11. Why do researchers suspect that Sahelanthropus was more likely a human ancestor, and not an ape ancestor? 12. Until quite recently, aprominent hypothesisin the origin of humans was that bipedalism and increased brainsizeevolved simultaneously. What evidence is calling this hypothesis into question now? 13. While brain size remained unchanged for 3-4 million years in hominid ancestors, what about those ancestors was changing, according to the evidence? 14. What is the evidence for Salaam’s brain becoming more human, compared to a chimpanzee? How did scientistsget this information, since brains do not fossilize? 15. How can scientists distinguish between random rocks and stone tools? 16. What features of Homo habilis made it different from Australopithicus (Lucy and Salaam)? 17. What do scientists think stimulated the huge selection pressure for increases in human brain size, like that seen going from Australopithecus to Homo habilis? 18. In trying to understand how rapid the climatic changes were for Homohabilis, how do scientists estimate the rates of change? 19. What was the African climate during the time when our ancestors’ brain size was “flat-lining” (from Sahelanthrous to Lucy). 20. When hominid brain size begins to increase (beginning with Homo habilis), what was happening to the African climate?