be said that understanding evolution and its various mechanism can result in increased benefits when physicians treat their patients

Blog 8: Bipedalism

After reading the posted articles there seems to be a few forces that led to the evolution of bipediality. One includes the increased ability to obtain and gather food and necessary materials. Walking on two legs allowed our ancestors’ arms to be free to use for the use of other things, such as, grasping, tool-making, gathering etc. Also, freeing up the arms lead to greater mobility and therefore increased the range in which territories could be traveled. Sexual selection also provided selective pressure, by walking on two feet males could obtain more resources in which females could benefit from and therefore were choosey for. Standing upright also allowed females to see male reproductive organs; the well-endowed obtained the greater number of copulations.

Forces that led to the evolution of larger brain size our shared primate ancestors included living in my complex groups, evolving different behaviors towards other individuals. They had to be able to remember certain behaviors that were beneficial to repeat or avoid. Freeing of the hands due to bipediality led to the enlarging brain since it allowed for multiple activities to be done at one time, increasing the neural connections within the brain.

Blog 7: The Conceit of Hindsight

The misconceptions that Dawkins warns the reader about were the idea that man is continually attempting to elucidate patterns throughout history that had a repetive nature to them. Humans have a tendency to view everything that came before in terms of how it has affected us and our own personal evolution throughout time until the present day. Trying to find a pattern should be something that Dawkins urges us to avoid. Evolution in the grand scheme of things is a pattern, even though at times the visible remnants may be present as seen in different taxa to times in which certain traits disappear. Patterns should not be expected to appear over and over. By looking at evolution from an egocentric view will hinder us from full comprehending evolution and its mechanisusms. Humans are constantly excepting an end, a finished product—yet evolution is the farthest from that. It is a never-ending circle that has no end and will continue if given the proper conditions. Evolution much be approached from the perspective that it is a constant and continually process.

To determine the time and origin of human beings, scientists trace back ancient human migrations by looking at and tracing genes. This method however does come with a drawback since tracing different genes can lead to different results due to their varying coalescent points. "Y-chromosome Adam" and "Mitochodrial Eve" are the original ancestors of humankind.

Several theories have been proposed as to when humans migrated out of Africa. Dawkins tends to favor the "Out of Africa Again and Again" hypothesis. Alan Templeton conducted extensive genetic research tracing many genes in order to find human origins. He concluded that there were three major migrations out of Africa through his extensive gene tracing.

The whole story will probably never be known. Other popular theories persist and present genetic evidence demonstrating that there may have been many small migrations to and from Africa, Asia as well as Europe.

Blog 6: Altruism

Altruism refers to any behavior by an individual that increases the fitness of another while decreasing their own fitness. Altruism can evolve as a result of benefiting both parties involved, although it may not be immediate for one, in the long run the altruist also benefits. Such an example is seen in vampire bats. They will share acquired blood meals with others who were unsuccessful hunting one evening in securing their own meal. They do this not because they are ‘Kind” and ‘Loving” but instead have ulterior motives. Sharing their meal with those who have none will increase the likelihood that if they were placed in a similar situation one night where food was not found they will secure the same help from those that they have helped in the past. However this behavior will only persist throughout time is if memory and learning also co-evolve. They must have the capability to recognize individuals whom helped and or hurt them in the past. This “learning” mechanism allows there to be a punishment of cheaters and reward to cooperators.
This time of scenario is called the prisoner’s dilemma.

By the prisoner’s dilemma the best way to receive the greatest reward is to be the individual who defects the other and gains all benefits while the other is punished. If both individuals cooperate, the punishment is still present but at a much lower amount along with a small benefit. The latter scenario is thought best for a first-time encounter between altruistic animals who can distinguish between individuals who have helped and punish those who cheated. It is always best to cooperate at the first time encounter although the greater benefit is to defect and run, it will only be advantageous for that particular time. Later on in the future the individual you betrayed will remember and punish you for cheating before by not helping you this time around.

Blog 5: Queen-Worker-Bee Conflict

Explain the conflict between queens and workers. Who wins and why? Are there any exceptions?

There exists and reproductive conflict between worker daughters and their queen mother. In social insects--such as bees--here occurs a very distinct sex-determination system that governs where selective pressure is placed when speaking in terms of reproduction. This system is called haplodiploidy. The father only has one set of genes to pass along, so the probability that an ant will share the same paternal genes as her sister is 100%. So the degree of relatedness for two sisters is:

(1 x ½) + (½ x ½) = ¾.

A typical female bee is genetically more closely related to her sister than to her mother or her daughters. This is why female workers would favor a 3:1 ratio, of producing more sisters rather than their own daughters. But this comes with a caveat-- their mother queen must only mate with one drone in order to ensure greater relatedness between the offspring sisters. If the queen is inseminated by more than one male, selective pressures will shift and cause daughter workers to reproduce their own young, since it guarantees a greater degree of genetic relatedness and therefore greater percentage of genetic fitness.

The queen’s genes however can benefit best if she invests equally in both sexes, supported by Fischer calculations on optimal sex ratios done by Trivers and Hare. Using 20 species of ants, Trivers and Hare estimated sex ratios in terms of investment in reproductives and found a 3:1 female to male ratio. “Workers are running the show for their own benefit.” With this study Trivers and Hare found that it was the workers who “won” the conflict between workers and queen because it was them who had the greatest investment in the offspring.

Since the workers were the ones making the greatest investment in caring for the offspring –they could therefore manipulate the sex ratio towards their benefit, that is, to a 3:1 female : male ratio. Exceptions to this included that in species that have “slaves” (ants from other colonies) caring for the offspring the queen has a greater ability to manipulate the ratios through the slaves since the queen can escape the slaves’ countermeasures because they do not work on her, being that she is totally unrelated to them.

Blog 4: Natural Selection vs. Sexual Selection

Natural Selection is the process by which a slight variation in a trait of an individual increases its likelihood of surviving relative to that of an individual not possessing the trait. Fitness describes an organism’s ability to survive and reproduce viable offspring. It is this second component of fitness (production of viable offspring) that gives sexual selection its relevance in terms of evolution. In contrast to natural selection, sexual selection is not dependent on a struggle for existence between individuals, but instead on a struggle between individuals of the same species and sex (usually males) for possession of the other sex.

In the On the Origin of Species, Darwin elucidates on Natural selection when he says: "It may be said that natural selection is daily and hourly scrutinizing, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, wherever and whenever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life." Here he states how Natural Selection is the evolutionary process by which species confer advantages over time and in slight variations. Therefore the slightest differences in structure can turn the scale for the struggle of existence; in turn, individuals possessing advantageous traits will survive and reproduce more. He uses the example of prey hawks and how natural selection gives them. Characteristics of natural selection that differ from sexual selection, by being utilitarian, functional, sensible, economical and constructive.

Sexual Selection is elucidated by Darwin when he discuses “We are, however, here concerned only with that kind of selection, which I have called sexual selection. This depends on the advantage which certain individuals have over other individuals of the same sex and species, in exclusive relation to reproduction.” Here sexual selection is seen as conferring advantages for a particular sex in the SAME species versus the entire population. Its characteristics include showy, elaborate displays that cause a preference for one mate over another and therefore increasing the reproductive fitness of that particular individual who posses that trait. This in turn causes treats preferences as adaptive.

Dawkins takes a similar stance on natural and sexual selection, but tends to make fewer distinctions between the two. He reinforces how the best genes continue and prosper throughout time and are selected for. He further explains since females begin with a disadvantage due to the fact that they invest more in the offspring from fertilization, there in turn must be selective pressure on the males—this comes in the form of sexual selection. Females begin to form preferences for certain males that have certain traits and only those who posses them secure copulations. An example is the domestic-bliss strategy, where females select their males carefully, searching for fidelity and domesticity traits. By insisting a long courtship/waiting period, they weed out casual suitors and only copulates with those who are faithful and will stick around. So here patience is a virtue and their genes for sexual selection will then be passed on to the next generations and will be favored in the gene pool.

Blog 3: Evolutionary Stable Strategy (ESS)

An evolutionary stable strategy (ESS) is a strategy that the majority of the population utilizes. It is the only strategy that persists and cannot be invaded by deviant individuals. An example of an ESS is Fisher’s sex ratio of 50:50 males to females. If a population begins to shift its preference on one sex over the other, that sex will on average have lower mating successes, and therefore have a reduced offspring-production. As time progresses, selection will seek to shift/favor genes that bias towards the opposite sex, until the 50:50 ratio is achieved.

Autosomal chromosomes, being equal in number and having homologs in both males and females, will likely favor the 50:50 sex ratio. Sex chromosomes however have a bias towards one sex over the other since the sexes differ on a single chromosome- the Y chromosome. It is probable that the X chromosome can select repressors on the Y-chromosome, and thus favor the production of females. Cytoplasmic elements, usually coming from the female, can also distort the 50:50 sex ratios. The majority of sex distorters are cytoplasmic and they favor the sex through which they originate from

Blog 2: Major Transitions

While reading Mayhew he discusses eight major transitions that caused evolutionary change, starting from the very simple single celled organisms to eventually the very complex multi-cellular humans arisen from genetic recombination and variation throughout multiple generations. Dawkins also has a similar approach in that he also believes that life spawned from simple organisms with the ability to replicate. Both authors suggested how these organisms underwent a process of transition to increase in their complexity. Behavior as well as language (as Mayhew suggests) evolved as well. Although they share similar views when it comes to the simplicity in the beginning, they significantly diverge from one another view when it comes to the process of which they underwent to become complex. Dawkin’s has a very gene-centric point of view that dominates his book. Like in Chapter 3 when he introduces the idea of the replicators, substances emerging from the earth’s “primordial soup” and over many generations developed into organized and complex beings with abilities that their predecessors only dreamed of. It is this heterotrophic viewpoint that I best relate to and agree with. Dawkins continue to add that these “survival machines” were incapable of producing their own nourishment and therefore became dependent on other organisms for consumption and energy source. Nonetheless as time went on their abilty to become more complex beings aided in their survival as opposed to other whom which they had also emerged with.
Mayhew on the other hand sees a different perspective from that of Dawkins. He introduces and supports the autotrophic view to the origin of life. Mayhew argues that early life lacked protein enzymes to catalyze reactions, instead utilizing RNA instead. This was a point that I disagreed with, I leaned more towards the heterotrophic theory Dawkins supports. Dawkins idea of emergence from a primordial soup which contained the precursors for DNA is a more appealing scenario to me. Dawkins to me better complements Darwin’s theory of natural selection than Mayhew. To the idea of lacking the ability to catalyze such fundamental processes leaves the scientist at a stalemate. This to me is a very unlikely probability.

Blog Question 1: Sept. 9, 2009

Before Darwin begins his examination on domestication, he thoroughly explains the possible process for which it occurred through his lengthy investigation of the rock-pigeon and its subsequent descendents. In his studies he examines arguments proposed by naturalists during his time and their reasoning to support their claims. While he may agree in some areas, he heavily criticizes the weak points presented in their arguments. Namely that of the high improbabilities assumed to be occurring, such as; that the wide variety of pigeons present today must have arose from not a few aboriginal stocks but instead from as many as six or seven stocks, otherwise how could have so many races have arisen. Other problems include the idea of the half-civilized man succeeding in thoroughly domesticating several species along with selecting abnormal and evolutionary advantageous traits and that these species have now become extinct.

These concerns could be addressed by running a microarray to find the possible genetic links between species in hopes of finding similar genes between related species. These genetic links will aid in forming a phylogenetic tree that examines the relationships between species and find the one or many original ancestors. Understanding the similarities between hybrids and there genetics can allow biologists a more clear view as to the links that bind many varieties of species.

In accordance to Dawkins, the problems with the argument would be a result of survival of those species that were not the most self-sacrificing but instead of those that were the most selfish. It was the selfish that continued to pass on their genes to their progeny while the altruists slowly died out. Survival of the fittest has now been rephrased by Dawkins to be “survival of the selfish”.

Lastly, while Darwin did not agree with Lamarck’s theory of acquired characteristics he did however acknowledge how while environmental factors are not the primary triggers of variation they nonetheless play an important role to the species. He supports his stance with the examples such as the availability of food or the climate and heat conditions in which species types are raised that lead up to domestication. Darwin concludes his findings with the fact that variation is primarily and substantially due to reproduction