Please view this essay by Gentle World: 10 protein packed plants.
Plants have protein, so vegans get their protein from plant sources. It is a myth that humans need a large amount of protein, in fact it is now recognised that most people eat too much protein, or at least more than they need. By eating a variety of whole plant foods, humans can easily meet their daily protein needs. The recommended dietary allowance (or RDA) of protein for humans depends on physical activity levels, pregnancy and other factors, including age. For example, the NZ Ministry of Health Food and Nutrition Guidelines for Healthy Adolescents from 1998 states: “Peak requirements of protein will coincide with peak energy requirements and therefore can be summarised as 12–14 percent of energy requirements. Protein intake is recommended to be in the range of 0.8–1.6 g/kg body weight. The aim is to maintain protein intake at moderate levels (Department of Health 1991).”
Some of the biggest animals in the world are “vegans”: elephants; giraffes; hippopotamuses; rhinoceroses; gorillas; not to mention cows and horses? We never hear anyone asking if these animals lack protein!