...He had sheep, oxen, male donkeys, male and female servants, female donkeys, and camels.According to Wikipedia and other sources, the order in which animals were domesticated is as follows: sheep (<9000 BC), cows and oxen (~8000 BC), donkeys (~5000 BC), and dromedaries and camels (~4000 to 2500 BC) . Servants or slaves were used regularly roughly about the same time as the domestication of donkeys was taking place (somewhere from 6800 to 4500 BC) . So, the order here in Gen. 12:16 fits perfectly with the order of domestication and the use of servants. The text says nothing about domestication, obviously, but it would not surprise me if the order was done intentionally this way, since this is the first reference in the Bible of camels, oxen, or donkeys. Considering that the odds of this being randomly correct is about 1 in 120, I would like to believe this is not just coincidence.
So, there you have it -- my huge speculation for the day.
 http://en.wikipedia.org/wiki/Domestication; et al.
 https://www.freetheslaves.net/SSLPage.aspx?pid=303; et al.