Travel Reference
In-Depth Information
of their nourishment from vegetation with a high cellulose content. But these
primates have expanded their mid-guts rather than their stomachs, and their
fermentative bacteria reside in this mid-region of their digestive tracts. The
swelling that results from this gut fermentation is not as obvious as it is in
proboscis monkeys and the other langurs. Mid-gut fermenters are also able
to eat a wider range of foods than the proboscis monkeys, because they do
not depend as strongly on fermentation.
We ourselves are at a dif erent dietary extreme. We non-fermenters are
the most omnivorous of the present-day primates, though we share the title
with the cute little capuchin monkeys (the “organ grinder” monkeys) of
South America. These monkeys are also catholic in their tastes, dining with
equal avidity on small mammals, insects, fruits, nuts, and tubers. No fermen-
tation takes place in their stomachs or mid-guts.
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Capuchins have adapted to the destruction of their habitat by humans,
because they are able to move into farmers' fi elds and eat crops like maize
and sugar cane. And we, because of our own versatile digestive system, have
been able to fan out across the entire planet. We are able to thrive on foods
ranging from witchetty grubs to seal blubber. Indeed, this digestive versatil-
ity has played a huge role in our success as a species.
Evolutionary convergence towards the laid-back
ruminant lifestyle
Now that the cast of characters is in place, we are ready to see how the evolu-
tion of ruminant-like digestion has taken the most probable of a number of
possible paths.
Ruminant-like fermentation of foodstuf s has had a long evolutionary
history. The ruminant lifestyle among browsing animals probably extends
back into the Age of Dinosaurs. Well-preserved fossils of some of the early
mammals that lived among the dinosaurs provide clues that they were prob-
ably fermenters. And a few equally well-preserved herbivorous dinosaur fos-
sils show traces of enlarged stomachs that could also have been involved in
fermentation.
