Show Summary Details

Page of

PRINTED FROM OXFORD HANDBOOKS ONLINE ( © Oxford University Press, 2018. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Handbooks Online for personal use (for details see Privacy Policy and Legal Notice).

date: 21 May 2019

Abstract and Keywords

Digestive tracts vary considerably because animals have evolved different processes to convert foods to essential molecular building blocks. Differences in digestive strategies distinguish, for example, foregut and hindgut fermenters, and animals utilising different dominant food types, for example herbivores, carnivores, and folivores. Neither the modern human diet nor the size and proportions of the human gut resemble those of other primates. The human digestive system has evolved and diverged in response to introduction of new food types and food preparation techniques. For example, persistence of lactase activity into adulthood occurred in populations that maintained cattle to harvest milk. Humans have utilised non-thermal food preparation for over 2 million years and cooking for 300,000–400,000 years. For most extant humans, prepared food comprises over 70% of the diet. The modern human digestive system is suited to pre-prepared food because of its smaller volume, relative to other species, and because of differences in dentition and masticatory muscles that results in lower bite strength. Adaptations of human digestion in response to diet involved genetic selection over thousands of years. However, transmissible changes linked to diet occur in a single generation. These are best documented for epigenetic changes related to obesity, and are maladaptive in some cases. Diets for most humans have changed substantially in the last half century, too rapidly for evolutionary change in digestive physiology. The capacity to adapt to recent dramatic dietary changes has proven insufficient to avoid deleterious effects leading to obesity, diabetes, fatty liver disease, and metabolic syndrome.

Keywords: digestive physiology, comparative anatomy, modern foods, digestive enzymes, microbiota, evolution, medicine

Access to the complete content on Oxford Handbooks Online requires a subscription or purchase. Public users are able to search the site and view the abstracts and keywords for each book and chapter without a subscription.

Please subscribe or login to access full text content.

If you have purchased a print title that contains an access token, please see the token for information about how to register your code.

For questions on access or troubleshooting, please check our FAQs, and if you can''t find the answer there, please contact us.