Travel Reference
In-Depth Information
the indigestible hemicelluloses and lignins that make life dii cult for the bac-
teria in the crops of hoatzins and the stomachs of proboscis monkeys.
If you could enzymatically unlock these strings of sugar into their com-
ponent parts by digesting the paper, you would gain the energy contained
in two kilograms of the sugar glucose, roughly 8,000 calories. At a liberal
daily allowance of 2,000 calories a day you could live for four days on one
Sunday paper! Of course you might prefer the sports or the food and dining
sections to the glossy magazine. The magazine's pages have been covered
with a truly indigestible layer of clay-based coating, in order to make the
paper shiny.
Hoatzins could in theory dine on the
New York Times
, though they would
certainly not care for the taste. So what would it take for us to do the same
thing? If our close relatives the proboscis monkeys and the gorillas can uti-
lize cellulose by fermenting it, what is to prevent us from solving our food
problem by following in their footsteps? It may only be necessary for us to
tweak a relatively small number of our genes.
The hoatzins' crops have become modifi ed, enabling them to carry out
long periods of fermentation. Their behaviors have also changed. To accom-
modate the fact that they are clumsy fl yers they build their nests on the banks
of rivers and lakes, so that they are less likely to crash into trees as they take
of and land. And of course they have a strong preference for diets made up
of leaves.
All these changes have been the result of natural selection. Could equiva-
lent changes, suitably tailored to our own needs, be introduced into our own
species?
Suppose we could modify our digestive systems so that they became
more like those of the hoatzins or proboscis monkeys. Some of the evolu-
tionary work has already been done. We already have a lysozyme gene that
has the potential to work well in a fermentative stomach, because some of
our ancestors had to adapt to a fermentative way of life repeatedly in the
past. In omnivores like us this gene has been turned of , but it would be rela-
tively simple to turn it on again.
More dramatically, we would need to modify the structure of our stom-
achs. The stomachs of fermenting primates such as the langurs and proboscis
