> - Is the general concept that a raw-vegan diet is not the best diet
>   for humans and is in fact insufficient in some way?
>
> - Would this include all humans or just some?

Paleodiet research says that humans are natural faunivores,
i.e. their natural diet includes some animal food.

>From experience, most of those who attempt to follow a raw vegan
diet sooner or later have deficiency symptoms.

> - Is the theory that we need to cook some of our food and that it
>   is a good and necessary thing,

In my opinion, a human living in a natural environment that provides
an abundance of animal and plant foods doesn't need to cook
food. However, in our modern world, for many reasons 100% raw diets
are more difficult to follow than prodominantly ones.

> OR
> - Is it that we need to include non-plant sources in our diet in order
>   to be healthy?

Very few people manage to stay optimally healthy without animal foods.

> - What specific nutrients are deemed to be too difficult or
> impossible to get?

Most difficult to get: vitamin B12, and some essential fatty
acids. Less difficult: iron, zinc, vitamin A.

The best source of B12 is liver. It is not (or barely) destroyed by
cooking. Vitamin B12 is present in all animal foods, but plant sources
are unreliable. See the following subarticle of the "comparative
anatomy" paper for a discussion about B12 in plant foods:

http://www.beyondveg.com/billings-t/comp-anat/comp-anat-7a.shtml#vitB-12

> - Is there a recommendation for the best source of the missing nutrients?
>     meat / eggs / dairy / fish / supplements

The easiest and most "natural" is to eat like Paleo humans: meat,
eggs, fish. However, any animal food or supplements can supply the
missing nutrients. Vegetarianism can work fine.

> - Humans do not seem to be efficient meat eaters without tools.
>   Is the thesis that tools make us omnivores and that this is an adaptive
>     and evolutionary-driven requirement now?

Early humans were scavengers, and didn't need tools to eat
meat. Then, they used simple stone tools to crack bones and eat the
marrow. It is true than humans cannot eat large amounts of
meat without tools (to hunt animals), but the use of tools and animal
food consumption are ancient enough to be considered as "natural",
that is, we are genetically adapted to meat eating.

Details about adaptation can be found in the comparative anatomy
article

http://www.beyondveg.com/billings-t/comp-anat/comp-anat-1a.shtml

--Jean-Louis Tu <[log in to unmask]>