There was a time when our jaws could comfortably accommodate all 32 teeth, including the third molars. You have to go back about 100 million years ago, though, to the prehistoric version of man. Instead of walking upright, this guy got around on all four limbs, with a massive protruding jaw leading the way.
Early man's jaws were larger and more prominent because teeth played a vital role in survival. With the front appendages occupied with balance and running, teeth were prehistoric man's means of catching, dismembering and consuming prey. Our ancestors subsisted on a tough and chewy diet of leaves, roots and raw meat. Having 32 teeth's worth of chewing ability was a huge advantage at this point, especially because early man didn't visit the dentist with the regularity we do today; third molars might have played an important backup role when teeth were lost or worn down.
Then evolution had its way with prehistoric man, and teeth weren't so important anymore. Hominids began walking upright, and arms took on a greater role in obtaining food. After that, brains became larger and jaws became shorter. Researchers still aren't exactly certain which came first, though in 2004, a team from the University of Pennsylvania announced they had discovered a gene called MYH16. Mutations in this gene lead to shorter jaws, which may have been the factor which allowed early man's brain to grow [source: Wilford]. However it happened, the change lessened the amount of space available to teeth in the mouth.
As our heads and jaws were changing, some cultural shifts were taking place as well. Around the same time, man was creating the first tools, including cooking utensils (designed, of course, by primitive prototypes of Food Network hosts). With bigger brains, man got wise to fire and its ability to soften food. Overall, man's diet became much more processed; compared to the roots and raw meat our ancestors ate, we might as well be eating strained applesauce. In fact, we wouldn't necessarily need any teeth at all to survive today, though dining out would be a dull affair. As it is, though, we definitely decreased our reliance upon the third molar.
Opponents of evolution place greater weight on the dietary shift and dental hygiene in lessening our reliance on wisdom teeth, discounting the role of our evolving jaws and brains. But when you line up a prehistoric jaw and a modern jaw, the space is clearly smaller. Can evolution explain the shift? And if our evolutionary history has lessened the need for wisdom teeth and created conditions inhospitable to third molars, will we ever lose them completely?