Question 1

Among the factors listed below, which explains the phenotypic differences seen between individuals in the human population?

Accepted Answer

Each factor listed (presence of parasites, amount of sunlight, altitude, and natural selection) can influence phenotypic differences among individuals in the human population. These factors can affect health, physical traits, and adaptations to environments, thereby contributing to the diversity observed in humans.

Question 2

Population genetic studies of humans show a significant amount of variation across all humans.

Accepted Answer

Population genetic studies have consistently shown that there is a high degree of genetic diversity among humans, reflecting the evolutionary history of our species and the effects of genetic drift, gene flow, and natural selection.

Question 3

If favism-being a heterozygote for specific mutations in the G6PD gene-confers resistance to malaria, where should those mutations be prevalent?

Accepted Answer

The answer of If favism-being a heterozygote for specific mutations...

Question 4

Of the following list, which two factors are the main causes of differences among humans?
1) genetic variation
2) differences in brain size
3) differences in metabolism
4) environmental differences

Accepted Answer

Genetic variation and environmental differences are the main causes of differences among humans. While brain size and metabolism may vary slightly among individuals, they are not major drivers of differences among humans to the same extent as genetics and environment.

Question 5

The hemoglobin gene is the only gene that is under selection for resistance to malaria.

Accepted Answer

Other genes, such as those for sickle cell trait (HBB), thalassemia, and G6PD deficiency, are also under selection for resistance to malaria, not just the hemoglobin gene.

Question 6

What would you expect to be the differences in the frequencies of mutant forms of G6PD in human populations living at different latitudes?

Accepted Answer

G6PD deficiency is linked to protection against malaria because the parasite that causes malaria cannot replicate as effectively in red blood cells that have reduced G6PD levels. Malaria is more prevalent in tropical regions closer to the equator where the climate is warmer and wetter. Therefore, populations living in these regions are more likely to have a higher frequency of G6PD deficiency to provide protection against malaria. As latitude increases and environments become less tropical, the frequency of G6PD deficiency should decrease because the selective pressure for the trait is reduced.

Question 7

When we compare levels of genetic variation in a contemporary African population with that of a contemporary non-African population, we find there is more variation in the African population. The reason we see this pattern is that:

Accepted Answer

Non-African populations are the products of founder events, which means that a small group of individuals migrated out of Africa and established a new population elsewhere. This small group had only a fraction of the genetic diversity present in the larger African population, resulting in less genetic variation in non-African populations.

Question 8

Travel around the world has gotten a lot easier in the past century. It has become very common for immigrants to move to new areas, establish lives in regions other than where they were born, and find spouses in new regions. What, if any, changes to genetic diversity between populations will be the likely result of changes in mobility of humans?

Accepted Answer

Increased mobility and intermixing of populations through immigration and finding spouses in new regions lead to gene flow, which decreases genetic differences among human populations.

Question 9

If the groups we recognize as different human races represented populations that have been genetically isolated for a long time, we would expect to see:

Accepted Answer

The answer of If the groups we recognize as different...

Question 10

Why is it that there is LESS variation among individuals in any one non-African population than among individuals in the contemporary African population?

Accepted Answer

The genetic diversity in Africa has been found to be greater than that in other populations. This is because humans evolved in Africa, and as populations moved out of Africa, they represented only a subset of the African genetic diversity. Therefore, any one non-African population represents only a small portion of the total genetic variation present in the human population as a whole.

Question 11

Based on comparisons of many human DNA sequences, the amount of DNA variation among individuals in the human population is:

Accepted Answer

The answer of Based on comparisons of many human DNA...

Question 12

The genomes of a randomly selected person from Europe and a randomly selected person from Africa would on average have a greater amount of variation between them than the genomes of two randomly selected people of European descent.

Accepted Answer

This is because Europeans and Africans are more genetically different from each other compared to Europeans among themselves. Thus, the genomes of two individuals from different continents would have more differences than those of two individuals from within the same continent.

Question 13

Which of the following explains why the human population has so many phenotypic differences despite relatively low numbers of nucleotide differences from individual to individual?

Accepted Answer

Sexual reproduction allows for new genetic combinations of phenotypic variants, leading to a greater diversity in phenotypes despite relatively low numbers of nucleotide differences from individual to individual.

Question 14

Why does hair color vary among humans?

Accepted Answer

Hair color is determined by both genetic and environmental factors. Genetics play a major role in determining natural hair color, but exposure to sunlight, chemicals, and other factors can also cause changes in hair color over time. Therefore, both genetics and environment contribute to the variability in hair color among humans.

Question 15

Approximately 85% of human genetic variation occurs between individuals within a population (e.g., the Yoruba in West Africa), whereas _____% occurs between races.

Accepted Answer

Approximately 7% of human genetic variation occurs between races, highlighting that the vast majority of genetic diversity is found within populations rather than between them.

Question 16

If modern humans came from Africa, what explains the loss of pigmentation seen in different races?

Accepted Answer

The answer of If modern humans came from Africa, what...

Question 17

When we compare levels of genetic variation in a contemporary African population with that of a contemporary non-African population, we find there is:

Accepted Answer

Studies and genetic evidence have consistently shown that there is more genetic variation within African populations than in non-African populations. This is attributed to the fact that modern humans originated in Africa and have had a longer time to accumulate genetic diversity. Non-African populations are descended from groups that migrated out of Africa, carrying with them only a subset of the genetic diversity present in the African populations from which they originated.

Question 18

Although we must be cautious about oversimplifying, when visible traits are markedly different among human races, a likely explanation is that the differences have been favored by:

Accepted Answer

Visible traits can be influenced by natural selection and/or sexual selection, leading to the development of differences among human races.

Question 19

What evolutionary force definitely did NOT contribute to the obvious differences between races?

Accepted Answer

Gene flow, or the transfer of genes between populations, tends to reduce differences between populations, not increase them. The other options can contribute to the development of differences between races through various mechanisms.

Question 20

Why do African populations of humans have HIGHER levels of genetic variation compared with non-African populations?

Accepted Answer

The Out of Africa hypothesis proposes that modern humans originated in Africa and subsequently migrated to other parts of the world. As a result, non-African populations are seeded by small groups with relatively small amounts of variation compared to the larger, more genetically diverse African population.

Quiz 24: Human Origins and Evolution