Red Meat Shaped Human Evolution, But Modern Consumption Differs Sharply, Review Finds

Red meat has been part of hominin diets for roughly 3 million years, but how much, how often and in what form humans eat it today looks very different from the past, according to an interdisciplinary review published in The Quarterly Review of Biology. Authors Juston Jaco, Kalyan Banda, Ajit Varki and Pascal Gagneux combined evidence from archaeology, epidemiology and molecular biology to trace the changing role of meat in the human diet.

The review finds that meat consumption predates the genus Homo, but early hominin diets remained dominated by plants. Fat, bone marrow, organs and brain tissue likely offered more nutritional value than today's prized cuts, packing more calories and lipids important for infant brain development. The authors also challenge the idea that eating meat alone drove human brain expansion, noting protein is not especially energy-dense; instead, they argue dietary flexibility across many foods better explains human success as early humans spread into new habitats. Agriculture, beginning roughly 10,000 to 12,000 years ago, narrowed diets toward staple grains and introduced deficiencies such as low iron that had been rare among hunter-gatherers.

Today, meat is the foundation of a $1.3 trillion global industry, with large studies linking greater red and processed meat consumption to higher risks of cardiovascular disease, type 2 diabetes, colorectal cancer and death from any cause. The International Agency for Research on Cancer classifies processed meat as a Group 1 carcinogen, meaning there is sufficient evidence it can cause cancer in humans, while unprocessed red meat is classified as probably carcinogenic.

The review also describes a biological mechanism called xenosialitis, involving a sugar molecule called Neu5Gc that humans lost the ability to produce about 2 million years ago but which remains abundant in red meat. When consumed, Neu5Gc can be incorporated into human tissue, where the immune system may attack it as foreign, producing chronic low-grade inflammation that could promote atherosclerosis and accelerate colorectal cancer. Industrial livestock production also generates roughly 15% of global greenhouse gas emissions and drives deforestation, water contamination and antibiotic resistance. The authors do not argue everyone must eliminate red meat, but say evolutionary history cannot be used as a simple defense of how much of it is consumed today.