Question

Why was the evolution of a large brain important to human evolution?

Answer 1

Homo sapiens is a member of order Primata; the order evolved from tree shrew like animals. Evolution of large brain is a characteristic of human line of evolution.

Explanation:

Our mouse like ancestor was arboreal and thus, primates were adapted to a life on trees. This helped them to develop a dependence on eye sight along with their sense of smell/hearing to remain aware of their surroundings.

Primates in early days of evolution developed binocular vision, as a result of gradual shortening of snout. This helped the primates to develop a better three dimensional perception of their habitat. This was first important change that required occipital lobes of brain to become large.

For leading active arboreal life, primates had opposable thumb and big toe. Extensive nerve connections to fingers and toes developed. A large brain supported simultaneous use of eyes and limbs, and better sense of balance while moving from tree to tree in monkeys.

As grasslands started to open up in Africa, apes had to leave tree dwelling habit (though they still may sleep on trees). A very small group of ape, probably of genus Australopithecus , developed bipedal habit, about 6 million years ago, due to a change in the way their legs fix in pelvic bone. This helped them to fix their eyes on horizon!

Now came the second chance when human ancestors required to develop larger brain: specially to support both the hands which are no longer used in walking. First species in hominid evolutionary line Homo habilis definitely had a bigger brain compared to its ape ancestors, including Australopithecus .**

With a large brain, in the beginning, our species learnt to pick up and throw stones. Then they sharpened the stones to make tools. Homo habilis was thus a 'handy man' who lived at least 2 million years ago. Later, our ancestors also designed weapons using wood and bone. They gradually advanced to making pottery, boat, clothes, even jewellery.

Human evolution became unique in providing non-genetic solutions to environmental challenges. *Thus natural selection definitely favoured large brained, intelligent individuals. This also meant that ancestors with large temporal lobes were able to communicate more successfully. This will again be of immense importance because childhood learning is extended in human.*

(Whenever a new hominid fossil is discovered, the story of human evolution changes. I have followed the most commonly accepted idea.)