Final answer:
The H2 haplotype in Icelanders is seen as an example of natural selection because of its protective benefits against historical diseases such as the plague or smallpox and its significant prevalence in that population. Genetic drift influences allele frequency, but natural selection can guide the retention of beneficial traits, as evidenced by the survival of this haplotype over time.
Step-by-step explanation:
Scientists believe that the H2 haplotype is likely a current example of natural selection at work on the genes of Icelanders due to its significant prevalence in that population and its connection to historical survival advantages. The H2 haplotype might have been selected for in European populations through exposure to diseases such as the plague or smallpox.
Research suggests that the mutation associated with this haplotype may protect individuals from these diseases - the mutation has been present long before HIV appeared and may confer a survival advantage that allows the haplotype to persist and increase in frequency over time.
In the context of genetic drift, such an advantage is crucial because genetic drift can lead to the elimination of an allele by chance, particularly in small, isolated populations like those found on islands. When alleles provide a survival benefit, they are more likely to be passed on to subsequent generations despite the random process of genetic drift.
Additionally, the historical pattern of human migration and reproduction, as depicted in the Viking invasions, shows how favorable mutations can spread within and beyond geographically isolated populations.
Therefore, the presence and prevalence of the H2 haplotype in Icelandic and other northern European genomes is indicative of evolutionary forces such as natural selection acting upon those populations, favoring the retention and spread of advantageous genetic variants.