Comparative Anatomy

Comparative anatomy is the study of how different body parts, such as organs and bones, are put together in different types of animals. It can provide valuable clues about what makes us human. Dr. Oz talks with comparative anatomist Dr. John Fleagle about how we can understand our bodies better by understanding the bodies of other animals. Dr. Fleagle also talks about whether humans are naturally predisposed to eat meat.

A comparative anatomist might look at how the shape of the heart of a human varies from the heart of a dog or an ape, Dr. Fleagle says. Most of the divisions within the animal kingdom are based on some sort of anatomical differences that have appeared through evolutionary time, he says. For instance, he says the presence of mammary glands or the ability to bear live young helps classify mammals; the presence of a backbone helps distinguish vertebrates from invertebrates and so on.

To help answer the question of whether humans are naturally predisposed to being carnivores, herbivores or omnivores, Dr. Fleagle says scientists have compared the digestive tracts of humans with those of other animals. By this measurement, he says humans tend to fall on the carnivorous side. "We have a lot more gut than totally carnivorous animals, but we have a whole lot less gut than animals that have to digest cellulose and other plant material and have to have special places to do that," he says.

Dr. Fleagle, who has studied the evolution of primates in detail, says there are other considerations to take into account that help explain present-day humans' diverse diets. While humans may lack the ripping teeth of most carnivores, they have other tools and the ability to cook foods and prepare them in ways that help break the food down and ultimately give them more energy. "Humans are cultural animals, and it has definitely affected our anatomical adaptations as well enabling us to do things beyond what we might do with fewer bones and tissues," he says.