Anything can be preserved under the right circumstances and control. If that burger and fries was exposed to moisture or had a bite taken out of it when it was new it would definitely grow mold and decompose. If you want proof that McDonalds is bad for you just look at the people that eat there frequently. You can usually see them on scooters at Wal-Mart. There are plenty of foods that are just not prone to decay or decomposition, the main element that triggers this is moisture. Honey is the prime example of a real "eternal food". There have been instances of edible honey dating back thousands of years found in Egypt: http://www.smithsonianmag.com/scienc...-life-1218690/