What is a Fossil??
Whenever we come across the term ‘fossil’, we always try to link them with dinosaurs and huge birds. According to a lay man, a fossil is always thought to be the skeletal remains of a dinosaur or huge reptiles.
But, fossils always do not link with the skeletal remains nor do they always link to dinosaurs.
The naturally preserved remains of any plant or animal that have lived millions of years ago i.e. in the prehistoric times are called as a Fossil.
It can be said that a fossil of an animal is a solid proof that, that particular animal once lived in that region. Fossils can be in the form of bones, imprint of a plant on a rock, shells, etc.
The size of a fossil depends on the size of the animal to which it belongs to. For example, a dinosaur’s fossil will be bigger than the fossil of a plant.
There are 2 types of fossils which are named as Body fossils and Trace fossils. Body fossils consists of the remains of the whole organism or some body parts of the organism whereas trace fossils consist of footprints or tracks of the animal indicating that such type of an animal existed.
The overall study of fossils i.e. to properly extract them from the Earth’s crust, to find out about the origin of the animal, to find its geological age and the geological era to which it belonged to, etc. comes under a comprehensive study called as Paleontology.
Paleontologists are the people who study fossils to understand the different phases of evolution and to understand how the different species evolved.
How is a Fossil Formed?
There are different steps required for a fossil to form. These steps are both lengthy as well as very sensitive to the pressure between the rocks and soil, environmental conditions, also the skin type of the animal, etc.
A proper or detailed fossil is formed in marshy environment where the soil is wet and consists of a lot of minerals.
The first step of fossilization will always require a body to be buried into the soil at a certain depth. This soil should be wet that is the soil present near a river bank or on a coastal land.
The fleshy portion of the body that is the muscle and all the soft tissue decays over a period of time. The remaining part that is the bones play an important part in fossilization.
The sediment or the soil (mud) settles on the top of the bones of the animal and then forms a hard substance commonly known as a rock.
The bones which are covered by the soil particles also start decomposing which causes the minerals to seep in it. These minerals then replace the organic material of the bones and then form a fossil.
This formation solidifies over a period of time thus, gaining the shape of the bones. The minerals which replace the bones generally include silica, calcite or pyrite, etc. This process is called petrification or permineralization.
Types of Fossilization
There are different types of fossil forming processes which vary according to the environmental factors. For example, sometimes, some bees or bugs get trapped in the sap of a tree.
This sap then solidifies along with the organism inside it. This process of accidental solidification is also considered as fossilization. In this type of process, the organism is preserved in such quality that its DNA can be extracted and species identification can be done.
Carbonization is another type of fossilization mostly common for plant fossils. When a plant is buried in the soil it is covered with a lot of soil.
This plant does not survive and under the excess pressure of the rock the plant gets compressed drastically. It can get compressed to less than one hundredth of its original size.
This leads to formation of coal which is very valuable fossil and takes thousands of years to form the good quality coal (natural resource).
Another type of fossil forming process involves a mold fossil or cast formation. In this type, an impression is formed on the rock when the organism undergoes decomposition. This mold is then later filled with minerals forming a cast.
Dating the Fossils
Once a fossil is discovered, a question about its age arises. This question can be answered by the process called “dating fossils”.
This is done when we have a database of different already discovered fossils. The newly found fossil is then compared with the different categories which are made according to the type of rock, size, etc.
Another type of dating technique involves calculating the age of the radioactive minerals present in the fossil rock. This is much more precise than the comparison method. This technique is called as the Radiometric Method.
Linnaeus and Darwin were the two well-known naturalists who wanted to name all the species which were present on the Earth at that time as well as those which had become extinct.
They utilized the evidence of fossils to study the evolution and also to characterize each species on the basis of its genetic hierarchy.
What are connecting links??
Ever heard about connecting links?? These are a diverse class of animals which are very important to understand how animals evolved.
We all know that life originated from organisms present in the aquatic environment. We also know that fish have originated before other classes of animals.
Due to evolution of the science and technological world, now we know that amphibians evolved from fish, reptiles evolved from amphibians, birds evolved from reptiles, etc. but have you ever thought how was this estimation done??
The answer is a connecting link. A connecting link is an animal having intermediate characteristics of two species of animals. The study of connecting links can be done by studying fossils.
For example, there is a fish called as a lung fish. This lung fish consists of intermediate characteristics between fish and amphibians.
The lung fish has a distinguishing factor of having both gills and lungs for the purpose of respiration. This explains that the amphibians might have developed from the fishes.
Another example is of an Archaeopteryx. This animal has wings like birds and claws like reptiles thus, forming a connecting link.
This is also a very good example of how animals might have evolved in a series like fish, amphibians, reptiles and then birds.
The human evolution is also better understood with the help of different fossils. The fossils found in different parts of the world were compared and it was found that they were not same.
This led to estimation of the fossil’s age and categorizing them on the basis of their skull size and estimating the cubic capacity to hold the brain and thus forming the phases of human evolution.
The role-played by fossils to study the process of evolution and also different connecting links which tell us what animal evolved from which animal is important and unique in its own way.
All we need is a genuine interest to understand the ancestors of all the present-day animals and proper equipment along with a fossil of course to go back into the prehistoric times.