What the actual hypothesis is talking about is cooked foods. NPR ran with the meat angle. But it’s all about cooked food, including vegetables, changing the way early humans chewed, hence changing the size of the jaw and gut. By eliminating the need for a large gut more calories could be devoted to brain development, instead of being primarily used for digestion. By decreasing time spent mechanically processing food, cooking improved the ability to get useful nutrition from the same amount of food. Hence, our brains had the energy it needed to grow.
Yeah that's sort of what that article states.
However it was meat that allowed us to feed our brains with required nutrition, especially cooked meat. Nothing at that time could compete if it comes to nutritive values.
Cooking vegetables was pretty pointless back then. There was a point to smash them with a rock though.
We became successful gatherers (able to grow domesticated, edible plants) long after we learned to cook and eat meat which boosted our brain's growth. Actually only 10000 years ago or so we learned to successfully grow our fruits and vegetables for food and it took much longer for them to be well domesticated. Till that time we were scavenging for anything we could but meat was obviously the best thing we could find. It involved a lot of hunting and since nature wasn't too generous for our bodies that had no natural weapons we had to develop more and more efficient tools. Hunting sparked our intelligence in a major way.
Most wild fruits and vegetables that we were able to find weren't nutritive enough earlier. Cooking them would reduce the needed amount of food-processing but would also make that food even less nutritious.
Perhaps we owe our intelligence to the fact, that our bodies were inferior to most other creatures. We had it tougher and just had to find some ways to survive. Then the smarter we were the faster we evolved. At some point we developed an instinct that made us want to discover, travel and develop new things - the reason behind most of our inventions.
Then we became able to consciously decide how do we want to evolve. A chain reaction.
Like I stated in my second post, eating and cooking meat definitely wasn't the only factor. We had to protect against predators but there are many other animals that have to do it too to survive yet that doesn't help them develop higher intelligence.
Also, evolution prefers active, offensive behavior and favors it with faster development than passive, defensive species. Finding food was the most important aspect of survival.
I think that we developed more tools, intelligence and strategies while hunting for food, for animals. Then it was about cooperation and secondary survival traits.
Right now we are successful enough with fruits, vegetables and science that we don't really need meat because we can replace it. We can grow our fruits to be way more nutritious than they were even a few hundred years ago.
And yes, I believe that we'll slowly start abandoning meat as our primary meals. It played its part, a big part for a very long time though. Thanks to our evolution we have a choice right now. Also intelligence and all required resources to make a free choice.
The fact that it's easier and faster to improve our fruits and vegetables than it is with livestock might make the choice easier in the future.