Chapter 24. Human Origins and Evolution

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

Humans originated in Africa, and subsequent migrations resulted in populations seeded by small groups with relatively small amounts of variation.

According to genetic analyses, approximately _____% of the genome of every non-African is derived from Neanderthals.

1-4

The fossil Lucy (Australopithecus afarensis) is significant because, at ____________ years old, hers is the first species to ____________.

3.2 million years; be fully bipedal

Imagine that one of your friends has just learned about the multiregional hypothesis, and she is astonished that humans evolved independently on different continents. What evidence would you provide your friend that contradicts the multiregional hypothesis?

Cann's research using mitochondrial DNA demonstrated that humans originated in Africa, and subsequently migrated to other continents.

All of the genetic differences between humans and chimpanzees are responsible for making us human.

False

Language is unique to humans

False

Cro-Magnon is the name of the group of the first Neanderthals found in Europe.

False It was a site in France

Which of the following organisms has the largest brain compared to their body size?

Human

There is a phenomenon called parental leakage, in which a small amount of the mitochondrial DNA from the father is found in the offspring. If parental leakage is assumed to occur in most matings, how would it change our interpretation of studies of mitochondrial DNA in human ancestors and in groups of different modern humans?

If it is truly a small amount, then those deviations shouldn't influence the conclusions generated from the study.

There is a phenomenon called parental leakage, in which a small amount of the mitochondrial DNA (mtDNA) from the father is found in the offspring. If parental leakage is assumed to have occurred throughout human history, how does it change our interpretation of Matthias Krings and Svante Pääbo's studies of mitochondrial DNA in specimens of Neanderthals and modern humans?

If paternal mtDNA with Neanderthal sequences did show up in the offspring alongside maternal mtDNA, these would have immediately indicated that the two groups interbred.

What is the order in which the ancestors of humans colonized the following regions?

Middle East; Asia; North America; Madagascar

There are seemingly conflicting studies that have taken a look at whether Neanderthals interbred with human ancestors. One study of mitochondrial DNA suggests that the two groups did not interbreed. Another study, of the whole genome, suggests that they did. Which of the following could explain these results?

Mitochondrial DNA is maternally inherited, so if Neanderthal females did not interbreed with our ancestors, Neanderthal mitochondrial DNA would never have entered the modern human gene pool.

Based on Figure 24.10, which of the following statements is TRUE?

Neanderthals are equally related to all non-African groups.

The first DNA comparison studies between humans and chimpanzees relied on which of the following?

The more complementary two strands of DNA are, the higher the melting point.

Which of the following is the most likely explanation for why the human brain is capable of so much more than what would be required for evolutionary fitness?

The additional capabilities are by-products of what was necessary for evolutionary fitness.

Which of the following explains how chimpanzees and humans can be so different with such similar genomes?

The genetic differences could have occurred in genes responsible for development.

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?

The number of differences among human populations will decrease.

There is some debate about whether Homo floresiensis is a separate species or an aberrant form of Homo sapiens. Regardless, what we do know is that H. floresiensis were only found on an Indonesian island and adults were only 3 feet tall. What factors would have selected for this distinct phenotype on an island habitat, specifically?

The smaller body size was advantageous for living on an island, as food is often limited on islands.

Consider the following hypothetical hominin lineage: Homo ergaster → Homo heidelbergensis → Homo sapiens. This is currently the accepted hypothesis because H. ergaster evolved into H. heidelbergensis.

True

In certain climates, specific hemoglobin and G6PD alleles have been selected for, as they confer some degree of resistance to malaria in humans.

True

It is possible that subtle changes in gene regulation allowed for human neoteny, whereby humans resemble juvenile chimpanzees more so than adult chimpanzees.

True

Phenotypic differences between humans and chimpanzees may be explained by the time during development when genes are turned on in humans and chimpanzees.

True

Why is it hypothesized that sexual selection is responsible for most of the variation seen in the human population?

because much of the variation is in visible characters

A young student is trying to figure out the order in which certain traits evolved in humans. Which of the arrangements below is most likely correct?

bipedalism → more dexterous thumbs → human jaw → language

Which of the following primates is the most closely related to humans?

chimpanzees

According to the multiregional hypothesis of human origins, modern H. sapiens evolved by _____ from _____ of H. ergaster.

convergent evolution; multiple Old World populations

You are visiting a relative many miles from your home, and you hear them complain about how all the squirrels in the area are making nests in the cars parked in the driveways. You note that their squirrels are the same species as the one you know from home. Where you live, most people park in their driveways too, but there the squirrels tend to nest in the roofs of houses. What does this difference in activity between these populations of squirrels reveal about the squirrels?

culture

A high degree of genetic variability among individuals of the same species means that these individuals will always appear morphologically different. For example, as all Adelie penguins look alike, this species must have a low degree of genetic variation.

false

Which of the following, if true, would force us to reevaluate the findings that Cann discovered with regard to the human family tree?

if early human material was discovered in Asia that had DNA completely different from the DNA found in early Homo sapiens in Africa

You are working in a lab and come across a gene, gene X, that you think might explain some of the differences seen between chimpanzees and humans. Which of the following results would support your hypothesis?

if gene X was active in humans, juvenile chimpanzees and inactive in adult chimpanzees

The neoteny hypothesis is supported by which of the following characteristics of humans? (Select all that apply.)

relative hairlessness large heads a foramen magnum positioned at the base of the skull

Although the FOXP2 amino acid sequence is highly conserved, humans have two unique amino acids that chimpanzees don't have. These unique amino acids are highly correlated with differences in _____ seen between chimps and humans.

speech and language

Cann's studies involving mitochondrial DNA showed that the two deepest branches of the human family tree are African. Which of the following observations explains this statement?

that all humans evolved in Africa and only later migrated to other places

The tree of human evolution is shallow. What does that mean?

that all humans, no matter how distantly related they are, share a recent common ancestor

Studies of the denaturation temperatures of hybrids of human and different apes' DNA provided us with what new information, after morphological studies fell short of resolving the primate phylogenetic tree?

that the chimpanzees are more closely related to humans than gorillas are

Which of the following would be considered types of culture?

the styles of dress demonstrated by different human populations the manner in which different populations of chimpanzees catch insects the songs sung by certain populations of birds the ability of certain bird populations to open milk bottles Correct: All of these choices are correct. All of these choices are correct.