From the air, they look like bull's-eyes.  Maasai bomas dot the landscape east of the Serengeti, each a set of three concentric circles enclosing a Maasai family group and its cattle, goats, sheep, and donkeys.  Some bomas are clustered together; others stand apart.  They provide home most of the year to Maasai cattle herders, but when the rainy season begins in November, the Maasai move their herds to temporary camps in the lowlands and let the long-grass fields of the highlands lie fallow.

Boma defined
"Boma" can refer either to the settlement as a whole or to the thick fence of acacia branches that forms its outer circle.  Such a fence comes with its own barbed wire.  Very sharp thorns, long and hard, stud the branches of acacia trees, so the packed branches of the boma make it formidable enough to resist most lions, elephants, and enemies.  The fence protects a ring of earth-colored houses, each built by a different woman.  The bull's eye of the boma is a pen for livestock.  The animals gather in the center of the compound, safe from lions and other predators, sometimes joined by older children who prefer to sleep outdoors.

A Polygamous Society
This is a polygamous society, where men may have several wives.  A family's wealth is measured in cattle.

Inside the houses, women sleep with their infants on wooden beds and piles of cowhides.  They take turns sleeping with their husband and may also entertain male guests visiting their husband from other bomas.  The women make the houses, cook the food, string small beads into elaborate collars, earrings, and belts, and generally control the daily life of the homestead.  Pre-adolescent boys herd the cattle over the plains during the day, and older men reportedly do little or no work.

Each married man has a "cattle gate" that penetrates the boma fence and acts as the focal point for his household.  His first wife builds her house on the right side of the gate, as one enters, the second builds on the left, the third on the right, and so on.  This division forms two clans or "gate post groups" within each household.  Women and their children living on the same side of the gate are closer both socially and legally.

Marriage and Livestock
When a woman marries, she receives cattle from her husband.  Technically, she holds the animals, marked by brands and ear notches for identification, in trust for any sons she might bear.  Full brothers and half-brothers who live on the same side of the gate post frequently exchange cattle, but half-brothers on opposite sides trade only in the less valuable currrency of goats and sheep.   A woman with no sons passes her cattle to the son of another woman on the same side of the gate post.

The life expectancy of a boma is between five and ten years, after which, presumably, the accumulation of dung and the erosion and re-patching of houses make it wise to build a new settlement from fresh materials.