Read the sentence from “Rivers and Stories,” Part 1. It was probably fishing and hunting on floating logs that led to boat-making, and boat-making must have increased enormously the mobility of the species.

What does the author mean by the phrase “the mobility of the species”?

the ability of humans to move from place to place

the ability of humans to find their own food

the ability of humans to live on the water

the ability of humans to learn how to build boats