An easy-to-read step-by-step explanation of natural evolution from the big bang to the rise of civilization.
Few people seem to be interested in questioning the existence of the
universe. Most people are too busy dealing with the responsibilities
and distractions of daily life. They do not have the time or the
inclination to contemplate the existence of the universe. They just want
simple answers that are presented to them in an interesting way.
Other people say that there is no point asking why the universe
exists, because without any evidence, we can only ever guess the answer.
But questioning the existence of the universe is essential, because
until we understand our relationship with the universe, then how can we
ever really know who we are or what we are supposed to be doing, other
than to blindly follow our instincts and attempt to satisfy our desires?
Unfortunately, debate about the existence of the universe is
still being clouded by popular religious myths that were devised at a
time when we knew very little about the universe. While some people
close their minds in blind acceptance of these myths, others close their
minds in blind reaction against them.
There are countless ideas and opinions that have been expressed
over the last three thousand years of written history. The most
influential of these ideas will be discussed later in this book. But
after stripping away all of the myths and misconceptions, and distilling
the answers down to their purest essence, there remains only two
possibilities.
One possibility is that our universe exists for no reason and
has no purpose, and so our lives have no meaning other than whatever
meaning we invent for ourselves. The other possibility is that we were
brought into existence by some kind of purposeful process beyond space
and time. A process which designed the universe and planned the events
that led to the natural evolution of intelligent life.
At this point in time, there is no conclusive evidence to prove
either way, and there may never be any evidence. In order to gain the
best possible understanding of our existence, we need to open our minds
to both possibilities and thoroughly examine them both to their eventual
conclusions. This book will attempt to undertake such an examination.
We will start our investigation by going back to the beginning,
to the birth of the universe and the evolution of humankind. From there,
we will follow the events of human history that led to the modern age,
to the discovery of computer technology and genetic engineering. Along
the way, we will look for clues that might reveal some kind of purpose
to our existence.
The journey will not be easy. Most of what we think we know
about our origins has only recently been reconstructed from scant pieces
of evidence. And when we read about history, it is hard to separate
fact from fiction. The truth always seems to become shrouded by
thickening clouds of myth. History is forever being revised to support
popular political or religious beliefs, and increasingly questionable
interpretations of history continue to appear.
Sometimes even scientific beliefs can turn out to be myths.
Science is about searching for the best explanation based upon the
existing evidence, knowing that some day new evidence might be
discovered and a better explanation might be found. In any case, the
credibility of any scientific theory depends on its popularity among
those who are in a position to impose their opinion.
The following account of human evolution has been kept simple in
order for it to be more understandable. Most of the information
presented here is widely accepted by the scientific community, but many
of the details are still being argued over by evolutionary biologists.
There are some things that we may never know for sure, and so when it
comes to exploring our origins, we may need to accept that there will
always be a degree of myth in our history.
The birth of the universe
At the beginning of time, the universe was born when space opened up
and was filled with an enormous explosion of energy. As the energy from
this explosion radiated out into space, it cooled down and began to
condense into matter.
Within a fraction of a second, most of the initial energy had
condensed into fundamental particles of matter. After hundreds of
thousands of years, as the universe continued to expand and cool down,
these particles began to condense into atoms.
Enormous clouds of atoms were drawn together by gravity. They
spiraled inwards and were crushed together to form massive solid bodies
of matter. The immense pressure and heat inside these bodies caused
nuclear reactions, and they exploded with intense light and heat to
become stars.
Great collections of these newly born stars were drawn together
by gravity to form galaxies. Today’s universe contains hundreds of
billions of galaxies, each containing hundreds of billions of stars. The
universe has continued to expand now for over twelve billion years.
The formation of the earth
Stars release enormous amounts of energy by converting lighter
elements like hydrogen into heavier elements like carbon and iron. All
of the heavy elements in the universe were forged in the hearts of
stars. Stars continue to burn brightly for billions of years, and then
when they run out of nuclear fuel, they often explode, scattering their
elements across space.
Our solar system was formed out of the rubble left behind by
nearby stars that had exploded. This rubble was drawn together by
gravity to form a huge spinning cloud of rocks and dust. At the center
of this cloud, the cosmic material was crushed together and exploded
into life as a medium sized star, our Sun.
As the remaining rubble continued to revolve around the Sun, it
was drawn together by gravity. Huge pieces of rock collided and were
fused together by heat to form the planets and their moons. Any material
that was not absorbed by the planets was left to circle the sun as
asteroids and comets.
Our Earth began as a mass of molten rock covered by a hard,
crusty, outer layer. Movements and eruptions in the Earth’s surface
produced mountains and valleys. As the surface of the Earth cooled down,
clouds of steam condensed and water fell from the sky to form rivers,
lakes, and oceans.
Organic molecules
Common elements like hydrogen, carbon, and oxygen are easily
attracted to each other. They bond together to form chemical compounds
like water and carbon dioxide. It is more natural for these elements to
combine into chemical compounds than it is for them to be found in their
pure form.
Under the right conditions, carbon has a tendency to bond with
other common elements to form long and complex chains of atoms known as
organic molecules. Organic molecules can then bond with other organic
molecules, and there seems to be no limit to how long and complex these
organic molecular chains can become.
Billions of years ago, the conditions on the surface of the
earth were very favorable for the formation of organic molecules. These
molecules were washed into the sea to form pools of organic matter on
the sea floor. Over millions of years, they continued to bond together
to form increasingly long and complex molecular chains.
The first spark of life
Life began when one of these complex organic molecules began
reacting with the other molecules around it in an unusual way. It was
able to attract all of the pieces that it needed to assemble an
identical copy of itself. The copy then split away from the original and
began to assemble its own new copy.
These self-replicating molecules may not have lasted long before
they were broken down by other chemical reactions, but they were still
able to spread through the pool of organic material fast enough to have a
lasting chain reaction.
The process of self-replication was not always perfect. Quite
often a piece was missing or the wrong piece was used, and the copy
would be different from its parent. Very few of these mutated molecules
were still capable of replicating, but occasionally, by pure chance, a
new molecule was created that could survive longer or replicate faster
than its parent.
Single cells
After millions of years and countless mutations, new and more
complex molecules developed a protective layer. The chemicals needed for
replication could still pass through this protective layer, but the
molecule was now safe from harmful reactions. The protective layer
slowly evolved into a cell wall, and safely contained within the cell,
the chemical reactions of life were able to evolve to become much more
complex.
It took hundreds of millions of years, but eventually a new
process evolved for producing a copy of a cell. This new process used a
number of molecules working together like an assembly line in a factory,
using chemical attraction to assemble sophisticated molecules known as
proteins, which then carried out all of the tasks associated with the
survival and reproduction of the cell. The instructions for how to build
these proteins were encoded in the main molecule, known as the DNA.
As the mutations continued over hundreds of millions of years,
new strains evolved the ability to use sunlight to convert common
chemicals into food. This ability, known as photosynthesis, has the side
effect of producing oxygen.
Before photosynthesis, there was no oxygen in the earth's
atmosphere. Then after millions of years of photosynthesis, the
atmosphere became rich with oxygen. We know this because the oxygen
reacted with dissolved iron in the seawater and deposited a layer of
rust on the ocean floor. Oxygen also formed the ozone layer, which still
protects the surface of the earth from the sun's deadly radiation.
There were occasions in the history of evolution, when a smaller
cell became trapped inside the body of a larger cell, and the children
of the smaller cell survived and reproduced inside the children of the
larger cell. Sometimes these smaller cells provided benefits to the
larger cell, and sometimes they continued to evolve inside the larger
cell over millions of years to become permanent organs of the larger
cell.
One of the most important steps in the evolution of life was the
appearance inside some cells of an organ called the nucleus. The
nucleus had evolved to become especially good at copying and repairing
its own DNA, and so the DNA inside the nucleus was able to become
thousands of times more complex. Cells with a nucleus soon evolved to
become thousands of times larger and more sophisticated than cells
without a nucleus.
The process of evolution
Evolution begins when there is an error during reproduction and the
new cell is different from its parent. Mutant cells usually die, and
those that survive are likely to be disadvantaged by their mutation.
Only very rarely will a mutant perform better than its parent. The
descendents of the mutant cell may then successfully compete against the
rest of the population and eventually replace them.
The more often an organism mutates, the faster it evolves, and
so the faster it can adapt to changing conditions and the more
successfully it can compete against other variations. The pressure to
evolve faster has forced cell reproduction to maintain a consistently
high rate of mutation. Only the need for enough healthy individuals to
survive stops the mutation rate from being higher.
A larger population has a higher chance of producing a
beneficial mutation. But then a considerable amount of time may need to
pass before the mutant population grows large enough to have any chance
of producing a second beneficial mutation.
This problem was overcome by the appearance of sexual
reproduction. By combining the DNA from two parents, a child cell can
inherit the beneficial mutations from two separate ancestries.
Beneficial mutations can then spread back into an existing population,
and this greatly magnifies the rate of evolution.
The rate of evolution is also increased by having only a limited
period of time during which an organism can breed. After the breeding
cycle is over, there is little evolutionary pressure to resist disease,
cell degradation, and the other signs of aging which lead to a natural
death. The lifespan of an organism becomes balanced between how much
more the parent can contribute to its offspring and how heavily the
parent must compete against its offspring for resources.
Multi-celled animals
After billions of years of evolution, the rivers, lakes, and oceans
of the world were swarming with a rich variety of single celled
organisms. Some cells, such as algae, got their energy directly from
sunlight, and some cells survived by eating other cells.
The most advanced single celled organisms had tiny arms that
could swim through the water. They responded to touch, had a sense of
smell, and were sensitive to light. They could swim towards food, avoid
obstacles and predators, and identify sexual partners.
Around a billion years ago, a mutation occurred during the
reproduction of an algae cell that caused the newly divided cells to
stick together. These cells formed sheets of algae that became the first
primitive form of seaweed.
Other mutations led to changes inside the cells each time they
divided. Different layers could now appear inside a growing organism.
The instructions for how cells changed each time they divided were
contained in the DNA. Any mutations to these instructions would change
the size and shape of the growing organism.
Around 600 million years ago, the first multi-celled animals
began to appear. The most successful of these were small, flat,
worm-like creatures that absorbed algae through the outer layer of their
bodies. Over time, they evolved the ability to wrap their bodies around
large particles of food. Digestive juices were released onto the food
to break it down before the nutrients were absorbed into the body.
Further mutations led to the development of an opening where
food could be drawn in, digested, and then passed out. This opening
slowly evolved into a tube running through the body. Food could be
broken down more efficiently as it passed through the tube from the
mouth to the rear.
Sensory perception
The success of an animal depended upon how much information it could
collect from its surroundings. Worms had inherited a sense of smell
from their single celled ancestors. They depended on this sense to
detect the chemicals released by food. The cells around the mouth
evolved so that when food was detected, signals would be passed through
the body, triggering muscle cells to expand and contract, causing the
worm to slowly wriggle towards the food.
The sensitive cells around the mouth and the cells that carried
signals through the body evolved into a network of nerve cells. Any
mutations to these nerve cells could change the way that the animal
behaved. Evolution favored mutations that drove the animal to find more
food, avoid danger, and breed more. The accumulation of advantageous
mutations to nerve cells over millions of years led to the development
of complex patterns of behavior.
However, it was not enough to always react in the same inherited
way to each type of sensation. A particular smell might indicate food
in some environments but danger in others. By remembering the
association between a sensation and its outcome, mistakes did not have
to be made a second time and successful outcomes could be pursued more
vigorously.
Worms also inherited sensitivity to touch, temperature, and
light from their single celled ancestors. A cluster of light sensitive
cells has the potential to form a picture, and so there was strong
evolutionary pressure for such clusters to evolve into early forms of
eyes.
There was also strong evolutionary pressure for a large cluster
of nerve cells to grow where the signal paths from the various senses
intersected with the control paths for the muscles. This cluster of
nerve cells evolved into the first primitive type of brain.
Predators and prey
Before worms could evolve to become larger, they first needed a
system to pump oxygen and nutrients through their bodies. While most
worms continued to feed on algae, the larger ones began feeding on the
smaller ones. Those with tougher skin were harder to eat, and so over
many millions of years, the skin of some animals evolved into a hard
outer shell.
Animals with protective shells were best suited to crawling
along the sea floor, but predators were able to move faster and find
more food by swimming through the water. The most efficient way to swim
was to wriggle from side to side. This style of motion was made more
effective by having hard parts inside the body. These hard parts began
as fluid-filled spaces which later accumulated minerals to take the form
of bones.
Early animals were very successful at swimming around, looking
for food, and finding sexual partners. As populations grew, so did the
number of mutations. As long as life was easy, food was abundant, and
partners were easy to find, then there would be nothing to stop new
variations from flourishing. This stage of evolution was like a ‘trying
out’ period for new animal designs. Within a short period of time, the
oceans were filled with animals that came in a multitude of weird and
wonderful shapes and sizes.
After millions more years of evolution, predators became larger,
faster, and smarter. Only those smaller creatures that could swim
faster, burrow into the sand, and those with protective shells were able
to avoid being eaten. As smaller creatures became better at surviving
in this hostile new environment, pressure grew on the predators to
sharpen their hunting skills. The competition grew so fierce that most
variations were wiped out. The only survivors were those whose body
designs were so successful that many of their descendents are still
alive today.
Plants
Around 500 million years ago, there were several hundred different
types of marine animals including early forms of crabs and fish. Fresh
water lakes had become fertile environments. Plants living in shallow
water were able to gain more nutrients by anchoring themselves into the
mud. Once anchored, they began branching towards the surface to collect
more sunlight.
Plants and animals living near the water's edge were regularly
exposed to the air by rising and falling tides, and lake water could
become dangerously shallow during times of drought. Creatures living in
these areas needed to survive for longer periods of time out of the
water. Plants adapted by becoming weatherproof and growing strong enough
to support their own weight. These changes allowed them to begin
growing branches permanently above the water line.
Around 420 million years ago, the first plants appeared that
could survive entirely on the land. Once they had taken their first
step, nothing could stop them from spreading across the empty
continents. They thrived in any region with regular rainfall and
nutrient rich soil. They evolved rapidly as they adapted to new
landscapes and climates. Within tens of millions of years, the land was
covered by a dense forest of trees with branches and leaves.
Plants were soon followed onto the land by creatures with hard
protective shells. Crabs, sea scorpions, and other shelled animals had
been very successful in the sea. As they crawled onto the land they
evolved into ants, beetles, spiders, and other insects. Within 50
million years, some variations had evolved wings and were able to fly.
Reptiles
Fish living in shallow water swamps and wetlands needed to propel
themselves through the mud and vegetation. This favored stronger muscles
around the fins, the bones in their fins became longer, and the tips of
their fins became more claw-like. Their gills were less effective in
the shallow muddy water, and so they developed lungs to draw more air
from the surface. Those with thicker scales and more weatherproof skin
were able to spend longer periods of time above the surface of the
water.
By around 360 million years ago, animals that were half fish and
half reptile were spending as much time crawling over the mud banks as
they were swimming through the water. These creatures continued to
evolve into reptiles, but they did not conquer the land for another 50
million years, not until their eggs had developed tough waterproof
shells allowing them to be laid out of the water.
Mammals
The temperature of seawater does not vary much, and so animals
living in the sea are able to keep a relatively constant body
temperature. Moving onto the land meant surviving a much wider range of
temperatures, with cold nights and cold winters. The chemical reactions
inside cells are sensitive to temperature. As the temperature drops,
these reactions become slower.
Reptiles depend on the warmth of the sun during the day. They
become sluggish at night and in cold weather, and they can only live in
regions that have mild winters. Their cells do not generate enough
energy for them to actively hunt for food, and so they usually wait for
prey to come near. Some early land reptiles evolved large fins on their
backs to absorb more heat from the sun.
Reptiles walk on four legs that sprawl from the sides of their
bodies, a configuration that helps them to move through the water.
Around 300 million years ago, a new family of reptiles appeared with
legs that were positioned beneath the body instead to give better
support for walking on the land. These new animals were the earliest
ancestors of mammals, and they rose to dominate a landscape rich with
plant and insect life.
Early mammals also adapted to living on the land by evolving
higher body temperatures. This allowed them to move faster over longer
distances and more actively search for food. They could hunt any time of
the day or night, in any season, and could survive further north or
south in colder climates. They evolved hairs on their skin to retain
body warmth in cold weather.
Dinosaurs
Around 240 million years ago, another successful branch of reptiles
evolved into the dinosaurs. These creatures also had legs that supported
them on the land, and they also benefited from a higher body
temperature. But the dinosaur's body weight was shifted back so they
could stand on two legs. This allowed them to run faster and reach
higher than the four legged mammals.
Maintaining a higher body temperature requires a considerable
amount of energy. Warm blooded animals use up to ten times more energy
than cold blooded ones do. They need to find more food and eat at more
regular intervals. Warm blooded animals also grow faster, reproduce
more, and evolve more rapidly. In the fierce competition for the
position of top predator, the dinosaurs proved to be superior to the
mammals, and by 200 million years ago, the dinosaurs had completely
conquered the land.
Only the smallest mammals survived. These were forced to retreat
into colder regions where they lived in burrows under the ground and
only emerged at night to hunt for insects. Mammals adapted to the colder
regions by giving birth to live young rather than laying eggs. The
developing young were kept safe and warm inside the mother's body where
they received oxygen and nutrients from the mother's blood. After being
born, the infants continued to receive nutrients by drinking their
mother's milk.
Learned behavior
Many animals are born with all of their survival skills. They do not
need to learn anything from their parents and are able to fend for
themselves as soon as they are born. But instinctual patterns of
behavior can take thousands of generations to evolve, and there are
limits to how complex this behavior can become. There are limits to how
much information can be passed down to the next generation through body
chemistry alone.
Some animals spend months or even years learning more complex
patterns of behavior by imitating their parents and other family
members. Mammals evolved an extra layer of brain tissue surrounding the
instinctual part of their brain. This extra layer helped them to
override their instinctual behavior with learned skills.
The more that mammals came to depend on learned behavior, the
less able their young were to care for themselves, and the more time
they needed to learn from their parents. The degree to which learned
behavior was able to replace inherited behavior depended on how
skillfully parents could care for and educate their increasingly
helpless infants.
Most of an animal's brain is used to control its body, and so
larger animals need larger brains. Animals that depend more on learning
need an even larger brain in proportion to their body size. But brains
can use up to ten times more energy than other organs in the body. And
so the evolution of a larger brain was partly limited by the ability to
find more food.
The evolution of a larger brain was also limited by how easily
the head of a baby can pass through the mother's birth canal. Animals
with larger brains need to be born at earlier stages of their
development, when their heads are smaller. This makes newborn babies
even more dependent on the care of their parents until their brains are
fully developed.
As mammals evolved to depend more on learning, they also
developed stronger emotional attachments. Strong instinctual feelings of
affection were needed to drive parents to care for their children,
drive children to imitate their parents, and keep family members
together long enough for the young to learn how to survive.
Cooperation and competition
In the natural world, the number of animals that can survive in an
area depends on the amount of food that the land can produce. Numbers
may grow until there is no longer enough food to support every animal.
Then competition between individuals to satisfy their hunger becomes
fierce. Younger animals may not be able to compete against stronger and
more experienced ones. The population will be limited by the number of
young that can survive long enough to breed.
Some animals develop such strong instinctual affections that
they continue to live together in family groups. Groups of animals must
compete against nearby groups for food, but animals within each group
can often do better by sharing their food with other group members and
by cooperating in other ways that help the survival of the young.
Members of the same group still need to compete against each
other. Stronger members will fight to breed with the most desirable
partners. When food is scarce, they will muscle each other for the
largest share of the meal. Weaker members will compete for the
affections of those who can secure them more food and better protection.
For each type of animal, there will be a balance between how
much they can cooperate and how much they need to compete against other
group members. When conditions change, so will the best balance between
competition and cooperation.
The extinction of the dinosaurs
Every day the earth is showered by rocks from outer space. Many of
these explode in the atmosphere, appearing as bright streaks of light in
the sky. Larger rocks can break through the atmosphere and smash into
the earth, sometimes causing enormous damage. Approximately once every
few thousand years, the earth is struck hard enough to destroy an area
the size of a small city. One impact every few hundred million years can
be so destructive that the whole world is shaken by earthquakes, tidal
waves, and volcanic eruptions.
Around 65 million years ago, a massive rock slammed into the
earth with devastating impact. The explosion was so powerful that it
incinerated everything within a thousand mile radius. Forest fires and
volcanic eruptions sent thick clouds of dust and smoke into the sky,
blocking out the sun around the world for many months. As the sunlight
faded, the temperature began to drop. Plants withered as they were
starved of sunlight and food became scarce. All of the large land
animals died, as did many of the smaller ones.
The only dinosaurs to survive were the birds, who were able to
fly above the carnage to search for scraps of food. Among the survivors
on the ground were the small furry mammals who were well adapted to cold
conditions. Being the only remaining land animal with warm blood, no
other animal could now compete against the mammals for dominance on the
land. Mammals rapidly evolved into a wide variety of shapes and sizes to
take advantage of all of the new opportunities left behind by the
extinction of the dinosaurs.
The evolution of mammals
Although there appears to be large differences between different
species of mammal, all mammals are variations of the same basic design.
For example, they all have the same set of bones. The bones of the human
hand are arranged in a similar way to the bones of a bat's wing or a
whale's flipper. The only significant difference is that the bones are
different sizes.
Large differences can appear between ancestors and their
descendents with only minor changes to those parts of the DNA that
control the timing of childhood growth and the rate at which different
body parts grow.
Species remain relatively unchanged for long periods of time.
Significant mutations are rare, but when they do occur, a new group may
break away from the original group and take over new environments for
which they are better adapted. If the new group is successful enough,
they may completely replace the original group.
Tree dwellers
While most mammals adapted to living on the ground, some adapted to
living in the trees. Trees were safe from most predators and they
provided a rich diet of fruit and insects. Some tree dwellers evolved
fingers and thumbs for grasping onto branches. Long snouts are awkward
when clinging to trees, and so their faces became flatter and their eyes
moved to the front of their face, allowing better judgment of distances
when leaping between trees.
Most animals that live on the ground need to be able to walk
soon after they are born. But tree dwellers can cling to their mothers
in the same way that their mothers can cling to trees. Being carried
around and cared for by their mothers for a longer period of time
allowed their brains to evolve to depend more on learned behavior and
less on instinct.
Some tree dwellers became too large to walk across the tops of
branches and began swinging beneath them instead. Their bodies became
too heavy for their tails to act as a counterbalance, and so they lost
their tails and developed a more upright posture to keep themselves
balanced. Fewer branches could now support their weight. Instead of
leaping between trees, they climbed down and walked between them.
The ancestors of humans
Around 7 million years ago, some of these ape-like creatures moved
away from the forests and began living on the grass covered plains. As
they spent less time in trees and more time traveling across open
ground, evolutionary pressure favored those with longer legs, and they
began walking upright.
Their hands were no longer needed for walking and could be used
for a variety of other tasks such as gathering food or using sticks and
stones as weapons. They could now hunt larger animals and carry the meat
back to share with the rest of the group. Being able to provide better
care for their increasingly helpless infants allowed them to continue to
evolve larger brains that were more adapted towards learning. These
animals were the early ancestors of humans.
They began breaking stones apart to create sharp edges which
could be used to cut wood, meat, and bone. Around one million years ago,
they learned how to keep fires burning and began cooking their meals.
Cooked food required less chewing and so their jaws evolved to become
smaller.
The competition between different groups of early humans was
fierce. Those who could make better weapons, and those who were more
skilled at using them had a distinct advantage. Increased competition,
better parental care, better communication, and an increasingly complex
lifestyle, all of these factors drove the evolution of a larger and more
adaptable brain. Groups that evolved larger brains outcompeted and
replaced groups that did not.
The power of speech
The shift towards learning was accompanied by an increased sense of
curiosity. When one member of a group discovered a new way of doing
something, the others would watch and imitate the idea. Older members of
the group might be slow to change their habits, but the younger ones
would grow up knowing only the new way. Group behavior usually adapts
over time to make the most efficient use of the available resources. New
discoveries are rare. New ideas usually come through contact with other
groups.
Animals communicate by making sounds and using body gestures to
express their emotions. As early humans became increasingly skillful,
the sounds they made with their mouths became more controlled and
meaningful. Grunting noises gradually changed into words. The need for
improved voice control led to changes in throat design. These changes
made it easier for them to choke while eating or drinking, but improved
voice control outweighed this disadvantage.
The immediate advantage of improved communication led to
stronger evolutionary pressure to learn more words and develop the
creativity to string words together to form sentences. They were now
able to learn more from each other and develop closer relationships by
sharing personal experiences. And they could now cooperate much more
effectively than ever before.
As cooperation between the sexes improved, the female body
evolved more towards facilitating reproduction, while the male body
evolved for more aggressive and physically demanding tasks such as
hunting large animals and protecting the group. Women focused more on
maintaining the camp, gathering and preparing food, and caring for
family members.
Men and women were drawn together by shared interests and
powerful sexual desires. The deeper emotional attachments that grow
through familiarity then helped them stay together to share in the
training of their children for adult life.
Human migration
Early humans lived in family tribes that moved around the
countryside following herds of wild animals and gathering different
fruits as they came into season. They slept in caves or made simple
shelters under trees. Clothes were made from animal skins. Hand axes
were the all purpose tools. Warm clothes and effective weapons allowed
them to slowly migrate to colder climates and less fertile environments.
They spread across Africa, Europe, and Asia in waves of
migration that continued for hundreds of thousands of years. Each new
wave either wiped out the previous inhabitants or interbred with them.
Interbreeding had the advantage that any successful qualities of the new
arrivals were combined with native adaptations that suited the local
geography and climate. The results can be seen today. Modern humans all
share similar abilities to our last common ancestor, but we come in a
variety of shapes and colors.
The development of culture
As speech gradually improved over the last hundred thousand years,
people began to entertain each other with stories about things they had
seen or heard. Casual conversations became an important force in shaping
human behavior. People were forced to restrain themselves and show more
respect for others. Wrongdoers would be shamed by the rest of the
group. Over time, each tribe developed its own set of rules to reduce
conflict in areas such as leadership, ownership, and sexual
relationships.
Human consciousness was slowly awakening, but people had nothing
more than their imaginations to help them understand their place in the
world. They sensed powerful forces at work around them in the
mountains, forests, rivers, seas, and in the sky. Some of these forces
were kind and generous, others were unpredictable and destructive. They
imagined these forces to have feelings and perceived them to be spirits
or gods. Believing their lives to be at the mercy of these spirits, they
prayed and offered sacrifices to gain their favor and avoid their
anger.
Stories about the spirits helped to explain the various
mysteries of nature. Often these stories were cleverly devised to
promote good communal values and strengthen existing tribal laws. As the
most popular myths and legends were passed down from generation to
generation, they gained a kind of sacred authority. Many of them became
the subjects of ritual songs and dances. People learned common values
and gained a common understanding of the world through their shared
mythology.
The development of language, laws, and customs marked a turning
point in evolution. Evolution would now be more about evolving human
cultures rather than evolving human brains. As cooperation improved
between groups sharing similar cultures, hostility increased between
groups with different cultures. People whose language, laws, and customs
allowed them to organize into larger groups, better educate their
young, and defend more territory, were more successful at preserving and
spreading their culture.
Farming villages
Over the last 2 million years, the earth has been frozen a number of
times in what is commonly known as the ice ages. During these periods,
many parts of the world became uninhabitable and much of the rest was
only marginally productive. The last ice age began around 80 thousand
years ago and receded only 12 thousand years ago. As the ice melted
away, vast areas of land were revealed. Rivers of fresh water began
flowing across fertile plains.
Around 10 thousand years ago, in some parts of the world, people
began planting seeds and covering the countryside with food producing
plants. The earliest and most successful crops were grasses with large
seeds such as barley, wheat, and rice. These grasses were easy to grow,
the seeds were high in protein, and they did not need to be eaten
immediately. Grass seeds could be kept in storage for months or even
years.
Early farming communities also began gathering herds of wild
animals. Very few animals were suitable for farming. Most were too
aggressive or too nervous to be kept on a farm. Farm animals needed to
be easy to feed and have temperaments that were easy for humans to tame.
The earliest farm animals were sheep and goats.
The change in lifestyle from hunting and gathering to farming
was only made possible in those parts of the world where some wild
grasses had large edible seeds, and where some wild animals were
suitable for domestication. The river valleys to the east of the
Mediterranean were among the first locations in the world to meet these
requirements.
People living in the river valleys no longer needed to go
searching for food. They had settled on land which could produce
abundant quantities of food year after year. Land being farmed could
produce hundreds of times more food than land being used to hunt and
gather. Plentiful food supplies allowed populations to grow, and
permanent farming villages began to appear.
As populations grew to become unsustainable, the farmers spread
out and established settlements in nearby lands. With more food, larger
populations, better organization, and superior technology, they quickly
replaced any earlier inhabitants. Through the taking of slaves and by
other means, the new arrivals would often absorb the native people and
adopt aspects of their culture and language.
Farming villages were attractive targets for bandits who
preferred to use force to take what they needed rather than produce it
themselves. Communities could join together to establish a common
defense, but they could not hold back larger invasions. Farms would
eventually fall under the control of the most powerful bandit army.
Successful bandit leaders rose to become regional warlords and kings.
Kings maintained their power by fighting off rivals, marrying for
alliances, and passing their kingdoms down to their sons.
Innovations such as plowing and irrigation allowed farmers to
produce more food with less effort. Surplus food could be traded for
clothes, tools, pottery, weapons, and other useful items. Farming
villages became towns populated by specialists such as carpenters,
merchants, and tailors. People would travel from miles around to trade
their goods and services.
The Bronze Age
Naturally occurring lumps of copper could be found in many parts of
the world. This reddish brown metal was reasonably soft and could be
beaten and shaped into tools, weapons, and ornaments. By around 3000 BC,
it was discovered that melting copper and tin together formed a hard
metal alloy called bronze. The durability of bronze and its ability to
keep a sharp edge led to the development of more sophisticated tools and
weapons.
The populations of some of the more fertile parts of the world
began to climb into the hundreds of thousands. Towns grew into cities
with marketplaces, courts, and temples. They were governed by royal
families who ruled from stone palaces and were protected by armies of
trained soldiers carrying bronze weapons.
Before the domestication of large animals, the only way for
people to travel was on foot, and the only way to carry goods was on
their backs. Now animals such as horses, donkeys, and camels were
carrying large quantities over long distances in shorter periods of
time. The invention of the wheel revolutionized transport. As horse
drawn chariots became popular, towns began building stone roads and
bridges.
The rise of empires
Trade between kingdoms became essential. Most regions enjoyed at
least one advantage in agriculture, mining, forestry, or the production
of some other resource. Although greed for resources often led to
conquest, nations that traded grew wealthy without the cost of war. New
ideas were spread by traders who journeyed to foreign lands.
As the volume of trade grew, merchants needed to keep track of
the amount of goods that were being traded. They began keeping records
by making impressions in pieces of clay. Clay could be found almost
anywhere and was already being used to make pottery. Markings on clay
tablets could be easily erased or made permanent by baking them in brick
ovens.
As the centuries passed, the markings on clay tablets became
more complex and meaningful. New symbols with more abstract meanings
allowed writing to be used for more than just trade and commerce.
Professional scribes began to record laws, myths, and historic events.
Great wars and invasions were fought by expanding empires
seeking to increase their wealth and power. The treasures of neighboring
cities were seen as a particularly tempting prize for conquest. But the
size of empires was limited by the speed of communication and travel.
Ancient temples
Desperate to give meaning to their confused and often miserable
lives, people listened to those who claimed to have special knowledge of
the gods. Ancient priests became skilled in the art of crafting idols
for the people to worship. Beyond calming people's fears and anxieties
about the unknown, religions helped to bind early civilizations together
under a common set of beliefs.
Priests worked with kings to prohibit unacceptable acts and
promote family and community values. They performed sacred rituals such
as crowning kings, sanctifying marriages, and burying the dead. Temples
offered ambitious men an alternative path to power. Priests often helped
to soften the cruelty of kings by forcing the palace to compete against
the temple for the loyalty of the people.
The Iron Age
Iron is one of the most common elements on earth, but it is rarely
ever found in its pure metallic form. In ancient times, metallic iron
could only be found in meteorites, making it much more valuable than
gold or any other precious metal. Only royalty could afford to own
weapons made of iron.
Around 1200 BC, people learned how to extract large quantities
of iron by smelting iron ore in furnaces. Knowledge of iron spread
rapidly through conquest with iron weapons. By 1000 BC, iron had become
the chosen metal for tools and weapons throughout the ancient empires.
Iron was stronger than bronze and its ore was much easier to find than
copper or tin.
The art of writing
In some parts of the world, the symbols used for writing changed to
represent sounds instead of whole words. The invention of the alphabet
allowed the written word to better reflect the power of speech. Animal
skins and papyrus scrolls started to replace clay tablets. The first
significant works of literature soon began to appear.
In the centuries that followed, the growing collection of
writings continued to inspire new ideas and developments, while at the
same time leaving behind a faint sketch of how history unfolded. As the
growing populations struggled through wars, famines, and plagues, the
battle for survival and the emergence of new ideas now came to depend
increasingly on the discovery of new technologies.
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