Question

What is the most advantageous difference between the ancestral primate skulls and the modern human skull?
A. Forward-facing eyes
B. Decreased brain capacity
C. Loss of canine teeth
D. Loss of the brow ridge
E. Reduction in jaw size

Answer 1

Hint: Man is the most highly developed primate. It has many features which distinguish him from his close allies, the apes in many ways. One such difference can be found by studying the skull of the ancestors of man to modern man's skull.

Complete answer:
Man's place in nature is a topic of great interest. Some people consider the man a special creation set apart from animals and even from nature itself. Biologists view man objectively and using knowledge of structure and working of his body, consider him "just another animal" close to some of the great apes such as gibbons, chimpanzees and gorillas. Swedish biologist Carolus Linnaeus who is regarded as the "father of taxonomy “gave man, like other animals, a two-word scientific name Home sapiens and placed him among the monkeys and apes.

We can study the features given above to know the answer.
Cranial capacity: Hominids have a larger cranial capacity,i.eApes have a cranial capacity of 400 cubic centimetres compared with 1400 cubic centimetres in humans. This is an indication of their brain size.
Brow ridge- It is located above the eye socket whose major role is to reinforce the weakened bones of the face. In apes, it is much larger due to the strain that is put on the cranium by their temporal muscles. It is one of the last traits being lost in modern man.

Canine teeth: Apes had a small diatreme between incisors and canine teeth. Apes have much larger canines that are used to eat meat but there are apes that are vegetarian and these teeth play a significant role in defence. In humans, canines are of the same size and roughly of not much use.

Mandible: The mandible is much larger in apes. This is associated with a more primitive diet consisting of eating leaves. In humans, a chain has developed to protect weak points of the jaw. These are not much in use for humans.

Eyes: Most apes have low contrast between their eyes and facial skin. Contrary to it humans have the outline of the eye and the position of the iris are clearly visible. It has not much significance between them.

Thus considering all options, we can infer that the difference in the cranial capacity is most advantageous for humans. So, the correct option is B.

Note: Charles Darwin remarked that man was one more animal species whose origin and evolution could be traced like that of any other species. He in his book "Descent of Man and Selection in Relation to Sex" put forward his theory of the evolution of man from ape-like ancestors. Human ancestors are now supported by molecular evidence based on proteins and nucleic acids.