EVIDENCES OF EVOLUTION
The word “evolution” is derived from the Latin word “evolvere” which means to “unroll” or “unfold”. Thus, the theory of Organic Evolution states that it’s a kind of gradual unfolding or formation of more complex, advanced and present day forms from simple and primitive organisms living in the past,millions of years ago.
There are various evidences available to prove this point. viz.
(a) Morphological and Anatomical Evidences
(b) Embryological evidences
(c) Paleontological (Fossils) evidences: The study of fossils (paleontology) is the best and most direct conventional type of evidence, e.g., the fossil of Archaeopteryx*. (“Archaeo” means primitive and “ptera” means wings in Latin) is a classical example of evolution of birds from reptiles, because it contains features of both the forms. Similarly, the world famous fossil of “Lucy” (Australopithecus afarensis) shows that “bipedal” locomotion arose for the first time in ancestral man here and finally led to the development of erect “modern” man.
(d) Biogeographical evidences
(e) Biochemical evidences: The most convincing evidence of common ancestry comes from similarities of certain biomolecules viz. composition of protoplasm, enzymes, cytochrome ‘C’ (respiratory pigment present in all eukaryotic cells), blood serum proteins, hemoglobin, insulin, etc. The degree of molecular homology is more in closely related forms and vice versa, e.g.,amino acid sequence for cytochrome ‘C’ of humans and chimpanzee is identical.
(f) Genetic evidences or Molecular evidences: These are the latest observable tools in determining the phylogenetic relationships between organisms and allow molecular comparisons even between very uncommon relatives with no morphological, behavioural, physiological or ecological relationships e.g., bacteria and humans. Some of the molecular tools used to prove evolutionary relationships are:
- Amino acid analysis or sequencing e.g., Hb, Mb sequencing in para and orthologous species.
- Nucleotide sequence analysis (data from 5S ribosomal RNA)
- DNA hybridisation
- Restriction enzymes: which cleave DNA into fragments at particular sites like ECORI from E. coli. They allow comparisons among DNA of different species
- RFLPs (Restriction Fragment Length Polymorphisms)
- Mitochondrial DNA and microsatellites, etc.
