Postorbital Constriction

A. anamensis

Moderate postorbital constriction (narrowing behind eye orbits). More constricted than modern humans but specific details limited due to fragmentary fossils.

A. afarensis

Pronounced postorbital constriction - skull narrows significantly behind the orbits. Much more constricted than modern humans, reflecting small brain and large face proportions.

A. africanus

Moderate to pronounced constriction, similar to A. afarensis. Less frontal lobe expansion than humans results in narrowing behind eyes when viewed from above.

A. sediba

Moderate postorbital constriction, somewhat reduced compared to other australopithecines. Shows trend toward reduced constriction seen in Homo.

P. aethiopicus

Extreme postorbital constriction - among the most pronounced in hominins. Massive face combined with small brain creates dramatic narrowing behind orbits.

P. robustus

Severe postorbital constriction due to massive facial width combined with relatively small brain. Very narrow frontal region behind huge zygomatic arches.

P. boisei

Extreme postorbital constriction - the most pronounced of any hominin. Enormous facial breadth combined with small brain creates dramatic "wasp-waisted" appearance when viewed from above.