Describe the major trends in hominin evolution, including bipedalism, brain size and tool use, with reference to key genera

What this dot point is asking

WACE wants you to describe the major trends in the evolution of modern humans and the skeletal evidence for them. Hominins are the group that includes modern humans and our extinct bipedal ancestors and relatives. You are not expected to memorise every species, but you should know the main trends and a few key examples.

Bipedalism: the defining hominin feature

Bipedalism, habitual walking upright on two legs, is the earliest and defining hominin trait, appearing before large brains. It is supported by a suite of skeletal adaptations you should be able to describe and explain:

• Foramen magnum (the hole where the spinal cord meets the skull) is positioned underneath the skull, so the head balances on top of an upright spine.
• Spine is S-shaped (curved) to centre the body's weight over the hips and absorb shock.
• Pelvis is short, broad and bowl-shaped to support the organs and anchor walking muscles.
• Femur angles inward (the carrying angle) so the knees and feet are under the body's centre of mass.
• Foot has an arch and a large, non-opposable big toe aligned with the others, for pushing off while walking.

Bipedalism freed the hands for carrying and using tools and may have helped with seeing over grass and reducing heat exposure.

Trends in the skull, brain and teeth

As hominins evolved, several skull and dental trends appear together:

• Brain size (cranial capacity) increased, from around 400 to 500 cubic centimetres in Australopithecus to about 1350 cubic centimetres in modern Homo sapiens. The forehead became higher and more vertical.
• Brow ridges and the overall robustness of the skull reduced.
• Jaw and teeth became smaller, the face flatter (less prognathous), and a chin developed in modern humans.
• The dental arcade changed from a rectangular ape-like shape to a rounded parabolic arch.

These trends are linked to diet, cooking and the increasing importance of tools and culture over powerful jaws.

Tool use and culture

Cultural evolution runs alongside the physical trends. Stone tools become more sophisticated through the record, from simple flaked pebble tools to finely worked blades, along with the controlled use of fire, art and eventually complex language and society. Culture allowed hominins to adapt to new environments far faster than biological change alone.

Key hominin genera (the examples to know)

You should recognise the broad sequence and the main genera, not exhaustive species lists.

• Australopithecus (for example the "Lucy" specimen, Australopithecus afarensis): bipedal, with a small ape-sized brain, lived in Africa several million years ago.
• Homo habilis ("handy man"): a slightly larger brain and associated with the earliest stone tools.
• Homo erectus: a larger brain again, taller body proportions like modern humans, use of fire and more advanced tools, and the first hominin to spread out of Africa.
• Homo neanderthalensis (Neanderthals): large-brained, robust, cold-adapted, made tools and buried their dead; a close relative rather than a direct ancestor.
• Homo sapiens: modern humans, with the largest and most rounded braincase, smallest face and teeth, a chin, and complex culture and language.

How this maps to the exam

Expect questions asking you to list and explain bipedal adaptations, describe trends in brain size, dentition and the skull, or compare two skulls or skeletons and identify which is more recent. You may be asked how a feature such as the position of the foramen magnum indicates bipedalism, so link each structure to its function.