Dates are a natural food and one which apparently many mammals, some of which are probably our ancestors, fiercely contest for in African jungles and rain forests. However, it's also got an embarrassingly high glycemic index and load. Is there any saving grace to this fruit? Perhaps it's got some special nutrients found nowhere else. I'm guessing that most primates have larger metabolic organs (liver and pancreas) organs than we do to deal with all the fruit they eat so dates wouldn't be as harmful to them.
I would place dates in the same category as other unprocessed but high-sugar foods, and treat its intake the same way as you would raw honey, maple syrup, etc. Because it is a whole food, it has a nutrient content, and probably fits in to evolutionary eating, especially as they are a sort of staple in traditional middle eastern cooking.
So if you're looking for a sweetener and don't want to use something like stevia, dates are a good option; they are especially good in dense baking (e.g. loaves, things like banana bread, fruit/nut bars) as they are sticky, add moistness and a caramel-like flavour. They are also very portable and practical, so quite convenient to take on a hike or camping trip.
Nutrition wise, dates have commendable amounts of minerals such as potassium and vitamins (though vitamin C is only present in notable quantities in fresh dates since heat significantly depletes it) and antioxidants. So it isn't an empty calorie sweetener by any means. It is also easier to find pure, unadulterated dates than truly unprocessed honey or maple sap with a good nutritional and antioxidant profile, so its definitely a good source of sweetness, though I don't think dates would perform well sweetening something more liquid like custard.
It's true that dates are very high in fructose, which is problematic, hard to digest for some folks and is most often stored as fat. However, dates are a whole food, not just sugar alone: food processing tends to have a knack for isolating components of foods, which leads to a consumption of that component that is way higher than what you could have ingested if you had eaten the whole food (HFCS, nut/seed oils all fall into this category). Early man would not have had access to such an amount of dates and other high-sugar plant material to consume enough fructose to affect the metabolism.
Studies on honey show that higher-antioxidant honey (e.g. acacia vs rapeseed honey) causes less of an elevation of serum fructose levels(http://www.ncbi.nlm.nih.gov/pubmed/20823899); so I suppose that the same would hold for consuming dates, which also have bioactive compounds that could well counter any potential damage.
However, once again, we did not evolve consuming a lot of such high-sugar foods; dates should be treated like any other high-sugar food and eaten in moderation. You should most certainly not rely on dates for nutrition: you would have to eat 100 grams of dates to just under 20% of the RDA for minerals like potassium, and under 10% of RDA for select vitamins, for a price of around 70 grams of carbs, most of them in fructose. So dates should be limited to post-workout, the occasional treat and perhaps on a hike where you're very active.
If you have weight to loose, or are just starting out on paleo and not yet fat-adapted, or if you have metabolic disorders, furthermore, I'd avoid dates altogether before you're ready to add more carbs to your diet. Needless to say that if you have fructose malabsorption you should avoid them altogether.
And remember that date syrup is not the same as dates - it does not contain the same nutrient profile and is essentially the same as something like HFCS - an isolated sugar!
So the bottom line is, dates are, per se, a whole food and can be classed as 'paleo', but should always be put in context of your lifestyle and carb tolerance.
Hope I helped,
Lots of paleo love :-)
I love dates. Here is what FitDay says 5 dates contain as nutrients - I'd say a good little supplement!