Biology - Trends in Human Evolution

Homo Sapiens-also called Cro magnon man

160 000 to now. Earliest ones in Europe called Cro Magnon Man. Brain smaller than Neanderthals. Skilled hunters often following migrating animals. Made bone and flint tools, used spears and spear throwers, maybe bows and arrows. Tools had fine points and blades. Made fish hooks and needles. Tools called Upper Paleolithic. Engraved and painted walls and carved statues. Had imagination.

Homo Erectus-also called upright man

1MYA to 300 000 YA. First to use fire. First to leave Africa. re Had a larger brain, probably more advanced speech but still incomplete sounds. Able to co operate and teach. Use of fire>cooked food>softens food for easier digestion>jaw, teeth, zygomatic arch decreased in size. Because of fire they could inhabit colder new environments and could extend day length therefore more time for everything else (teaching, planning hunts and creation of better tools). Fire killed bacteria and parasites therefore increased survival rates. Tools called Acheulian or tear drop stones, double edged hand axes. Also used bamboo to make containers and rafts. Increased brain development due to diet>curiosity>explored new areas. Population increased>some moved to new areas to survive. Built shelters-huts with wooden poles.

Homo Habilis-also called Handyman

2.4-1.5 MYA. First thought to have speech but no voice box so just grunts. More sophisticated brain with a bulge in broca's area (speech area). Successful hunters, killing a wide range of hunters in a co operative manner. Used simple tools called Oldowan, round stones with one end chipped. Used hands and tools to throw clubs, butcher, dig, etc. Made simple shelters. Lived in groups. ATe meat therefore better protein therefore better brain development.

Homo Neanderthalensis-also called Neanderthals

230 000 to 28 000 years ago. Thick heavy boned, short limbs-a bit like eskimos. Intelligent, able to adapt to extremes of weather. Lived in caves and built low walls at entrance. Made large hearths with flat stones and used them like hot plates. Dressed in hides for clothing. Stampeded herds over cliffs and into bogs. Fine stones called Mousetarian, flakes, scrappers and spears. They attached handles to stone tools. Buried their dead-often with tools, flowers and they were sometimes decorated with red ochre (red clay) showing they believed in the 'afterlife'. Strong social bonds as they looked after the old and the sick. Cannibals. All died out>evolutionary dead end (maybe?).

Australopithecus afarensis-also called Lucy

3.9-3 MYA (million years ago). First bipedal ancestor. They are very sexually dimorphic meaning the males and females were different sized. Possibly scavenged meat or caught small prey but mainly ate nuts, fruits, tubers etc. Did not use tools. Lived in dry, open lands and wooded area of Africa. Didn't have articulated speech. Lived in groups.

Homo Heidelbergensis-also called Archaiac Homo Sapiens

300,000 years ago. Fossils found in Europe, Africa and Asia. Next species to move throughout the length and northern breath of Africa and beyond. Used fire. Hunted large prey>rich diet>increased body size. Were cannibals. Used Acheulian tools. Built shelters.

Primate Features

5 fingers on hands and feet, prehensile (capable of grabbing) grasping hands and some tails, nails and not claws, binocular stereoscopic colour vision, good hand eye co ordination, wrist, elbows, shoulder and hip joints are mobile, enlarged brain, bony ridges above eyes for protection, usually found in groups, carry out mutual grooming, hierarchies and extended families, extended infant care and single birth common, have an oestrus cycle in females rather than definite breeding season, snout reduced as they rely on smell less than vision, posture usually quadrupedal with ability to sit upright and run bipedal, have a generalised dental pattern.

Bipedalism

All primates show a tendency to an upright posture at times-such as when feeding a baby, swinging from trees or just sitting. Humans have taken this to the extreme and walk on two legs all of the time. Prehumans/hominins were bipedal by nearly 4 million years ago. It is thought that being bipedal allowed humans to exploit the ground niches, which probably offered more variety of food at a time when forests were shrinking. It certainly allowed humans to use their hands in ways that no other primate can. This change to bipedalism was probably the most important step in our evolution because it freed the hands, allowing us to take advantage of our larger brain.

Multi regional

Also called parallel evolution or regional continuity. This states that Homo Erectus left Africa about 1.8MYA and spread to Europe and Asia. In the three areas Homo Erectus evolve paralled into Homo Sapiens, with some genetic contact and gene flow between populations in different areas. Homo Sapiens evolved simultaneously in the 3 continents. Evidence to support this hypothesis: Some transitional fossils have been found in many places esp the Asian fossils which show a clear transition from older hominid to modern H Sapiens. High levels of gene flow would be needed for this hypothesis to be correct which is not very likely. The hypothesis is highly questioned based on the more recent genetic research especially use of mtDNA and Y chromosome DNA. For this hypothesis to be correct current humans would have large genetic variation. However when mtDNA and Y Chromosome DNA was analysed there was less variation than expected. This means they didn't leave Africa until much later.

BIOLOGICAL EVOLUTION: Key differences between humans and apes / Bipedal and quadrupedal

Apes have a large sagittal crest along the centre top of the skull. This is where the jaw muscles attach to the skull. A large jaw requires a larger sagittal crest. In humans this no longer exists. Apes have their formen magnum (hole in the underside of the skull where the spine enters) is towards the back of the lower side of the skull. While in humans/bipedal the formen magnum is more central underneath. Apes have very strong muscles which attach to the nuchal crest on the top of the back of the skull to prevent the head from dropping forward. Human skulls are balanced above the first vertebrae so we don't have strong muscles therefore our nuchal crest is absent. Apes have large brow ridges with a sloping face. While humans have a longer brow ridge and the face is flattered. Apes have a much smaller brain size 450cm^3 vs 1400cm^3. Humans cerebral cortex is well developed and therefore they have a higher level of thinking, speech, memory etc. while apes have no specialised area for language. An apes jaw has parallel sides "U" while humans have a round more bow shaped jaw. Human teeth have thicker enamel and smaller canines, while apes, especially males have very large canines (sexual dimorphism). Humans have an S shaped spine with a shorter straight stiff broader more bowl like pelvis. While apes have a C shaped spine and a longer narrow pelvis. Humans knees are angled inwards (valgus angle) so the knee sits near the centre of gravity. The knee joint is larger. These result in more efficient walking as the organism does not waste energy swinging from side to side and is much more balanced as they walk. In apes the knees bend outwards under the hips as their femur angled into the knee so when they lift one foot off the ground they lose balance. They must lean to one side to counterbalance. This produces a swaying movement as they walk. Apes feet have an opposable big toe and their foot is arched which acts as a shock absorber and enables humans to spring off their feet when walking therefore making walking more efficient. Apes fingers are more curved with less mobile fingers. Like all primates both can grip objects with a power grip, but only humans can use a precision grip. Ape hairs are longer and more coarse with few sweat glands while humans have the same numbers of hair but it is much finer with more sweat glands.

Hominoids and hominin

Apes, humans and their recent ancestors are classified in the super family Hominoidea. They are referred to as hominoids (human-like species). While humans and their recent bipedal ancestors are classified as hominin.

Acheulian first used by Homo Erectus and Archaiac Homo Sapiens

Bi Faced, tear drop shaped which had been carefully crafted to standard design. Much more crafted than oldowan as more chips removed. Tools took much longer to craft with on average 65 blows per tool. Used as hand axes and cleavers. Made for specific jobs eg basic design altered to make scrapers etc.

Biological Evolution

Biological evolution occurs through our genes; it can only be passed on genetically and therefore occurs at a slow rate. Biological evolution is strongly linked to all skeletal changes which have occurred as a result of becoming bipedal. The head-skull features, internal and external. Upper limb and our ability to manipulate our hands and shoulders. Spine features. Lower limb features-hip joint, femur, knee joint, ankle and foot.

Advantages of bipedalism

Carrying the noir-human females do not have enough hair to grasp, nor do their babies have prehensile feet to hang on, so females must carry their young. This requires free arms. A hominin that had a less opposable big toe would have been less good at clinging onto mum so its mother would have had to rely more on its legs to walk so she could carry her baby. This would select any feature that made her better at bipedalism, such as a less opposable big toe. This, in turn, would make the young less able to grasp mum and be more dependent on being carried. This is called positive feedback where one change reinforces another change effects. Once started, positive feedback would produce very rapid change. Free hands are free to carry objects eg tools, food etc. This meant more food could be carried back to their house site for sharing. Heat regulation. Bipedalism raises the body surface higher above the ground, where there is more wind and cooler temperatures. Greater wind focus means more heat loss by convection. Bipedalism also conserves body water by needing less evaporation to cool down. Standing upright also reduces direct solar exposure during the time of the day when solar radiation is most intense. The brain is especially sensitive to increased temperature, so we have kept hair on the head to reduce the heating effect of the sun. Standing upright allows animals to see predators more easily-remember that primates use smell less than other mammals. By being bipedal less energy is needed to move long distances as the bipedal motion is more efficient.

Advantages of Fire

Cooking makes food softer and easier to digest and eat. Kills microbes (bacteria, fungi and parasites) reducing the risk of disease. Fire detoxifies some plant toxins making the cooked food safe to eat eg potatoes. Fire helps keep predators away allowing safety and gathering stability. Source of warmth allowing Homo Erectus to exploit new, cooler areas with more resources. Having a source of light extended day length therefore more time to make tools, plan hunts etc>hunts became more successful>didn't have hunt each day>more 'free time' for social interactions. Fire used to harden wooden spear points, therefore leading to better tools.

Cultural Evolution

Cultural evolution is the non genetic passing on of information through teaching of ideas, beliefs and knowledge by learning from other members of the group. Because it occurs through learning and more than one person can be taught at a time, cultural evolution occurs at a faster rate. There are treads of increasing complexity through use of:tools, fire, shelter and clothing, food gathering, abstract thought especially communication, language, burial and art, domestication of plants and animals.

Farming and domestication of animals

Early humans were nomadic hunter-gatherers, relying on what was present in the environment and moving as the population grew or resources ran out. Later they followed the herds around eventually and they became less nomadic. This gave humans a greater variety of food which was of better quality and close by. First animals to be domesticated were dogs, goats, then sheep and pigs. First plants were wild wheat about 18 000 years ago. The millet, rice, soya, beans, yams, maize, cotton etc. As this happened their dwellings became more permanent and larger.

Advantages of farming

Food supply easier to obtain with a much more dependable food source. Fewer people died of starvation. Fewer people needed to work at providing food for many. Specialised skills able to be developed by those not involved in getting food and while living in a permanent settlement meaning they get better at their job benefitting the whole group. As people become more skilled at farming they developed more permanent settlements at the best sites near sources of water. They were able to produce more food then they needed so traded with other people for things they needed. As a result of this they had more time to develop other skills such as art, pottery, etc. Made technological advances eg wheel, plough, hoe, which eventually led to the Industrial Revolution.

Disadvantages of being bipedal

Giving birth to a larger headed baby means babies are born helpless and birth is painful. Because babies are born so helpless they require a lot of parental care. Takes about a year before a baby can walk. Humans are prone to back ache due to S shaped spine.

Dispersal

Homo Erectus moved out of Africa to other parts of the world relatively quickly. This movement was most likely linked to climate change about 1 MYA. When the climate cooled resulting in dropping sea levels exposing new land making land bridges and causing forest to shrink and be replaced by open savannahs open grasslands. Because of the climate change new food supplies became available and those organisms which could adapt to this changing climate survived. There are two main hypotheses about the origin and dispersal of modern H Sapiens. Multiregional and out of Africa. Both of these hypotheses agree that humans originated in Africa.

Primate Groups

Prosimian, eg Tree shrew, tarsier and lemur. New World Monkeys eg spider monkey, cebus-prehensile tail, quadrupedal, strictly aboreal (tree dwelling), widely separated nostrils. Old World Monkeys-eg baboon, colobus monkey-tail not prehensile, quadrupedal, some ground living, nostrils close together. Great apes-eg gibbon, gorilla, chimpanzee, orangutan-brachiating (swinging using arms), quadrupedal, flattened nose, bony eye ridges. Hominins eg Australopithecus, Homo Erectus, H. Sapiens-bipedal due to modified feet, legs etc. Large cerebral cortex, reduced canines, nose, chin prominent, reduced eye ridges, highly sensitive skin with body hair short.

Mousterian first used by Neanderthals

Sophisticated tools which were finely worked, made of stone but often had other materials attached for more accurate handling. These tools require high levels of skills and time to learn and make eg spears, axe, scrapers etc.

Disadvantages of farming

Their diet was restricted to what they could grow. They become more dependent on the weather for their crop growth. Because there was a higher population disease carrying and disease causing organisms flourished as they had more people closer to infect eg rats, fleas, viruses etc. Growing crops etc is time consuming. People begin to fight over ownership of land and territory.

Out of Africa - Also called replacement hypothesis

This hypothesis states that we left Africa as Homo Sapiens much later about 200 000 years ago. So we evolved from Homo Erectus in Africa. They spread gradually/killing off making other hominin species extinct as they came upon them. NOTE:this was the second movement out of Africa as H Erectus left Africa about 1.8 MYA but they became extinct outside of Africa due to harsh environments at the time. Those that remained in Africa evolved into H Sapiens and left much later. Every person who is not of African descent is related to a single group of about 200 people who left Africa and crossed the Red Sea. These movements were made possible by an ice age which caused sea level to drop. Evidence to support this hypothesis:All modern humans have similar genes and nuclear sequences. If parallel evolution had occurred there would be much greater variation in humans genetic make up. mtDNA are passed down the female line unchanged except mutation. NOTE mtDNA is replicated independently of the rest of the cell's DNA therefore does not get altered by crossing over etc. mtDNA is used because it is passed on from mother to child and is not changed due to meiosis. Mutations occur at a steady rate in mtDNA and can be used to estimate how long ago two species shared a common ancestor. Y chromosome can be used the same way but when this is passed down the male line without being altered. When both mtDNA and Y chromosome was analaysed it was observed that DNA had been highly conserved-hadn't changed much. Therefore it was predicted that mitochondrial eve left Africa much later, about 100 000 years ago. People that live in Africa have the greatest genetic variation as they have been around for the longest time and have had more time to develop genetic diversity. The greatest variability is found within African populations which are the oldest. There is less genetic diversity in Asian and European populations, which suggests they are not as old as African populations. Modern Europeans share between 1 and 4 percent of their genes with Neanderthals, from this it is thought that there was an overlap of Neanderthals and modern humans in space and time resulting in the possibility of interbreeding. Evidence both for and against interbreeding have been put forth based on the analysis of modern human DNA. This analysis has led scientists to believe modern humans last exchanged genes between 37 000 and 86 000 years ago. Stone axe and sharp flint arrowheads of both branches of the human race were discovered in the limestone caves at the Nahal Me'arot nature reserve at Mount Carmel in Haifa. None of the bones uncovered at the World Heritage site had lethal wounds, which suggested to researchers that prehistoric men lived in peace with Neanderthals 80 000 years ago. Many believed peaceful cross breeding was more likely the result of rape attacks.

Upper paleolithic first used by Homo Sapiens and Neanderthals

Tool making techniques were further refined. Most flake edges were sharpened for cutting. Had a large variety of tools for many different jobs. Tool shaped to fit into handles. Tools not just made of stone many other materials used including bone, anthers, gut plant fibres etc. Tools included things like needles, ropes, nets, snares etc. These tools allowed hunters to kill much larger prey and process it quickly, as well as allowed them to preserve food. Animal hides would be stretched over wood to make tent type structures, they also made clothes out of hides.

Development of technology: Tools

Very early tools most likely sticks and bones used to dig and get things out of holes.

Oldowan first used by Homo Habilis

Very simple tools with few flakes removed. Used to chop and scrap.

The Naked Ape

We are the only naked ape. Current theories do not link nakedness to climate change as first thought. Now they think very early hominins still lived in a forest. But the key ideas still hold true: hair on the head is used to reduce heat loss and to reflect heat off the head therefore helping the brain at correct temperature. By having reduced body hair the control of parasites becomes easier which was important when hominins started living in home bases.By having shorter hair and well developed sweat glands all over our body we increased heat loss which helped us keep cool.

Primates

When humans are compared to other animals in terms of their structures, chemicals and DNA, they are more similar to a group of animals called primates, than to any other animal group.