Those are two sides of the same coin -- civilization IS deforestation, and I've come to believe that grain agriculture is the method, deforestation is the goal, not vice versa.  Just look at the coins of hundreds of countries depicting bundles of wheat, corn, rice, what not -- all the way to antiquity.  They encircle whatever else the coin signifies -- the head of the dominant baboon, the seal (they seal cages so the prisoners don't escape), the spell...   However...   "The diet of our forest ancestors was a rich mixture of leaves and fruit."  The diet of our forest ancestors procured in the periods specified above which coincide with the great ice ages could not possibly rely on what wasn't there.  Fruit edible for humans appeared at around the same time grain agriculture did, and were the outcome of manipulation, cultivation, in short sedentary agriculture all over again.  Unlike me, the author of the article you quoted must have never set foot in a wild forest.  Wild apples you can find there are small, hard, and very bitter.  Some are bitter-sour.  None are edible.  Same deal with pears -- you can break a tooth on a wild pear but aside from an "eeewww" it will yield little else, it's woody, not juicy.  The wild grapes are outright poisonous.  The wild berries are delicious, but don't grow in Ice Age conditions.  Neither do "leaves' of which we are supposed to have consumed "several kilos" daily -- with an 80,000 year break here and there while we waited for them to become available during the next (short) interglacial.    My favorite philosopher (nodding to another recent thread, from which he was unjustly absent) is Karl Popper.  "Scientific=falsifiable" is all one needs to know about the source of articles as the one above.  It's simply made up.  A fairy tale...    We developed big brains because we ate super high fat animals -- the fattest in the environment, mammoth, whale, seal were our first choices -- 60% of the human brain is made of saturated fat, and that's something not obtainable from "leaves and fruits" even if they were there, which they weren't.  Prolonged nursing (several years) is what allowed the human brain to develop its bulk and brawn, and whatever one eats after the first 5-6 years is irrelevant for the size of the brain whose formation is completed by that time.  We're not losing brain power to not eating enough leaves.  We're losing it to not using them, and letting someone else (who does not strike me as human at all) educate us as to which soy-fluoride formula is best for our young.