11B PP - Skull Changes

Major trends in skull evolution

The zygomatic arch is the curved structure on the side of the skull that protects the eye and provides attachment points for jaw muscles.

It became smaller over time, reflecting reduced jaw musculature.

What happened to the zygomatic arch during evolution?

The zygomatic arch is the curved structure on the side of the skull that protects the eye and provides attachment points for jaw muscles.

It became smaller over time, reflecting reduced jaw musculature.

What is a diastema?

A diastema is a gap between the incisors and canines.

It accommodates large canines and helps move food into the cheek so feeding can continue efficiently.

How did jaw shape change from chimpanzees to humans?

Chimpanzees

• U-shaped dental arch

• Large canines

• Diastema present

Australopithecines

• Reduced canines

• Less U-shaped jaw

• Diastema still present

Humans

• Parabolic dental arch

• Smaller teeth

• No diastema

What happened to teeth during hominin evolution?

There was a gradual reduction in tooth size.

Canines became smaller and the diastema disappeared in modern humans.

What happened to the sagittal crest over time?

The sagittal crest became smaller.

This reflects a reduction in jaw muscle size and strength as hominins evolved

What happened to cranial capacity during hominin evolution?

Cranial capacity increased over time, producing a larger brain case and larger brains.

Trend in brain size

The image sequence shows increasing cranial capacity from:

Chimpanzee → Australopithecine → Homo erectus → Homo neanderthalensis → Homo sapiens.

What happened as brain size increased?

As brain size increased, the cerebrum became more folded.

This increased surface area, allowing for:

• More neurons

• More neural connections

• Greater processing ability

What cognitive abilities increased during hominin evolution?

Increasing brain complexity led to:

• Speech

• Emotions and feelings

• Higher-order thinking

• Decision making

• Self-control

• Planning abilities

Important exam point: brain size vs bipedalism

Bipedalism evolved before the major increase in brain size.

Why are humans considered cognitively unique?

Compared with other apes, humans have:

• Advanced cognitive capacity

• Complex language

• Complex belief systems

• The ability to think about abstract concepts

How is language linked to cognitive evolution?

Humans can communicate using complex language and pass knowledge between generations, contributing to cultural development.

Neanderthal brains vs modern human brains

Although Homo neanderthalensis had slightly larger brains than Homo sapiens:

• H. sapiens had a larger cerebellum.

• The cerebellum is associated with language processing, learning, reasoning and social abilities.

• Neanderthal brain growth was slower during infancy.

What is cultural evolution?

Cultural evolution refers to changes in human societies over time through behaviours that are learned, copied and passed between individuals

Examples of cultural evolution

Examples include:

• Agriculture

• Tool use

• Fire use

• Social organisation

• Food gathering practices

• Art

How are biological and cultural evolution linked?

Biological changes in humans, particularly increased cognitive capacity, enabled the development and transmission of culture

Exam summary: major evolutionary trends

From early hominins to modern humans:

• Brain size increased.

• Skulls became rounder.

• Faces became flatter.

• Brow ridges became smaller.

• Teeth and jaws became smaller.

• Diastemas disappeared.

• Cognitive abilities and culture became more complex.