Evolution Test - 77

Homo habilis, known as 'handy man' is a species of the genus Homo which lived from approximately 2.33 to 1.4 million years ago, during the Gelasian Pleistocene period. The discovery and description of this species is credited to both Mary and Louis Leakey, who discovered the fossils in Tanzania between 1962 and 1964.

The skull of A. afarensis and P. troglodytes have the same forward cutting jaw, the same enlarged brow ridge and the same general skull.

• As the population is in Hardy Weinberg equilibrium, the frequencies of alleles will remain the same for the next generation also. 
• According to the question, the frequency of recessive allele is (q =  0.2) Frequency of dominant allele= p= 1-q= 1-0.2=0.8. 
• Hardy Weinberg law states that the sum of all genotype frequencies is represented as the binomial expansion of the square of the sum of p and q. 

According to the Hardy Weinberg law, the allele and genotype frequencies in a population remain constant under absence of factors responsible for evolution. These factors are namely mutation, recombination, gene migration, genetic drift and natural selection. Mutation is defined a sudden inheritable changes in the genetic material of organisms and thereby introducing the new alleles and disrupting the allelic frequency of the population. Recombination occurs through the process of cross over and independent assortment of chromosomes during meiosis and by random fusion of gametes. Gene migration is the flow of genetic material between two populations through incoming of new individual and thereby introducing/removing alleles from the population gene pool. Genetic drift or allelic drift refers to the change in the frequency of an allele in a population due to random sampling of organisms. Natural selection is the survival and reproductive advantage to certain allelic combination; the favored alleles increase their frequency in population by their higher reproductive rates. Thus, option D is the correct answer.

The sequence of stages in the evolution of modern man is Dryopithecus, Ramapithecus, Australopithecus, Homo habilis, Homo erectus, Homo sapiens, Homo sapiens sapiens and modern man. The earliest Homo sapiens were Neanderthal man and earliest Homo sapiens sapiens were Cro-magnon man. Homo erectus were the first erect ape man. The Home erectus gradually evolved into the Homo Sapiens. Cro-magnon man are considered extinct modern man.

It has been known as Cro- Magnon man, because its fossils were first discovered in 1868 from Cro-Magnon rocks of France by MacGregor. Cro-Magnon man emerged about 34000 years ago in Holocene epoch. Thus, it is regarded as most recent ancestor of today's man. The Cro-Magnon man had, like us, about 1.8 metres tall, well-built body. Its face was perfectly orthognathous (jaws do not project forward) with an arrow, elevated nose, broad and arched forehead, moderate brow ridges, strong jaws with man-like dentition and a well developed chin. Its cranial capacity was, however, somewhat more than ours, being about 1650 cc. It is, therefore, believed that Cro Magnon man was somewhat more intelligent and cultured than the man of today. It could walk and run faster and lived in families in caves. It made excellent tools and even ornaments, not only of stones and bones, but also of elephant tusks. Its tools included spears, bows and arrows, as he was omnivorous. Use of the skin clothes by this man is also confirmed. So, the  most nearest prehistoric ancestor of present man may be Cro-magnon man compared to Java man, neanderthal man and Peking man.