Human Evolution

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Biological Evolution

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Changes at genetic level over time

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Primate characteristics

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Primates are an order of the Mammal class, chracterised by large brains, a generalised dental pattern, prehensile digits, binocular colour vision and complex social groupings

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Quadrapedal

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Habitual movement on 4 limbs

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Bipedal

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Habitual movement on 2 limbs

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Diet

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Different hominin species had differing dietary requirements

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Sagittal crest

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The bony crest on top of the skull used for attachment of powerful jaw muscles which run down to the mandible

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Zygomatic arch

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The arch of bone through which muscles run from the top of the skull down to the mandible.

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Mandible

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The jaw bone

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Molars

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The teeth at the back of the jaw used for grinding and mashing

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Dental arch

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described as having a U shape in apes, with the molars parallel to each other and a V shape in modern humans

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Brow ridge

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Protect the eyes

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Gait

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Describes the style of locomotion. In human evolution there is a trend to improved bipedal efficiency. All ancestral hominins were bipedal, with modern humans having a range of anatomical features which have improved bipedal efficiency.

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Nuchal crest

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The bony protrusion at the back of the skull used for the attachment of neck muscles

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Foramen magnum

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The hole in the base of the skull through which the spinal column enters

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S-shaped spine

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Acts as a shock absorber to efficiently carry the weight above the pelvis

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Valgus angle

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In modern humans the legs are angled under the pelvis so that the weight of the body is better supported when one leg is off the ground in bipedal gait.

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Bowl shaped pelvis

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Describes the shape of the human pelvis which efficiently carries the weight of the upper body above the legs. The narrowing of the birth canal means that humans give birth to relatively undeveloped offspring which require prolonged parental care.

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Femur modifications

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In modern humans the femur is lengthened which improves the stride length and therefore bipedal efficiency

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Arched foot and forward facing toe

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The human foot is arched to act as a shock absorber and the relatively short big toe is forward facing alongside the other digits. This provides the final push off in a bipedal gait and makes the gait more efficient

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Fully opposable thumb

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Unlike other apes, the human thumb is fully opposable. The thumb is relatively long and is able to touch the end of the other digits.

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Australopithecine sp

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The genus of extinct hominins which show a mixture of ape like and human like chracteristics.

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Paranthropus sp.

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The genus of extinct hominins which are characterised by anatomical features indicative of a vegetative diet

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Homo sp.

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The genus of hominins chracterised by expansion of the brain, defined tool cultures and increasing cultural complexity.

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Multi-regional hypothesis

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One of the models used to describe human dispersal. Multi regional theory proposes that significant gene flow between homo erectus populations (which were distributed through Africa, Asia and Europe) were able to simultaneously evolve into modern Homo sapiens. The model predicts that present day human populations should show the same amout of genetic variation as they were established at the same time and were subject to the homogenizing effect of gene flow and any localized variation is the product of variation being carried forward from the ancestral Homo erectus forms.

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Out-of-africa hypothesis

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One of the models used to describe human dispersal. The out-of-africa hypothesis is sometimes called the replacement model as it describes two waves of outward migration from Africa. Homo erectus populations were spread across Africa, Asia and Europe, evolving into a number of hominin species. Approximately 200,000 years ago in south africa, homo sapiens evolved and began an outward expansion into other continents replacing the other hominin forms to become the sole remaining species of the genus. This model predicts that there should be the greatest amount of genetic diversity in African populations, with reduced genetic diversity further from Africa as populations were more recently established.

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Intelligence and Brain Size

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The general trend in hominin evolutio is toward an increasing brain size. Natural selection favoured individuals who inherited mutations for the building of larger brains, as the increased intelligence provided an adaptive advantage in the exploitation of the environment. Increasingly complex tools, fire and weapons for hunting would have improved the diet and provided the ncessary energy allowing for an expansion of the brain.

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Cranial capacity

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Estimates of brain size extinct hominin are taken by measuring the volume of the cranium, with a measure of intelligence estimated by comparing brain size to body size.

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Wernicke's and Broca's area

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These two regions of the brain are well developed in modern humans with Wernicke's area associated with comprehension of language and Broca's area used in the production of sounds needed for complex language

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Languages and communication

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Modern humans have sophisticated language skills, and are able to communicate complex ideas for planning, hunting, learning, cooperating and other social transactions.

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Cultural evoltuion

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Refers to the transmission of ideas over time, it can happen continuously over a life time

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Oldowan tools

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associated with homo habilis. These tools were simple river worn pebbles crudely fashioned with a minimum number of flakes being removed.

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Acheulian tool

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Associated with homo erectus. These tools were tear-drop like and more flakes were removed.

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Mousterian tools

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Associated with homo neanderthalensis. Made with flint which breaks more predictably, these tools have many flakes removed.

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Upper palaeolithic tools

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Associated with homo sapiens. Modern humans had the necessary intelligence to produce and an increased range of tool types using a range of techniques.

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Fire and cookiing

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Fire is first associated with homo erectus. Provides warmth in cooler climater, deterring predators and hunting. Light is able to extend the time in which hominins can socialise and carry out the necessary activities required of them. It can also cook food, which improves nutritional value by making food more palatable or easily digestible.

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Domestication of Plants and Animals

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The domestication of plants and animals began simultaneously across a number of modern human populations approx 10,000 years ago.

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Art and Spirituality

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Neanderthals and modern humans used artistic representations to convey meaning through symbolism to other individuals, representing ideas about the unknown, hunting, fertility and death.