A fossil may look the same as the plant or animal when it was alive, but it is not the real leaf or bone you see. The fossil has changed to stone through a special process, and the stone has kept the shape of the leaf or the bone. This rock shape is called a fossil, or a body fossil.

Below you can see a photo of a fossil of the head of a dinosaur, and the next image shows you what scientists think this dinosaur looked like.

This fossil of the dinosaur's head is not the actual bones, but it is actually now a rock in the shape of the dinosaur's bones. Over millions of years, the bones turned into rock. So, a fossil is the remains of an ancient plant or animal which has been preserved in a rock. Most of the organisms that paleontologists study are now extinct. This means that they are no longer alive today.

The Earth's past is fascinating to us! Imagine being around when all the dinosaurs were walking on Earth. As humans, we want to find out about Life's History on Earth.

In recent history, we have books written that record what happened. This means we can read what people who lived long ago wrote about that time period. But no human was around millions of years ago to record what happened then!

So we have to use other ways to find out about what life was like on Earth millions of years ago. To do this, scientists use fossils! Fossils are actually our most valuable source of information about the ancient past!

But what can fossils tell us about life long ago? Fossils tell us about the organisms that lived long ago. Imagine the first scientists that discovered a dinosaurs bones! These bones were much bigger than the bones of any other animal on Earth today! This immediately told the scientists that the animals from the past were really big!

Fossils can tell us much more than just which organisms lived millions of years ago. By studying fossils of plants and animals, scientists can also gather information on how these organisms grew, what they ate, the environment they lived in and even some aspects of their behaviour and how they interacted!

For example, studying fossilised faeces of an animal can give evidence about what an animal used to eat.

By working out which plants used to grow during a particular time period in Earth's history, scientists can work out what the climate was like during that time. We now know when there were ice ages where the whole Earth was covered in ice for thousands of years, and when it was warmer and there were droughts.

A fossilised footprint can tell lots of things about a prehistoric animal, such as how much it weighed, how big it was, and even what speed it was running at!

The layers of rock which are lower down will be the oldest as they were deposited first. So the fossils in these layers will be from earlier times than fossils in rock layers which are closer to the surface.

Have you perhaps seen the body of a dead bird? Dogs, flies, ants and beetles all take away the parts of the body. The wind blows away the feathers and soon there is nothing left to see.

But sometimes it does not happen like that. Imagine an animal died in a river. There was a flood and the river quickly covered the body with sand. In years after that, more floods brought more sand and put it on top. The heavy sand pressed down on the bottom sediments. Slowly, the bottom sediments became sedimentary rock.

Let's try make our own model to understand how fossils are formed in sedimentary rock!

Now that you have seen you an impression of an object can be made by using plaster of Paris, let's have a closer look at how a dinosaur fossil was made millions of years ago.

Look at the pictures below and read the explanations for each stage of the fossil formation process.

Long, long ago, a dinosaur dies on the banks of a river, such as this triceratops in the picture.

The flesh of the dinosaur decomposes, or other animals eat it. So, only the skeleton remains.

There was a flood and the river rose and covered the skeleton with mud and sand.

Over time, more floods deposit more layers of sand and mud over the skeleton. Over thousands of years, the bottom layers start to become compacted and turn into sedimentary rock. Under the ground, water carried substances from rock into each little space where a bone had been. Rock took the place of bone. We say the bones were fossilised. A fossil bone has the same shape as the original bone but much heavier.

Millions of years later, the conditions of the environment above the skeleton may change. The rock is eroded and weathered over time by wind and water and the fossil is exposed on the surface. A scientist sees the fossil and a great discovery is made!

Other scientists join in and they excavate the fossil by carefully removing the rock and sand around the skeleton. The fossils will be carefully packed and taken to a museum or research centre where the scientists will study them to see what they can learn about prehistoric life. They will try to reassemble the bones into a full skeleton - this may take many months to do!

Some of the most ancient fossils that are known to exist were found in rocks in Barberton area in Mpumalanga.

Do you know where this is in South Africa? Look it up on a map! These fossils are more than 3000 million years old! That is very, very old. They look like blue-green bacteria. Do you remember when we discussed microorganisms in the soil in Chapter 2? Bacteria are a kind of microorganism.

Do you know where Grahamstown is in the Western Cape? Grahamstown is famous in the archaeological world for having some of the oldest and best preserved fossils of early plants from millions of years ago.

Look at the shape of Africa and South America on the classroom globe. The shapes could fit together like in this picture below. This diagram shows how scientists think the continents of Earth used to look millions and millions of years ago. This was called Pangaea.

A South African scientist thought that perhaps Africa and South America had been joined together long ago. But nobody knew if this was true.

Then scientists found fossils of a plant called Glossopteris in rocks in South Africa and they found fossils of the same plant in South America. This made more people think that perhaps Africa and South America were once joined, very long ago. The image below shows how scientists think the plant Glossopteris used to grow in the world, in the dark green.

Fossils of dinosaurs have been found all over the world. But, one of the best places in the whole world is the sedimentary rock in the Drakensberg Mountains and the Maluti Mountains in southern Africa.

Reptiles came before mammals. However, the fossil record shows us some animals which were similar to mammals as we know them today, but they were actually reptiles. They were in between! They are called therapsids. Fossils of these animals have been found in the Karoo in South Africa.

Fossils of some of the first mammals on Earth were also found in the Drakensberg rocks in the Eastern Cape and in Lesotho.

Look at the picture below. This fish that was caught in the sea near East London. The fish is called a coelacanth.

Scientists from other countries rushed to South Africa to see this coelacanth fish. They could not believe that any coelacanths still lived in the sea. The scientists knew about coelacanths because they had studied their fossils in England and Germany, but the fossils were 80 million years old. The scientists thought that coelacanths had all died millions of years ago! We now call coelacanths "living fossils"!

The Cradle of Humankind is a World Heritage Site. It is called the "Cradle of Humankind" as many people and scientists now believe that this was where humans first evolved. The birthplace of humans is right in our country!

The Cradle of Humankind is found in Maropeng just outside of Johannesburg in Gauteng. The name Maropeng, a Setswana word, means "return to place of origin".

In the Cradle Of Humankind about 1000 fossils of pre-humans have been discovered, dating back to millions of years!

Altogether there are 15 major fossil sites in the Cradle of Humankind. The Sterkfontein Caves is the most famous. Swartkrans and Bolt Farm are also sites at Cradle of Humankind where fossils have been found.

The fossils of `Mrs Ples' and `Little foot' were both discovered at Maropeng. Thousands of hominid fossils (hominids are human ancestors) as well as plants and animals have also been discovered there.

Tourists come from all over the world , including South Africa, to view the caves and fossils at the Cradle of Humankind and get immense knowledge on the history of humankind. If you live in or near Johannesburg, maybe you have been lucky enough to visit Maropeng and the Cradle of Humankind?!

As we have seen, there are many important fossil findings all over South Africa! Let's put all these places on a map in the next activity.