1. Australopithecus afarensis
They had ape-like faces and their brains were a third the size of modem humans' brains. They lived 3-3.9 million years ago. Fossils were found in Ethiopia in 1974.
2. Paranthropus boisei
Covered with fur, they had strong arms and gorilla-like faces. They lived 1-2.5 million years ago. Fossils were found in Tanzania in 1959.
3. Homo habilis
Homo habilis, which actually means "handy man", was the first species to make and use primitive stone tools. They lived 1.6-2.2 million years ago. Fossils were found in Tanzania in 1960.
4. Homo erectus
With skeletons very similar to those of modern humans, they were probably the first to use fire. They lived 30,000-1.8 million years ago. Fossils have been found in Africa and Asia since 1893.
5. Homo heidelbergensis
They were skilled hunters who used spears to kill animals. Their bodies were similar to ours, although more muscular and larger boned. They lived 200,000-500,000 years ago. Fossils have been found in Ethiopia, Germany, France and Spain since 1921.
6. Homo Neanderthal
Their brains were at least as large as those of the average modem humans, while their smaller bodies helped them deal with cold climates. They lived 30,000-230,000 years ago. Fossils have been found in France and Iraq since 1856.
What is considered more important in the development of the human？

A. Man could stand on two feet.
B. Man's brain became big enough.
C. Man's arms became strong.
D. Man could use the stone tools.