HUMAN BIOLOGY

458 Chapter 23

Recently, paleoanthropologists

announced the discovery in a South

African cave of fossil remains of a new

species of hominin, Australopithecus

sediba. It is the most humanlike

australopith discovered so far, with a

humanlike face. It also walked upright.

Some researchers are pointing to

A. sediba as a long-sought “missing

link” between apes and the hominin

lineage to which humans belong. Future

study may reveal if this is the case.

your future

Figure 23.26 Genetically, the world’s remaining cheetahs vary

only a little—the result of inbreeding. (© Maggy Meyer/Shutterstock.com)

5. Comparative biochemistry.
   a. is based mainly on the fossil record
   b. often reveals similarities in embryonic development
   stages that indicate evolutionary relationships
   c. is based on mutations that have accumulated in the
   DNA of different species
   d. compares the proteins and the DNA from different
   species to reveal relationships
   e. both c and d


6. Comparative morphology.
   a. is based mainly on the fossil record
   b. shows evidence of divergences and convergences in
   body parts among certain major groups
   c. compares the proteins and the DNA from different
   species to reveal relationships
   d. both b and c


7. In , new species of a lineage move into a wide range
   of habitats by way of bursts of microevolutionary events.
   a. an adaptive radiation
   b. natural selection
   c. genetic drift
   d. punctuated equilibrium


8. The pivotal modification in hominin evolution was.
   a. the transition to bipedalism
   b. hand modification that increased manipulative skills
   c. a shift from omnivorous to specialized eating habits
   d. less reliance on smell, more on vision
   e. expansion and reorganization of the brain

CritiCaL tHinKing

1. The cheetahs in Figure 23.26 are among the roughly
   20,000 of these sleek, swift cats left in the world. One
   reason cheetahs have become endangered is that about
   10,000 years ago cheetahs experienced a severe loss in
   their numbers, and since then the survivors have been
   inbreeding. As a result, today’s cheetah gene pool has very
   little variation and includes alleles that reduce the sperm
   counts of males and impair the animals’ resistance to
   certain diseases. Based on what you’ve read in this chapter
   about genetic variation, does it seem likely that a “gene
   therapy” program might be able to correct the genetic
   problems and help cheetahs make a comeback? Explain
   your answer.


2. Humans can inherit various alleles for the liver enzyme
   ADH (alcohol dehydrogenase), which breaks down alcohol.
   People of Italian and Jewish descent commonly have a
   form of ADH that detoxifies alcohol very rapidly. People
   of northern European descent have forms of ADH that are
   moderately effec tive in alcohol breakdown, while people

of Asian descent typically have ADH that is less efficient at

processing alcohol. Explain why researchers have been able

to use this information to help trace the origin of human

use of alcoholic beverages.

3. In 1992 the frozen body of a Stone Age man was discovered
   in the Austrian Alps. Although the “Iceman” died about
   5,300 years ago, his body is amazingly well preserved and
   researchers have analyzed DNA extracted from bits of
   his tissue. Can these studies tell us something about early
   human evolution? Explain your reasoning.

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