Question

Which characteristic of living monkeys suggests that the earliest anthropoids were monkey-like?
A. All monkeys lack tails, like prosimians.
B. All monkeys are arboreal, like prosimians.
C. Like prosimians, monkeys rely more on smell than on eyesight for finding food and avoiding predators.
D. Of all the anthropoids, monkeys have brains that are most similar in size (relative to body size) to those of prosimians.

Answer 1

Hint: Anthropoids are a group of primates currently represented by New World and Old-World monkeys, apes, and humans. Anthropoids and prosimians are two groups of primates descended from tree-dwellers. They display adaptations to brachiation like rotating shoulder joints, a big toe and thumb that are widely separated from other fingers or toes, and three-dimensional vision. 
Complete Step-by-step answer:

Anthropoids (living monkeys, apes, and humans, together with their fossil relatives) share a host of structural, behavioural, and genetic characteristics that are absent in other primates. These characteristics include relatively huge brains, complete bony eye sockets, and several changes to the genome referred to as short interspersed repetitive element (SINE) insertions.

Consequently, anthropoids were recognised as biologically distinct. Anthropoids are sometimes known as “higher primates” due to the wide gap that separates them from other primates and their evolutionary proximity to humans.

Prosimians have smaller brains compared to their body sizes than monkeys. Though body weights and the brain are associated not only based on the brain incorporating sensorimotor functions but also based on the body's requirement to support the vigorous needs of the brain.

Prosimians are different from monkeys in that they have lower rates of oxygen turnover. When body size is adapted for its rate of oxygen turnover, monkeys and prosimians have comparable relative brain sizes. A consideration of the brain's energy requirements helps explain brain-body relationships.
Therefore the correct answer is Option D.
Note: Anthropoids are the higher primates, excluding prosimians. They are also called simians. Though, they belong to the infraorder Simiiformes or flat-nosed primates under the suborder Strepsirrhini of the order Primates. At the same time, the two parvorders of anthropoids are Catarrhini and Patyrrhini.