Final answer:
The Moors were the most important ancient people of the Iberian Peninsula to later Spanish culture.
Step-by-step explanation:
The most important ancient people of the Iberian Peninsula to later Spanish culture were the Moors. The Moors were an alliance of Arab-Berber peoples who invaded Spain in the 8th century and ruled parts of the Iberian Peninsula for several centuries. Their influence thrived in Iberia and left a lasting legacy on Spanish culture, including architecture, art, science, and mathematics.