[switknee]

Unlikely, unless by "gathering" you mean scavenging kills and eating carrion. Developing the large fatty brain without a herbivorous digestive system suggests that our ancestors ate dead animals. The modern human digestive system is more similar to a wolf's than a chimp's.

There's also not much evidence that there were enough human available calories present year round to support a nomadic vegetarian population. Yes, apples existed, but the current evidence suggests humans only started eating lots of them after we wiped out the mastadon.