The fossil record is clear–our prehistoric ancestors ate meat. But does that mean that vegans are going against human’s evolutionary history and are bound to be weak, sickly, and even stupid? That steak is part of a healthy diet and that “meat makes the man?”

Does Meat Make Us Human?

Scientists don’t agree on the role of meat in human evolution. The “meat made us human” theory rests on evidence of meat eating in the fossil record dating back to our prehistoric ancestors. Sharpened stone marks on the skulls of animals suggests that humans were cutting flesh away from bone. It turns out that much of the meat-eating evidence comes from the era when our ancestors developed larger brains. Hence, scientists reasoned, eating meat made possible the development of humans’ oversized brains.

But more recent studies have concluded that the reason meat eating and big brains are found together in the fossil record is simply an artifact of the sites where archeologists were digging. Scientists have sampled more archeological sites during the time when humans brains were evolving than sites prior to that period. And that if we were able to find more archaeological sites further back in time, we would have seen just as much evidence of meat eating. In other words, big brains developed during a period where there is an ample archeological record but meat eating does not explain why humans are so smart.

Other explanations have been offered for the evolution of the large human brain. In his book, “Catching Fire: How Cooking Made Us Human,” Harvard biological anthropologist Richard Wrangham argues that once our hominid ancestors invented cooking, they were able to obtain more calories than from raw foods because cooked protein is more digestible. The extra energy our ancestors gained from eating cooked food led to the evolution of larger brains.

Or maybe human brain size can be explained by the grandmother hypothesis, which holds that grandmothers gathered food for their grandchildren, making it possible for mothers to give birth to more babies. The lucky women who lived long enough to become grandmothers passed on their longevity genes to their children and grandchildren. And mammals who live longer generally have larger brains–the best predictor of brain size is how long it takes to develop.

Whatever the explanation for our large brains, we’re near certain that our evolutionary ancestors ate meat. They also ate fruits, nuts, tubers, and grains. But the question lingers: Does meat make us human? Do we still have to eat at least some meat to be healthy humans, or can we abandon meat altogether?

Vegan Athletes

Although many athletes are convinced that they need meat to remain competitive, studies have failed to find robust differences in endurance or strength between athletes eating vegan and omnivorous (anything goes) diets. Part of the uncertainty may be due to whether vegans–athletes or not–are mindful of getting essential nutrients. Proteins are generally not the problem–there are plenty of protein-rich plant foods, from tofu, garbanzo beans, lentils, nuts, and seeds, to whole grains.

The bigger challenge for vegans is making sure they get enough calcium, Vitamin D, iron, zinc, and iodine, along with omega-3 fatty acids and B12. Kale, broccoli, and other dark green vegetables (as well as calcium-enriched cereals, juices, and plant-based dairy products) supply calcium. Some cereals and plant-based dairy may also be fortified with Vitamin D. Dried beans and peas, lentils, enriched cereals, whole grains, dark leafy green vegetables, nuts, wheat germ, and dried fruit are sources of iron and zinc. To supply their body with iodine, vegans should consume iodized salt or seaweed. For omega-3 fatty acids, try canola, walnuts, or soybeans. The nutrient completely lacking in vegan diets is B12. Here is where nutritional yeast enters the palate–it adds a cheesy flavor to popcorn and rice, corn, or bean dishes, and contains ample amounts of B12. Supplements are another way vegans can ensure they get adequate amounts of micro-nutrients.

Another way to make sure you get adequate micro-nutrients is to eat meat or dairy occasionally. Body builder Arnold Schwarzenegger describes his diet as 80% vegan. He consumes fish and low-fat yogurt mixed in with plant-based burgers, salads, and protein shakes. Tennis champions Venus and Serena Williams describe themselves as “chegans”–vegans who favor plant-based foods but eat the occasional meat.

But Formula 1 champion Lewis Hamilton appears to be 100% vegan, eschewing any type of meat.

I have more energy; I’m so much more productive. I wake up feeling way better, clearer in thought and fresher in my body…I’m physically in better shape than I’ve ever been, and I’m more successful than ever right now, and my plant-based programme has played such a big role in that.

And vegan ultrarunner Scott Jurek has come in first in nearly all the high profile ultra-running races including the 153-mile Spartathlon in Greece. Jurek, who broke a record by running the 2190-mile Appalachian Trail in under 47 days, says:

A lot of people assume that one needs to eat animal products to gain a lot of muscle mass or sufficient muscle mass for even power sports, and that’s definitely been proved false time and time again.

Win-Win-Win Diet

Whether by becoming a vegan or a “chegan,” or adopting a Mediterranean diet with lots of vegetables, fruit and seafood and moderate amounts of poultry, pork, lamb and beef, people in rich countries who lower their red meat consumption decrease their risk of chronic disease. They also reduce their environmental footprint and can stimulate the economy. Here are some facts and figures.

Transitioning toward healthy, plant-based diets would prevent approximately 11 million deaths per year, which represent between 19% to 24% of total adult deaths. Those who crave meat can improve their diet health score and reduce their dinner’s carbon footprint by over 50% by simple substitutions–like replacing beef with chicken in tacos or beef burgers with turkey burgers. Compared to the average omnivorous diet with high amounts of red meat, the Mediterranean diet reduces rates of type II diabetes by 16% and cancer by 7%, as well as dying from coronary heart disease by 26%.

Relative to continuing current eating trends through 2050, if everyone in the world followed a healthy diet with no more than three portions of red meat per week, we would reduce emissions by 29%. If everyone followed a vegetarian or vegan diet, food-related emissions would decline by 63-70%.

The economic benefits of transitioning to healthy plant-based diets would also be substantial. Depending on whether one uses cost-of-illness measures (direct health care, informal care, and lost work days associated with deaths from specific diseases) or estimates of people’s willingness-to-pay for reductions in mortality, savings from switching to a healthy diet would be between 1 and 31 trillion US dollars, which is equivalent to 0.4–13% of global GDP in 2050.

In other words, vegan and other plant-based diets are a win-win-win for health, climate, and the economy.

If you were to serve a “planetary health plate” you would cover half of the plate with vegetables and fruits and the other half with whole grains, plant protein sources, and (optionally) modest amounts of animal sources of protein.

Transformation to healthy diets by 2050 will require substantial dietary shifts. Global consumption of fruits, vegetables, nuts and legumes will have to double, and consumption of foods such as red meat and sugar will have to be reduced by more than 50%. A diet rich in plant-based foods and with fewer animal source foods confers both improved health and environmental benefits. Prof. Walter Willett MD, Harvard T.H. Chan School of Public Health

Does Meat Make Me Human? Find Out for Yourself

If you want to find out if you still feel human after lowering your meat consumption, consider following these tips from the Mayo Clinic.

• Start gradually–go meatless one meal a day or one day a week, or eat plant-based till dinner.
• For breakfast, replace eggs and bacon with whole grains, like whole-wheat toast or oatmeal.
• Add greens like spinach or kale, as well as ample fruits and vegetables, to your daily meals.
• Swap out meat in a recipe for a plant-based option like black beans or tofu.
• You can get enough protein from whole grains, lentils, chickpeas, tofu, artichokes, asparagus, broccoli and spinach. Ensure your calcium and vitamin needs are met from tofu, tahini, leafy greens, iodized salt, dried fruits, nutritional yeast, and other foods or supplements.
• Encourage your friends and family to join you in trying out new foods at home and in restaurants. It’s more fun to explore new things together and you can reinforce each other’s commitment to eat foods healthier for you and the planet.

Who knows? Maybe you will feel better than ever, and like Arnold Schwarzenegger, still be bodybuilding at age 77.