Question

Describe one evolutionary change in the human lineage that did not result from positive natural selection. Your answer should reference at least one evolutionary mechanism.

Answer 1

Apart from Natural selection there are other mechanisms that has influenced evolution in human lineage like Genetic Drift, Mutation, non-random mating and Gene flow.

Mutation is one such crucial event that has resulted in bringing genetic variation in the population which is prerequisite for evolution. One such example is resistance to malaria.

# Haemoglobin gene HbS codes for protein which make red blood cells, any mutation in these genes, causes the ed blood cells take on a curved, sickle-like shape, the codition called sicke cell disease.

# The scientist investigated that found that African population ( from country  Burkina) have different variant of this mutation, the variant of called HbC. This gene codes for abnomal haemoglobin, by substituting glutamic acid residue with a lysine residue at the 6th position of the β-globin chain. Due to this the shape of the red blood cells become sickle shaped.

# People with one copy of mutated gene( heterozygous) confers 29 % of resistance to malaria, whereas people with two mutated genes ( homozygous) confers approx 93% of resistance to malaria.

# The basis of this phenomenon is still not understood completely, however, they are many hypothesis which were put forth, one such hypothesis is the enhanced immunity by sickle shaped red blood cells against malaria parasite. Another

# One more example benefecial mutation in the africal population is mutation in the duffy gene. This gene codes for the receptor proten on the red blood cells to which malaria parasite anchors and coferes the pathogenecity. Few regions of African polulation are resistant to Malaria due mutation in the duffy gene.