always more aggressive than females, although, testosterone levels are a much more feasible explanation. Other evolutionary and genetic explanations of violent behaviour include: dopamine receptors mutations, DRD2 and DRD4, that, when mutate simultaneously, are hypothesized to cause personality disorders, low serotonin levels increasing irritability and gloom and the effects of testosterone on neurotransmitter functioning to explain the increased occurrence of aggression in males. Effects of mutations on mating Behavioural mutations play a detrimental part towards the genomes of many species, however, they can greatly affect the outcome of mating; affecting the success of fitness, how many offspring will arise and the likelihood that the male will actually procreate. When mutations affect the mating habits of species, different traits that would otherwise benefit the species procreating are compromised. A couple chemicals that are altered from mutation and have a great impact on mating, are dopamine and serotonin. Each of these chemicals either has a reaction to how the animal acts, or how the species body is formed to benefit their mating success. An example of a mutation in serotonin was found in a species of Nematodes. The serotonin caused their tails to curl during mating, when the mutation occurred the tails did not curl. Without the curling of the tail the nematode was unlikely to find the hermaphrodites sex organs to procreate, and results in less of that nematodes sperm being spread to other offspring. Another example is when the D1 dopamine receptor has a mutation on it; the arousal of a Drosophila melanogaster is increased, which also increases the courtship of the animal. One example of a study was found in the 'yellow' D.melanogaster, the mating of these males was only beneficial when it was dark outside, or when they were in a dark environment. The mutation is not yet known why it occurs this way, but studies have mentioned that the females of this fly species may be turned off by the certain colour of the mutated fly, and therefore in the dark the female is less likely to tell what colour this fly is. A beneficial component of a mutation in the behaviour of a mating D. melanogaster, was when the mutation caused the male to have a longer courtship time period. The flies that had a longer courtship had a tendency to have a higher probability of procreating. This means that the fly that took longer to