Eggplant is old world and is a nightshade. So that premise is wrong.

I was out browsing articles on the Paleo diet and here is an excerpt from the author of one Paleo Diet book.

"Eat lots of produce. Paleolithic diet contained about 10-12 portions of produce per day, with a portion being around a half cup.

and

The nutrients in produce are not particularly affected by cooking. In fact, cooking breaks down some of the cellulose that we have no enzymes to digest, making the vitamin and mineral content of the vegetables much more available. This is even more important for those with weak digestive systems. For this reason, we recommend that vegetables be eaten mainly in the cooked form, with raw foods as a condiment for the most part.