Social development as biology, sociology and geography … and historically, regional differences especially from the geography.
Morris has devised a quantitative “social development index” based on evaluating a civilization’s energy capture, organization (size of largest cities), information management, and war-making capability. (The details of his method are online here.) When you graph human progress since the last ice age 15,000 years ago, the results show that the West led for all the millennia up till the 6th century CE, fell behind for 1,200 years, then leapt ahead again up to the present day. (The “West” for Morris is the civilizational core that developed agriculture and then cities and empires in the eastern Mediterranean, later spreading across Europe and North America. The “East” is China.)
Geography determines how and when regions develop, but new societal capabilities keep redefining what geography means. At first agriculture was limited to regions with reliable rainfall, but once societies grew able to manage large-scale irrigation, the empires of parched regions like Mesopotamia and Egypt could take off, and their rivers became trade routes. The vast steppes of north-central Asia long separated Western and Eastern empires, but once their riches became worth plundering, mounted nomads from the steppes invaded repeatedly, defeating the agrarian armies and carrying germs that unleashed waves of epidemics.
The West had the advantage of a trade highway in the Mediterranean that wasn’t matched in the East until the 6th century, when the Sui emperors built the Grand Canal 1,500 miles long linking north and south China. Everything then changed with the invention of ocean-going ships and guns in the 13th and 14th centuries.