Hominin

What general trend is seen in hominin cranial capacity over time?

Cranial capacity gradually increased over millions of years, moving from roughly 430 cm³ in early Australopithecines to over 1300 cm³ in later Homo species.

How did changes to the frontal lobe affect skull shape?

An increase in frontal lobe size and convolutions led to the development of a noticeable, more vertical forehead and a flatter face.

What is prognathism and how did it change during hominin evolution?

Prognathism is the forward protrusion of the jaw; it gradually reduced over time as the cranial portion of the skull enlarged to accommodate a bigger brain.

Differentiate between primitive (ape-like) and modern (human-like) cranium bones.

Primitive skulls feature thicker bones and a lower, less dome-shaped cranium, whereas modern skulls have thinner bones and a highly dome-shaped cranium.

Compare the positioning of the foramen magnum in ape-like versus human-like skulls.

In ape-like skulls, it is located towards the back of the skull (post-central), while in human-like skulls, it is located directly underneath the centre of the skull.

What are three primitive characteristics of the hominin jaw and teeth?

A more prognathic jaw, a heavier/thicker mandible with no chin, large molars, a prominent canine, and the presence of a diastema gap.

What are three modern characteristics of the hominin jaw and teeth?

A flatter face, a smaller/more slender mandible with a definite chin, smaller teeth with no diastema, and an even parabolic dental arcade.

How does the torso differ between primitive and modern hominin skeletons?

Primitive hominins have a narrower pelvis and a wide, barrel-shaped ribcage; modern humans have a broader pelvis and a smaller, more barrel-shaped chest.

How do upper limb proportions change from ape-like to human-like forms?

Ape-like limbs have longer arms relative to legs, longer/curved fingers, and a shorter, less mobile thumb; human-like limbs have shorter arms, shorter/straighter fingers, and a longer, highly opposable thumb.

What lower limb adaptation indicates the presence of a "carrying angle"?

The femurs slant inwards towards the knee rather than remaining parallel, which positions the weight directly under the pelvis for efficient bipedal walking.

What are the key differences between the feet of primitive and modern hominins?

Primitive feet feature a splayed, opposable big toe and longer curved toes; modern feet feature a non-opposable big toe aligned with the others, shorter toes, and an enlarged heel bone with transverse and longitudinal arches.

State the timeline, location, and cranial capacity of Australopithecus afarensis.

Lived 3.9–2.9 million years ago in East Africa, with a cranial capacity of approximately 430 cm³.

State the timeline, location, and cranial capacity of Australopithecus africanus.

Lived 3.3–2.1 million years ago in Southern Africa, with a cranial capacity of approximately 460 cm³.

List three anatomical differences between the skulls of A. afarensis and A. africanus.

A. africanus has a rounder cranium, smaller canines, a more parabolic dental arcade, and rarely possesses a diastema compared to A. afarensis.

What does the classification of "gracile" versus "robust" refer to in hominins?

It refers exclusively to differences in the skull, jaw, and teeth layout; everything else in the post-cranial skeleton remains largely the same.

What is the timeline and location of Paranthropus robustus?

Lived 2.7–2.3 million years ago in Southern Africa.

Explain the evolutionary relevance of a prominent sagittal crest in Paranthropus robustus.

It indicates a specialized diet requiring heavy chewing, serving as an attachment site for massive jaw muscles operating a large mandible and huge molars.

List three distinct skull features of Paranthropus robustus.

A prominent sagittal crest, massive zygomatic arches (cheekbones), a heavy robust mandible, and small front teeth relative to enormous molars.

What is the common name, timeline, and cranial capacity of Homo habilis?

Commonly known as "Handy man", lived 2.3–1.5 million years ago, and had an increased cranial capacity of approximately 610 cm³.

What structural bulge appears on the skull cast of Homo habilis that indicates speech development?

A noticeable bulge for Broca's area, which is the region of the brain responsible for speech production.

Why is Homo habilis considered a transitional hominin species?

While it displays modern skull traits like a rounder cranium, smaller jaw, and a parabolic dental arcade, it retains primitive limb proportions like long arms, short legs, and slightly curved fingers/toes.

Outline four ways in which being bipedal helped with hominin survival.

It freed hands to carry infants/tools/food, freed hands to pick vegetation from branches, allowed individuals to cover large open distances efficiently, and made it easier to spot predators over long distances.