Evolutionary Medicine

Modern medicine does need an evolutionary perspective, because one must know how the lock and key metaphor works. As diseases develop, the body must find a way to protect itself so it evolves a defense system which the disease or virus ultimately will find a key for. It is this battle between evolutionary developments of locks and keys that it is vital to know about evolution in treating a patient. If a doctor hands out antibiotics like it is candy, the bacteria are likely to find the key to surviving even in the presence of that antibiotic. Then, all the antibiotics become pointless. Just like a mechanic needs to understand each individual part, how a car was made, and technological advances to fix a car, so a doctor does the body and the things that can go wrong with it. If a mechanic does not understand the new technology, he may install old outdated things that no longer work with the rest of the newer components, just like an older antibiotic will not work on a bacteria that already has a resistance to it.

Bipedality blog

The forces of natural selection that led to the evolution of bipedality would be the environment. Ardipithecus was a forest dweller and may have evolved walking on two legs to be able to carry food. The other benefit of bipedality is it freed up the hands for use of tools. They were not a aggressive creature (found potentially by the smaller canines which are used in other primates for aggressive interactions). They may have had to reach up into the trees for their nutrition as well. Their hands were not made for walking on, but for grasping.
Brain size may well have evolved if the social groups were gettting more and more complex. The ability to store information of past meetings to remember for future encounters, and problem solving.

ancestor's tale

In the Ancestor's Tale Chapter 1 Dawkins warns the reader to avoid looking for repeating patterns in nature's past. Dawkins also warns of the assumption that we are the ultimate creation, that all other species that have ever lived monumentally lead to us and that was their purpose. Patterns of course do exist, however they are generally patterns in random. As for the thought that all species ultimately having us as the end result is thrown off by evolution and the fact that things are ever changing.
To look at history out of Africa Dawkins states that one must look at haplotypes, or the long lasting tightly bound parts of DNA that survive over many generations. Y chromosomes only pass through the male line, and contain the material to switch an embryo into male pattern development. On the other hand, Mitochondrial DNA is passed exclusively down the female line. Y chromosomes are useful in studying recent populations, while mtDNA are more effective for studying ancient patterns. Not as easy to use Y-chromosomes for that purpose. This is not the whole story because you cannot rely solely on a single gene. The out of Africa story holds that all people outside of Africa descend from a single exodus around a hundred thousand years ago. Each gene tells a different story so could be several stories.

Ultimately Altruism can only develop if the act of altruism by an individual is as big as the gain that individual gets in return... One example of this is mutualism. Cleaner fish set up cleaner shops to clean large fish of any parasites. This is highly dangerous because at any time the big fish could decide to eat the cleaner fish. But these large fish are recieving the benefit of having less harmful parasites and the cleaner fish are getting a meal in exchange. So ultimately it works. As for the example of donating to a blood bank it could be said that a person does it to just be nice, however one could argue that ultimately a person may at some point also need the benefit of having someone else's blood. Dawkins talks of the Cave theory and the never break ranks theory which at first glance seem altruistic by putting a warning individual at risk of being found by predators, when it really is quite selfishly just trying to keep other individuals quite so he is not found. Stotting also at first glance seems to be altruistic by diverting predators attention away from the group but really says to the predator, " I am not an easy meal, I am strong and will fight hard for my life, pick an easier target!" Symbiotic relationships also could have developed altruistic behavior.
In a simple game of prisoner's dilemma, there is no way of ensuring trust so it does not lead to altruism only best strategy which is both defect. In an Iterated or more repeated gamme of prisoner's dilemma repeated indefinitely, there is opportunity to build trust and to give that back. Tit for tat strategy in that you trust your opponent but do to him what he does to you in the previous round. Defectors are punished so to teach them a lesson. Looking at the British versus the Germans and their live and let live strategy, both had something to gain in this situation... their lives. As for the Vampire bats, their lives hang in the balance at any given moment when a meal is not available, so they share as they know they will be ultimately share with when theirtime of need comes, and the benefit to the one individual is much greater than the cost to the donator so it works!

Social Insect Blog

We saw last week how Kin Selection explained the altruism seen in the social insects and in animals that direct their benefits to kin. But even in the social insects there is some room for selfishness. Explain the conflict between queens and workers. Who wins and why? Are there any exceptions?





The ultimate conflict is explained by Trivers and Hare. They state that insects of the group Hymenoptera has a sex determination system that there is a queen who has made one mating flight to store up sperm for the rest of her life. Females have a father and therefor have a double set of chromosomes, whereas a male has only a single set of genes in each body cell and therefore all males in a colony are identical. The relatedness between hymenoptera sisters is 3/4 which is very different from other species in that the relatedness by full sisters is normally 1/2. It means that a hymenoptera female is more closely related to her full sisters than she is to her offspring of either sex. Hamilton realized that this predisposes females to "farm" thier own mothers as a sister making machine, but they must curb her natural tendency to give the 1:1 sex ration of equal sisters and brothers. From the workers point of view, the chance of any brother containing one of her genes is only 1/4, so for the profit of the workers, she cannot produce children in equal ratios. A worker always wants a 3:1 and a queen always wants a 1:1 sex ratio. THe conflict of interest is the queen trying to invest equally in males and females, while the workers try to shift the ratio to a 3 females to every male. Trivers and Hare took 20 species of ants and investigated the sex ratio and found very close to the 3:1 ratio. It turns out that the genes trying to manipulate the world through the queen bodies are outmanuevered by genes manipulating the world through workers bodies.
There are a couple exceptions to this is the slave making species which the queens can disguise male eggs to appear females to the workers. Some queens could mate with multiple males on the mating flight as well and the relatedness would thus decrease.

Blog week 4 Sexual Versus Natural Selection

Natural Selection is defined as a selection where only the organisms best able to adapt in their environment tend to survive and transmit their genetic characteristics in grater numbers to following generations while those less adapted tend to be eliminated all together. Sexual Selection is considered by some, to be a type of natural selection, that affects traits that influence an individuals ability to choose or get a sexual partner, rather than traits that effect a beings ability to survive. Sexual Selection is thought to be responsible for the evolution of many extravagant physical features, such as long plumes in birds, bright colors in many animals, and complex display behaviors to attract a mate.

Darwin defined sexual selection as the effects of the "struggle between the individuals of one sex, generally the males, for the possession of the other sex". In sexual selection, a male individual may have better traits for fighting other males so that he may be selected for by a female, or may just have ornamental traits that may catch the eye of a potential mate and increase mating success. Darwin states that, "The sexual struggle is of two kinds: in the one it is between the individuals of the same sex, generally the males, in order to drive away or kill their rivals, the females remaining passive; while in the other, the struggle is likewise between the individuals of the same sex, in order to excite or charm those of the opposite sex, generally the females, which no longer remain passive, but select the more agreeable partners." This is where sexual dimorphism comes into play and why many males and females differ in size, color, and other physical differences.

Dawkins talks more about why natural selection does not favor a shifted sex ratio and why it is that so many males exist when there need not be so many. He states that Darwin did not solve this, but Fisher did. Dawkins takes the stand stated in the first paragraph that sexual selection is a type of natural selection. The selfish gene must be passed forward so you must find a suitable mate to help that occur.

Week 3 blog response ESS

Dawkins states that an ESS is the best strategy for an individual depending on what the majority of the population are doing. An ESS is most important because it is applicable wherever we find conflict of interest and that is everywhere! Fisher states that a sex ratio of 50:50 is an ESS. This is due to the fact that if at any point a single sex outnumbered the other, the mating numbers would be disproportionate. If males outnumbered females, the opportunity for each male to have a mate is thus decreased and vice-versa. If each individual is trying to maximize his "own" success, then there must be an equal sex ratio being the 50:50 half males half females.
Conversely if you were to look at sex ratios of autosomal nuclear genes are transmitted to offspring through both of the sexes, so the sex ratio that must be favored is a balance between producing male and female offspring a 50:50 ratio. One can argue however that due to the fact that male species cannot produce offspring themselves, they are not necessary which would discount the male altogether. In contrast, cytoplasmic genes are mainly inherited through the egg cytoplasm and thus transmitted to offspring only through females. This means there is a strong selective pressure for cytoplasmic genes that distort sex ratio toward female production placing the sex ratio to 100:0 in favor of the females. And as previously stated, the sex chromosomes favor the 50:50 ratio potentially solely for mating purposes.
Two of these sex ratios could be the same because of the passing of genetic information through both sex chromosomes and autosomal chromosomes(as long as males were not discounted for not having the ability to produce progeny). The sex ratio of cytoplastic elements is different because that is only passed on through the mother and the male can completely be discounted.