Animal Products Aren't Necessary for Humans
When we look at the historical record, we can see that for the most part, most humans ate a plant-based diet. This has been true for much of history — until the very recent past — and it is still true for the vast majority of the world’s people today. Only in the last few generations has there been a significant movement in human diet away from plants and toward meat and dairy.
The history of plant-based cuisine demonstrates that people have consumed a plant-based diet at various eras and in many societies.
This is the argument stated in Lierre Keith’s 2009 book The Vegetarian Myth. Keith contends that humans are herbivores who should consume only plant foods. She contends that the history of human eating demonstrates that people have thrived on plant-based diets for millennia, and that the transition to animal-based diets is a recent phenomenon (as opposed to a universal practice). She also gives evidence that humans and other primates are herbivores in the book.
She advocates for a return to this cuisine, claiming that it will have health, environmental, and ethical advantages. Keith argues that animal-based meals are not more nutritious than plant-based foods, and that present meat, dairy, and egg production is harmful and wasteful. She also claims that we are not evolved to consume animal products and that eating meat and dairy products may be harmful to human evolution.
Keith says that eating animals is unethical and immoral, and that it is not required for human life. She claims that humans are born vegetarians and that eating meat is an unnatural and harmful activity. She says that a plant-based diet is also more sustainable and will aid in the fight against global warming and other issues.