What is a fossil? How are fossils formed?Newspapers, magazines and friendly talks go on referring to fossils without fully knowing what a fossil really is. Fossils are petrified (converted to stone) living organisms which take millions of years to form. When a living body is buried under tons of mud, soil or sand, it gradually decomposes. Softer parts like skin, blood, flesh, fat bodies and various organs like heart, lungs,intestines and glands decompose without a trace. But the skeleton system is made of very hard substance, which gradually, over millions of years and under very heavy weight and pressure, turns into stone. Grain by grain, the bone matter decomposes and the decomposed particle is replaced by sand particles till the whole bone converts into stone.
The interesting part is that the petrified bone fully retains its anatomical features in every detail. The protuberances of muscle attachments on the fossil give an idea about the bulk and strength of muscles that had been attached to them.
“Fossil impressions” are the impressions of insect invertebrates or plants in the layers of rocks. They are two dimensional. They also help in reconstructing the part. But full three dimensional solid fossils tell us much more.
Fossil of a skull gives us a wealth of informationIt tells us how the fellow looked like. Muscle attachments of the neck will tell whether he walked straight or had a stoopy posture. It cranial index (ratio of the length and width of skull), nasal index (ratio of length and width of the nose), forehead and chin will tell us its place in the evolutionary ladder.
The impressions on the endo-cranial crust will tell about how much speech it had developed, how much IQ it possessed and whether it was left or right handed. If the left side of lobes has more convulsions, he was right handed and vice versa.
Fossils of teeth also give us useful information in placing a fossil in the evolutionary ladder. Earlier, the molars had six cusps. But when softer food was eaten for a long time, they gradually reduced to five cusps. Today we have four cusps in our molars. A few million years ago, the last molar used to be the biggest molar. Today it is the smallest and is known as “wisdom tooth” because it emerges when the individual is 25-30 years old. In some societies among white races, it may not show up at all.
Age of the fossil can be determinedIt is very easy to determine the age of the individual whose fossil was found. Cranial structures give a sure indication of the age of the person at the time of his death. Skull or arm bones give a clue about the gender of the individual. Even if the whole skeleton is not found, the reconstruction of the entire body structure, total height etc can be determined. In some cases, only a thigh bone was found and gave enough information about the height and posture of the person who lived two lac years ago.
Evolutionary process is continuous since times immemorial. Evolutionary process still continues. Then, how do we determine the age of a given fossil? First of all, we study the strata in the rocks where the fossil was discovered. In rocks there are individual distinct layers of varying colors and thickness. Each layer signifies the period of time of its formation which gives us a geological calendar. Another way of determining age is to study the design and technology of the human artifacts found with the fossil or in the same layer, elsewhere. This will also give a lot of information about the period in which that “fossil” lived in flesh and blood. The anatomical details of the fossil gives further details about the type of features and thus gives an idea about the time in which those kind of features existed.
Paleontologists have to have sufficient knowledge, about anatomy as well, to classify a fossil as to which era it belonged to and study the particular features of that time. Fossils have much more to them than what meets the eye, which makes them a tough yet engrossing field of interest.
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Mating Pattern seen in Indian Tribes
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