Page 28. " That radiation can serve as a model for the longer, larger scale, and less understood radiation of societies on different continents since the end of the last Ice Age, to become variously hunter-gatherer tribes and empires. "

http://www.history.com/topics/ice-age

Page 28. " That analysis of proximate causes is the easy part of this book; the hard part is to identify the ultimate causes leading to them and to the actual outcome, rather than to the opposite possible outcome of Ataullpa's coming to Madrid and capturing King Charles I of Spain. "

http://www.encyclopedia.com/humanities/encyclopedias-almanacs-transcripts-and-maps/charles-v-1500-1558-king-spain-and-holy-roman-emperor

Page 30. " "We shall see why Aboriginal Australians remained hunter-gatherers even while most peoples of neighbouring New Guinea became food producers." "

https://www.britannica.com/topic/Australian-Aboriginal

Page 31. " Of more lasting significance was a large scale population shift within Africa itself, the Bantu Expansion. "

http://www.oxfordbibliographies.com/view/document/obo-9780199846733/obo-9780199846733-0165.xml

 

https://courses.lumenlearning.com/boundless-worldhistory/chapter/early-africa/

Page 35. " "This date corresponds approximately to the beginnings of village life in a few parts of the world, the first undisputed peopling of the Americas, the end of the place to see era and last Ice Age, and the start of what geologists term the recent era." "

https://www.livescience.com/40311-pleistocene-epoch.html