QCEBiology
Human Evolution
| Great Apes | Chimpanzees, Gorillas, Orangutans, Humans |
|---|---|
| Lesser Apes | Gibbons, Siamangs |
| Primates | |
|---|---|
| Great Apes, Lesser Apes, Monkeys, Prosimians | |
| Five digits with an opposable thumb | Forward binocular eyes with 3D and colour vision |
| Nails instead of claws | Long gestation period for brain development |
| Relatively high cranial capacity | Live in social groups |
| Hominoids | |
|---|---|
| Great Apes, Lesser Apes | |
| Locomotion by tree swinging, knuckle walking or bipedalism | Posture is fully or partially erect to allow use of hands |
| Relatively broad palates and broad nasal regions | Flatter ribcage that creates a wider chest |
| Larger and more complex brains | Absence of a tail |
| Hominins | |
|---|---|
| Modern Humans and Close Relatives with Bipedalism | |
| Decreased prominence of brow ridges | Reduced jawbones and jaw muscles |
| The use of language and art | Large cranial capacity |
| Bipedalism | Flatter face |
The fossil record of hominins is very poor, and even if we do have the fossils, they are generally incomplete. Hominins have not been around for very long, don’t live in places conducive to fossilisation and have behaviours such as burying the dead that make the fossilisation of humans extremely rare
The out of Africa theory hypothesises that H. sapiens evolved from a discrete African population and then migrated relatively recently throughout the world, replacing archaic populations, without interbreeding. The multiregional theory hypothesises that H. sapiens emerged gradually throughout the world, evolving simultaneously and, as the populations dispersed, they remained in genetic contact
Bipedalism is the ability to walk sustained on two legs, providing more efficient locomotion, hands for other tasks and eyes positioned higher than a quadruped. Bipedalism requires the foramen magnum to be in the base of the skull, the tibia to be at an angle to the femur, a short and wide pelvis and the absence of an opposable toe
Australopithecus afarensis were found in Africa. Their fossils showed that they waked upright, but still climbed trees. They had both ape and human features – a flat nose, a projecting chin, a small braincase, long arms and long, curved fingers adapted for climbing trees
Paranthropus robustus were found in Africa and are characterised by their large teeth and powerful jaws. They were bipedal, had a sagittal crest and a muscular build. It is thought they were more specialised and less adaptable than Homo species. Therefore, this lack of adaptability in changing environments may have led to their extinction. They also demonstrated significant sexual dimorphism, with males being taller and heavier than females
Homo habilis were found only in Africa and are the earliest known Homo species. It had a much larger braincase than its predecessors and has been associated with some of the earliest tools. It is hypothesised that Homo habilis commonly used tools to break open bones and fed on the bone marrow. It has more ape-like features than later species, with longer arms and jaws that project forward
Homo erectus was the earliest Homo species to expand out of Africa. They had similar body proportions and behaviours to Homo sapiens. From fossils, scientists hypothesise that they looked after the sick, old and young, as well as being the first to construct tools using stones and the first to cook food – controlled use of fire
Homo neanderthalensis is our closest extinct human relative. They differed from Homo sapiens in a variety of ways including – they had large faces with angled cheek bones, large noses for coping with cold, dry air, and chunkier, shorter builds suited to colder climates. It is thought that they had complex social structures and were possibly the first humans to have language. They were also the first species to wear clothes and jewellery, have burial rituals and display symbolic behaviour. Their brains were on average bigger than those of Homo sapiens.
Approximately 80,000 years ago, fossil evidence suggests that Homo sapiens and Neanderthals coexisted in the same regions. Additionally, analysis of mtDNA in the current population shows the presence of some Neanderthal mtDNA which points to the string possibility that Homo sapiens and Neanderthals may have interbred. Thus, raising the question of whether they are two races of the same species
Homo denisovans were discovered in Siberia, Russia. Analysis of the mtDNA from the fossils of Homo denisovans reveal that they were closely related to both Neanderthals and Homo sapiens, but genetically distinct. Therefore, the evidence suggests that Homo denisovans interbred with both Homo neanderthalensis and Homo sapiens. mtDNA studies suggest that 17% between the genomes of Homo denisovans and Homo neanderthalensis are shared. Nuclear DNA studies also show that 3-5% of the DNA in Homo sapiens is shared with Homo denisovans
Modern Homo sapiens can generally be characterised by a leaner, more agile bipedal build than our predecessors. Our pelvis is narrower and deeper than that of our ancestors, and our skulls have a large cranial capacity and short base, with rounding at the back indicating reduced neck muscles. Our brow ridge is much flatter than that of our predecessors, and we have squarer eye sockets, smaller faces and reduced canine teeth. Homo sapiens also have a complex larynx, allowing the development of complex languages. Our hands also have a precision grip.
Although the braincase capacity of Neanderthals is larger than that of Homo sapiens, researches have suggested that Neanderthal brains were specialised for vision and movement, with less brain volume devoted to social interactions and problem solving.
The fossil remains of our ancestors demonstrate a few significant changes in physical, mental and cultural traits. Arms got shorter, legs longer, the pelvis become lower and broader and the foramen magnum moved forwards to the base of the skull as they spend less time in trees and more time walking upright. Bodies became leaner and taller with less hair as climates became warmer and drier. As their diets moved away from plant material and towards a more omnivorous diet, teeth became smaller, and the increase in cooking food further allowed for a reduction in jaw muscles. This led to an increased capacity for the skull to get larger and accommodate a larger brain.
Culturally, the increased control our ancestors had over the environment enabled progressively less movement, more building of permanent shelters and the gradual development of technology, ritual and societal structures
Culture is the accumulated knowledge passed on to the next generation by verbal, written or symbolic communication. A very important step for humans was the development of language and the ability to record information. The study of relationships of different languages, together with information from skeletal remains, artefacts and DNA, provides evidence of the evolution of the different cultures of Homo sapiens living today.
Cultural evolution refers to the changes in a population due to the social transmission of accumulated knowledge. e.g. the change in lifestyle of modern humans from nomadic hunter-gathers to permanent settlers who domesticated animals and adopted agricultural practices. Evidence includes musical instruments, cave paintings. The fundamental biological consequence of human cultural evolution is that humans have increasingly intervened in the evolution of other species by changing the environment, causing extinctions, hunting, over-exploitation of a species, clearing of habitats and by manipulating organisms through selective breeding and domestication
Technological evolution refers to the progressive development overtime of technologies giving greater human control over the environment. Examples include the change from stone tools to metal tools and the development of industrial technologies such as steam and electric power
Biological evolution occurs through genetic variation and reproduction, and involves the transfer of genes from one generation to the next under the influence of natural selection