1.4 Chronological considerations We have said that the past is the source of the present and this is true in the academic field of human evolutionary genetics as much as in real life. This exciting subject owes its current status to developments and debates over the last 150 years in genetics, paleontology, archaeology, anthropology and linguistics. In this book we have avoided cataloging this history, instead taking a twenty-first century perspective, but we discuss key developments where they are relevant, and provide a time-line in Figure 1.6. In describing the origins of our species and its spread across the world it would be inappropriate not to take a chronological course, and this we do in Chapters 7 to 12; Figure 1.7 summarizes many of the important events in human evolution in a time-line. Data on human genetic variation are accumulating at an unprecedented rate. The only practical way to keep abreast of this tide of discovery is to use the internet, both to survey the latest publications on a topic through web databases such as PubMed (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi? ata as they appear through many websites, some of which are listed in Box 1.3