Posture

Bent over or quadrupedal "knuckle-walking" common

Upright or bipedal

Leg and arm length

Arms longer than legs; arms adapted for swinging, usually among trees

Legs usually longer than arms; legs adapted for striding

Feet

Low arches; opposable big toes, capable of grasping

High arches; big toes in line with other toes; adapted for walking

Teeth

Prominent teeth; large gaps between canines and nearby teeth

Reduced teeth; gaps reduced or absent

Skull

Bent forward from spinal column; rugged surface; prominent brow ridges

Held upright on spinal column; smooth surface

Face

Sloping; jaws jut out; wide nasal opening

Vertical profile; distinct chin; narrow nasal opening

Brain size

280 to 705 cm³ (living species)

400 to 2000 cm³ (fossil to present)

Age at puberty

Usually 10 to 13 years

Usually 13 years or older

Breeding season

Estrus at various times

Continual