Evolution is the development of life on earth. This process began billions of years ago and is continuing to this day. Evolution tells us how the enormous diversity of life could develop. It refers to any change in the distribution of alleles within a population over time. In the early 19th century Jean-Baptiste Lamarck (1744–1829) was the first to fully form an evolution theory of the transmutation of species. In 1858 Charles Darwin and Alfred Russel Wallace, both naturalists published a new evolutionary theory by natural selection. For a population to evolve, it must meet 5 main mechanisms.
Migration can be a strong agent in evolution. The movement of populations, groups or individuals can introduce new alleles or existing alleles but in different proportions than those who are currently already in the population. 60,000 years ago, the first humans left Africa, where we are thought to have originated from. Neanderthals became extinct shortly after humans entered Europe 40,000 years ago.
Mutation is the source of gene variation. Random changes in DNA described as copying errors that may be caused by toxins, other chemical substances or radiation. Sickle cell disease, the abnormal development of red blood cells is a mutation. It happens when two faulty copies of the gene are inherited by both parents. Although it does share a survival advantage against malaria fatality.
Natural selection is a process that favours heritable traits which are better adapted to an environment that will survive and reproduce. Advantageous alleles will then be passed on to offspring. An adaptation in humans is lactose tolerance. The ability to digest lactose usually disappears before adulthood but there was a mutation in the lactase gene. Therefore, individuals who could digest new foods had a selective advantage and the allele became common in Europe due to the increased nutrition from cow’s milk.
Genetic drift consists of two effects. The founder effect, smaller groups breaking off from a larger population resulting in the original population not being able to represent the full genetic diversity. The bottleneck effect, natural disasters can be the result of this. A severe amount of population is reduced and only a small assortment of survivors is left. In 1780 a typhoon wiped out Pingelap. 20 people survived including the king who was profoundly colour blind, who went on to reproduce passing on his characteristic, Pingelap is now known as ‘The Island of The Colour Blind’.
Non-random mating won’t make allele frequencies in the population change by itself, though it can alter a genotype frequency. Assortative mating is the preference for certain genotypes or phenotypes and disassortative mating is the complete opposite. For example, a person may choose according to their religious, professional interest or physical traits.
Argument – Attitude that evolution isn’t real is common amongst religious people as they already have their conclusion on how the world and humans came about. However, many people believe evolution is unscientific because it is not testable. It makes claims about events that were not observed and cannot be re-created.