Bryson stresses that evolving to walk on two limbs entails a great deal of risk for early hominids. This highlights how lucky humans are to be here and how easily things could have gone south for our ancestors before we evolved. Bryson also shows that a lot of scientific confusion about hominids—specifically, how many species of hominid there are—persists in this research area, once again indicating that the vast majority of the scientific journey still lies ahead.