Chapter 20

Vocabulary flashcards based on lecture notes about human evolution.

Hominins

Anything more closely related to Homo sapiens, the anatomically modern human, than to other apes.

Synapomorphies

Shared derived characters; examples in humans: elongated skulls, enlarged brow ridges, shortened canines, wrist bone fusion, reduced hair.

Ancestral polymorphisms

Genetic variants that arose prior to the speciation event that generated the species in which they are currently found.

Introgression

The stable integration of genetic material from one species into another through repeated back-crossing.

Sahelanthropus tchadensis

The earliest known hominid, dating back 6-7 million years; discovered in Chad, Central Africa.

Australopithecines

Among the earliest humans, characterized by two main body forms (robust and gracile) and bipedalism.

Homo habilis

The first Homo species, characterized by larger brain cases and smaller teeth than Australopithecus.

Homo ergaster

A more recent ancestor from Africa.

Homo erectus

The first human species to leave Africa.

African Replacement Model

Hypothesis that H. sapiens evolved in Africa, migrated to Europe and Asia, and replaced H. erectus and H. neanderthalensis without interbreeding.

Multiregional Evolution Model

Hypothesis that H. sapiens evolved concurrently in Europe, Africa, and Asia with sufficient gene flow to maintain their continuity as a single species.

Hybridization and Assimilation Model

Hypothesis that H. sapiens evolved in Africa and migrated to Europe and Asia with some amount of hybridization, assimilating some European and Asian genes.

Homo floresiensis

A hominin species found on the island of Flores, characterized by diminutive stature and small brain size.