In a parallel narrative, Jondalar, a young Cro-Magnon man of the Ninth Cave of the Zelandonii, accompanies his impetuous younger half-brother Thonolan on a traditional rite of passage called the Great Journey.

In these episodes, we learn of the Cro-Magnon's paleolithic nature religion, centered on the worship of the Great Mother of All, and follow their adventures and sexual exploits.

However, over the course of his adventures, Jondalar starts to question this prejudice, noting that no other animals have fire, tools or communicate intelligently, nor are they actively hated or attacked-as-sport by his people.

Ayla, alone and ritually ostracized from the only people she has ever known, travels steadily from the Black Sea peninsular home of her former tribe north for around half a year until finding the book's titular valley sunk deep into the windy landscape of the periglacial loess steppes in Ukraine.

Finding a suitable cave and many conveniences in the valley, she establishes a comfortable but lonely life there.