article_snippet: Scroll down for video .
article_snippet: Dr Neil Roach, an anthropologist at The George Washington University in Washington, said: '
article_snippet: They had brains no larger than a chimpanzee's .
article_snippet: - Paranthropus, lived in woods and had massive jaws for chewing .
article_snippet: Brain size increases rapidly .
article_snippet: However, archaeological evidence of weapons like spears have yet to be found.