Beans and Peas
Beans and peas belong to the third largest
family among the flowering plants (after the
orchid and daisy families), and the second
most important family in the human diet, after
the grasses. The distinctive contribution of the
legumes is their high content of protein, two
to three times that of wheat and rice, which
they develop thanks to their symbiosis with
certain soil bacteria. Species of Rhizobium
bacteria invade the roots of legume plants and
convert abundant nitrogen in the air into a
form that the plant can use directly to make
amino acids and thus proteins. Legumes have
long been an essential alternative to protein-
rich but more costly animal foods, and are
especially prominent in the foods of Asia,
Central and South America, and the
Mediterranean. A remarkable sign of their
status in the ancient world is the fact that each
of the four major legumes known to Rome