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.