Evolution can be defined as a change in alleic frequencies within a population over time. Thus, considering a small population of 100 sins players, we have two alleles, A and a. The allele A codes for a phenotype, something you can observe, and so does allele a. Since humans, like sins players, are diploid, meaning they have 2 of each chromosome, humans can have two alleles for a particular trait. It follows that within our small population of sins players, some players will have the genotype, or allelic configuration, AA, some will have Aa, some will have aA, and some will have aa.

It is important to note that allele A is dominant, meaning that one copy is sufficient to produce its phenotype.

In a perfect system, unaffected by evolution, we can predict the frequencies of the two alleles given the two Hardy Weinberg equations:

1) A + a = 100%

2) A^2 + 2Aa  + a^2= 100%

The first formula is easy to derive. It simply states that all the alleles in the population together equal 100% of the alleles. The second is a little trickier. You can see how it is derived below, or you can just take my word for it.

* Derivation of second formula:

Remember that there were 4 possible genotypes? You can calculate the probability of the first genotype (AA) by multiplying the probabilty of getting one A allele by the probability of getting a second (A * A = A^2). The same goes for the genotype (aa). For the other two genotypes (Aa and aA), you do the same thing. Find the probability of having one A allele and multiply it by the probability of having one a allele (A * a = Aa). Now multiply that by 2 since (A * a == a * A) and aA is the final genotype.

*

Now back to our model system of sins gamers. Let's say the initial frequency of the A allele (gamers who spam Advent illuminators) is 40%. From equation 1 we can tell that the frequency of the a allele (gamers who build heavy cruisers and crush Advent illuminators as God intended) is 60%.

Now using the second equation, we can calculate the frequency of gamers at equillibrium who have each genotype.

A^2 = 16%

2Aa = 48%

a^2 = 36%

Since we know that A is dominate, both AA and Aa will exhibit the illuminator spam phenotype (64%, or 64 of the 100 gamers)

Now, in the case of evolution, even given those allelic frequencies, you would find either A) more heterozygotes, or individuals who have one of each allele or more homozygotes, individuals who have only one allele

The first case occurs when 1) selection, or the tendency for the environment to favor one allele over another 2) gene flow, or the introduction of alien alleles from another population 3) non-random mating, or the tendency for individuals to select a certain trait (think a peacock's tail) 4) genetic drift, random variations in frequencies (sometimes evolution misfires, but it is usually corrected)  favors the A allele. Hence, the A allele occurs less frequently in the AA genotype (relatively) and more frequently in the Aa genotype. This happens for the sole reason that some aa individuals die or fail to reproduce as much. Aa individuals, on the other hand, succeed just as well.

The second case (more  homozygotes) occurs when one of the criteria (1 - 4) favors the a allele. This is because all heterozygotes are afflicted with the A allele are also selected against. Only aa is favored.

Evolution is a change is allelic frequencies beyond what would be predicted by the Hardy Weinberg equations in a population.

Thus, if the devs nerf illuminators, we would certainly expect to see more homozygotes (aa). This is evolution.

Importantly, 5) mutation, the random creation of new alleles is a fifth means of evolution. If a newly created allele is favored, that works a lot like a new allele flowing into the population, say a new dominate allele that causes players to spam fighters.

P.S. The preceeding information describes microevolution. Macroevolution includes the concept that microevolution cummulates in speciation, through the formation of either a pre-zygotic or a post-zygotic barrier between two sides of a population. This can happen through geographical isoltation or bi-directional selection, in which case two distinct forms of a species are viable. One simple example of speciation is the formation of a new species through polyploidic events. These occur commonly in plants. Abstract evidence for the role of speciation through time include: molecular conservation, morphological homology, embryological evidence, fossil evolution through strata, and adaptive radiation.

                               --     Docta' Cscoles