No study will ever prove or disprove the meat contention. The random, unaccountable differences between individual humans make strict science and human nutrition mutually exclusive fields.
In order for a study to say anything conclusive, the scientists would have to do something like grow 100 genetically identical clones, and then make sure each one got exactly equal amounts and types of water, sleep, stress, excercise, exposure to illness etc etc etc. Feeding half of this group a carefully controlled omnivorous diet and the other half a carefully controlled vegetarian diet with identical levels of macro and micronutrients for 12 months and then measuring their resultant "health" would be somewhere APPROACHING scientific.
For all the discussion on teeth, I saw a lecture on skull bones once.
From it, I learned that human teeth are:
-Not like dogs - some of their teeth are for gripping, some for chopping up bones to get at the marrow, and some for ripping flesh
-Not like cats, large or small - their teeth are mostly for ripping and slicing flesh
-Not exactly like baboons - males have huge canines for fighting other males
-Not like horses - front teeth for tearing and back teeth for grinding with a gap in between
-Not like rodents - front teeth for gnawing, always growing-A lot like bears and pigs - people have mistaken their skulls for the skulls archaic skeletons because of the similarities between the teeth
Bears and pigs eat a lot of the same things that humans like to eat, basically everything. In fact, a certain grizzly bear in Yellowstone really liked an entire case of beer he found in a camp and was nicely drunk at the camp when they found him. But then again, when I think of bears eating meat, I think of them clawing at salmon...