Are there any scientific grounds to those assertions ? If humans were born with canine teeth, maybe it's because they are meant to eat meat ...
This same question comes up time and time again. I don't think it's something you can look at as black or white and many people will argue one extreme or the other. I like to think of it in a slightly different way.
There may have been a point in time where humans were more adapted to eat meat. At this present moment in time, I like to think of us as "opportunistic omnivores"...with our bodies being adapted mostly to vegan eating and tolerating small amounts of meat when the opportunity or need presents itself.
As far as our bodies being more adapted to a mostly vegan diet....it's not hard at all to understand why that is true. Disagreeing with that is like saying the world is flat. Just look at the new research that comes out every single day. How often do you hear that chicken is good for you, beef is good for you, etc...almost never. How often do you hear new evidence that a particular fruit, vegetable, bean, or nut is good for you?....almost every day. It's just a fact that our bodies respond very well to plant food...and negatively to most animal products.
I think it's always pretty futile for anyone to argue over the semantics of whether or not an optimal diet contains small amounts of meat or not...just not enough evidence to really say that for sure. But when it comes to where you should get the vast majority of your calories from....plant foods obviously win hands down.