For each of the seven early civilizations being compared, I compiled information regarding its environmental setting, population density and distribution, family and community organization, government, legal system, technology, land tenure, subsistence patterns, trade, manufacturing and distribution of goods, art, architecture, religious beliefs and practices, moral codes, specialized knowledge, and beliefs concerning the universe, the nature of the individual, and esteemed forms of behaviour. My goal was to ascertain how these elements were articulated in individual civilizations before attempting comparisons.

I sought to determine empirically the amount of research that was required by noting when I began to encounter a sharp and consistent decline in information that either supplemented or contradicted what I had already collected. Reaching that goal necessitated taking notes on as many as one hundred books and monographs dealing with each civilization as well as reading a large number of recent papers. After this stage was reached, I read mainly newly published works that provided general overviews of specific early civilizations or dealt with aspects that had been poorly covered in earlier studies. By doing the research myself, I sought to ensure comparability in the way data were collected and processed.

In the course of this research I became aware that there were many biases and limitations both in the sorts of data available concerning each early civilization and in modern interpretations of these data. Understanding the reasons for such variations and making allowances for them are vital for the success of any comparative investigation.