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