Data from molecular genetics have changed our views on the origin, spread and timescale of our species across this planet. But how can we reveal more detail about the demography of ancient human populations? For example, is it possible to determine when and how many people arrived at a certain continent, and which route they took from a choice of geographically plausible options? One of the most promising tools for such investigation is computer simulation incorporating various demographic scenarios. The simulation outcomes must be evaluated by teams with archaeological expertise, since archaeological evidence is generally the best evidence currently available on the population histories of geographical regions. This book is a summary of the landmark conference held in Cambridge in 2005, where specialists in simulations and molecular genetics as well as archaeologists came together to present and evaluate the state of the art, and to discuss future possibilities.