megadont
large teeth; megadont hominids are characterized by expansion of the posterior teeth
synchronic
at the same time; thus synchronic species coexist in time
mosaic habitats
areas characterized by a range of habitat types, from forrest to grassland
aridification
a drying trend resulting from lower seasonal or annual precipitation levels
savannah hypothesis
the now discredited idea that the development of open savannah grass-land created conditions leading to the evolution of hominins
gallery forest
dense, canopied forest found along water courses such as rivers and lakeshores
forest hypothesis
the suggestion that the hominid clade diverged from pains while still occupying a woodland/forest habitat, as suggested by paleoecological reconstruction of fossil localities
variability selection hypothesis
a model that suggests that the operating factor in hominin evolution was environmental disparity, rather than stability, which promoted adaptive flexibility in hominin traits, including locomotion, dental adaptations, and technology
genetic divergece
an estimate of the time since two genomes diverged, based on the number of differences observed and assuming a constant rate of mutation
species divergence
an estimate of time since speciation; because genetic differences are constantly accumulating within lineages, estimates of genetic divergence time will always be older than species divergence time
assemblages
the collection of all remains of pants or animals from paleontological contexts
stem hominin
the progenitor of all later hominin species within a clade, arising from the last common ancestor
foramen magnum
“large passage”, the foramen magnum is the largest hole in the cranium, though which the brain stem passes to become the spinal cord
eurytopic
organisms that are able to live in diverse habitats and geographic ranges; the prefix “eury” means “broad, wide” and the affix “topic” refers to “place”
gracile
small or slightly built; among australopithecines, refers to those species lacking the skeletal and dental features associated with the megadont adaptation
robust
rugged or strongly built; several australopithecine species possess skeletal and dental features associated with large chewing muscles and crushing and grinding of hard foods
phyletic sequence
an unbroken lineage of ancestor- descendent species
mandibular symphysis
the midline of the lower jaw, where the left and right sides of the dental arcade meet
orthognathic
“ortho” refers to verticle or flat, and gnathic to the jaws, so means flatfaced
prognathic
refers to the degree to which the lower face projects forward
competitive exclusion
a phenomenon in which two species closely related in phenotype and ecology come into direct competition or resources. in these cases one species will either become extinct or adopt a new phenotype, allowing it to exploit other resources
Liem’s paradox
a model in biology that describes the apparent paradox between a specialized phenotype and a generalized behaviour; the paradox is resolved if the specialized phenotype does not restrict an organism from nonspecialized behaviours
fallback foods
resources on which a species relies when its preferred, more easily acquired and processed foods are unavailable