http://www.thepaleodiet.com/articles...er%202006a.pdf

...the bottom line is that the human genome likely evolved with between 10% - 15% saturated fatty acids as a percent of total energy consumed.

For those who don't like math: in a 2000 calorie diet, that would be 200 - 300 calories per day or 22 - 33 grams of saturated fat per day.