Yes scavenging for meat is generally considered a very important part of human evolution. Our stomachs are particularly acidic when compared to other great apes. This is believed to have evolved due to a high consumption of scavenged meats.

You are right though plants generally did form a large portion of our and our ancestors diets.

Important to note that as our brain size increased it did correlate with increased meat consumption as well. This all goes into calorie densities, available nutrients, and evolutionary pressures.