In this world, there are millions of different species of organisms differing in a variety of ways. Biologists believe that these species were not always like this; they have evolved to their present form from their pre-existing forms. It is estimated that the characteristics of modern human beings developed some 2,00,000 years ago as a result of their continuous interaction with the environment.
Evolution refers to gradual and orderly biological changes that result in a species from their pre-existing forms in response to the changing adaptational demands of their environment. Physiological as well as behavioural changes that occur due to the evolution process are so slow that they become visible after hundreds of generations.
Evolution occurs through the process of natural selection. You know that members of each species vary greatly in their physical structure and behaviour. The traits or characteristics that are associated with high rate of survival and reproduction of those species are the most likely ones to be passed on to the next generations. When repeated generation after generation, natural selection leads to the evolution of new species that are more effectively adapted to their particular environment. This is very similar to the selective breeding of horses or other animals these days. Breeders select the fittest and the fastest male and female horses from their stock, and promote them for selective breeding so that they can get the fittest horses. Fitness is the ability of an organism to survive and contribute its genes to the next generation.
Three important features of modern human beings differentiate them from their ancestors: (i) a bigger and developed brain with increased capacity for cognitive behaviours like perception, memory, reasoning, problem solving, and use of language for communication, (ii) ability to walk upright on
No comments:
Post a Comment