The theories that explain the evolution are
hypothetical. There is no practical proof for them. In fact, it is not possible
for anybody to observe even a single change in favour of evolution that occurs
in the body of organisms as our life span is too short to notice such slow
changes. Hence scientists collected evidences from different branches of the biology.
Some of them are
a.
Evidences from palaeontology,
b.
Evidences from embryology,
c.
Evidences from comparative anatomy
d.
Evidences from cell and molecular biology
a) Evidences from
Palaeontology: Palaeontology (Gr. Palaios - old, on-existing, logos - to study) is the study of prehistoric
life through fossils. Fossils are the remnants of plants or animals that were preserved in the layers
of the earth and have been excavated from the soil. They are of various types
like moulds,
casts, petrifications, traces, coprolites (fossilized faecal matter), actual remains of animals, etc. They support
the idea that life has gradually evolved on the earth. The biologists and
palaeontologists have found the fossils of many transitional forms (connecting links) which link all the major
groups of vertebrates e.g. Eusthenopteron between fishes and amphibians, Seymouria between amphibians and reptiles,
Archaeopteryx
between
reptiles and birds, Cynognathus between the reptiles,mammals, etc.
A complete fossil record of the various stages in the
evolution of horse is available. It indicates that evolution is a gradual
process and not a sudden creation of a species.
Geological Time Scale: The earth contains different
layers of sediments of which, the bottom layer is the oldest layer and the
upper layer is the most recent layer. Based on the age of rocks, a time scale
was prepared and it is called the geological time scale, it depicts the different
stages of the evolution of life on the earth over the past millions of years.
It consists of five Eras
which are divided into Periods that may be further subdivided into
Epochs. These Eras, Periods and Epochs depict the time of origin and dominance
of certain groups of animals during certain Eras or Periods. It provides the most direct
evidences for the concept of evolution.
