Contents

Section 1
Palaeoanthropology


Photogallery

Outline of Human Phylogeny

Evolutionary Trees
and DNA


Brain Evolution

Hand and Bipedality

Section 2
Social and socio-
cultural systems


Primate societies

Social relations and the evolution of culture

Social relations, communication and cognition

Human socio-cultural patterns

Tools and symbolic behaviour

Palaeolithic Art

Contemporary hunter-gatherer art

Section 3
Ontogeny and symbolism


Editorial Introduction: Ontogeny & Phylogeny

The role of ontogenesis

Brain, cognition, and language

Early interaction and cognitive skills

Language and thought

Theories of symbolization
and development


Children's drawings and the evolution of art

Section 4
Language systems


Spoken language and
sign language


The gestural primacy hypothesis

Comparative cognition

Animal language and cognition

Language acquisition

Language
reconstruction


The prehistory of grammar

Writing systems

Links

Links Policy

Relevant Links

Evolution of the Human Brain


Ralph Holloway


Abstract In the last 3-4 million years brain volume within the hominid lineage has increased from less than 400 ml to roughly 1400 ml. The first clear increase in hominid brain size is seen in early Homo at c.2 m.y.a. in East Africa (most reliably in cranial specimen KNM-ER 1470). This is an evolutionarily significant change that cannot be simply accounted for in terms of increased body size alone. From the appearance of H. erectus at c.1.7 m.y.a. to the present, the brain increases nearly twofold: from c.800 ml to 1500 ml in Late Pleistocene H. sapiens, without any apparent change in body size.

With regard to brain reorganization, left-right cerebral hemispheric asymmetries exist in extant pongids and the australopithecines, but neither the pattern nor direction is as strongly developed as in modern or fossil Homo. KNM-ER 1470 shows a strong pattern that may be related to handedness and tool-use/manufacture. The degree of asymmetry appears to increase in later hominids.

The appearance of a more human-like third inferior frontal convolution provides another line of evidence about evolutionary reorganization of the brain. None of the australopithecine endocasts show this region preserved satisfactorily. There is a consensus among palaeoneurologists that the endocast of the specimen KNM-ER 1470 does show, however, a somewhat more complex and modern-human-like third inferior frontal convolution compared with those of pongids. This region contains Broca's area, which in humans is related to the motor control of speech. Unfortunately, later hominid endocasts, including H. habilis and H. erectus through archaic H. sapiens to the present, seldom show the sulcal and gyral patterns faithfully. Thus nothing palaeoneurological can be said with confidence about possible changes with the emergence of anatomically modern H. sapiens. On the other hand, there is nothing striking about Neanderthal brain casts in comparison to more recent H. sapiens, except their slightly larger size, suggesting no significant evolutionary change thereon [Eds].

Links
For further details, use this image as a link to Trevor Henderson's materials on the Evolution of the Human Brain at the Department of Anthropology, University of Toronto.

See also materials on brain evolution at the National Museum of Health and Medicine, University of Wisconsin