This is Scientific American's 60-second Science, I'm Susanne Bard.If you watch nature documentaries, it's easy to come away with the impressionthat lush tropical forests have been largely undisturbed until modern times."Tropical forests have sort of long been considered to be these pristine wildernesses that humans haven't really toucheduntil recent industrial forces have started to invade them and challenge them with 21st-century capitalism."Archaeological scientist Patrick Roberts of the Max Planck Institute for the Science of Human History."However, in the last two decades, archaeological data have shown that,actually, human societies have occupied and modified these environments over many millennia."Roberts says some of the trees alive in tropical forests are up to a thousand years old.And they're sort of like time capsules, storing a record of past human activity in their tree rings, chemistry and DNA."So we wanted to see how different existing methods might come together to explore past tree populations, tree growth, tree agesby looking at the largest witnesses of the changes in human activity in the tropics―the trees themselves."For example, indigenous peoples of the Amazon basin cultivated Brazil nuts for thousands of years.Roberts's colleague Victor Caetano-Andrade analyzed tree ringsto determine the age and growth rates of Brazil nut trees near the city of Manaus.He found that many trees were established in the late 1600s,
