Human Dietary Flexibility Appears Designed

During one of my ministry trips to Hong Kong, several Chinese science professors took me to a famous restaurant for a traditional Chinese dinner. The two-meter-diameter lazy Susan was heaped with an enormous variety of foods of which the only items I recognized were the sea cucumbers. The professors told me they had proof that Eve was not Chinese. They asserted that if Eve were Chinese she would have eaten the serpent. They then informed me that I had just consumed the tail portion of a snake.

A new study shows that the Chinese are not alone in eating an extreme variety of foods. Human beings are the most widely distributed terrestrial mammal. The study shows the ability of humans to rapidly adapt to newly encountered environments and accelerate their population, civilization, and technology. That ability is due, in part, to their hyper-omnivory (highly varied diet) and prey-switching ability. No other species consumes such a wide variety of organisms in their diet.1 Humans are extremely opportunistic omnivores. We manifest an amazing ability to consume across multiple trophic levels from the base of the food web up to the apex predator.2

The Diet Study
A team of five research environmentalists led by Michael Bird conducted a global study on the history of the human diet.3 They accomplished this through 13,666 globally distributed analyses of ancient and modern human collagen and keratin samples. The keratin source came from the hair and nails of the individual humans. The collagen source was from either the bones or muscles.

The environmentalists first demonstrated that the carbon-13 to carbon-12 and nitrogen-15 to nitrogen-14 isotope ratios in a human individual’s collagen and keratin are excellent proxies for the diet being consumed by the individual. Their analyses revealed a much broader diet prior to industrialized agriculture. In particular, they observed that “the isotope dietary breadth of modern humans is highly compressed when compared to populations predating the development in 1910 of modern industrial fertilizer by the Haber-Bosch method.”4

The Haber-Bosch process permits the industrial production of near limitless amounts of fertilizer from atmospheric nitrogen anywhere in the world. Global use of such industrial fertilizer now exceeds 100 million tonnes (110 million US tons) per year.5 This fertilizer, combined with widespread irrigation, has greatly increased both the efficiency and volume of food production for human use. It has also made possible the intense cultivation of wheat, rice, millet, corn, soybean, and sugar well outside their natural realms and for their shipment across the world. However, with the exception of the few humans still living in isolated stone-age technology tribes, it has also dramatically shrunk the diversity of foods humans consume.

Diet Study Implications
The diet study reveals unique design features in human beings. It adds to the evidence that humans were designed to thrive in both low- and high-technology environments.

Humans, Neanderthals, Denisovans, and the Homo floresiensis species were all living during the last ice age. Of these, only humans survived the ice age and multiplied into a large population. During the last ice age, atmospheric carbon dioxide levels fell to 180 parts per million.6 At that level, the production of sugars, starches, fats, and proteins via photosynthesis becomes seriously impaired. Humans survived and even thrived because they had the specialized anatomical features that allowed them to be, by far, the most efficient hunter-gatherers. Humans are the only species that has ever existed on Earth that can gather and hunt the full spectrum of foodstuffs with relative safety. As Genesis 1:26 declares, God made humans so that they can rule over all Earth’s creatures.

The human digestive tract complements the anatomical features that permitted efficient gathering and hunting. It is designed to process a broad spectrum of foodstuffs without inhibiting mobility and high-productivity work. Thanks to unique designs in the human brain, arms, and hands, immediately after their creation humans were able to control fire and manufacture grinding tools and hearths that made possible the roasting and boiling of foods and the production of bakery products.7 Such technologies greatly expanded the range of foodstuffs that humans could consume and lowered the amount of time and labor humans needed to sustain their caloric and nutritional needs.

The march of human civilization has been one of progressively lowering the time and labor needed to produce food requirements. Today, in the United States only about one percent of the labor force is engaged in producing raw foodstuffs. This food production efficiency sets free nearly the whole labor force to engage in science, engineering, technology, medicine, education, art, music, and recreation. This transfer of labor has made possible the technological revolution of the past hundred years. With this revolution has come a much more specialized diet. Amazingly, the human body is designed to thrive on both a hyper-omnivorous and a modestly omnivorous diet. This design allows humans to expend energy to contemplate far more than mere survival, but purpose as well.


  1. Stefani A. Crabtree, Douglas W. Bird, and Rebecca Bliege Bird, “Subsistence Transitions and the Simplification of Ecological Networks in the Western Desert of Australia,” Human Ecology 47 (April 2019): 165–177, doi:10.1007/s10745-019-0053-z; Jennifer A. Dunne et al., “The Roles and Impacts of Human Hunter-Gatherers in North Pacific Marine Food Webs,” Scientific Reports 6 (February 17, 2016): id. 21179, doi:10.1038/srep21179.
  2. Stefani A. Crabtree, Jennifer A. Dunne, and Spencer A. Wood, “Ecological Networks and Archeology,” Antiquity 95, no. 381 (April 30, 2021): 812–825, doi:10.15184/aqy.2021.38; Dunne et al., “Roles and Impacts.” 
  3. Michael I. Bird et al., “A Global Carbon and Nitrogen Isotope Perspective on Modern and Ancient Human Diet,” Proceedings of the National Academy of Sciences USA 118, no. 19 (May 11, 2021): id. 2024642118, doi:10.1073/pnas.2024642118.
  4. Bird et al., “A Global Carbon and Nitrogen Isotope Perspective,” 1.
  5. Chaoqun Lu and Hanqin Tian, “Global Nitrogen and Phosphorus Fertilizer Use for Agriculture Production in the Past Half Century: Shifted Hotspots and Nutrient Imbalance,” Earth System Science Data 9, no. 1 (March 2, 2017): 181–192, doi:10.5194/essd-9-181-2017.
  6. Jochen Schmitt et al., “Carbon Isotope Constraints on the Deglacial CO2 Rise from Ice Cores,” Science 336, no. 6082 (May 11, 2012): 711–714, doi:10.1126/science.1217161; J. R. Petit et al., “Climate and Atmospheric History of the Past 420,000 Years from the Vostok Ice Core, Antarctica,” Nature 399 (June 3, 1999): 433, doi:10.1038/20859.
  7. Hugh Ross, “Confirmation That Early Humans Were Making Bread,” Today’s New Reason to Believe (August 27, 2018).