springing forward 53The “resources” Harlan refers to are old varieties, heirlooms and land
races—the thousands of locally adapted varieties of every crop plant im-
portant to humans (mainly but not limited to wheat, rice, corn, and pota-
toes), which historically have been cultivated in the region where each
crop was domesticated from its wild progenitor. Peru had its multitude of
potatoes, Mexico its countless kinds of corn, in the Middle East an infi n-
ity of wheats, each subtly different from the others, finely adapted to its
region’s various microclimates, pests and diseases, and the needs of the
humans who grew it. These land races contain a broad genetic heritage
that prepares them to coevolve with the challenges of their environ-
ments.
Disease pathogens and their crop hosts, like all other predators and
prey, are in a constant evolutionary dance with each other, changing and
improving without cease as one evolves a slight edge over its opponent,
only to have the opponent respond to this challenge by developing its own
edge. Evolutionary ecologists call this the Red Queen principle (named
in 1973 by Leigh Van Valen), after the Red Queen in Through the Looking
Glass, who observed to Alice: “In this place it takes all the running you
can do to keep in the same place.” Both predator and prey must continu-
ally change or go extinct. Thus the rabbit and fox both get faster over the
generations, as their most successful offspring pass on more genes for
speediness. Humans develop new and stronger medicines against our
bacterial predators, while the bacteria continue to evolve antibiotic-
resistant strains of themselves. (The people who don’t believe in evolu-
tion, incidentally, are just as susceptible as the rest of us to this observable
occurrence of evolution. Ignorance of the law is no excuse.)
Plant diseases can attack their host plants in slightly new ways each
season, encouraged by changes in prevailing conditions of climate. This is
where genetic variability becomes important. Genetic engineering can-
not predict or address such broad- spectrum challenges. Under highly var-
ied environmental conditions, the resilience of open- pollinated land races
can be compared approximately with the robust health of a mixed- breed
dog versus the finicky condition of a pooch with a highly inbred pedigree.
The mongrel may not perform as predictably under perfectly controlled