The novel references the advance of the polar ice sheets, setting the story before 18,000 years Before Present (BP), when the farthest southern encroachment of the last glacial period of the current ice age occurred. Auel's time-frame, somewhere between 28,000 and 25,000 years BP, corresponds generally with archaeological estimates of the Neanderthal branch of humankind disappearing.
A five-year-old girl, who readers come to understand is Cro-Magnon, is orphaned and left homeless by an earthquake that destroys her family's camp. She wanders aimlessly, naked and unable to feed herself, for several days. Having been attacked and nearly killed by a cave lion and suffering from starvation, exhaustion, and infection of her wounds, she collapses, on the verge of death.
The narrative switches to a group of people who call themselves "The Clan" and who we come to understand are Neanderthal, whose cave was destroyed in the earthquake and who are searching for a new home. The medicine woman of the group, Iza, discovers the girl and asks permission from Brun, the head of the Clan, to help the ailing child, despite the child being clearly a member of "the Others", the distrusted antagonists of the Clan. The child is adopted by Iza and her brother Creb. Creb is this group's "Mog-ur" or shaman, despite being deformed as a result of the difficult birth resulting from his abnormally large head and the later loss of an arm and eye after being attacked by a cave bear. The clan call her Ayla, the closest they can come to saying her "strange" name. After traveling with them for a while and starting to heal, Ayla wanders away from the group when they stop to discuss what they should do since they haven't found a new home and she discovers a huge, beautiful cave, perfect for them; many of the people begin to regard Ayla as lucky, especially since good fortune continues to come their way as she lives among them.
In Auel's books, the Neanderthal possess only limited vocal apparatus and rarely speak, but have a highly developed sign language. They do not laugh or even smile, and they do not cry; when Ayla weeps, Iza thinks she has an eye disease.
Ayla's different thought processes lead her to break important Clan customs, particularly the taboo against females handling weapons. She is self-willed and spirited, but tries hard to fit in with the Neanderthals, although she has to learn everything first-hand; she does not possess the ancestral memories of the Clan which enable them to do certain tasks after being shown only once.
Iza trains Ayla as a medicine woman "of her line", the most prestigious line of medicine women out of all of the Clans. It takes her much longer to train Ayla than it will her own daughter, Uba, since Ayla does not possess the memories of the Clan. When Ayla grows up, Iza is concerned she will never find a mate and no one will want her, making her a burden to the Clan, so she trains her to be a highly respected medicine woman so she will have her own "status" and will not have to rely on the status of a possibly lowly mate.
Ayla's main antagonist is Broud, son of the leader, an egomaniac who feels that she takes credit and attention away from him. As the two mature, the hatred between them festers. When they are young adults, Broud rapes Ayla, but she becomes pregnant, and rejoices in the birth of a son. Her son is almost taken away from her because he seems deformed to the Clan, since he does not look like them and, in the beginning, cannot hold up his head.
The book ends with Creb's death, Broud's succession to the leadership, and his banishment of Ayla, who sets off to find other people of her own kind. She is not allowed to take her son with her.
The sequel, The Valley of Horses, continues Ayla's story, which is further developed in other books of the Earth's Children series, which include The Mammoth Hunters; The Plains of Passage; The Shelters of Stone; and the sixth and final installment in the series, The Land of Painted Caves.
The archaeological and paleontological research for this book was carried out by Auel from her public library, by attending archaeological conventions, and touring extensively on sites with briefings by working field archaeologists. Some of the descriptions are based on the first adult Neanderthal skeletons found in Iraq from the cave burial at Shanidar, dating between 60-80,000 years BP. Other data is clearly linked to the widespread Aurignacian culture and Gravettian culture, and their tell-tale Venus figurines which Auel uses as one center of her Cro-Magnon religious practices.
In 1986, the novel was adapted into a film directed by Michael Chapman and starring Daryl Hannah.
In 2014, the Lifetime television network ordered a pilot episode, based on the series of novels. Ron Howard, Brian Grazer, Jean M. Auel, and Linda Woolverton are executive producers, with Woolverton writing the teleplay. The launch was slated for some time in 2015. The Pilot was canceled by Lifetime and has been shopped around to various networks with no luck, and presumed to be dead, as of March 2016.
The filming of a pilot for a series is due to start in 2016, with Ireland as one location.