On November 12, 1997, at the invitation of Professor Henry Hooghiemstra, Colinvaux gave the annual Christian Huygens lecture of the Netherlands National science foundation (NWO) at the Nieuwe Kerk in The Hague. The theme of the lecture was The ice-age Amazon and the problem of diversity. The lecture was followed by a commentary from Professor Hooghiemstra with the title Tropical Rain Forest versus savanna: two sides of a precious medal? This chapter is a shortened version of the printed Colinvaux lecture that was published as a brochure by NWO. Some, but not all, of the first-person language of a lecture has been removed from this version.