Did Humans Evolve to Eat Meat?

Supported by 3 cited sources

Key Points

• 1The Expensive Tissue Hypothesis (Aiello & Wheeler, 1995, Current Anthropology) proposes that a shift to higher-quality foods -- including meat -- allowed early hominins to develop smaller guts and larger brains. The brain and gut are both metabolically expensive organs, and reducing one may have freed energy for the other. This is a credible and widely cited hypothesis, though it remains debated. It does not prove that modern humans require meat -- it proposes that calorie-dense food (which could include cooked starches) enabled brain growth.
• 2Richard Wrangham (2009, Catching Fire) argues that the control of fire and cooking -- not meat per se -- was the key dietary shift that enabled Homo erectus to emerge ~1.8 million years ago. Cooking makes both plant and animal foods more digestible and energy-dense. This hypothesis suggests it was food processing, not specifically animal food, that drove our evolution.
• 3Humans have real genetic adaptations to specific foods that demonstrate ongoing dietary evolution. Lactase persistence -- the ability to digest milk as adults -- evolved independently in European and African pastoral populations within the last 7,000 years via mutations near the LCT gene (Tishkoff et al., 2007). AMY1 gene copy number variation shows that populations with high-starch diets evolved more copies of the salivary amylase gene, enabling better starch digestion (Perry et al., 2007). These are examples of recent, diet-specific adaptations -- they prove humans continue to evolve in response to diet, not that we are locked into any single dietary pattern.
• 4Comparative anatomy shows humans are omnivores -- neither strict herbivores nor strict carnivores. Traits shared with herbivores: lateral jaw movement for grinding, longer intestinal tract relative to body length (~10:1 vs. 3-6:1 in carnivores), flat molars, alkaline saliva with amylase for starch digestion. Traits shared with carnivores/omnivores: forward-facing eyes, moderate stomach acidity (~pH 1.5, between herbivore ~pH 4-5 and strict carnivore ~pH 1), canine teeth (though ours are small compared to true carnivores), and the ability to absorb heme iron and preformed vitamin A. The honest conclusion: humans are anatomical generalists adapted to a flexible diet.
• 5Evolutionary capacity does not equal modern necessity. Humans also evolved to survive famine, fight parasites, and reproduce in early adolescence -- none of which we treat as prescriptions for modern life. The Academy of Nutrition and Dietetics (2025 position paper) confirms that appropriately planned vegetarian and vegan dietary patterns are nutritionally adequate for adults and may provide health benefits for cardiometabolic disease prevention. The key caveat: the 2025 position focuses on adults and recommends attention to B12, vitamin D, iron, and calcium. Supplementation of B12 is essential.
• 6The strongest version of this argument is not 'humans must eat meat' but 'humans can eat meat.' That is true. What it does not establish is that humans need to eat meat in the modern world, where supplemented plant-based diets are available, affordable, and confirmed as adequate by every major dietetic organization.

Evidence Summary

Practical Takeaways