Tools and hand bones excavated from the Swartkrans cave
complex in South Africa suggest that a close relative of early humans known as
Australopithecus robustus may have made and used primitive tools long before
the species became extinct I million
Line years ago. It may even have made and used primitive tools long
before humanity’s direct ancestor, Homo habilis, or “handy man,” began doing
so. Homo habilis and its successor, Homo erectus, coexisted with
Australopithecus robustus on the plains of South Africa for more than a million
years.
The Swartkrans cave in South Africa has been under
excavation since the 1940’s. The earliest fossil-containing layers of
sedimentary rock in the cave date from about 1.9 million years ago and contain
extensive remains of animals, primitive tools, and two or more species of
apelike hominids. The key recent discovery involved bones from the hand of
Australopithecus robustus, the first time such bones have been found.
The most important feature of the Australopithecus robustus
hand was the pollical distal thumb tip, the last bone in the thumb. The bone
had an attachment point for a “uniquely human” muscle, the flexor pollicis
longus, that had previously been found only in more recent ancestors. That
muscle gave Australopithecus robustutJ an opposable thumb, a feature that would
allow them to grip objects, including tools. The researchers also found
primitive bone and stone implements, especially digging tools, in the same
layers of sediments.
Australopithecus robustus were more heavily built- more
“robust” in anthropological terms-than their successors. They had broad faces,
heavy jaws, and massive crushing and grinding teeth that were used for eating
hard fruits, seeds, and fibrous underground plant parts. They walked upright,
which would have allowed them to carry and use tools. Most experts had
previously believed that Homo habilis were able to supplant Australopithecus
robustus because the former’s ability to use tools gave them an innate
superiority. The discovery that Australopithecus robustus also used tools means
that researchers will have to seek other explanations for their extinction.
Perhaps their reliance on naturally occurring plants led to their downfall as
the climate became drier and cooler, or perhaps Homo habilis, with their bigger
brains, were simply able tomake more sophisticated tools.
26. Where in the passage does the author mention the
materials from which tools were made?
(A) Lines 7-9
(B) Lines 12-13
(C) Lines 15-17
(D) Lines 21-23
Questions 27-38
The first two decades of this century were dominated by the
microbe hunters. These hunters had tracked down one after another of the
microbes responsible for the most dreaded scourges of many centuries:
tuberculosis, cholera, diphtheria. But there, remained some terrible diseases
for which no microbe could be incriminated: scurvy, pellagra, rickets,
beriberi. Then it was discovered that these diseases were caused by the lack of
vitamins, a trace substance in the diet. The diseases could be prevented or
cured by consuming foods that contained the vitamins. And so in the decades of
the 1920’s and 1930’s, nutrition became a science and the vitamin hunters
replaced the microbe hunters.
In the 1940’s and 1950’s, biochemists strived to learn why
each of the vitamins was essential for health. They discovered that key enzymes
in metabolism depend on one or another of the vitamins as coenzymes to perform
the chemistry that provides cells with energy for growth and function. Now,
these enzyme hunters occupied center stage.
You are aware that the enzyme hunters have been replaced by
a new breed of hunters who are tracking genes-the blueprints for each of the
enzymes-and are discovering the defective genes that cause inherited
diseases-diabetes, cystic fibrosis. These gene hunters, or genetic engineers,
use recombinant DNA technology to identify and clone genes and introduce them
into bacterial cells and plants to create factories for the massive production
of hormones and vaccines for medicine and for better crops for agriculture.
Biotechnology has become a multibillion-dollar industry.
In view of the inexorable progress in science, we can expect
that the gene hunters will be replaced in the spotlight. When and by whom?
Which kind of hunter will dominate the scene in the last decade of our waning
century and in the early decades of the next? I wonder whether the hunters who
will occupy the spotlight will be neurobiologists who apply the techniques of
the enzyme and gene hunters to the functions of the brain: What to call them? The
head hunters. I will return to them later.
27. What is the main topic of the passage?
(A) The microbe
hunters
(B) The potential of genetic engineering
(C) The progress of
modem medical research
(D) The discovery of
enzymes
28. The word “which” in line 4 refers to
(A) diseases
(B) microbe
(C) cholera
(D) diphtheria
29. The word “incriminated” in line 4 is closest in meaning
to
(A) investigated
(B) blamed
(C) eliminated
(D) produced
30. Which of the following can be cured by a change in diet?
(A) Tuberculosis
(B) Cholera
(C) Cystic fibrosis
(D) Pellagra
31. The word “strived” in line 9 is closest in meaning to
(A) failed
(B) tried
(C) experimented
(D) studied
32. How do vitamins influence health?
(A) They are necessary for some enzymes to
function.
(B) They protect the
body from microbes.
(C) They keep food
from spoiling.
(D) They are broken
down by cells to produce energy.
33. In the third paragraph, the author compares cells that
have been genetically altered by biotechnicians to
(A) gardens
(B) factories
(C) hunters
(D) spotlights
