PETROLIUM
Petroleum is one of the most valuable natural resources
in the world. Some people call petroleum black gold, but it may
be better described as the lifeblood of industrialized
countries. Fuels made from petroleum provide power for
automobiles, airplanes, factories, farm equipment, trucks,
trains, and ships. Petroleum fuels also generate heat and
electricity for many houses and business places.
Altogether, petroleum provides nearly half the energy
used in the world.
In addition to fuels, thousands of other products are
made from petroleum. These products range from paving materials
to drip-dry fabrics and from engine grease to cosmetics.
Petroleum is used to make such items in the home as aspirins,
carpets, curtains, detergents, phonograph records, plastic toys,
and toothpaste.
Although we use a huge variety of products made from
petroleum, few people ever see the substance itself. Most of it
comes from deep within the earth as a liquid called crude oil.
Different types of crude oil vary in thickness and color,
ranging from a thin, clear oil to a thick, tarlike substance.
Petroleum is also found in solid form in certain rocks and
sands.
The word petroleum comes from two Latin words meaning
rock and oil. People gave it this name because they first found
it seeping up from the earth through cracks in surface rocks.
Today, petroleum is often referred to simply as oil, and most of
it is found in rocks beneath the earth's surface.
People have used petroleum for thousands of years. But
few people recognized its full value until the 1800's, when the
kerosene lamp and the automobile were invented. These inventions
created an enormous demand for two petroleum fuels, kerosene and
gasoline. Since about 1900, scientists have steadily increased
the variety and improved the quality of petroleum products.
Petroleum, like other minerals, cannot be replaced
after it has been used. People are using more and more petroleum
each year, and the world's supply is rapidly running out. If
present rates of consumption continue, petroleum may become
scarce sometime in the mid-2000's.
Most industrialized nations depend heavily on imported
petroleum to meet their energy needs. As a result of this
dependence, oil-exporting countries have been able to use
petroleum as a political and economic weapon by restricting
exports to some of these nations. Oil exporters have also
strained the economies of a large number of countries,
particularly the poorer ones, by drastically increasing the
price of petroleum.
To prevent a full-scale energy shortage, scientists are
experimenting with artificial forms of oil and with other
sources of fuel. But even if new energy sources appear quickly,
people will have to rely on petroleum for many years.
Conservation of oil has thus become urgent for every country.
People now need to be just as inventive in finding ways to
conserve petroleum as they have been in finding ways to use it.
ASTRONOMY
Astronomy is the study of the universe and the objects
in it. Astronomers observe the sky with telescopes that gather
not only visible light but also invisible forms of energy, such
as radio waves.
They investigate nearby bodies, such as the sun,
planets, and comets, as well as distant galaxies and other
faraway objects. They also study the structure of space and the
past and future of the universe.
Astronomers seek answers to such questions as: How did
the universe begin? What processes release energy deep inside
stars? How does one star "steal" matter from another? How do
storms as big as Earth arise on Jupiter and last for hundreds of
years?
To answer such questions, astronomers must study
several subjects besides astronomy. Almost all astronomers are
also astrophysicists because the use of physics is essential to
most branches of astronomy. For example, some parts of
cosmology, the study of the structure of the universe, require
an understanding of the physics of elementary particles, such as
the bits of matter called quarks that make up protons and
neutrons. Astronomers use chemistry to analyze the dusty,
gaseous matter between the stars. Specialists in the structure
of planets use geology.
Astronomy is an ancient science. Like today's
researchers, ancient scholars based their ideas of the universe
on what they observed and measured and on their understanding of
why objects move as they do. However, the ancients developed
some incorrect ideas about the relationships between Earth and
the objects they saw in the heavens. One reason for their errors
was that they did not understand the laws of motion. For
example, they did not know that a force--which we know as
gravitation--controls the movements of the planets. Another
reason was that their measurements did not reveal the movements
of the planets in sufficient detail.
The ancients noted that the positions of the sun, moon,
and planets change from night to night. We know that these
movements are a result of the revolution of the moon about Earth
and the revolution of Earth and the other planets about the sun.
The ancients, however, concluded that the sun, moon, and planets
orbit a motionless Earth. In many places, religious teachings
supported this conclusion until the 1600's.
Although ancient people misinterpreted much of what
they saw in the heavens, they put their knowledge of astronomy
to practical use. Farmers in Egypt planted their crops each year
when certain stars first became visible before dawn. Many
civilizations used the stars as navigational aids. For example,
the Polynesians used the positions of the stars to guide them as
they sailed from island to island over thousands of miles or
kilometers of the Pacific Ocean.
ISRAEL
Israel is a small country in southwestern Asia. It
occupies a narrow strip of land on the eastern shore of the
Mediterranean Sea. Israel was founded in 1948 as a homeland for
Jews from all parts of the world, and more than 4 out of 5 of
its people are Jews. Even Jews who live elsewhere consider
Israel their spiritual home. Almost all the non-Jews in Israel
are Arabs. Jerusalem is Israel's capital and largest city.
Israel makes up most of the Biblical Holy Land, the
place where the religious and national identity of the Jews
developed. According to the Bible, Abraham, the father of the
Jewish people, established a Semitic population in the Holy
Land. Many scholars believe this happened sometime between 1800
and 1500 B.C.
Eventually this land fell to a series of conquerors,
including--in 63 B.C.--the Romans. Following unsuccessful Jewish
revolts against Roman rule in A.D. 66-70 and A.D. 132-135, the
Romans forced most of the Jews to leave. The Romans then began
to call this region by the word that became Palestine in
English. Palestine was ruled by the Roman and then the Byzantine
empires until the A.D. 600's, when Arabs conquered the region.
From that time until the mid-1900's, the majority of people in
Palestine were Arabs.
In the late 1800's, European Jews formed a movement
called Zionism, which sought to establish a Jewish state in
Palestine. Jewish immigrants began arriving in Palestine in
large numbers, and by the early 1900's friction had developed
between the Jewish and Arab populations. In 1947, the United
Nations (UN) proposed dividing the region into an Arab state and
a Jewish state.
On May 14, 1948, the nation of Israel officially came
into being. The surrounding Arab nations immediately attacked
the new state, in the first of several Arab-Israeli wars. In
1967, at the end of one of the wars, Israeli troops occupied the
Gaza Strip and the West Bank--territories that are home to more
than 1 million Palestinian Arabs. Israel's occupation of these
territories further inflamed Arab-Israeli tensions. In 1994,
Israeli troops withdrew from the Gaza Strip, and by 1996, they
had withdrawn from most cities and towns of the West Bank. The
withdrawals were part of 1993 and 1995 agreements with the
Palestine Liberation Organization (PLO), which represents
Palestinian Arabs. For more details, see the Recent developments
section of this article.
Israel has few natural resources and imports more goods
than it exports. Still, it has achieved a relatively high
standard of living. Almost all of its adults can read and write,
and the level of unemployment is low. Jewish settlers have
established major industries, drained swamps, and irrigated
deserts. Although it is a small country, Israel has a diverse
terrain that includes mountains, deserts, seashores, and
valleys. Israel has a pleasant climate, with hot, dry summers,
and cool, mild winters.
TENSIONS BETWEEN ISRAEL
AND THE PALESTINIANS
Recent developments. From the mid-1980's to the early
1990's, thousands of Ethiopian Jews moved to Israel. Also,
hundreds of thousands of Soviet Jews moved there. The influx of
newcomers led to problems in housing and employment. Israel
continued to build new settlements in occupied territories, in
part to accommodate the immigrants. Despite protests from
Palestinians, Shamir and Likud backed these construction
projects.
In August 1990, Iraq invaded Kuwait. In early 1991, the
United States and other countries defeated Iraq in the Persian
Gulf War. During the war, Iraq fired missiles at Israel. In
October 1991, peace talks began between Israel, Syria, Lebanon,
and a joint Jordanian-Palestinian delegation. Israel's Labor
Party gained control of the government in June 1992
parliamentary elections. In July, Labor Party leader Yitzhak
Rabin replaced Shamir as prime minister. Rabin agreed to limit
construction of new Jewish settlements in the occupied
territories as a step toward a peace agreement.
The PLO was not a participant in the peace talks that
began in October 1991. But in September 1993, Israel and the PLO
recognized each other and signed an agreement that included
steps to end their conflicts. As a result of this agreement and
another signed in September 1995, Israel withdrew its troops
from the Gaza Strip and most cities and towns of the West Bank
by early 1996. Palestinians took control of these areas. In
October 1994, Israel and Jordan signed a peace treaty that
formally ended the state of war that had technically existed
between the countries since 1948. Not all Israelis agreed with
the peace process, and some protested it. Some opponents argued,
for example, that Israel was giving away land that should
historically belong to it. On Nov. 4, 1995, Rabin was
assassinated in Tel Aviv by a right-wing Israeli university
student who was opposed to his policies. Following the
assassination, Peres, who had been foreign minister, became
prime minister.
In May 1996, Israel held its first elections in which
the people directly voted for the prime minister. Benjamin
Netanyahu, the Likud leader and a critic of the Israeli-PLO
peace agreements, defeated Peres in the elections. Netanyahu
claimed that the peace agreements do not include enough
provisions for Israel, such as guaranteed security and allowance
for its population growth.
Tensions between Israel and the Palestinians grew after
the 1996 elections. In 1996 and 1997, Israel announced plans to
expand Israeli settlements in the West Bank and to build new
Israeli housing in East Jerusalem. Both decisions met with angry
and violent protests from the Palestinians. Also in 1997,
however, Israel completed an agreement with the PLO over the
withdrawal of Israeli troops from most of the West Bank city of
Hebron.
In October 1998, Israel and the Palestinians signed
another agreement, called the Wye Rive Memorandum. The accord
called for Israel to turn over more land in the West Bank to
Palestinian control, and it allowed a Palestinian airport in the
Gaza Strip to open. Also as a result of the agreement, the PLO
revised its charter to remove language calling for the
destruction of Israel. Many conservative members of the Israeli
parliament and in Netanyahu's Cabinet opposed the accord. In
December 1998, Netanyahu, claiming that the PLO was not
fulfilling its security commitments, suspended Israeli troop
withdrawals. That same month, the Israeli parliament voted to
dissolve itself and scheduled new elections.
In May 1999, Ehud Barak, leader of the Labor Party, was
elected prime minister of Israel. Barak favored renewing the
peace process with the Palestinians. In September, Barak and
Palestinian leader Yasir Arafat signed a new agreement that
revived and expanded on the previous Wye River Memorandum.
Israel resumed its troop withdrawals from the West Bank shortly
after the agreement was signed.
In May 2000, Israel withdrew its troops from the
security zone it had established in southern Lebanon. Hezbollah
guerrillas then took control of the area. Hezbollah, also
spelled Hizbollah, is a movement that opposed the Israeli
occupation of Lebanon. Guerrillas from the group had often
clashed with the Israelis and the Israeli-backed South Lebanon
Army.
BILL GATES
Gates, Bill (1955-...), is a cofounder and the chairman
and chief software architect of Microsoft Corporation. From 1975
until 2000, he also served as Microsoft's chief executive
officer. Microsoft is the world's largest developer and
publisher of software programs for personal computers.
William Henry Gates was born in Seattle. He set up his
first software company at age 15 with a schoolmate named Paul
Allen. In 1975, he and Allen began to design programs for
personal computers, which had just entered the marketplace. The
two founded Microsoft that year. In 1980, International Business
Machines Corporation (IBM) chose Microsoft to develop the
operating system for its first personal computer, the PC. An
operating system is a special type of program that contains
instructions for the operation of the computer. Gates devised
the Microsoft Disk Operating System (MS-DOS) for IBM. Millions
of copies of MS-DOS were sold for use in IBM and IBM-compatible
PC's.
Microsoft continued to grow under Gates's guidance. In
1985, the company introduced the first of a series of PC
programs called Windows. These programs enable users to perform
multiple tasks through "windows" on the computer screen and to
issue commands by pointing at onscreen symbols rather than by
typing instructions. Microsoft has sold millions of copies of
Windows.
Microsoft Corporation is the world's largest developer
and publisher of software programs for personal computers. In
addition, Microsoft operates online services and a
cable-television news channel. The company also produces
software for the operation of electronic devices other than
computers.
Microsoft began in 1975 as an informal business
partnership between former schoolmates Bill Gates and Paul
Allen. The two men adapted the programming language BASIC
(Beginner's All-purpose Symbolic Instruction Code) for use with
the earliest home computer, the MITS (Micro Instrumentation and
Telemetry Systems) Altair 8800. They were soon writing programs
for other manufacturers' computers. In 1980, International
Business Machines Corporation (IBM) chose Microsoft to develop
the operating system for its first personal computer, the PC. An
operating system is software that contains instructions for all
of a computer's functions. Millions of copies of the Microsoft
Disk Operating System (MS-DOS) were sold for use in IBM
computers and IBM-compatible PC's.
In 1985, Microsoft introduced the first of a series of
operating systems called Windows. These programs employ a
graphical user interface (GUI), which allows people to issue
commands by pointing to on-screen symbols and clicking a mouse
rather than by typing instructions. The program also enables
people to perform multiple tasks, each in a different "window"
on the computer screen. Microsoft has sold millions of copies of
Windows. The company also produces other software products for
business and consumer use. These products include Excel, a
spreadsheet program; FoxPro, a database-management program; and
Word, a word-processing program.
In 1998, the United States Department of Justice, along
with 20 state attorneys general and the corporation counsel for
the District of Columbia, filed an antitrust suit against
Microsoft. Later that year, one of the states, South Carolina,
withdrew from the suit. The lawsuit charged that the company
used unfair practices to destroy its competitors. Following a
1999 trial, a federal district court judge, Thomas Penfield
Jackson, found that the Microsoft Corporation is a monopoly that
has harmed competitors and consumers. He appointed a judge of
the U.S. Court of Appeals to help the company and the government
negotiate a settlement. In April 2000, settlement talks broke
down, and Jackson found Microsoft guilty of violating U.S.
antitrust laws. In June 2000, Jackson ordered the corporation to
be split into two different companies--one that would produce
only operating systems and another that would produce and manage
other products and services. Microsoft officials appealed the
order.
GREECE
Greece is a small country where Western civilization
started about 2,500 years ago. In those days, Greece controlled
much of the land bordering the Mediterranean and Black seas.
Athens is the capital and the largest city of Greece. In Athens
and other parts of Greece, magnificent ruins stand as monuments
to the nation's glorious past.
About one-fourth of the workers in Greece earn their
living by farming, and agriculture is an important economic
activity. But mountains cover most of Greece, and the land is
rocky with little fertile soil. A Greek legend tells that God
sifted the earth through a strainer while making the world.
He made one country after another with the good soil
that sifted through, and threw away the stones left in the
strainer. According to the legend, these stones became Greece.
No part of Greece is more than 85 miles (137 kilometers) from
the sea. The Greeks have always been seafaring people. About a
fifth of Greece consists of islands. The mainland makes up the
southern tip of the Balkan Peninsula, extending into the
Mediterranean Sea. Many ancient Greek legends, including those
about Ulysses and Jason, center on sea voyages. Today, Greece
has one of the largest merchant fleets in the world.
The Greeks came under the control of invaders for more
than 2,000 years. They lost their independence to the
Macedonians in 338 B.C. The Greeks did not regain their
independence until A.D. 1829, from the Ottoman Empire. Since
then, Greece has had many serious political problems, largely
because of weak or undemocratic governments.
In ancient times, the Greeks established the traditions
of justice and individual freedom that are basic to democracy.
Their arts, philosophy, and science became foundations of
Western thought and culture.
World War I began in 1914. Venizelos urged that Greece
fight with the Allies against Germany and its partners. But King
Constantine, whose wife was a sister of Kaiser Wilhelm II of
Germany, kept Greece neutral. Venizelos started a revolutionary
movement. It was supported by the Allies, who had established a
military base at Thessaloniki. In 1917, Constantine was forced
to give the throne to his son, Alexander I. Greece entered the
war on the side of the Allies on July 2, 1917.
Thousands of Greek troops joined the British, French,
and Serbians at their Thessaloniki base, from which they
attacked the Bulgarians and Turks. In September 1918, the Greeks
and other Allied forces moved north. They defeated the
Bulgarians, who signed an armistice at Thessaloniki. The entire
war ended on November 11.
The peace treaties that followed World War I gave
Greece most of the territories it had long sought. From the
Ottoman Empire, Greece got eastern Thrace; some islands in the
Aegean Sea, including two at the entrance to the Dardanelles;
and temporary control of the Smyrna (now Izmir) region in Asia
Minor. The Greeks gained western Thrace from Bulgaria.
King Alexander died in 1920, and Constantine I returned
to the throne. In 1921, Constantine renewed the war against the
Ottoman Empire by sending Greek forces into Asia Minor. The
Ottomans dealt the Greeks a crushing defeat in 1922, and a
military revolt forced Constantine from the throne. His son,
George II, replaced him. A revolution ended the Ottoman Empire
in 1922. It became the Republic of Turkey the next year.
In 1923, under the Treaty of Lausanne, Greece returned
the Turkish territories it had gained after World War I. The
treaty also provided for ending the tensions produced by Turkish
rule over Greeks. It required over 1,250,000 Greeks in Turkey to
move to Greece and 400,000 Turks in Greece to move to Turkey.
After the Greek migration, the only Greeks under foreign rule
were in northern Epirus in Albania, British-held Cyprus, and the
Italian-held Dodecanese Islands.
WORLD
World is the planet earth viewed especially as the home
of human beings and other living things. The earth is just one
of countless heavenly bodies in the universe. But it is the only
one known to support life.
From the very beginning of their life on the earth,
people have had to adapt to conditions in the world to survive.
The earliest human beings lived by hunting and gathering wild
plants. They made clothing from animal hides and furs and used
branches and other natural materials to build shelters. About
10,000 years ago, some people began to raise plants and animals
after food became scarce. People who farmed could settle in one
place and produce enough food to feed many others. Villages grew
up, and people developed methods of living in large groups. New
occupations and forms of government became necessary. Over the
years, people created more advanced technology and increasingly
complicated forms of social life. They built great cities,
developed civilizations, and found ways to control many powerful
natural forces.
The world's surface consists of water and land. Air
surrounds the surface and extends to outer space. Water--chiefly
the great oceans--covers about 70 percent of the world's
surface. All living things must have water to live, just as they
must have air. People also use water for irrigation, industry,
power, and transportation. In addition, the oceans, lakes, and
rivers provide fish and other foods.
The oceans separate huge land masses called continents.
Most of the world's countries lie on the continents. Others are
on islands. Each country has its own political and economic
systems. However, countries cooperate with one another in many
ways. For example, they make trade agreements and sign treaties
designed to reduce the likelihood of war.
The physical features of a country strongly influence
where the people of that country live. People can most easily
grow food on plains or in river valleys, where the soil is rich
and deep. Mountainous regions generally are not suitable for
crop farming because the soil is thin and easily washed away by
rainfall. Many of the world's biggest cities began as important
trading centers on seacoasts, lakeshores, and riverbanks. Thus,
the majority of the world's people live on flat, fertile plains
and in large cities that border major water transportation
routes.
About 6 billion people live in the world. They are
distributed unevenly over the land. Many areas are heavily
populated. Other areas have no people at all. The population is
increasing far more rapidly in some countries than in others.
World is the planet earth viewed especially as the home of human
beings and other living things. The earth is just one of
countless heavenly bodies in the universe. But it is the only
one known to support life.
About 6 billion people live in the world. They are
distributed unevenly over the land. Many areas are heavily
populated. Other areas have no people at all. The population is
increasing far more rapidly in some countries than in others.
All the world's people belong to the same species, Homo sapiens,
which means they have a common ancestry. But many groups of
people have lived apart for such a long time that they have
developed certain physical variations.
Nations of the world The world has 192 independent
countries and about 40 dependencies. An independent country
controls its own affairs. Dependencies are controlled in some
way by independent countries. In most cases, an independent
country is responsible for the dependency's foreign relations
and defense, and some of the dependency's local affairs.
However, many dependencies have complete control of their local
affairs.
ENCYCLOPEDIA
Encyclopedia is a collection of information about
people, places, events, and things. It may deal with all areas
of knowledge or it may confine itself to just one area. A
general encyclopedia, such as World Book, includes information
on topics in every field of knowledge. Specialized encyclopedias
provide more detailed and technical information on specific
areas of knowledge, such as art, medicine, or the social
sciences.
In ancient times, scholars found that the information
they needed was scattered in manuscripts and scrolls in various
parts of the world. Some scholars made their own reference works
by copying long quotations from the works of other authors.
Others copied items of information from a variety of sources.
These ancient reference works were the ancestors of the
encyclopedia. But they differ from encyclopedias in many ways.
Early scholars presented information in any order they chose,
and they had few ways to check its accuracy. In addition, they
wrote only for themselves or other scholars.
Encyclopedia editors, on the other hand, carefully
organize their material and demand accuracy. They also present
information to a large, diverse audience.
The word encyclopedia comes from the Greek words
enkyklios paideia, meaning general or well-rounded education.
The word did not come into common use until the 1700's.
A well-planned general encyclopedia presents facts
about humanity; about beliefs, ideas, and achievements; about
the world people live in; and about the universe of which they
are a part. It presents these facts without prejudice, using
language that is easy to understand.
An encyclopedia is concerned with the who, what, when,
where, how, and why of things. For example, an article on radar
tells what radar is and who developed it, as well as when and
where. It also describes how radar operates and why it is
important in everyday life.
No one person can create a general encyclopedia. Such
an enterprise calls for the combined talents of scholars and
specialists, of editors and educators, of researchers and
librarians, and of artists, mapmakers, and production
specialists. It also calls for a large investment of money by
the publisher. To keep an encyclopedia abreast of events in all
fields of knowledge, the publisher must revise it on a regular
basis.
IMMIGRATION
Immigration is the act of coming to a foreign country
to live. The act of leaving one's country to settle in another
is called emigration. Immigrants who flee their country because
of persecution, war, or such disasters as famines or epidemics
are known as refugees or displaced persons (DP's).
Most people find it very hard to pull up roots in their
native land and move to a strange country. But throughout
history, countless millions of people have done so. The heaviest
immigration worldwide took place from the early 1800's to the
Great Depression--the economic hard times of the 1930's. In that
period, about 60 million people moved to a new land. Most came
from Europe. More than half emigrated to the United States.
Other destinations included Canada, Argentina, Brazil,
Australia, New Zealand, and South Africa. Today, the
availability of fast, safe, and cheap transportation helps make
migration easier. Asia is replacing Europe as the major
immigrant-sending area. The United States remains the chief
receiving nation. Causes of immigration
People forsake their homeland and move to another
country for various reasons. Some people emigrate to avoid
starvation. Some seek adventure. Others wish to escape
unbearable family situations. Still others desire to be reunited
with loved ones. However, the main reason for immigration has
long been economic opportunity--the lure of better land or a
better job. During the 1800's, for example, the rich prairie
land of the United States and Canada attracted many European
farmers. Today, professional people commonly emigrate because of
better opportunities elsewhere. Such emigration has sometimes
been called brain drain. For example, many Philippine doctors
and nurses and numerous Indian engineers and scientists have
moved to the United States and Australia. Religious persecution
has led many people to move to a new land for the freedom to
practice their faith. Such immigrants include Jews expelled from
England in the 1200's and Baha'is fleeing Iran in the 1980's.
Wars, revolutions, and political unrest have driven innumerable
people to find new homes. In the 1990's alone, millions of
refugees fled from warfare in Iraq, Rwanda, Liberia, and
Bosnia-Herzegovina. Some immigrants were brought to a new land
against their will. From the 1500's to the 1800's, Europeans
shipped black Africans to the Western Hemisphere as slaves. The
United Kingdom transported convicts to Australia from the late
1700's to the 1860's to relieve overcrowding in British jails.
Before that time, the United Kingdom sent convicts to the
American Colonies.
Effects of immigration
Many immigrants to a new country first settle in a
community made up of people from their native land or even their
native village. They keep their old customs and acquire a
limited knowledge of their new country's culture, language, and
values. In time, however, most immigrants begin to assimilate
(adapt to a new culture). Immigrants who adapt most quickly
usually have a background similar to the new cultural
environment and much contact with the new society. They also
plan to remain permanently in the new country. Most immigrants
find a job and strive to buy a home. They try to provide their
children with the education and opportunities not available in
the immigrants' native land. They become citizens of the new
country and take part in politics and government. Immigrants
have made enormous contributions to the culture and economy of
such nations as Australia, New Zealand, Israel, Argentina,
Brazil, Canada, and the United States. But their accomplishments
have been made with great difficulty. Many of the receiving
countries have restricted immigration to maintain a homogeneous
society in which all the people shared the same ethnic,
geographic, and cultural background. Although some immigration
laws have been relaxed, many newcomers of different backgrounds
still face challenges in gaining acceptance.
HUMAN BEING
Human being has the most highly developed brain of any
animal. The human brain gives people many special abilities, the
most outstanding of which is the ability to speak. Language has
enabled human beings to develop culture, which consists of ways
of behaving and thinking. These ways are passed on from
generation to generation through learning. Culture also includes
technology--that is, the tools and techniques invented by people
to help satisfy their needs and desires. The richness and
complexity of human culture distinguish human beings from all
other animals.
The human brain helps make people the most adaptable of
all creatures. They behave with the most flexibility and in the
greatest variety of ways. The human body is highly adaptable
because it has few specialized features that could limit its
activities. In contrast, a seal has a body streamlined for
swimming, but it has difficulty moving about on land. People
cannot swim as well as a seal, but they can also walk, run, and
climb. Human adaptability enables people to live in an extremely
wide variety of environments--from the tropics to the Arctic.
People are inquisitive and have long sought to
understand themselves and their place in the world. Throughout
much of human existence, religion has helped provide such
understanding. All societies have assumed one or more gods
influence their lives and are responsible for their existence.
Since ancient times, philosophy (the study of truth and
knowledge) has also provided definitions of what it means to be
human.
Today, religion and philosophy remain important parts
of people's efforts to understand the nature of human existence.
But many other fields of study also help human beings learn
about themselves.
For example, anthropology is the study of human
cultures and of human physical and cultural development.
Linguistics is the scientific study of language. Specialists in
psychology study human and animal behavior and mental processes.
Sociology deals with the groups and institutions that make up
human societies, and history is the study of past human events.
Prehistoric people are human beings who lived before
writing was invented about 5,500 years ago. Writing enabled
people to record information they wished to save, including
descriptions of events in their lives. In this way, the
invention of writing marked the beginning of history. The period
before human beings learned to write is called prehistory, and
people who lived during this period are known as prehistoric
people.
Most scientists believe the first human beings lived
about 2 million years ago. But early people probably arose from
pre-human ancestors who first lived more than 4 million years
ago. These ancestors were small, humanlike creatures who walked
erect. This article will discuss both prehistoric people and
their near ancestors. Scientists first discovered evidence of
prehistoric people during the mid-1800's. Most of this evidence
consisted of ancient, sharp-edged tools that prehistoric people
had made of stone. The first fossilized bones of prehistoric
people were also found during this time.