”Culture is a system of storing and altering patterns of behavior not in the molecules of genetic code, but in the cells of the brain.”

Crosby explains the difference between physical and cultural evolution. Physical evolution is a constant force that has slowly altered every organism on earth as the organisms that were most suited to their environment were able to reproduce most effectively. Cultural evolution, on the other hand, is something that only the human species is capable of to a significant degree. Cultural evolution does not change our physical form but is still a critical component to the way human history has occurred, especially as historical cultures began to mix more and more.

“Where conditions were particularly suitable - where, for instance, wild wheat grew in solid stands and included strains with ears that did not shatter and scatter wastefully when harvested with flint sticks - the jigsaw pieces of domestication camp together, and gatherers became farmers.”

This passage highlights the randomness involved in the Neolithic Revolution. Agriculture was not predestined to exist and is not inherently a better system than hunting and foraging. Humans developed agriculture for myriad reasons and on different timelines across the globe.

“Norse sailors minimized their risks, and so made few voyages of discovery. Only a fool with a new theory would sail off into an ocean without a very specific idea of where he was going; the Norse always had a specific idea.”

The stereotype of Vikings sailing the Atlantic to find new land is inaccurate. Iceland, their only successful colony outside of Europe, was first discovered by Irish monks, who gave the Norse detailed information about the island and how to reach it.