October 12, 2005
Human Diversity Quiz Answers
When it comes to human diversity, what differences really make a difference?
Question 1: Approximately how old are modern humans?
(A) 170,000 years
(B) 40,000 years
(C) 70,000 years
(D) 1.2 million years
(E) 5 million years
A -170,000
The earliest hominids evolved from apes about 5 million years ago but modern humans (homo sapien sapiens) didn’t emerge until 150,000 to 200, 000 years ago, in eastern Africa. Early humans first left Africa only about 70,000 years ago and quickly spread across the entire world. All humans are descended from these African ancestors.
Question 2: Which group has the most genetic variation?
(A) Humans
(B) Chimpanzees
(C) Penguins
(D) Fruit flies
(E) Elephants
D-Fruit flies
Fruit flies have existed for a long time and they have a short life span, so lots of genetic mutations have accumulated over millions of generations. Modern humans are a relatively young species and have always moved, mixed and mated. Humans are one of the most genetically alike of all species.
Question 3: What causes genetic variation in humans?
(A) Mutation
(B) Genetic Drift
(C) Natural selection
(D) Sexual selection
(E) Environment
A - Mutation
Genetic drift and natural selection act to distribute traits, but new variants arise only through mutations – copying errors during reproduction. All humans have the same 35,000 or so genes, but some come in different forms, called alleles, producing variations like A, B or O blood type. Some mutations are harmful, leading to stillbirth or deadly diseases like spina bifida. Those that are neutral or cause an evolutionary advantage are passed on and spread through successive generations.
Question 4: What two present day populations are most likely to be genetically similar?
(A) Italians and Ethiopians
(B) Senagalese and Kenyans
(C) Italians and Swedes
(D) Chinese and Lakota (Sioux)
(E) Saudi Arabians and Ethiopians
E - Saudi Arabians and Ethiopians
Populations that live near each other tend to be more alike than those that live far apart. We tend to think of Saudi Arabians and Ethiopians as different races, but they are most similar because there has been more “gene flow” (intermixing) between these two groups. Often when genetic variation seems to follow “racial” lines, it is more accurately explained by geographical distance
Question 5: What caused differences in skin color to evolve?
(A) The environment
(B) Natural selection
(C) Sexual selection
(D) Tanning oil
(E) We don’t know
E - We don’t know
People in tropical areas tend to be darker, while northern and southern populations are lighter. Some scientists think this is the result of natural selection in response to different levels of ultraviolet (UV) light. Other scientists believe that superficial physical differences arose from cultural preferences, known as sexual selection.
Question 6: If you know a person’s skin color, what can you predict about them?
(A) Their blood type
(B) Their height
(C) The likelihood they will get certain inherited diseases
(D) Whether or not they have musical talent
(E) None of the above
E - None of the above
Most traits are governed by different genes, so they’re inherited independently. The presence of one trait doesn’t necessarily signal the presence of another trait. Some think people come packaged into groups, even – as anthropologist Jon Marks jokes, “color-coded for our convenience” – but they don’t. Visual traits – skin color, for example – tell us nothing about internal differences or abilities.
Question 7: An individual from which of the following countries is most likely to carry the sickle cell trait?
(A) Ireland
(B) Greece
(C) South Africa
(D) Samoa
(E) Mexico
B - Greece
We often think sickle cell is a ‘racial’ disease affecting people of African descent, but it evolved as a trait that confers resistance to malaria. It occurs in people whose ancestors are from regions where malaria was most common, like the Mediterranean, Arabia, Turkey, southern Asia and western and central Africa, but not areas such as southern Africa. Ancestry, not race, is a better indicator of whether one carries the marker for sickle cell, Tay Sachs, porphyria and other genetic diseases.
Question 8: Which of the following is likely to be your ancestor?
(A) Nefertiti
(B) Julius Caesar
(C) Qin Shi Huang, first emperor of China
(D) All of the above
(E) None of the above
D - all of the above
We each have two parents, four grandparents, eight great-grandparents. Steve Olson and Joseph Chang have shown that if we go far enough back in time, only about 30 generations, we each have a billion potential ancestors, more than the population of the earth at the time. This means that any historical person living 1,600 years ago whose children had children is likely to be one of your ancestors. Olson writes that because of human migrations and mating, “the DNA now in our cells consists of bits and pieces of DNA from thousands of people’s cells a millennia ago.”
Question 9: Which continent has the greatest human genetic diversity?
(A) Europe
(B) Asia
(C) North America
(D) South America
(E) Africa
E - Africa
All modern humans originated from Africa, and we spent most of our evolution as a species together there. All the other populations of the world can be seen as subset of Africans. Every human trait found elsewhere can also be found in Africa, with the exception of a few recent variations favored by the environment, sexual selection or drift – such as light skin.
Question 10: If a catastrophe wiped everyone except people in Asia, how much of the total genetic variation in our species would be left?
(A) 50%
(B) 38%
(C) 94%
(D) 21%
(E) 74%
C - 94%
If only the Hmong or Hakka people survived, we would still retain about 85 percent of our genetic variation. That’s because most variation is within rather than between “races.” On average any local population contains 85 percent of all human genetic variation, and any continent contains 94 percent. This is because humans have always migrated and mixed their genes. Two random Swedes, for example, are as likely to be as genetically different as a Swede and a Senegalese.
NOTE: From the PBS special “Race, The Power of an Illusion.” http://www.pbs.org/race/004_HumanDiversity/004_00-home.htm
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