A population of rabbits comes in a range of fur colors from black to white furs. Most of the rabbits, however, have gray fur. The color of the fur is not related to the sexes of the rabbits. Several generations into the future, majority of the population is either black rabbits or white rabbits. This population may be affected by

Astudy by solloch and et. al., in 2017, gives the map above which shows the frequency of alleles with a ccr5-delta32 mutations over 87 different countries. this mutation deletes the presence of a co-receptor (ccr5) on the outside of human t-cells (lymphocytes). some viruses, such as the one responsible for the black death and human immunodeficiency virus (hiv), require this receptor for attachment to host cells during the infection process. the black death was an epidemic that passed over northern europe during the 14th century killing nearly 60% of europeans. according to this information, which explanation best explains why northern europeans show a greater immunity for hiv than some other parts of the world?