The human digestive system evolved over millions of years, and there is not much that is known with certainty about the human diet over that span of time - however, it is known that humans have a better ability to process starchy foods than other primates. So the assumption that a 'paleo' diet wouldn't include lots of starch is not based on science. Take a look at this article: http://news.bbc.co.uk/2/hi/6983330.stm
If you read my comment a little more carefully, you'd know I'm not anti-starch. I avoid anti-nutritious and harmful grains like wheat, but I eat potatoes with zeal.
