The First Humans
Every civilization has contributed to the scientific knowledge that we use today. Some early civilizations such as the ancient Egyptians, Greeks, Chinese, and Romans lasted longer than others and left many records, so we know more about them. But others, such as the earliest known societies in Africa, India, and Europe, left few records. We have to try and interpret what these cultures knew from the things they left behind.
An archaeologist is a scientist who studies the remains of past peoples. Archeologists dig up ancient fossils (bones that have been turned to stone) and artifacts (objects made by humans, such as primitive tools, weapons, cooking pots, or works of art). They then study these artifacts to determine when humans first used fire, when they made their first stone tools, the types of crops they first cultivated, and so on. The oldest artifacts have been found in an area known as the Olduvai Gorge in Tanzania, Africa.
To learn more about some of the earliest humans and their discoveries, try the activities in this chapter.
The Stone Age
It's thought that the first humanoid apes walked the plains of west and south Africa over 4 million years ago. But the first stone tools didn't appear until about 2.4 million years ago. These first crude stone tools were used for scraping and hammering, and they marked our departure from other species of animals. Simple stone tools were the technology that first made us human. Try this activity to learn the science behind how simple tools make work easier.
1-yard (1-m) piece of 1/2-inch- (1.25-cm) diameter dowel felt marker sharp knife adult helper
1. Take the dowel outside to a lawn area.
2. Stick one end of the dowel into the ground. How hard is it to push the dowel into the ground? Use the marker to mark on the dowel the depth the dowel goes into the ground. How deep does the dowel go?
3. Have the adult use the knife to sharpen one end of the dowel into a point.
4. Stick the pointed end of the dowel into the ground near where you previously stuck the dowel. How hard is it to push in this time? Again, mark the depth the dowel goes into the ground. How deep does the dowel go?
The dowel with the pointed end goes deeper into the ground than the dowel with a flat end, and it's easier to push. It may seem simple, but the tool you made in this activity actually took early humans thousands of years to figure out. When a dowel or a stick is sharpened, it becomes a digging tool or a spear. Rocks that have certain shapes, like the kind you found in More Fun Stuff to Do, can be used as hammers, knives, scrapers, or ax heads.
A sharpened object is an example of a simple machine called a wedge. Many archaeologists believe that the wedge was the first simple machine discovered by early humans. A wedge makes work easier because it causes force to be concentrated in a smaller area. When you push the dowel without a point into the ground, the force of your push is spread out over the entire end of the dowel. But when you sharpen the dowel, the same force is concentrated at the point of the dowel, making it easier to stick in the ground. When digging up edible roots for an ancient dinner, a pointed stick could save time and energy that would otherwise be expended scraping and grubbing with flat stones or fingers.
Ancient Science in Action
During Paleolithic times, or the Old Stone Age, the first stone tools were crude fist-size wedges made by splitting one stone with another. These first tools were probably used to cut up and chop plant and animal materials, as well as for digging. Sharpened stone tools, called hand axes, date back to about 1.3 million years ago. Hand axes were used for cutting, scraping, digging, and probably killing. At the beginning of Neolithic times, or the New Stone Age, stone tools were made smoother by polishing the sharp edges with sand.
By the end of Neolithic times, stone tools were being used to make other tools out of softer materials, such as wood and antlers. Late Neolithic humans made sewing needles and fishhooks out of antlers.
Make It Grow
Humans in the Old Stone Age were nomadic, meaning they moved in groups from place to place, taking everything they owned with them. They were hunters and gatherers, which means they hunted animals and gathered plants and fruit for food. But around 10,000 B.C.E. some early humans began to settle in communities that revolved around agriculture, cultivating plants and raising animals. To supply food for the people in the community, they began to grow their own plants rather than just eating the ones that they found in nature. But there is more to growing plants than just throwing a few seeds on the ground, as the humans in the first agricultural communities no doubt understood. Try this activity to investigate the conditions needed to cultivate plants.
2 plastic cups potting soil sand felt marker millet seeds (available from a pet store) water paper pencil
1. Fill one of the plastic cups halfway with soil and the other cup halfway with sand. Use the felt marker to label the outside of each cup "soil" or "sand."
2. Sprinkle several millet seeds in each cup.
3. Cover the seeds in the soil cup with a thin layer of soil, and the seeds in the sand cup with a thin layer of sand. 4. Water the soil and sand until they're just damp.
5. Place the plastic cups on a windowsill so that they get sunlight.
6. Water the seeds every other day.
7. Observe and record what you see happening to the seeds every day.
The seeds in both cups should sprout and begin to grow in a short time. However, the millet seeds will grow better in soil than in sand.
Most plants require sunlight, water, and nutrients in order to grow. Green plants use water and minerals in the soil, carbon dioxide from the air, and sunlight to make glucose in a process called photosynthesis. Sand has few minerals in it, so it is not good for growing plants.
The first humans settled in the Indus Valley between modern India and Pakistan, the area between the Tigris and Euphrates rivers in modern Iraq, the Yellow River valley in China, and the Nile River valley in northeastern Africa. These are all areas with good soil, plenty of water, and a lot of sun. In these regions, large nearby rivers would flood every spring, depositing a rich silt that turned desert into farmlands. The river also gave a supply of fish and water birds to eat, as well as mud to build shelters.
Millet, which you grew here, and other cereal crops such as wheat, barley, and sorghum, were the first plants to be grown by early humans in the Nubian Desert of northeastern Sudan, in Africa. Along with the cultivation of crops, early humans also domesticated animals, such as sheep and goats.
Ancient Science in Action
Because early humans could now stay in one place for a longer period of time, they began to make more permanent structures of mud and brick, and towns and villages were born. Growing crops and domesticating animals meant more food, which allowed the populations to rapidly increase. It also meant that new implements, such as stones for grinding and pots for storage, were needed to manage the supplies. And it also led to trade between communities, as food surpluses could be exchanged for other kinds of food. For example, surplus millet grown near the Nile River could be traded for wild honey from mountain communities. As communities grew, civilizations were born.
While early humans were growing cereal grains in Africa, early humans in other areas were raising other types of plants. Around 3000 B.C.E., an early civilization centered in the Indus Valley (along the border between modern India and Pakistan) began to grow plants that were found in their region, such as einkorn (a wild form of wheat), barley, and date palms.
In 327 B.C.E. Alexander the Great, the king of Macedonia and conqueror of much of Asia, reported that a plant he had never seen grew in the Indus Valley near modern-day India. We now know that this plant was sugarcane. Sugar was first removed from the cane by chewing and sucking the stalk of the sugarcane plant. But by 300 C.E., people in India had developed a process in which sugar syrup could be extracted by boiling and pressing the canes. Once sugar syrup was made, it wouldn't have been long before people noticed what happened when sugar syrup hardened. Try this activity to find out how to turn sugar syrup into sugar crystals.
drinking glass water saucepan spoon sugar string scissors pencil paper clip paper towel adult helper
1. Fill the drinking glass about one-third full of water. Empty the water into the saucepan.
2. Have your adult helper heat the water to boiling, then remove the pan from the heat.
3. Use the spoon to stir sugar into the water until no more sugar will dissolve. (Note: You can dissolve a lot of sugar in the water, about two times as much as the amount of water you started with.) You should end with a thick syrup that has a few grains of undissolved sugar floating in it.
4. Pour the sugar syrup into the drinking glass.
5. Cut a piece of string so that it is slightly longer than the drinking glass is tall.
6. Tie one end of the string to the pencil and the other end to the paper clip.
7. Wet the string and paper clip with water, then roll them through some dry sugar so that a few sugar crystals stick to them.
8. Place the pencil across the rim of the glass so that the string and paper clip are suspended in the syrup solution.
9. Place the glass where it won't be disturbed and cover it with a paper towel to keep dust and dirt out of the solution.
10. After about five days, observe the string. What has happened?
11. Take the string and sugar crystals out of the solution and taste the crystals. What do they taste like?
After several days, sugar crystals will begin to form on the string and paper clip. If the water evaporates slowly, the crystals will become quite large. The crystals will taste sweet. If you do the More Fun Stuff to Do activity, the sugar will look like small crystals through the magnifying glass. These crystals look like smaller versions of the large crystals that formed on the string and paper clip.
When sugar is dissolved in water, it becomes a sugar solution. In a solution, one substance is completely dissolved into another. To get the sugar out of the solution, all you have to do is let the water slowly evaporate. When that happens, sugar crystals are left behind. A crystal is a chemical compound that forms a solid in a specific pattern that repeats regularly in all directions. Only certain chemicals, such as sugar and salt, will form crystals. Crystals can form cubes, diamonds, pyramids, and other regular shapes.
Ancient Science in Action
Sugarcane isn't the only plant that sugar comes from. Native Americans found out that the sap of maple trees could be boiled to make maple sugar syrup. No one knows how long they had been doing this, but the practice was probably well established before Columbus introduced the sugarcane plant to the West Indies. Sugar also comes from sugar beets, a fact that was discovered in Germany in the 18th century.
People have been navigating (steering a course) on rivers, lakes, and oceans since long before recorded history. Archaeological discoveries show that the Vikings and the Polynesians made epic voyages long before the invention of the magnetic compass. They left no record of how they accomplished these feats, but they probably used their knowledge of prevailing winds and the positions of the sun and stars to determine direction. One very important star in navigation is Polaris, also called the North Star. It can always be seen on a clear night in the northern sky of Earth's northern hemisphere, so if you stand facing it, you know you're facing north. Try the following activity to learn how to find the North Star.
Note: This activity should be done outdoors on a clear night.
1. Lay the compass flat in your hand, allowing the needle to spin freely. When the needle has stopped, it will be pointing north. Look in that direction.
2. Look at the northern part of the sky and locate the Big Dipper. The Big Dipper is a group of seven stars that looks like a ladle. Three stars make a curved handle, and four stars make the ladle's bowl.
3. Find the two stars on the outside part of the Big Dipper's bowl. Follow these two pointer stars to a star of average brightness. This is Polaris, the North Star.
When you look at the northern sky on a clear night, you should be able to locate the North Star. With practice, you will be able to locate many constellations as well.
Because the Earth spins on its axis, the North Pole always points in the same direction. Polaris is called the North Star because it is located almost directly above the North Pole. For years, people used the North Star and other constellations to navigate.
If you watch the stars for many nights, you will see that the whole dome of the sky seems to move from east to west. But the sky dome isn't actually moving. The spinning of the Earth on its axis causes the stars to appear to move. Because the stars are so far away, they appear to move as a group, always keeping the same relative position in relation to each other. Stars do move, but so slowly that it takes thousands of years before there are any visible changes in the night sky.
Ancient Science in Action
Early mariners (people who traveled on water) didn't travel very far from the coast. They usually followed the coastlines, where they knew the position of their ships by identifying objects on land. They would travel during the day and go ashore at night. After they learned to use the stars to navigate, sailors began to travel at night as well, increasing the distance they could go.
There have been many ancient peoples who have studied the stars for navigation. The people living near the Mediterranean Sea-the Sumerians, Cretans, Egyptians, Phoenicians, and Greeks-became gifted seamen, as did the Scandinavians in northern Europe and the South Pacific's Polynesians.
Archaeologists have discovered what may have been one of the first musical instruments, a hollow bone used as a whistle. The first horns and pipes were made in prehistoric times from natural substances such as bone, horn, wood, and reeds. Drums also date back to prehistoric times, and probably began as hollow logs that people banged on. Stringed instruments began to appear around 2500 B.C.E. Music seems to have always been a part of our lives. But how did the earliest instruments, like the whistle and drum, make different sounds? Try this activity to find out how they make different sounds.
6 empty glass pop bottles, the same size and shape paper pencil water
1. Line up the bottles on the table and label them from 1 to 6, using the paper and pencil.
2. Pour water into the first bottle to a level of about 1 inch (2.5 cm).
3. In the second bottle, pour water so that it is about 1 inch (2.5 cm) higher than the first, to a level of 2 inches (5 cm).
4. Pour water into each of the next bottles so that it is about 1 inch (2.5 cm) higher than in the previous bottle. This will give you 6 bottles, each with a different amount of water.
5. Use the pencil to gently tap the sides of the first bottle. What happens? Try tapping the rest of the bottles.
6. Now blow across the top of each bottle in order. What happens?
When you strike the bottles or blow across their mouths, they will make different sounds. The relative highness or lowness of a sound is called the sound's pitch. When you hit the bottles, the bottle with little water in it will make a sound that's a higher pitch, while the bottle with more water in it will make a sound that's a lower pitch. When you blow into the bottle with little water in it, it will give a sound with a lower pitch, while the bottle with more water in it will make a sound that's a higher pitch.
Excerpted from Ancient Science by Jim Wiese Copyright © 2003 by Jim Wiese. Excerpted by permission.
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