There is much confusion surrounding the evolutionary diet of humans. We really need answers in order to stick as closely as possible to our species-appropriate diet! A huge topic of debate is cooking: are we adapted to – and biologically hooked on – a cooked diet? Can we survive and thrive on a raw diet? Or are we hooked on getting our nutrition from cooked foods?
For quick readers:
Are humans adapted to cooked foods? Humans have no major biological adaptations to cooked foods except for a higher tolerance for fire toxins and a decreased immune response to cooked foods! Are humans hooked to a cooked diet? No, we can be sustained by a raw diet. A raw diet, however, has to be done right, meaning it must be our species-specific diet, which is based on tropical fruits. Why fruits? Like our direct ancestors and all apes, we are anatomically and physiologically adapted to a frugivorous diet. However, if we cannot live in our natural habitat – the tropics – with abundant, highly nutritious tropical fruits throughout the year, we are forced to integrate cooked fallback foods into our diet.
But let’s get to the nitty gritty of humans and their evolution with cooked foods:
Cooked foods are fallback foods
Humans originate from tropical habitats and remain adapted to warm climatic conditions and tropical food sources (mainly fruits). When migrating out of our natural habitat into colder climates, we had to find new foods and survive by cooking otherwise inedible food sources. We later included food sources like dairy, fermented foods, and grains.
Those foods were fallback foods, to which we had to build a tolerance as a species while we remain biological frugivores. This is why a frugivorous raw diet might still be the optimal diet.
Our ancestors ate mostly fruits
Our early ancestors ate a raw frugivorous omnivore diet similar to modern chimpanzees and basically all modern apes (see here). Most of their food came from the arboreal canopy, meaning fruits (see here):
“The diet of the earliest hominins was probably somewhat similar to the diet of modern chimpanzees: omnivorous, including large quantities of fruit, leaves, flowers, bark, insects and meat” (citation from nature). Also the more recent ancestor Australopithecus afarensis “had a blander diet, mainly based on ripe fruit and plants from secondary forests” (see here).
Further, the long-hold theory of meat-eating and cooking enabling the emergence of a large brain in human evolution is being more and more challenged:
The energy of large amounts of fruit – instead of meat – can be the driver of the evolution of large brains (here). Moreover, the actual “paleolithic diet” shows to have been much less meat-heavy than previously thought.
However, frugivorous humans were a tropical species (we still are!) that migrated into colder areas, and did not have abundant, nutritious fruits. Instead, our ancestors had to rely on cooking roots and also meat to survive.
We have evolved very few adaptative traits to cooked foods: humans are still biological frugivores (see below)!
Our understanding and picture of the heavily meat-eating hunter-gatherers remain uncertain. But we know that somewhere along the timeline, humans needed to start cooking because of lacking fruit availability outside tropical forests. Cooking opened a whole new spectrum of fallback foods outside their fruit-rich habitat.
Cooked foods are still not part of our species-appropriate diet
The natural and suitable food for a species is everything that is appealing and palatable straight from nature. Thus, instincts are the key for animals to know what to eat in the wild and thus determine what the species-appropriate diet is. This is theoretically no different for humans. Therefore, everything that needs to be cooked to become edible or seasoned to be tasty and appealing is not actually human food.
But for humans, the question emerges: have we evolved with cooked foods in a way that we cannot be sustained by a raw diet in the wild anymore? Is our optimal diet still raw, similar to the diet of chimpanzees, or do we need cooked foods for health and survival? The concise answer is no! We are fine on a raw diet if we do it the right and species-appropriate way – as tropical frugivores!
Why? Let’s elaborate…
Do humans have adaptations to cooked foods?
Humans do not show to have evolved major physiological adaptations to eating a cooked diet! So far, there is evidence for a lower immune response to cooked foods and a higher tolerance to fire smoke toxins. The human body is typical for a frugivorous primate with distinct adaptations to a high-fruit diet (see here).
No adaptations to a cooked diet – we are not “cookivores” biologically!
These researchers explored genetic adaptations to cooked foods, and explain:
“… our current understanding of human digestive specialization compared with other primates is largely restricted to anatomical rather than physiological features, including diminution of mouth, teeth, stomach, and large intestine. Although these changes strongly indicate adaptation to reliance on easily chewed and rapidly digested food, some raw foods fit this description, for example, fruits, marrow, brains, liver, honey, and select items like seeds that benefit substantially from nonthermal processing. Without understanding molecular adaptations to a cooked diet, it is therefore impossible to be sure whether habitual cooking has shaped our physiology, and if so, how.”
Carmody et al. (2016)
In this study, the researchers found an immunologic, genetic signal as a possible adaptive response to cooked foods: they found immune regulatory genes (related to diet) that were positively selected in humans. Those genes downregulate the immune response to cooked foods (yes, cooked foods trigger an immune response!) to prevent costly immune reactions and thus save energy.
This type of adaptation shows that it was vital to evolve a higher tolerance to cooked foods – but it does not imply that humans are biologically hooked to eating cooked food (see below): we are not “cookivores” by nature. We are culturally cooked food eaters, which allows us to be “cultural omnivores.” Biologically we are tropical frugivores!
Humans have evolved to tolerate fallback conditions
Humans seem not to have adaptations to cooked foods. However, we have experienced selective pressure for some traits when migrating into habitats where we depend on fallback foods.
Adaptations to fallback foods and cooking that we know of:
- Fire toxin tolerance
- Immunological higher tolerance to cooked foods (see above)
- Lactase/dairy digestion
From an evolutionary perspective, adaptation can indicate that a new condition (new food source, new climate) requires a higher tolerance to this challenging condition. Those are selective pressures. In other words, an adaptation to a new condition does not reflect a maladaptation to the original condition – in this case, raw foods! After all, we know raw fruits and vegetables are still crucial for human health…
We have, for example, adapted a greater tolerance to toxins of smoke from fire (cooking). But does this mean that smoke is now healthy or necessary? No, it is a toxic stressor.
Humans evolved to survive on their fallback foods, but the digestive system and many other traits are still typically that of a frugivore.
Another diet-related example is the tolerance of lactase and dairy as a fallback food source in cold-native people:
We find improved lactase digestion in regions where people survived on loads of milk and cheese as fall backfood. But this evolutionary adaptation does not signify that dairy has now become obligatory in the human diet. Despite their adaptations to dairy, we know that dairy is not the optimal food for any human!
Cold-native people enjoy and digest tropical fruits just as well as tropical-indigenous people, and Europeans still only survive in tropical temperatures without warm clothing.
The natural human diet – our optimal diet – does not contain cooked foods!
Humans seem to have hardly evolved with a cooked diet, which is a fallback diet in cold climates with low fruit availability. Thus cooked diet is a survival diet, not the optimal diet.
Nevertheless, there are some differentiated questions to be answered related to cooked foods and to what extent they are needed in the human species-appropriate diet:
Do humans have adaptations to cooked foods? Yes, humans do have some genetic adaptations to tolerate cooked foods and also to tolerate fire fume toxins. We have an anatomical specialization to eat a soft diet, but we don’t know whether this has evolved with cooked foods or a frugivore diet.
Explore the adaptations of humans to a frugivorous diet here.
Are cooked foods now necessary for survival? No, if we adopt our species-specific tropical frugivorous diet. Humans are not obligatory cooked food eaters! Numerous reports of people on raw fruit-based diets that enjoy good health over decades show that it is possible to live without cooked foods. However, we really need to know what we are doing and have access to our original foods to thrive on an entirely raw fruit-based diet! A high-raw, high-fruit diet is the best solution for many of us in the long run.
Can we survive (and thrive) on a raw diet? Yes, if it is our species-appropriate tropical frugivorous diet. Read more here.
Are cooked foods part of our species-appropriate diet? Cooked foods are not part of an optimal diet within an optimal environment. However, this highly depends on food availability and other factors, which is why cooked foods are an important fallback food for humans.
Conclusion: Humans are not biologically hooked to cooked foods
Cooking was a cultural adaptation as a response to migrating out of the tropical arboreal habitat, where our ancestors fed primarily on fruits. Humans are not hooked to a cooked food diet, but need to adopt a biologically appropriate tropical high-fruit diet, to be sustained by a raw diet!
References
- Daanen, H.A.M. and Van Marken Lichtenbelt, W.D. (2016a) ‘Human whole body cold adaptation’, Temperature, 3(1), pp. 104–118. doi:10.1080/23328940.2015.1135688.
- B. Pobiner, Evidence for Meat-Eating by Early Humans (2013) Nature news. Available at: https://www.nature.com/scitable/knowledge/library/evidence-for-meat-eating-by-early-humans-103874273/ (Accessed: 29 May 2023).
- Milton, K. (2006a) Diet and primate evolution, Scientific American. Available at: https://www.scientificamerican.com/article/diet-and-primate-evolution-2006-06/ (Accessed: 29 May 2023).
- L. M. Martínez et al., (2016) A new study verifies the varied diet of human speciesʼ most remote ancestors in East Africa. Available at: https://web.ub.edu/en/web/actualitat/w/a-new-study-verifies-the-varied-diet-of-human-species-most-remote-ancestors-in-east-africa- (Accessed: 29 May 2023).
- N. Davis (2017) Fruit foraging in primates may be key to large brain evolution (2017) The Guardian. Available at: https://www.theguardian.com/science/2017/mar/27/fruit-foraging-primates-may-be-key-large-brain-evolution (Accessed: 29 May 2023).
- Barras, C. (2016) Ancient leftovers show the real paleo diet was a veggie feast, New Scientist. Available at: https://www.newscientist.com/article/2115127-ancient-leftovers-show-the-real-paleo-diet-was-a-veggie-feast/ (Accessed: 29 May 2023).
- Carmody, R.N. et al. (2016) ‘Genetic evidence of human adaptation to a cooked diet’, Genome Biology and Evolution, 8(4), pp. 1091–1103. doi:10.1093/gbe/evw059.
- The mutations that make US human. (2021) Understanding Evolution. Available at: https://evolution.berkeley.edu/evo-news/the-mutations-that-make-us-human/ (Accessed: 29 May 2023).
- Hubbard, T.D. et al. (2016) ‘Divergent ah receptor ligand selectivity during hominin evolution’, Molecular Biology and Evolution, 33(10), pp. 2648–2658. doi:10.1093/molbev/msw143.
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