An apple a day may well keep the doctor away, if you ensure that the one apple accounts for your entire carbohydrate consumption that day. However, one has to remember that typically, fruit is 1) seasonal, and 2) evolutionarily speaking, not very abundant.
Fruit is something a lot of people getting into the Paleo lifestyle misintepret as being ‘real’ food and in line with most paleo tenets. Don’t even get me started on the saturated fat-phobes, who tuck into a bowlful of mixed fruit, convincing themselves they’re having a healthy snack, while their waistlines increase and metabolic & gastric processes get progressively messed up.
Two reasons why this thinking does not tie in with a paleo viewpoint. Fruit is rich in fructose and sugars, so it should seem intuitive to avoid these (Read up on fructose in any paleo blog, or listen to Doug McGuff speak on this). Many people however, assume fruits are healthy as they’re packed with essential minerals, vitamins and trace elements. However, ensuring to eat varied bits of animal protein – bones for soup, liver for minerals, fatty cuts etc, you could get significantly more nutrients you would in consuming the sugary, carb rich fruit.
The second thing to remember is paleolithic fruits look nothing like today’s cultivated, selectively bred sugar bags called fruit. Also most forms of wildlife would have had access to fruit well in advance of a human forager, so the concept of freely available fruits in a paleolithic scenario is, in my opinion, incorrect.
I would recommend eating seasonal, locally sourced fruit if you absolutely need to have fruit in your diet. Else, stick to fresh meat.