Which statement explain why humans have a highly developed forebrain and midbrain compared to other primates? a. humans have complex social skills. b. humans have developed tools to aid them in their tasks. c. humans have the ability to communicate. d. humans have the ability for rational thought.

The right answer is D. Humans have the ability for rational thought.

The American Academy of Sciences thinks they have found the beginnings of an answer. An international team of researchers has highlighted a new structural asymmetry of the human brain that could indeed explain our cognitive advance. It is the upper temporal sulcus (STS) - a fold of the cortex - that is located in the upper temporal lobe of the brain.

By comparing 73 brains of chimpanzees to 177 others of humans, there appeared, in the latter, an asymmetrical structure of about 4.5 centimeters long in the right hemisphere. An asymmetry that is only very little found in our ape cousins.