Biochemical Evidence:

As we had said earlier in section 13.2, Darwin had  recognized  that humans and the great apes shared many physical characteristics. This led him  to conclude, that humans and apes descended from a common stock. Darwin's conclusions were based on the study of fossils and the physical similarities  that he had observed. Now, a century later biochemical studies of  proteins and the genetic material-DNA  show how good his guess  was, Biochemical studies show us that, as evolution proceeds and the species get differentiated,  they accumulate changes in the structure of  their proteins and DNA. Longer the separation time, greater the changes. These changes are expressed in terms of  percent genetic distance which indicates  the proportional difference between the DNA of  the two species. Comparative studies of the proteins of  the African apes and humans showed that chimpanzees, gorillas and humans are closely related  to one another, while the Asian apes, i.e. the gibbon and orangutan were the more distant cousins of  this trio  .

Once the Asian and African apes were considered to be closely related and it was thought that  the hominids developed from apes prior  to 15 million years ago. Biochemical evidence, however, indicates that the ape-human divergence may have been much closer to five million years and that  thc gorilla split off  first, leaving the chimpanzees and the human-like creatures to share a common ancestor briefly before separating. Ramapithecus fossil specimen found in Asia, Europe and Africa was at one time thought to be closely related  to the species of modem man. However, on the basis of biochemical evidence, it has now been  shown that  it cannot be considered a homonid, because it  lived before  the Asian apes diverged from hominids. Same is true for Sivapithecus indicus, a fine fossil specimen of which was discovered in  1980 from the foothills of  the western Himalayas in  Pakistan.