Where does descent collide?

In optimization, descent is the strategy of improving a candidate solution by repeatedly stepping in the direction that most reduces a function's value. Cauchy's 1847 Méthode générale pour la résolution des systèmes d'équations simultanées introduced moving against the gradient to drive a function toward a minimum, the procedure now called gradient or steepest descent. Later work formalised step sizes and convergence guarantees for this family of methods. Here descent is a numerical motion through a space of parameters toward a lower value, and it has nothing to do with a shared line of ancestry among organisms or a rule for assigning people to kin groups.[1]

Unit

One iterative step that lowers the objective function's value

Recovery means

Not applicable

Measured by

Tracked by the decrease in the objective value and the shrinking size of the gradient across iterations

In evolutionary biology, descent is the passing of traits from ancestors to their offspring across generations, so that living groups are joined to earlier ones by an unbroken line of reproduction. Darwin's 1859 On the Origin of Species argued for descent with modification and for the common descent of related forms from shared ancestors, making a branching genealogy the explanation for the diversity of life. The referent is a biological relationship of ancestry among populations and species, read over deep time, and it is distinct from a numerical step toward a lower value or a cultural rule for allocating people to kin groups.[2]

Unit

An ancestor-to-descendant lineage relationship among organisms

Recovery means

Not applicable

Measured by

Inferred from shared traits, the fossil record, and phylogenetic trees reconstructed from molecular and morphological data

In social anthropology, descent is the culturally recognised rule that traces a person's membership in a kin group through a line of ancestors, for example only through fathers or only through mothers. Rivers's 1924 Social Organization gave the word its technical meaning by separating descent, the transmission of group membership, from kinship reckoned more broadly, and Fortes's 1953 The structure of unilineal descent groups set out descent theory and how such groups order rights, land, and authority. The referent is a social principle for placing people into lineages and clans, and it differs from a numerical step toward a minimum or the biological inheritance of traits between generations.[3][4]

Unit

A rule assigning a person to a kin group through a traced ancestral line

Recovery means

Not applicable

Measured by

Documented from genealogies, residence and inheritance patterns, and classification of descent as patrilineal, matrilineal, or cognatic