source of danger transmits the wholeof the risk. In other words, there
is no "dose-effect" here. Contagious substances do not lose their
harmful powers with dilution. Third, the system specifies that any
contact with sources of pollution transmits it, although the aversive
reactions are especially strong with ingestion.^21 These principles are
specific to the domain considered. The contagion inference system
may in some circumstances seem overly cautious, as when subjects in
Paul Rozin's experiments refused to drink from a glass that once shel-
tered a cockroach and that was then thoroughly disinfected. But the
system was tuned to ancestral conditions, under which there was no
[120] such thing as thorough disinfecting.^22
LIFE IN THE COGNITIVE NICHE
Taking this evolutionary stance leads us to ask very general ques-
tions, such as: What do humans need? What is special about their
needs, as opposed to those of giraffes and wombats? Obviously,
humans need oxygen to breathe and a complicated cocktail of nutri-
ents to sustain themselves, but that is fairly general among animals.
What humans especially need, more than any other species, are two
types of goods without which existence is impossible. They need
information about the world around them; and they need cooperation
with other members of the species. These two are so much a part of
our environment that it is difficult to realize to what extent they are,
literally, a matter of daily survival; it is also difficult to realize to what
extent our minds have been shaped through millennia of evolution to
acquire these commodities and have become ever more dependent
upon their supply.^23Humans are information-hungryHuman behavior is based on a rich and flexible database that provides
parameters for action. Very little of human behavior can be explained
or even described without taking into account the massive acquisition
of information about surrounding situations. This is why some
anthropologists have described the proper environment of humans as
a "cognitive niche." Just as frogs need ponds and whales need seawa-
ter, humans are constantly immersed in a milieu that is indispensable
to their operation and survival, and that milieu is information-about-RELIGION EXPLAINED