During which era did the first humans develop?

During which era did the first humans develop?
On the biggest steps in early human evolution scientists are in agreement. The first human ancestors appeared between five million and seven million years ago, probably when some apelike creatures in Africa began to walk habitually on two legs. They were flaking crude stone tools by 2.5 million years ago.

Reference:
When Humans Became Human - The New York Times
Feb 26, 2002

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