they gauge the reliability of these partners for long-term cooperation
and child rearing.^20
Life in ancestral environments was fraught with danger, not just
from the obvious predators but also from a variety of microbes, viruses
and toxins. Ancestral foods obtained through foraging, scavenging and
hunting were quite "natural" and therefore far from healthy. Many
plants are full of dangerous toxins and so are dead animals. Also, many
animals carry pathogens that adapt easily to life in a human body. The
danger is especially high for a "generalist" species like humans—that
is, one that finds its nutrients in a great variety of sources and adapts to
new environments by changing its diet. Being a generalist species [119]
requires not only that you have immune defenses like most other
species but also that you make specific cognitive adaptations to mini-
mize the danger of contamination and contagion. Rats, too, are gener-
alists; this shows in their extremely cautious approach to novel foods,
and in the way they quickly detect the correlation between a new food
and various somatic disorders. They detect such connections better
than other, non-food-related correlations, which shows that the sys-
tem that produces such inferences is indeed specialized.
Humans too have special cognitive adaptations in this domain. For
instance, very young children are open to a whole variety of tastes as
long as the food is given by their caregivers, which helps them adapt to
local conditions; later, they become rather conservative, which limits
their forays into dangerous foods. Pregnant women develop specific
food aversions, mainly to tastes of toxin-rich foods. Morning sickness
seems to target precisely those foods that would be dangerous to fetal
growth in an ancestral environment. Food is obviously not the only
source of danger of this kind. Contact with rotting corpses or with
wounded or diseased people, ingestion of feces or dirt: these are
avoided for good evolutionary reasons.
Indeed, the human mind seems to include a specific inference sys-
tem that deals with such situations and triggers strong emotional reac-
tions to even to the mere suggestion of such situations. Psychologist
Paul Rozin, who has studied the psychology of disgust, its connections
to evolved food preferences and its relation to the risk of contamina-
tion, showed that this contagion system obeys specific inferential prin-
ciples. First, it assumes that the source of danger is not necessarily vis-
ible; what makes a rotting carcass a bad source of food was not
detectable before microscopes and microbiology. Second, the conta-
gion system assumes that even limitedcontact, however brief, with a
THEKIND OF MIND ITTAKES