are often infested with insects, so that frugivores are incidental insect eaters. Jordano mentions in his chapter 'Fruits and
Frugivory'(5), that a gut dominated by the intestines is also characteristic of strong frugivores (p.145). For example
frugivorous bats such as Wahlberg's fruit bat are reported to have small intestines that makes up 94% of the total digestive
system(16), although frugivorous bats may spit the fruit fibres out, ingesting only the juices. Jordano also points out (p.138)
that frugivores require no special adaptations or special digestive processes for processing fruit, the same claim usually
made for "omnivores".
In contrast to Chivers findings(1), Hladik, Chivers and Pasquet(12) plotted the area of functional mucosa vs. functional
body size for folivores, frugivores and faunivores, and found that humans fitted the frugivore trend. Each trend line was
completely separate in this study. This technique therefore seems to be somewhat more accurate at prediction than Chivers
methods, yet both researchers basically confirm that human gut anatomy is effective for speedily digested foods.
In summary, digestive anatomy research shows features of the human digestive system consistent with a diet of foods
digested more rapidly than tough plant fibres. The surface area to functional body size ratio is consistent with that of
frugivores. In terms of ratio of intestine to colon, humans fall between the figures found for the foli-frugivorous apes, and
the extreme condition of soft fruit and juice eating bats (see table below). The digestive system in humans is dominated by
the small intestines, a feature common to frugivores, but also to faunivores and omnivores.
Proportion of Intestine and Colon in Apes, Humans and a Frugivorous Bat
Foli-frugivore Intermediate? soft fruit/fruit
juices
* for chimpanzees (The Feeding Ecology Of Apes, Nancy L. Conklin-Brittain,1 Cheryl D. Knott,1 and Richard W. Wrangham)
Reducing the highly complex digestive system to a few simple measurements and in the absence of consideration of the
chemistry and physiology is over-reductive. Digestive system anatomy can tend to reflect the physical properties of the
food, rather than the source of food, and as such cannot determine the fine details of the diet, or may be misleading and is
certainly inconclusive. Even so, there is no reason to exclude humans from being classed as highly frugivorous based on
their digestive system anatomy.
Just as human digestive anatomy does not reflect the trend found in the great apes, similarly humans have dental and oral
anatomy that sets them apart from nearly all of the other primates. In the great apes, prominent canine teeth are the rule,
and they play a role in display, defence and in feeding. The remaining teeth are however strikingly similar to human teeth,
for example, bonobo teeth and human teeth look almost identical, as pictures in the book 'Bonobo: The Forgotten Ape'
reveal(10). This suggests a very similar diet or dietary strategy and thus evolution. In contrast to the other great apes, the
human canine tooth is no longer prominent and resembles the size and shape of the incisors. Because of this similarity,
human canines are known as "incisiform" canines, and it has been suggested(8) that they function as extensions of the
incisors and by analogy perform the same function.
Incisiform canines that are large and spatulate are found in herbivores. The Dusky Titi monkey whose diet is 54% fruit,
