Download
1 / 37
370 likes | 551 Views
The expansion of the brain. The expansion of the brain followed bipedalism. We suggest this because the australopithecines were bipedal apes with brains only slightly bigger than chimpanzees. The development of the brain became possible when the hands became free.
E N D
The expansion of the brain • The expansion of the brain followed bipedalism. • We suggest this because the australopithecines were bipedal apes with brains only slightly bigger than chimpanzees. • The development of the brain became possible when the hands became free. • Higher intelligence led to tool making
Expansion of the brain • Australopithicines on the left had similar sized brains to chimpanzees, Homo Habilis on the right had a larger brain and learned to make and use tools.
Expansion of the brain • Making tools required learning and memory. • The expansion of the brain made this easier. • The tools then became more complex as the genus evolved.
Oldowan Tools • Oldowan tools culture was probably made by Homo habilis dating back to about 2.6myo • They found river worn pebbles and knocked off edges flakes from several edges. • This would then leave a core with a cutting edge. • The sharp flakes were useful in cutting.
Oldowan Tools • Some tools were used to work wood, some to cut meat and others to cut reeds. • What advantages would this enable? • Large animals could have been butchered. • The cores may have been used for cracking bones to extract the marrow. • Crushing tough plant food. • Digging edible bulbs and roots. • This will have allowed a wider diet then ever before.
Acheulian Tools • These tools were made by Homo erectus, Homo heidelbergensis and archaic Homo sapiens. • They had a classical ‘tear drop’ shape. • They had a ‘biface’ shape that bulges outwards on both sides. • It would have taken many more blows then Oldowan tools to make Acheulian tools. • Oldowan and Acheulian tools are classified as the lower Palaeolithic or ‘early stone age’.
Mousterian Tools • Mousterian tools were trademark of Homo Neandathalensis. • Mousterian tools were shaped from flakes themselves. • They would prepare a core, and then smash the flint rock against it • This is known as the Levallois method • They used the rock flint as it chipped in a predictable way.
Upper Palaeolithic Tools • Made by the modern Homo Sapiens and the last of the Neanderthals about 35,000 years ago. • Finer workmanship using a technique called the punch blade. • Long, thin flakes were removed and shaped into a large number of different tools. • They used other materials such as bone, ivory and antler to produce fine tools such as needles.
Upper Palaeolithic tools • Stone tools were more finely made with more cutting edge per kg of stone used. • As well as using a variety of materials they also used a composite tools (combination of materials) • E.g. spearhead of stone and carved antler to wooden handles, using thongs of skin and plant gum to hold it.
Homo habilis and Homo rudolfensis • Homo habilis remains were found in Olduvai in 1959. • He had a small cranium and a small jaw and teeth compared to australapithicines. • In 1972 it was thought another species was found (H. rudolfensis) which had a larger cranium and larger jaw and teeth. • There is a debate as to whether Homo rudolfensis existed because some suggest it was just a single sexual dimorphic species of H. habilis.
Homo Erectus • H. Erectus was the first pre-human to leave Africa. • Erectus was also the first known to use fire! • Some were found in Indonesia and China. • Some also have been found in East Africa which differ in a number of ways. • Some people regard the Asian species to be called H. Ergaster because of these differences.
Homo Erectus • Evidence for the use of fire is the presence of charcoal and charred bones and thermally altered stones in a ring shape. • It is not known whether H. erectus could create fire but it is thought that they maintained it when it occurred naturally (lightening).
Homo erectus • What are some benefits of fire? • Warmth – (ice ages) • Illumination at night – (tool making and butchering) • Predator protection • Harden wooden spear points • Stampede animals into traps • Cooking • Social organisation!
Homo heidelbergensis • Originally classified as archaic H. sapiens until the early 1990’s when well preserved remains of around 30 adult and juvenile remains were found. • It is now believed that this species may have given rise to H. neanderthalensis • They used the acheulian hand axes.
Homo neanderthalensis • The most recent pre-modern humans. • Found in Europe and western Asia. • They had a slightly larger brain size • Had a prominent occipital bun. • Strong teeth and jaw. • Prominent brow ridges • Thick limb bones.
Homo neanderthalnesis • There is evidence the cared for their elderly. • Many intact skeletons • Bones sometimes covered with game animals • Tools found • Pollen grains of flowers have been found with skeletons. • They used the mousterian tool culture.
The origin and spread of modern Humans • The ‘regional continuity’ or candelabra hypothesis is a challenging model. • In this model humans evolved more or less simultaneously across the entire Old World from several ancestral populations. • In this model is suggest there was some ‘gene flow’ between the regions in order for them to evolve at a similar rate. • This suggests that ‘racial’ characteristics would be very ancient.
Regional Continuity Hypothesis • There are many criticisms of this theory. • Some are… • Molecular and genetic evidence suggest evolution and then migration rather than evolution simultaneously in different continents. • MtDNA suggest the Neanderthals were a dead end species rather then evolving into humans. • It appears Neanderthals and modern humans co-existed and therefore wouldn’t have evolved into modern Europeans.
The Out of Africa Hypothesis • Another more supported model is the ‘replacement’ or the ‘Out of Africa’ hypothesis. • This suggested modern humans evolved relatively recently in Africa before spreading to Asia and Europe to replace the existing, less advanced populations. • This would suggest that racial characteristics would be relatively recent.
Out of Africa Hypothesis • The matter is not finally resolved but this is one hypothesis
Mitochondral DNA evidence • Mitochondria are self replicating and have their own DNA. • It is inherited only via females, so your mtDNA is passed on from your mother, and hers from her mother and so on. • This means in theory you can go back to one maternal ancestor. • It also means that it will only change by mutation (mtDNA mutates about 10 times that of nuclear DNA because it doesn’t have the proof reading mechanisms that nuclear DNA has).
Mitochondral DNA • When mtDNA was compared from different human populations they found people from the same ethnic group showed fewer differences than people of different ethnic groups. • They then used the differences to measure the relatedness and constructed an evolutionary tree from ‘restriction maps’. • It had two main branches, one leading to Africans and the other to Asians, Europeans, and native Australians.
Migration out of Africa • It is thought that modern humans inhabited east Asia around 67,000 years ago and Australia around 50,000 years ago. • Why did modern humans appear in Europe only 40,000 years ago considering it is so close to Africa? • Modern humans migrated to other parts of the world in an ice age where they were able to cross easily. • To get to Europe they will have encountered ice shelves such as the Southern Elps making this more difficult. • It is thought the crossed to America between 30 and 15 thousand years ago when there was a temporary ice-age land bridge.
Domestication • How do we know whether and animal or plant is wild or domesticated? • When something becomes domesticated, selection then becomes a factor, and the characteristics of it will change. • E.g. tusk size in pigs has decreased • Wild barley grains are in two rows on the central axis, whilst cultivated barley are in six rows. • Animals killed by hunting are of various ages compared to those killed under domestication which are usually young adults.
Domestication of Animals • Advantages: • Source of milk or hair providing a steady supply of food and material. • If the animal is alive, the meat won’t decay. • It may be killed at the optimum age. • Used to carry and lift lowering energy expenditure.
Domestication of Animals • Disadvantages: • Diseases that affect modern humans were originally caught by domesticated animals. • E.g. smallpox, measles and tuberculosis are probably from cattle. • Resistance is slowly developing in Eurasian populations but Maori had no resistance when these diseases were introduced by Europeans.
Domestication of Plants • Advantages: • Large surpluses could have been built up and used to trade for raw materials for tool making (e.g. obsidian). • Disadvantages: • Surpluses accumulated after harvest and attracted insects and rodents. • Single species crops were more vulnerable to disease such as fungi.
Social Consequences • Moving from food gathering to food production may have led to establishment of permanent settlements. • They would build larger and more permanent dwellings • The necessity to carry material around got less so they had time to develop more specialised tools such as pottery.
Social Consequences • With a food surplus, not everyone needed to produce food and could trade services such as carpenters, merchants and priests. • This spawned a development of social complexity known as the ‘Neolithic Revolution’. • Crop planting was seasonal and therefore may have led to astronomy and the keeping of the calendar.
