Fossils

Human beings have always tried to know their past. We have always been interested in finding out what the earth was like before we came into existence. But the past does not give up its secrets easily. It is buried in the earth for all time in the form of fossils. From the in depth study of fossils, we can gain important knowledge and evidence of life that existed in ancient times. From the study of fossils, scientists have been able to even find out the atmospheric conditions that existed in the distant past!!

What are fossils? Where are they found? How do they form? What do fossils tell us about? Nice questions and we will try our best to answer them. First questions first.

What exactly are fossils?

Fossils are the preserved remains or traces of animals, plants and other organisms from the past. Simply put, anything that was a part of a prehistoric plant or animal or any other organism is called a fossil.

Where are fossils found?

Now that is a tough question to answer. We generally think that fossils are found in dry, dusty desert like places. But actually that is not true. Fossils are present in just about all types of places. But the reason palaeontologists (the smart guys who study and research fossils) are generally found in dry, dusty places is that they are the places where the chances of spotting fossils are maximum. A fossil can be anything from a partially or fully complete skeleton, a leaf   or an egg or even faeces (ewww!!!!). Sometimes fossils are no more than impressions or lines in stones. All these things are easier to find in rocky places than in bogs, swamps or rain forests.

How do fossils form? 

Well, will take up an example. Let us assume you are a fish living in a river about 100 million years ago. (Yes, fishes existed even before then!!). Now prepare to get disappointed, it is not going to be easy to become a fossil. Research by scientists’ shows that 99.99 % of species that have ever lived on the earth have not left any fossils. So the chances that you will die and form a fossil are extremely rare. But let us say, you are one lucky fish that will form a fossil. One fine day, you die. (Sorry, but you cannot become a fossil without dying). Now while your dead body slowly sinks to the river bed, your skin decomposes and the flesh is generally eaten by the other sea creatures. When you sink to the river floor, the skeleton is the only thing that is left. This produces an impression in the soft seabed. And as time passes, your skeleton is covered by fresh sediment. As even the bones disintegrate over time, the sediments enter the cavities left behind and solidify to take the shape of the bones.

The sediment layer turns to rock due to the pressure of the layers above and you are a fossil entombed in rock for all time. Then, over time, the river which was once your home, changes course and the rock layer of the river bed is exposed to the elements. Then the natural forces of erosion start acting and after some millions of years, the rock layer in which you are buried is exposed to the sky. If by some lucky chance, you are found by a human, you will be taken to a scientist and treasured as a fossil. Then you will be subjected to all kinds of tests and inferences which will help the scientists reconstruct the times in which you lived.

Now, what exactly do fossils tell us about?

Needless to say, fossils tell us a lot about the past. By looking at the fossil, we can reconstruct the animal’s shape, size, eating habits, how it died and also the conditions in which it lived. Many times, a fossil can be as small as a tooth or a claw, but based on that single claw or tooth, scientists often reconstruct the entire animal. For example, a dinosaur called the Iguanodon was first classified as herbivorous dinosaur just based on the study of its tooth. Similarly, mammoths are the ancestors of modern day elephants and have been reconstructed from their fossilised skeletons. There once lived a great palaeontologist called Georges Cuvier. It was said that he could describe the look and nature of an animal from a single tooth or scrap of jaw, and often name the species and genus into the bargain!!

Fossil study or palaeontology is very important in knowing the diversity of life on earth. The entire world of dinosaurs as we know it today has been reconstructed from fossils. Use of all these techniques has enabled palaeontologists to discover much of the evolutionary history of life, almost all the way back to when Earth became capable of supporting life, about 3,800 million years ago. The oldest fossils on Earth are about 3.8 billion years old or almost a billion years younger than the planet itself. Fossils aren't used only to understand individual organisms. Geologists also use fossils for what's called bio stratigraphic correlation, which allows researchers to match layers of rock in different locations by age based on how similar the fossils in each rock layer are.

Perhaps one of the most important functions of fossils from a scientific perspective is that they constitute one line of evidence for understanding evolution. Using information pieced together from fossil evidence, scientists can reconstruct body types of animals that no longer exist and put together a "Tree of Life" to describe the evolutionary relationships between organisms.

Now, after this brief article, here are some things for you to find out.......

What was the oldest fossil ever found?

Do fossils really prove the theory of evolution?

How reliable are the data obtained from fossils?

HAVE FUN FINDING OUT ABOUT FOSSILS!!

BY

BHARAT, NSS VOLUNTEER