Quote:
Originally Posted by Sljslj
(Post 873747)
But isn't it possible that if a species reaches some sort of harmony with their environment and the environment itself doesn't undergo any major changes, that mutations aren't necessary, nor beneficial? That seems to be where we're at right now. Also, for the first time, a species is able to create things to meet our needs rather than having to physically adapt to them. For example, instead of fur to keep us warm, we make clothes. Instead of having to actually physically catch our food, we can grow our food or use weapons to kill other animals. Am I making any sense or am I just making an ass of myself?
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Some will always do "better" than others, even if it's purely by chance (
genetic drift). Such harmony is not really attainable, but it is perhaps approachable to some degree. The Hardy-Weinberg principle says that there's an equilibrium (or harmony if you will) where allele frequencies remain constant (you could interpret this as evolution does not take place) in a population that satisfy some criterias :
"Random" mating - which means mates are chosen at random. You don't choose a mate based on favourable characteristics that make them attractive (assortative mating) and you don't do inbreeding.
Infinite population size (no genetic drift) - Basically, it has to be infinitely huge because then stochastic effects like rock slides killing off some germans here f.ex won't have much impact on the common human genome.
No natural selection - Nothing in the social, biotic, abiotic, whatever environment that makes one trait more favourable than another.
No gene flow - No input of alleles from different populations that may disturb the equilibrium.
No mutations - Mutations will create new alleles and if these increase in the population, that violates the HW equilibrium criteria.
In a population that satisfy all these criteria, the new generation should have the same genes (alleles) in the same proportions as their parent generation. This means that although the population may create different individuals, the genome as a whole doesn't change much - it contains the same varieties of genes at the same frequencies. As I wrote, this is not attainable. For example mutations do happen whether we like it or not and we do have sexual preferences. There are also a range of selection pressures, but they vary very much with where you are. Some places in the world, malaria can f.ex be a real selection pressure which favours some mutations. Where I am, it is not.
Whether or not there is gene flow is a question of definition because you then have to define the human population or populations that gene flow can occur between, so that's relative. Also, depending on how you see it, you could argue that the human population size is huge ;)
So sometimes, large populations of organisms may "approach" what looks like a HW equilibrium. Depending on how you define a human population - f.ex if you only look at Norway or some other western country, you could probably find that we do as well. However, it's never quite attainable and at any rate, it's only temporary. Some stronger selection pressures are bound to come along soon enough.
edit :
Quote:
that mutations aren't necessary
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Remember that in my example, a mutation which caused irritable bowels suddenly helped people survive cholera. I mentioned malaria and the exact same thing goes for the mutation which causes sickle cell disease. It protects against malaria so while this mutation causes a disease which is not beneficial to us, it can be if you're someplace with malaria.
http://en.wikipedia.org/wiki/Sickle-cell_disease
In other words, which mutations are beneficial or not may simply depend on the environment you're in and environments change over time.
