### Conclusion

All the models we have mentioned could be more thoroughly explored, and many
other branches of mathematics could be fruitfully investigated, e.g. set theory,
graph theory, network analysis, and marginal analysis. Those interested are
encouraged to read any of a number of first-rate texts in basic, applied
mathematics for inspiration, such as Mizrahi and Sullivan, 1979; Kemeny, Snell,
and Thompson, 1974; and Williams, 1975. Without wishing to end on a discordant
note, we feel obliged to mention at least two major obstacles we have
encountered that have hindered our own efforts develop mathematical models in
nutritional anthropology. The first of these lies mainly on the anthropological
side of the field. Frequently, socio-cultural variables, e.g. food preferences,
customary behaviour, socio-economic status, or degree of acculturation or
modernization, are not measured precisely enough to permit the construction of
interval or ratio scales. This limitation is especially vexing when one observes
that the field of nutrition is blessed with an abundance of finely measured
quantities. Here, then, is an area where anthropology needs to catch up. The
second, which at least holds the prospect of being overcome, is the dearth of
longitudinal data collected from more than one time period. This is, in part, a
logistical problem. Field-workers cannot be everywhere all the time. But we
think that, with adequate sampling procedures, more effort should be expended in
systematically researching smaller samples of representative cases, over time,
in conjunction with the numerous surveys of large samples of cases at a single
point in time.

For the model builder in nutritional anthropology, a direct consequence of
both obstacles is that the full conceptual and analytic power of the calculus
(and differential equations), so essential for constructing dynamic models, must
remain largely dormant. We believe that if these two problems could be resolved
a great leap forward would take place, which would serve to place nutritional
anthropology on a more equal footing with her sister
disciplines.