It’s true that human beings evolved the ability to digest a wide range of foods including meat, but this isn’t the same as needing meat for survival.
Rather than worrying about what our ancestors ate, the more important question is whether it’s possible for a human being to get all their necessary nutrients as a vegan. Happily, it is – and the only supplement required is B12.
This vitamin is present in animal products, but it isn’t made by the animals themselves, it’s created by bacteria that live inside them. The B12 used in vegan supplements or fortified foods such as Marmite is made by ‘farming’ the bacteria directly and harvesting the vitamin, so it’s the same substance made in exactly the same way.
Hardly unnatural – or in any case, no more unnatural than any other use of microorganisms in food production (bread, cheese, yoghurt, wine, beer…. you get the idea).
There are a lot of ways in which non-vegan food may be considered unnatural, for example the consumption of the milk of another species, so it’s probably wise to ditch the concept of what’s ‘natural’ (you’re reading this on the internet after all!) and simply concentrate on getting all the right nutrients.