Actually, hunter gatherers lived five years longer and were 5 inches taller, on average, than the first agrarians, who were relatively poorly nourished and overworked. Paleolithic folks were within a couple of inches of being as tall as we are today. With their lower population densities, nomadic lifestyle, diversified diets, healthier bodies, and egalitarian ethos, they were less at risk of disease and malnutrition, or famine than early farmers.
War is largely an expensive, surplus intensive luxury that most paleolithic folks avoided most of the time out of sheer necessity.