The first part of the Royal Commentaries of Peru describes the manners and customs of one of the two great civilised communities of the New World, and was written by an author who had known the country from his childhood, and had peculiar qualifications for his task. The writer was not one of those travellers or explorers who set out from Europe in search of adventures in the New World. He had even greater advantages as a describer of a distant and little known land; for he was the son of such an adventurer by a native mother, and thus began to acquire the knowledge which enabled him afterwards to write this invaluable work, in his very cradle. So that his travels over all parts of Peru were not commenced until he had learnt the traditions and customs of his mother's people, and had become intimately acquainted with their language. The young Ynca had a wonderful start of all other contemporary travellers, for he was born, as it were, in the midst of his work, and began to store his material as soon as he could speak.

Our author's father, Garcilasso de la Vega, was a son of Don Alonzo de Hinestrosa de Vargas and his wife Doña Blanca Suarez de Figueroa. His paternal ancestry, the lords of Sierrabrava, descended from that gallant warrior who fought by the side of St. Ferdinand at the capture of Seville from the Moors—Garci Perez de Vargas, in 1348.