I have debated with many vegans/vegetarians over a long period & also researched the health benefits & downsides of various diets & these are my findings:
Humans have most definately had a past of hunter/gatherer ancestors.
We are constantly told that cholesterol is bad for us or at least that LDL cholesterol is bad for us but HDL cholesterol is good for us. The truth is however that both LDL & HDL cholesterol is good for us!!! Both of these cholesterols are just transportation systems for fatty acids. LDL cholesterol is what our brains are made of & is important for repairs to the arterial walls of our cardiovascular system. So despite the bad press LDL has been given, it is an important & necessary part of a healthy diet!
Longevity: I have seen research papers indicating that omnivores & vegetarians live to about the same age but vegans don't live as long.
I believe people should be very careful about getting involved in vegan diets particularly & at least question the cumulative longterm effects of veganism on mental health. I would also recommend NOT putting children on vegan diets because whilst they are developing & growing it could severely impact on the health of their central nervous systems etc.
Fats have been targetted as evil monsters by mainstream health advisors but saturated fats obtained from quality, organic, grass-fed livestock meat are easily broken down & utilised by the human body & are a very simple molecule for our guts to handle.
If nothing else, this should be food for thought!!!