Read carefully the passage given below and write your answers to the questions that follow in clear, correct, and concise language: Not so long ago a book on human origins would have devoted a substantial number of pages to descriptions of the fossil evidence for primate evolution. This was in part because it was assumed that at each stage of primate evolution one of the fossil primates would have been recognizable as the direct ancestor of modern humans. However, we now know that for various reasons many of these taxa are highly unlikely to be ancestral to living higher primates. Instead, this account will concentrate on what we know of the evolution and relationships of the great apes. It will review how long Western scientists have known about the great apes, and it will show how ideas about their relationships to each other, and to modern humans, have changed. It will also explore which of the living apes is most closely related to modern humans. Among the tales of exotic animals brought home by explorers and traders were descriptions of what we now know as the great apes, that is, chimpanzees and gorillas from Africa, and orangutans from Asia. Aristotle referred to 'apes' as well as to 'monkeys' and 'baboons' in his Historia animalium (literally the 'History of Animals'), but his 'apes' were the same as the 'apes' dissected by the early anatomists, which were short-tailed macaque monkeys from North Africa. One of the first people to undertake a systematic review of the differences between modern humans and the chimpanzee and gorilla was Thomas Henry Huxley. In an essay entitled 'On the relations of Man to the Lower Animals' that formed the central section of his 1863 book called Evidence as to Man's Place in Nature, he concluded the anatomical differences between modern humans and the chimpanzee and gorilla were less marked than the differences between the two African apes and the orangutan. Darwin used this evidence in his The Descent of Man published in 1871 to suggest that, because the African apes were morphologically closer to modern humans than to the only great ape known from Asia, the ancestors of modern humans were more likely to be found in Africa than elsewhere. This deduction played a critical role in pointing most researchers towards Africa as a likely place to find human ancestors. As we will see in the next chapter, those who considered the orangutan our closest relative looked to South-East Asia as the most likely place to find modern human ancestors. Developments in biochemistry and immunology during the first half of the 20th century allowed the search for evidence about the nature of the relationships between modern humans and the apes to be shifted from traditional morphology to the morphology of molecules. The earliest attempts to use proteins to determine primate relationships were made just after the turn of the century, but the first results of a new generation of analyses were reported in the early 1960s. The famous US biochemist Linus Pauling coined the name 'molecular anthropology' for this area of research. Two reports, both published in 1963, provided crucial evidence. Emile Zuckerkandl, another pioneer molecular anthropologist, described how he used enzymes to break up the protein haemoglobin from blood red cells into its peptide components, and that when he separated them using a small electric current, the patterns made by the peptides from a modern human, a chimpanzee, and a gorilla were indistinguishable. The second contribution was by Morris Goodman, who has spent his life working on molecular anthropology, who used techniques borrowed from immunology to study samples of a serum (serum is what is left after blood has clotted) protein called albumin taken from modern humans, apes, and monkeys. He came to the conclusion that the albumins of modern humans and chimpanzees were so alike in their structure that you cannot tell them apart. Proteins are made up of a string of amino acids. In many instances one amino acid may be substituted for another without changing the function of the protein. In the 1960s and 1970s Vince Sarich and Allan Wilson, two Berkeley biochemists interested in primate and human evolution, exploited these minor variations in protein structure in order to determine the evolutionary history of the molecules, and therefore, presumably, the evolutionary history of the taxa being sampled. They, too, concluded that modern humans and the African apes were very closely related. (a) What does the author say about earlier assumptions regarding evolution? (b) According to the author, how are modern humans and apes related? (c) What later developments took place in the twentieth century in investigating the relationship of apes and humans? (d) What were the attempts made to use proteins to determine primate relationships? (e) In what way does the latest research prove the relationship between apes and humans?