Read the following passage given below and answer the question.
We humans walk with two legs (called 'bipedal') and use two hands. The evolution of bipedalism began in our ancestors, the primates, about 4 million years ago. The primates not only gave us our blood groups, but our two feet and two hands as well. Primates exhibit characteristics that distinguish them from less evolved mammals. These include adaptations to live in trees (as monkeys do), big brains, heightened sense of vision, opposable thumbs to grasp the four fingers in each hand, and more flexibility in shoulder movements.
Dr. Tetsuro Matsuzawa of the Kyoto University, Japan, writes that the shared ancestor primates moved into tree tops and developed four hands from the four legs possessed by the terrestrial ancestor. This was an adaptation to arboreal life; enabling the efficient grasping of branches and tree-trunks. Subsequently, early human ancestors left the trees to start walking long distances across the land, bipedally. Thus, we created two feet from four hands during the course of evolution from our primate ancestors.
The anthropologist Carol Ward of the University of Missouri, US points out that the way we humans get around the world is different from any other animal on earth. We move around on the ground, upright on two feet, but in a unique way: with one foot after the other; holding our body fully upright in a characteristic series of motions. So, it's a big deal to figure out how and why we walk the way we do, and how our lineage really diverged so much from ape like creatures.
The human brain is about three times as big as the brain of our closest living relative, the chimpanzee. Moreover, a part of our brain, called the cerebral cortex - which plays a key role in memory, attention, awareness and thought - contains twice as many cells as the same region in chimpanzees. We are, thus, smarter than apes.
