Recent Adaptations in Humans
This tutorial describes three examples of recent human adaptations: lactose tolerance, sickle cell disease, and bitter taste perception.
Human populations in different parts of the world exhibit differences in traits, which may be adaptations to their local environments. In this Click & Learn, students learn about the evolution of three traits that vary in prevalence among human populations. The story of each trait touches on a different aspect of natural selection.
The first trait, lactose persistence, is the ability of adults to produce the enzyme lactase. Lactase is needed to digest lactose, a sugar found in milk. The second trait, sickle cell disease (also known as sickle cell anemia), is caused by a mutation in the protein hemoglobin. Although this mutation can change the shape of red blood cells and reduce blood flow, it may provide some advantages against the mosquito-borne disease malaria. The third trait, bitter taste perception, is the ability to taste the bitter substance phenylthiocarbamide (PTC). This ability depends on taste receptors on the tongue.
The accompanying worksheet guides students’ exploration.
Student Learning Targets
- Explain how lactase persistence is an example of gene-culture coevolution.
- Describe the correlation between the worldwide distribution of malaria and sickle cell disease.
- Propose a possible advantage of bitter taste perception.
allele, balancing selection, G6PD deficiency, genotype, haplotype, heterozygote advantage, lactose intolerance, mutation, natural selection, recombination
HS-LS4-2, HS-LS4-4; SEP6
EVO-1.C, EVO-1.D, EVO-1.G, EVO-1.H, EVO-1.J, EVO-1.O, EVO-3.A, SYI-1.G, SYI-3.D; SP1, SP6
3.1, 5.1, 5.2, 10.3
Topic(s): 2.6, 3.8, 5.3
Learning Objectives & Practices: ERT-2.H, EIN-1.C, EIN-2.C, SP5
CC1, CC2; DP1