Chapter 6: Brains and Tools

1. Physical evidence documenting the course of human evolution is sparse. The complexity of the story allows different experts to come up with credible yet conflicting explanations of the same facts.

2. The most important ecological change has been greater brain mass, and the increased information-processing power it provided. It made possible a survival strategy that no previous species had pursued: relying on tools to overcome innate biological limitations.

3. When looking back over the course of human evolution, one can hardly miss the close relationship between brain development and technological change. Both seem to follow the punctuated-equilibrium pattern of evolution characterized by rapid bursts of change followed by long periods of stability.

4. For those who imagine the human species raising itself to global dominion by dint of intelligence, ingenuity, and hard work cannot explain why our ancestors' brains began to expand in the first place.

5. A new species cannot be too different from its immediate ancestor. Evolution is conservative. If a mutant offspring is to survive, it must represent only a slight modification of a proven genetic design.

6. Jolted onto a new evolutionary trajectory by frigid weather, our lineage began to be shaped by a feedback loop of bigger brains-better tools-more food.

7. By retaining the unquenchable curiosity of young apes throughout an ever- lengthening lifespan, our ancestors acquired the intellectual potential for discovery.

8. The "purpose" driving our ancestors' innovative behavior was not a striving for progress toward some cosmic goal. Our capacity for innovation did not make us a "better" or "higher" species.

9. Our lineage is unique because our anatomy allowed our ancestors to supplement their genetic evolution with technological evolution. Through creativity and innovation our ancestors were able to satisfy their most fundamental economic needs.

10. It is serendipitous that we are here. But we are here, nonetheless.