Despite the importance of tropical forests in conservation of the Earth's resources, surprisingly little is known about their history. By studying five sites in east-central Africa, one group now concludes that current biodiverse ‘hotspots’ were not always so species rich. Forests are thought to have survived the vicissitudes of the last glacial episodes in certain ‘core’ areas. But when the climate became warmer and wetter, equatorial forests seem to have expanded from these favourable locations in which they established themselves.
