Deck 6: Human Variation and Adaptation

Question 1

This chapter's "Appreciating Diversity" segment describes recent DNA analysis of Australian Aborigines, which revealed that their ancestors branched off from ancestral Europeans and Asians 70,000 to 50,000 years ago. This research indicates

A) Aborigines developed a dark skin color independently from Africans.
B) Australian Aborigines are direct descendants of the first modern humans to leave Africa.
C) Aboriginal Australians have a more recent population history than Europeans.
D) Aborigines maintained regular contact with people from other continents.
E) Ancestral Aborigines had cultural but not genetic isolation.

Answer 1

Australian Aborigines are direct descendants of the first modern humans to leave Africa.

Question 2

Bergmann's rule states that average body size tends to

A) decrease at high elevations and increase in low ones.
B) increase in cold climates and decrease in hot ones.
C) decrease in cold climates and increase in hot ones.
D) decrease at low elevations and increase in high ones.
E) decrease where the air is thinner and increase where it is thicker.

Answer 2

increase in cold climates and decrease in hot ones.

Question 3

In understanding the problems with attempts at human racial classification, why is it important to understand the difference between genotype and phenotype?

A) Phenotypic traits typically used to classify humans into races go together as genetic units.
B) Phenotypic similarities and differences always have a genetic basis.
C) Attempts at human racial classification have typically used genotypic traits like blood type as markers of common ancestry, and these traits pass on from generation to generation in discrete bundles.
D) Although phenotypic characteristics may change, the genetic material of populations stays the same for a long time.
E) Attempts at human racial classification have typically used phenotypic traits like skin color as markers of common ancestry, but many such traits do not reflect shared genetic material. Instead, they are often the result of different populations biologically adapting to similar environmental stressors in similar ways.

Answer 3

Attempts at human racial classification have typically used phenotypic traits like skin color as markers of common ancestry, but many such traits do not reflect shared genetic material. Instead, they are often the result of different populations biologically adapting to similar environmental stressors in similar ways.

Question 4

What does the relationship between genetic traits and the prevalence of diseases such as malaria and smallpox illustrate?

A) how with technology, human biology is less important to human survival
B) the shortcomings of research that focuses on environmental variability but ignores populational genetics
C) how despite some evidence to the contrary some human races are better than others
D) the mechanisms of hominid evolution
E) the ways in which human biological diversity reflects adaptation to such environmental stresses as disease, diet, and climate

Question 5

Traditional racial classification assumed that biological characteristics such as skin color were determined by heredity and remained stable over many generations. We now know that

A) skin color is actually determined throughout child development.
B) skin color is determined by sun exposure and the amount of melanin in our diets.
C) a biological similarity such as skin color is also the result of natural selection working among different populations that face similar environmental challenges.
D) skin color is determined by a single gene that is prone to mutations over many generations.
E) a biological similarity such as skin color is always the result of both common ancestry and natural selection.

Question 6

An examination of racial taxonomies from around the world would indicate that

A) all cultures classify races similarly.
B) the classification of racial types is an arbitrary and culturally specific process.
C) classifying racial types can best be done by considering only phenotypic traits.
D) classifying racial types can best be done by considering only genotype.
E) the best classification of racial types considers genotype as well as phenotype.

Question 7

What is the term for a gradual shift in gene frequencies between neighboring populations?

A) cline
B) genotype
C) phenotype
D) cluster
E) allele

Question 8

What is a phenotypic adaptation, and what makes it possible?

A) It is a genotypic adaptation that is expressed in the phenotype. It is made possible by the close relationship between our manifest biology and our genes.
B) It occurs when genetic changes occur during an individual's lifetime. It is made possible by human genetic plasticity.
C) It is a phenotypic adaptation made possible by culture's power over biology.
D) It happens when adaptive changes occur during an individual's lifetime. It is made possible by human biological plasticity, our ability to change in response to the environments we encounter as we grow.
E) It is a biological adaptation that occurs during an individual's lifetime and, if critical enough to survival, will actually modify the genotype.

Question 9

According to Allen's rule, the relative size of protruding body parts, including limbs, ears, tails, fingers, and toes,

A) decreases with temperature.
B) increases with altitude.
C) decreases with altitude.
D) increases with temperature.
E) increases with humidity.

Question 10

Which of the following statements about the concept of race as applied to humans is true?

A) It is a discredited concept in biology.
B) It is based on the Western science of genetics.
C) It is determined by the juxtaposition of alleles.
D) It does not include what used to be called subraces, because these are now known as ethnic groups.
E) It has been verified by recent fossil finds in the Neanderthal Valley in Germany.

Question 11

Which of the following statements about attempts to assign humans to discrete racial categories purportedly based on common ancestry is true?

A) They are applied to endogamous breeding populations.
B) They are based on genotypic rather than phenotypic characteristics.
C) They are based on global racial categories that vary little from one society to another.
D) They are a recent phenomenon brought on by globalization.
E) They are culturally arbitrary, even though most people assume they are based in biology.

Question 12

The explanations given in this chapter for the differences in and distribution of skin color in populations around the world are examples of

A) punctuated equilibrium.
B) the social construction of so-called scientific categories.
C) attempts at classifying human groups into clines.
D) explanatory approaches to human biological diversity.
E) how having a political interest in justifying racial policies interferes with objective science.

Question 13

Which of the following statements about human skin color is NOT true?

A) Skin color varies because of differences in ultraviolet radiation between different regions of the world.
B) The amount of melanin in the skin affects the body's production of vitaminD.
C) The amount of melanin in the skin affects the body's ability to process lactose.
D) Light skin is at a selective advantage outside the tropics because it admits ultraviolet radiation that causes the body to manufacture vitamin D, helping to prevent rickets and osteoporosis.
E) Light skin is at a selective disadvantage in the tropics because it is more susceptible to the destruction of the folate that is needed to produce folic acid, which protects against neural tube defects in human embryos.

Question 14

Which of the following is the best example of how diseases have been powerful selective agents for humans, particularly before the arrival of modern medicine?

A) Smallpox, which appeared after people and animals started living together, has worked as a selective agent against people with sickle-cell anemia.
B) Blood type A individuals are more prone to stomach and cervical cancer. Since these diseases usually occur after reproduction has ended, they are particularly powerful agents in adaptation and evolution through natural selection.
C) Blood type O will soon become something of the past, since it does not confer an advantage to any disease.
D) Smallpox, which appeared after people and animals started living together, has worked as a selective agent for people with blood types B and O who have an ability to produce antibodies against smallpox.
E) Diseases no longer work as powerful selective agents for humans, thanks to the widespread availability of modern medicine.

Question 15

Recall the mechanisms of genetic evolution discussed in the previous chapter. What is the relationship between gene flow and the existence of clines between human populations?

A) Gene flow increases the genetic isolation of neighboring groups, resulting in discrete populational genetic differences instead of clines.
B) There is no relationship between gene flow and clines.
C) Gene flow, the exchange of genetic material across populations, results in clines, which are gradual shifts in gene frequencies between neighboring groups.
D) Clines accelerate gene flow and genetic change due to chance.
E) Gene flow causes abrupt differences in gene frequencies between neighboring groups.

Question 16

East Asians who have migrated recently from India and Pakistan to northern areas of the United Kingdom have a higher incidence of rickets and osteoporosis than the general British population. This illustrates that

A) natural selection continues today.
B) genetic adaptation of environmental stressors can occur within one generation.
C) cultural adaptation provides effective shortcuts to the genetically disadvantaged in a foreign environment.
D) because of global warming, the lack of sunlight that people are exposed to in these northern regions is made up for by the intensity of the sunlight.
E) natural selection's role in determining skin color is a thing of the past, relevant only prior to the sixteenth century when massive populational migrations altered the geographic distribution of dark-skinned people.

Question 17

Which of the following is the best plan of action for a light-skinned woman of childbearing age living in the tropics and concerned about giving birth to a child with neural tube defects (NTDs)?

A) using a tanning booth to give her skin accelerated protection against the sun
B) taking vitamin D supplements
C) drinking plenty of fluids to boost her body's thermoregulation
D) doing nothing, since a woman's chance of giving birth to a child with NTDs is genetically determined
E) taking folic acid/folate supplements and protecting herself against the sun with sunscreen, clothing, and shelter

Question 18

In the early twentieth century, anthropologist Franz Boas described changes in skull form among the children of Europeans who had migrated to North America. He found that the reason for these changes could not be explained by genetics. His findings underscore the fact that

A) phenotypic similarities and differences don't necessarily have a genetic basis.
B) though the environment influences phenotype, genetics is a more powerful determinant of racial differences.
C) diet affects which genes get turned off and which on, resulting in a particular phenotypic characteristic.
D) describing changes in skull form is the most accurate way to study the impact of migration on traveling populations.
E) observing changes over one generation is not enough to make conclusions about changes in genotype and phenotype.

Question 19

What term refers to an organism's evident traits, its "manifest biology"?

A) manifest destiny
B) genotype
C) biological circumscription
D) phenotype
E) hereditary inequality

Question 20

In theory, a biological race is a geographically isolated subdivision of a species. Humanity (Homo sapiens) lacks such races because

A) although humans exhibit biological differences, these are only skin deep.
B) human populations have experienced a type of controlled breeding distinct from that of dogs and roses.
C) human populations have not been isolated enough from one another to develop such discrete groups.
D) they are politically incorrect.
E) humans are less genetically predictable than animals and plants susceptible to domestication.

Question 21

Thanks to medical advances, genetic resistance to diseases no longer confers any selective advantage.

Question 22

Higher amounts of melanin in the skin inhibit the body's ability to manufacture vitamin D. This confers an adaptive advantage in environments with excessive sun exposure.

Question 23

There is much greater variation within each of the traditional so-called races than between them.

Question 24

Biological races have been scientifically discredited in their application not just to humans but to all living species.

Question 25

The only chance for human racial classification schemes to work is to shift from using phenotypic to genotypic characteristics of human populations.

Question 26

Phenotypic similarities and differences always have a genetic basis.

Question 27

Physical features cluster into discrete genetic units.

Question 28

Biologists have rejected the idea of three great races (white, black, and yellow) largely because it fails to account for Native Americans.

Question 29

One of the selective advantages of dark skin color in the tropics is that it reduces the susceptibility to folate destruction and therefore diminishes the likelihood of neural tube defects among human embryos. Folate is also necessary in men in order to maintain normal sperm production.

Question 30

Human biological differences are evident only to individuals who wrongfully sustain the validity of human races.

Question 31

The indigenous communities in the tropical regions of the Americas are not as dark skinned as populations living in other tropical regions, because the dense vegetation in this continent blocks out much of the sunlight.

Question 32

Genes and phenotypic adaptation work together to produce a biochemical difference between human groups in the ability to digest large amounts of milk. This is an adaptive advantage when

A) herding societies shift to a sedentary agricultural lifestyle.
B) mothers cannot wean their children from breast milk after they turn one year old.
C) other foods are scarce and milk is available, as it is in herding societies.
D) there is not enough lactose in the diet.
E) lactase, the enzyme that breaks down lactose, is not produced in enough quantities to keep up with dietary intake.

Question 33

Rickets is caused by an overabundance of vitamin D in the body.

Question 34

Historically, scientists have approached the study of human biological diversity in two main ways: racial classification (now largely abandoned) versus the current explanatory approach, which focuses on understanding specific differences.

Question 35

Skin color is a simple biological trait that is influenced by one gene and environmental exposure to sunlight.

Question 36

Indigenous highlanders living in the Andean Altiplano in South America, in the Tibetan plateau in Asia, and at the highest elevations of the Ethiopian highlands in East Africa have all adapted to living in an environment of oxygen-thin air. Researchers have found that

A) each population has evolved its own distinctly different biological adaptation to this environment.
B) these populations share the same mechanism of adaptation to hypoxic environments, proving that there was gene flow among these groups until very recently.
C) Andeans and Tibetans rely more on cultural means of adapting to hypoxic environments than highland Ethiopians do.
D) these populations illustrate humans' capacity to survive in extreme environments that have remained unchanged for more than 20,000 years.
E) cultural adaptations are more important than biological adaptations.

Question 37

Native Australians are closer genetically to tropical Africans than they are to Asians.

Question 38

Humanity (Homo sapiens) lacks distinct races because human populations have not been isolated enough from one another to develop into discrete groups.

Question 39

The role of natural selection in producing variation in human skin color illustrates the explanatory approach to explaining human biological diversity.

Question 40

In the case of skin color, natural selection is no longer active today, thanks to human cultural adaptations that confer an advantage no matter the skin color or environment one lives in.

Question 41

Populations living at high altitudes have all developed similar biological and cultural adaptations to hypoxic conditions.

Question 42

Populations in equatorial Africa and Papua New Guinea are phenotypically similar. They are both dark skinned, with similar hair and facial features. How would a typical racial model explain these similarities? How would evolutionary biology's explanation differ? Which model does a better job of explaining such data?

Question 43

According to Thomson's nose rule, longer noses are more adaptive to colder climates than shorter ones.

Question 44

Why do differences in skin pigmentation exist around the world?

Question 45

What is the difference between phenotypic adaptation and genetic adaptation? What role does each play in human evolution?

Question 46

How has contemporary work in genomics helped scientists address questions of human biological diversity?

Question 47

Support or refute this statement: By rejecting the race concept, anthropologists are ignoring obvious human biological variations.

Question 48

How does the concept of race used by anthropologists today differ from the concept used by early biologists?

Question 49

Allen's rule states that protruding body parts grow shorter as temperature increases.

Question 50

The Columbian exchange was a crucial early form of globalization, which led to the exchange of people, products, and pathogens between the Old and New Worlds. How does globalization remain an important component in the modern spread of disease? What are some present-day examples? How have humans adapted to the negative consequences of globalization?

Question 51

This chapter's discussion of lactose tolerance highlights how genes and phenotypic adaptation can work together to produce human biological diversity.