This video highlights some of the key ideas that will be covered in this topic.
Biology 3.6 AS91606
Trends in human evolution refers to change over a period of time in relation to:
• human biological evolution
• human cultural evolution
• patterns of dispersal of hominins. Hominins refers to living and fossil species belonging to the human lineage. This is a subgroup of hominids, a group which includes both humans and the great apes.
Trends in human biological evolution begin with early bipedal hominins and may require comparison with living hominids. These trends involve:
• skeletal changes linked to bipedalism
• changes in skull and endocranial features
• changes in the manipulative ability of the hand, arms, scapula and rib cage.
Trends in human cultural evolution involve:
• use of tools (stone, wood, bone)
• use of fire
• clothing
• abstract thought (communication, language, art)
• food-gathering (hunter-gatherer, domestication of plants and animals)
• shelter (caves, temporary settlement, permanent settlement).
Cultural evolution covers the following tool cultures and key species associated with them, through to development of agriculture and early settlements:
• Oldowan - Homo habilis
• Acheulean - Homo erectus
• Mousterian - Homo neanderthalensis
• Upper Palaeolithic - Homo sapiens
• Neolithic - agricultural Homo sapiens
Dispersal of hominins covers the period up to 6 000 years ago. Candidates should be able to demonstrate understanding of the ecological/evolutionary changes that could drive such dispersal.
Scientific evidence relating to human evolution may include skeletal remains, nuclear and mitochondrial DNA, tools, evidence from scientific and comparative dating.
Walking with Cavemen
Narrated by Sir Robert Winston, the four part series Walking With Cavemen brings human prehistory to life. By answering the questions following each episode, you will engage with the key ideas explaining biological and cultural evolution.
Biological Evolution - Bipedalism
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| Laetoli footprints |
This video shows the site and highlights the careful consideration that goes into working with and preserving the fossil record.
The discovery of Lucy (Australopithecus afarensis) by Don Johnason and his team provided key fossil evidence for early bipedal hominins. The video below highlights the key skeletal features used to determine the likely locomotion of Lucy's species.Try adding your own narration using the following terms:
skull - foramen magnum, nuchal crest
spine - s-shaped curvature
pelvis - bowl shaped
femur - valgus angle
foot - in-line big toe, foot arches
Dated between 2 and 5 million years ago, Australopithecus fossils show evidence of adapting to a new form of locomotion that is consistent with a drying period in Africa.
How could this change in climate provide a selection pressure for waling upright.
What are the adaptive advantages to walking upright?
What other changes in environment, biology and culture can account for the development of the current structures and functions that define our species?
Becoming Human
This three part video series explores the fossil and geological evidence for the evolution of hominin species.
Video 1 - Australopithecus to Homo habilis
Key Ideas include:
1) The development of bipedalism in response to changes in environmental selection pressures producing savannah woodlands
2) The use of endocasts to provide evidence for the evolution of human brain architecture allowing for different thinking
3) The appearance of Homo habilis with its unique broad thumb bone allowing precision grip and increased brain capacity
4) The links between bipedalism, freed hands, increased brain capacity and the invention of stone tools to meet the needs of an increasingly difficult and changing environment
Video 2 - Homo erectus
Key ideas include:
1) Change in brain capacity and architecture to increase creativity, planning and communication (Broca's Area)
2) The birth of technology through the production of the acheulean hand axes
3) The shift from scavenging to persistence hunting
4) The loss of body hair and the development of sweating for thermoregulation
5) Harnessing of fire for cooking (related to evolution of smaller teeth and gut and increased brain development)
6) Importance of fire in promoting communication and society.
7) Migration out of Africa
8) Homo floresiensis as the oldest living Homo erectus
Video 3 - Homo heidelbergensis, Homo neanderthalensis and Homo sapiens
Key Ideas include:
1) Evidence for consciousness, burial of the dead
2) Hunting culture of neanderthals and limitations of mousterian tools
3) Megadrought in Africa pushed Homo sapiens to adapt to coastal life - changing diet, driving brain development and influencing culture
4) Technological advancements of Homo sapiens to use diverse materials, throwing spears, fishing hooks
5) Evidence of art
6) Out of Africa migrations
7) Presence of Neanderthal DNA in modern humans
8) Use of DNA molecular clocks to determine divergence
Biological Evolution - Brain Size and Brain Architecture
The basic trend in hominin brain development shows increasing cranial capacity, particularly greater development of the frontal lobe. This area of the brain is associated with problem solving, and planning which would have enabled Homo habilis and Homo erectus to develop the first stone tool cultures. In later species, this area houses strategy, creativity, imagination, art and spirituality.
Although cranial capacity (brain size) is an extremely important factor in determining intelligence, increased development of specific areas provides better evidence of specific adaptations. Broca's area located in the frontal lobe is known to be responsible for spoken, written and signed language. It is necessary for the ability to produce meaningful sounds.
Wernicke's area located in the temporal lobe is known to be responsible for hearing and comprehending language, with some function related to short term memory necessary for engaging in conversations.
These two areas work together to allow for more advanced communication.
While there is some evidence that these areas were significantly better developed in Homo erectus, whether or not they would have had sufficient control of breathing and mouth muscles required for sophisticated speech remains highly debated.
When compared to other mammals such as whales and elephants, we don't actually have a particularly large brain. The following video by Suzana Herculano-Houzel examines what's so special about our brains... and which selection pressure is likely to account for our status as Earth's "wise men".
Diet and Brain Development
A large brain requires a lot of energy to fuel. Trends in brain development are seen to follow trends in changes in diet:
Australopithecus - 400cc - primarily vegetarian/insectivore
Homo habilis - 600cc - omnivorous scavenger (meat/marrow)
Homo erectus - 800cc - omnivorous hunter/gatherer
Homo neanderthalensis 1300cc - peak carnivore
Homo sapiens 1200cc- omnivorous hunter/gatherer (including fish)
Hominin Tool Cultures
A defining moment in the understanding of hominin evolution came when Homo habilis remains were found with clearly identifiable stone tools. Since this time, the development of better tools, changes in diet and associated brain development that comes with energy rich meat have been intimately intertwined.
1) Oldowan tools were fashioned by striking two riverstones together to produce a sharp edge used for cutting and scraping meat off of animal carcasses and cracking open bones to reach the marrow.
2) Acheulean tools have a typical bifacial teardrop shape. The typical handaxes are the result of a well worked core stone with sharpened edges created by knapping. Increased working is able to create a serrated edge for butchering larger game.
3) Mousterian tools were created with the Levallois method. this method involved shaping a stone core so that it has a thick central body with flakes removed on all sides before preparing a flattened dull striking platform. The final tool which is sharp on all sides is struck off the core with a single blow. Clearly, a greater amount of planning and technique is required. Some of these stones were fastened to wooden handles
More complex tools could be used for chopping wood, building shelter from wood and bone.
4) Upper paleolithic tools are associated with modern Homo sapiens, beginning in southern Africa 60 000 years ago. These tools mark the invention of tools to make other tools. Fishing hooks, oil lamps, sewing needles, throwing spears and sticks. Use of flint, bone, antler, etc.
This video provides an overview of tool use to improve techniques for hunting.
5) Neolithic tools are associated with the development of agriculture.
Cultural Evolution
The video below describes changes in culture from Paleolithic to neolithic times. Try to associate each of the examples in the video below to the appropriate hominin group(s).
Human Migrations and Dispersal Out of Africa
Dispersal of African
Hominins and the Origin of Homo sapiens
Dramatic climate changes over the
past 3 million years have driven biological evolution and also hominin
migrations/dispersal out of Africa and across the globe. The positive feedback
loop involving: anatomical adaptation—technological advancement (culture) –
improved nutrition – cognitive function, provided the process for hominins to
quickly overcome changes in selection pressures and evolve into unique regional
species across the globe during periods of isolation, before later coming back
together once barriers to gene flow were no more.
1.8 million years ago - Homo erectus followed migrating herds of
herbivores out of Africa during a period of wet weather in the middle east.
Evidence of Acheulean stone tool culture can be found scattered along the
Indian Ocean coastal route and into Asia. Shortly afterward return to Africa
became closed due to desertification. Stone
tools made of rocks not naturally found in the area they are discovered provide
evidence of how far Homo erectus
travelled.
600 000 years ago - a second
migration of hominin, Homo
heidelbergensis (archaic Homo sapiens),
left Africa. Heading into Europe, they soon encountered an increasingly cold
climate and evolved independently into Neanderthal
and Denisovan hominins by 400 000
years ago. Further refinement of stone tools and new design and manufacture
techniques produced Mousterian flake tools (blades and points). The production
of spears and clothing helped to meet the challenges of a cooling climate. Flint
and obsidian were valuable stones collected and carried long distances. Evidence
of cultural burial of the dead appears at Neanderthal
sites along with evidence of caring for their young and sick. Bodies found in
graves positioned in a foetal position and accompanied with gifts and tools
provides evidence for a change in thought during this time.
In Africa, Homo heidelbergensis populations were devastated by mega drought
conditions and pushed to southern regions and coastlines, giving rise to Homo sapiens around 200 000 years ago. The
upper paleolithic stone tool culture of thin blades and microliths was born
during a population bottleneck in Africa.
These tools showed a change in thinking and were used to fashion new
tools such as fishing harpoons, hooks and sewing needles from bone, ivory,
horns and antlers. This new species migrated out of Africa in several waves,
most significantly approximately 60 000 years ago when the rains returned to
Africa.
Tracing the arrival of cultural
advancements, it becomes clear that Homo
sapiens rapidly followed costal routes and used land bridges created by an
ice age to travel all the way into Australia. Throwing spears, projectile
arrows and other upper paleolithic tools, along with art (ochre and charcoal)
and jewellery appear 45 000 years ago in Australia and France. Ritualised
burials included gifting of tools, animals, jewellery and art. These
advancements are likely the result of more advanced speech and the development
of complex and abstract language, with Homo
sapiens having a more developed parietal and occipital lobe compared to Neanderthal (and a different placement
of the larynx in the throat allowing for more vowel sounds).
The combination of the eruption of
the supervolcano Mt Toba in Indonesia 74 000 years ago and the increased
competition for limited resources across Europe which was still under the
effects of a severe ice age made life difficult for migrating hominins. By
approximately 20 000 years ago, at the height of the last glaciation, Homo sapiens had replaced Neanderthal in Europe and Homo erectus in Asia.
Beginning 15 000 years ago, Homo sapiens followed migrating herds
and used boats to travel along the north Pacific and into the Americas. Low
seas levels between Siberia and Alaska allowed Homo sapiens to travel across the Bering Strait. As the Earth
warmed and the glacial sheets melted, rains returned to desert areas and the
amount of fertile land increased. With plentiful foods in areas like the
fertile crest, people no longer followed migrating herds, but stayed in more
permanent settlements. An understanding of agriculture developed independently
in several places around the globe and a new Neolithic stone tool culture
developed characterised by farming tools and pottery. As men and women spent
more time together and less time apart on hunting expeditions, human
populations expanded and nomadic hunter-gatherer lifestyle was replaced by
farming. The domestication of animals (dogs, goats, pigs, cows) soon followed
providing safety, a ready supply of meat and working animals. Selective
breeding and cultivation of new food sources rapidly changed the nutrition of Homo sapiens.
DNA Analysis and the origins of modern humans
Mitochondrial DNA analysis traces
the origins of present day populations by comparing the degree of similarity of
DNA inherited continuously along the maternal line, since mtDNA doesn’t undergo
recombination. It is assumed that mtDNA undergoes mutation at a fairly constant
rate. This means, the greater the genetic diversity of a population, the further
in the past they shared a common ancestor. MtDNA analysis suggests that all
living Homo sapiens shared a common female
ancestor (“mitochondrial eve”) in Africa approximately 120 000 years ago. Specific
mitochondrial DNA genes responsible for respiration rate and efficiency can be
observed in specific regions. For example, a mutation reducing the efficiency
of respiration and favouring excess heat production can be found amongst
populations that lived at high altitude and travelled north into Siberia and
across to the Americas.
In a similar way, Y-chromosomes can
be used to determine migratory routes and relationships along paternal
lineages. The Y-chromosome does not undergo recombination and is passed on from
father to son. African populations have the greatest degree of genetic
variation in the Y-chromosomes, whereas all humans outside Africa show
remarkable similarity. Y-chromosome analysis suggests that all males alive today
shared a common male ancestor approximately 60 000 years ago in Africa.
Admixture is the word used to
describe evidence of gene flow from one population into another. From analysis
of Neanderthal, Denisovan and Homo sapiens
DNA it is apparent that interbreeding took place between Homo sapiens migrating out of Africa and Neanderthal in Europe, and between Denisovans and Homo sapiens
and travelling along the costal route to Melanesia. Modern Homo
sapiens share between 1 and 4% Neanderthal
DNA and Melanesians and Polynesians share between 1 and 4% Denisovan DNA.
Resource: Atlas of Human Evolution
Resource: Atlas of Human Evolution
The Homo sapiens story
This video provides a good overview of the key ideas in the most accepted model of human evolution.
The Great Human Odyssey
Thank you Mr Cooper
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