Wikipedia is good for somethings and not others. For straightforward information regarding dates, they are quite good. Anything a bit more contextual, not so. If in doubt check the sources at the bottom of the page.

Lack of Vitamin B12 is one of the weaknesses of a vegan diet. However, we can get it from foods such as cereals and plant-based milks that are fortified with Vitamin B12. Another option is to use supplements. Humans have this problem because we don't chew the cud or eat our own shit.

I would argue we have more in common with herbivores, but we are able to eat meat (cooked) and remain healthy. We have done so for thousands of years. Whether we live as a herbivore or an omnivore comes down to choice.