GENETIC DIVERSITY QUIZ
What differences make a difference?
- Approximately how old are modern humans?
- 170,000 years
- 40,000 years
- 70,000 years
- 1.2 million years
- 5 million years
- Which group has the most genetic variation?
- Fruit flies
- What is the source of genetic variation in humans?
- genetic drift
- natural selection
- sexual selection
- Which two present-day populations are most likely to be genetically
- Italians and Ethiopians
- Senegalese and Kenyans
- Italians and Swedes
- Chinese and Lakota (Sioux)
- Saudi Arabians and Ethiopians
- What caused differences in skin color to evolve?
- The environment
- Natural selection
- Sexual selection
- Tanning oil
- We don't know
- If you know a person's skin color, what can you predict about
- their blood type
- their height
- the likelihood they will get certain inherited diseases
- whether or not they have musical talent
- none of the above
- An individual from which country is most likely to carry
the sickle cell trait?
- South Africa
- Your ancestors are likely to include:
- Julius Caesar
- Qin Shi Huang - first emperor of China
- All of the above
- None of the above
- Which continent has the greatest human genetic diversity?
- North America
- South America
- If a catastrophe wiped out everyone except people in Europe,
how much of the total genetic variation in our species would
- A. 170,000 years
The earliest hominids evolved from apes about 5 million years
ago, but modern humans (Homo sapien sapiens) didn't emerge
until about 150,000 to 200,000 years ago in eastern Africa.
Our species first left Africa only around 70,000 years ago and
quickly spread across the entire world. All of us are descended
from these African ancestors.
- D. Fruit flies
Fruit flies have existed for a very long time and they also
have a short life span, so lots of genetic mutations have accumulated
over many generations. Modern humans are a relatively young
species, and we have always moved, mixed and mated, so we are
one of the most genetically similar of all species.
- A. Mutation
Genetic drift, natural selection and sexual selection act to
distribute traits, but new genetic variants arise only through
mutation - copying errors during reproduction. We all have the
same 35,000 or so genes, but some genes come in different forms,
called alleles. For instance, the gene that governs blood group
proteins comes in three variants, resulting in A, B or O blood
type. Some mutations are harmful, leading to stillbirth or deadly
diseases like spinal bifida. Those that are neutral or create
an evolutionary advantage are passed on and spread through successive
- E. Saudi Arabians and Ethiopians
Populations that live near each other geographically tend to
be more alike than populations 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 recent
"gene flow" - intermixing between these two groups. Often when
variation seems to follow "racial" lines, it is more accurately
explained by geographic proximity.
- E. We don't know
People in tropical areas tend to be darker, while northern and
southern populations tend to be lighter. Some scientists attribute
this to natural selection in response to ultraviolet (UV) light.
Dark skin blocks some UV radiation. Other scientists believe
that superficial physical differences arose from cultural preferences,
an evolutionary force known as sexual selection.
- E. None of the above
Most traits are governed by different genes, so they are inherited
independently. The presence of one trait doesn't necessarily
signal the presence of another trait. We think people come packaged
into groups, even - as anthropologist Jon Marks jokes, "color-coded
for our convenience" - but it turns out they don't. Visual traits
- skin color, for example - tell us nothing about deeper internal
differences or abilities.
- B. Greece
We often think of sickle cell as a "racial" disease that affects
people of African descent, but it evolved as a trait that confers
resistance to malaria. It occurs in people whose ancestors came
from regions where malaria was once common, like the Mediterranean,
Arabia, Turkey, southern Asia and western and central Africa,
but not in areas such as southern Africa. Ancestry, not race,
is a better indicator of whether or not one carries the markers
for sickle cell, Tay Sachs, porphyria and other genetic diseases.
- D. All of the above
We each have 2 parents, 4 grandparents, 8 great-grandparents.
Steve Olson and Joseph Chang point out 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 among
our ancestors. Olson writes that because of human migrations
and mating, "the DNA now in our cells consists of bits and pieces
of the DNA that was in thousands of people's cells a millennia
- E. Africa
All modern humans originated in Africa, and we spent most of
our evolution as a species together there. All the other populations
of the world can be seen as a 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.
- C. About 94% of our total human genetic variation would
If only the Swedes or Poles survived, we would still retain
about 85% of our genetic variation. This is because most variation
is within, rather than between, races. On average, any local
population contains 85% of all human genetic variation, and
any continent contains 94%. This is because humans have always
migrated and mixed their genes. Two random Swedes, for example,
are likely to be as different as a Swede and a Senegalese.