Battle of the Sexes

According to Dawkins, an evolutionary stable strategy (ESS) is a strategy that the majority of the population employs. In a population of individuals maximizing their own successes, the only strategy that persists will be the one that cannot be bettered by any deviant individual. An example of an ESS is Fisher’s sex ratio of 50:50 males to females. If a population suddenly began to shift its preference on one sex over the other, in succeeding generations, that sex will on average have lower mating successes, and thus, offspring-production is reduced. In time, selection will favor genes that biases towards the opposite sex, until the 50:50 ratio is reached. The strategy of a 50:50 sex ratio is an ESS in the sense that any deviation from it leads to a net loss (Dawkins, 145).

Autosomal chromosomes, being equal in number and having homologs in both males and females, will likely favor the 50:50 sex ratio. Sex chromosomes will be biased 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 (Werren, 1998). Cytoplasmic elements, usually obtained from the female, can also distort the 50:50 sex ratio. Indeed , the majority of sex distorters are cytoplasmic and they favor the sex through which they will be transmitted (Hardy, 2002).

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Brave New Worlds

Both Dawkins and Mayhew assert that early life dawned from some sort of entity that was able to replicate. Both pointed out how these “replicators” transitioned from simple forms to sophisticated organisms to a thriving ecosystem, from which advances like communication and behavior emerged. However, how the transition came about is where the two differ.

Dawkins’ gene-centric view suggests that replicators, which emerged from substances of the earth’s primitive environment, became receptacles for genes called “survival machines.” Such machines “fed” on substances available in the “primordial soup”, and gradually developed into organized structures. In this connection, he proposes that these machines were not capable of producing their own “food” and were reliant on the substances available in such pre-biotic broth. In evidence he states how the scarcity of “food” in the soup paved way for a food-producing organism to later arise.

Mayhew holds a different approach. In Brave New Worlds, he stresses the autotrophic theory on the origin of life. To prove the likelihood of an earth consisting initially of food-producing organisms, he emphasizes the difficulties of early cell membranes to have permeability to molecule transport and the fact that metabolic cycles can emerge spontaneously.

There has been much evidence supporting the latter scenario. One is that NH4SCN and H2CO acted as raw materials for the synthesis of bio-organic compounds by photosynthetic structures (Herrera, 2003). Evidence also suggest that photosynthesis was an early acquisition. In evidence, early life used RNA to catalyze reactions due to a lack of sophisticated protein enzymes. As Mayhew pointed out, it isn't a coincidence that chlorophyll synthesis involves molecules bound to RNA. This provided a new abundant energy source, light, which have massively increased potential productivity (Mayhew, 2006).

Homework 1

Darwin’s phrase “all races of dogs have been produced by crossing a few aboriginal species," seems contrary to his breakthroughs. It seems to suggest that all variations can occur only through crossing for several, several generations. More so it implies that new species form only through crossing itself. That is certainly not the case. How about his observations on the unique finches of birds that exhibited slight variations from island to island?

Take for example the makeup of a Labradoodle. From Mendelian genetics , we know that alleles for each trait segregate randomly during crossing, so there is an equal probability that the dominant and recessive alleles for each of the Labrador and poodle’s traits will be passed on, paving way for many variations among offspring. It is thus possible to obtain a new race of dog, in this case the Labradoodle, between two distinct races even on the first filial cross.

In the same light, Dawkins’ view, according the The Selfish Gene, illustrates that the origin of our species is not merely as vague as Darwin implied, nor is it as clear-cut as solely due to crossing species. He asserts that individuals in a specie advances, much in part due to the success of the selfish gene (Dawkins, 1976). This means that evolution takes place for the good of the individual and never for the good of the species. Moreover, this concept offers a new approach from a somewhat fixed view of the “survival of the fittest” phrase. He restates it to a more general law of “survival of the stable” (Dawkins, 1976). How individual species of dogs came about may be governed by the principle that speciation is simply a selection of the most stable kinds of dogs and the rejection of unstable ones.

Peter Mayhew also offered insights about understanding species richness. In Where Two Fields Meet, he asserts that the environment plays an important role in how species form, from geographic separation to subsequent differentiation (Mayhew, 2006). With the help of domestication, a dog lineage may split into many distinct ones due to differences in human habitat, from a freezing tundra to a humid plain. The lineages evolve in isolation and through natural selection, traits that permit better survival will be passed on from generation to generation. This can explain how differences between a Collie and a Chesapeake Retriever came about.