Human Evolution
Last Common Ancestor
Evidence from fossils, genetic studies, and proteins indicate that humans and chimpanzees had a common ancestor millions of years ago. Most scientists believe that the human family tree diverged from chimpanzees and other apes seven million years ago. Until recently, it was thought that the common ancestor looked like a chimpanzee, with features such as a short back, arms, and hands adapted to grasping, swinging branches, and wrists and forearms meant for knuckle-walking (Blaxland, 2018).
In 2014 a skull was found in Kenya in the Napudet area. It was named Alesi since it means ancestor. Alesi shows exactly what the ancestor of all modern apes and humans looked like. The Lemon sized skull had baby teeth present, which were used to determine the age by using the enamel rings (similar to the rings on a tree). The teeth revealed that Alesi was 16 months old. She belonged to the genus, or group of species, known as Nyanzapithecus, a sister group to the hominoids discovered about 30 years ago. However, Alesi's teeth were much larger, implying that they belonged to Nyanzipithecus alesi. These species existed in Africa 10 million years ago and were close to the origin of apes and humans and originated in Africa. The skull looked like a baby gibbon since it's a close relative to living apes. The specimen could give us ideas of what the common ancestor might have looked like, and since the specimen looks like a gibbon, it would support the idea that the common ancestor of all apes and humans looked like a gibbon(Choi, 2017).
Sahelanthropus tchadensis
It is one of the oldest known species in the human family tree. This species lived sometime between 7 and 6 million years ago in West-Central Africa (Chad).
Upright walking based on the foramen magnum (the large opening where the spinal cord exits out of the cranium from the brain) is located further forward (on the underside of the cranium) than in apes or any other primate except humans. This feature indicates that the head of Sahelanthropus was held on an upright body, probably associated with walking on two legs.
Ape-like features included:
Small brain (even smaller than chimpanzee’s)
Sloping face
Prominent brow ridges
Elongated skull
Human like features included:
Small canon teeth
Short middle part of the face
The spinal cord opens underneath the skull instead of towards the back, as seen in non-bipedal apes.
Orrorin tugenensis
Living around 6 million years ago,
Approximately the size of a chimpanzee
Had small teeth with thick enamel, similar to modern humans. From Orrorin's low, rounded molars and small canine teeth, paleoanthropologists can infer that this species ate mainly a plant-based diet. This probably included leaves, fruit, seeds, roots, nuts, and insects.
The most important fossil of this species is an upper femur, showing evidence of bone buildup typical of a biped -
Orrorin tugenensis individuals climbed trees but also probably walked upright with two legs on the ground.
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Ardipithecus ramidus
4.4 million years ago Eastern Africa (Middle Awash and Gona, Ethiopia)
The foot indicates a divergent large toe combined with a rigid foot concerning bipedal behavior.
The pelvis, shows adaptations that combine tree-climbing and bipedal activity.
A good sample of canine teeth of this species indicates very little difference in size between males and females in this species.
Australopithecus afarensis
3.85 to 2.95 million years ago
Eastern Africa (Ethiopia, Kenya, Tanzania)
Australopithecus afarensis is one of the longest-lived and best-known early human species
This species survived for more than 900,000 years, which is over four times as long as our own species has been around.
Au. afarensis had apelike face proportions (a flat nose, a strongly projecting lower jaw) and braincase (with a small brain, usually less than 500 cubic centimeters -- about 1/3 the size of a modern human brain), and long, strong arms with curved fingers adapted for climbing trees.
They also had small canine teeth like all other early humans and a body that stood on two legs and regularly walked upright.
Australopithecus africanus
3.3 to 2.1 million years ago
South Africa
Au. africanus combination of human-like and ape-like features. Compared to Au. afarensis,
Au. africanus had a rounder cranium housing a larger brain and smaller teeth, but it also had some ape-like features including relatively long arms and a strongly sloping face that juts out from underneath the braincase with a pronounced jaw.
The pelvis, femur (upper leg), and foot bones of Au. africanus indicate that it walked bipedally, but its shoulder and hand bones indicate they were also adapted for climbing.
Homo habilis
2.4 to 1.4 million years ago
Eastern and Southern Africa
This species, one of the earliest members of the genus Homo, has a slightly larger braincase and smaller face and teeth than in Australopithecus or older hominin species. But it still retains some ape-like features, including long arms and a moderately-prognathic face.
Its name, which means ‘handy man’, was given in 1964 because this species was thought to represent the first maker of stone tools. Currently, the oldest stone tools are dated slightly older than the oldest evidence of the genus Homo.
Homo rudolfensis
1.9 to 1.8 million years ago
Eastern Africa (northern Kenya, possibly northern Tanzania and Malawi)
A large cranial capacity consisting of 775 cubic centimeters, which is considerably above the upper end of H. habilis braincase size.
Larger braincase, longer face, and larger molar and premolar teeth.
H. rudolfensis didn’t have the heavily-built jaw and strong jaw muscle attachments seen in robust early humans.
Different diets between H. rudolfensis and earlier australopith species capable of more powerful chewing.
Like other early Homo species, Homo rudolfensis may have used stone tools process their food.
There is fossil evidence that this species cared for old and weak individuals. The appearance of Homo erectus in the fossil record is often associated with the earliest handaxes, the first major innovation in stone tool technology (Smithsonian, 2021).
Homo erectus
1.89 million to 110,000 years ago
Northern, Eastern, and Southern Africa; Western Asia (Dmanisi, Republic of Georgia); East Asia (China and Indonesia)
Oldest known early humans to have possessed modern human-like body proportions with relatively elongated legs and shorter arms compared to the size of the torso.
Loss of earlier tree-climbing adaptations, with the ability to walk and possibly run long distances.
Expanded braincase relative to the size of the face.
Microscopic study of the teeth indicates that he grew up at a growth rate similar to that of a great ape.
There is fossil evidence that this species cared for old and weak individuals.
First major innovation in stone tool technology.
Homo neanderthalensis
400,000 to 40,000 years ago
Homo, is a Latin word meaning ‘human’ or ‘man’. The word neanderthalensis is based on the location where the first major specimen was discovered in 1856 – the Neander Valley in Germany. The German word for valley is ‘Tal’ although in the 1800s it was spelt ‘Thal’. Homo neanderthalensis therefore means ‘Human from the Neander Valley’ (The Australian Museum, 2021).
Neanderthals are our closest extinct human relative.
Some defining features of their skulls include the large middle part of the face, angled cheek bones, and a huge nose for humidifying and warming cold, dry air.
Their bodies were shorter and stockier than ours, another adaptation to living in cold environments. But their brains were just as large as ours and often larger - proportional to their brawnier bodies.
Neanderthals made and used a diverse set of sophisticated tools, controlled fire, lived in shelters, made and wore clothing, were skilled hunters of large animals and also ate plant foods, and occasionally made symbolic or ornamental objects.
Homo naedi
335,000 to 236,00 years
Homo naledi possessed a mixture of traits that are Australopithecus-like (particularly in the pelvis and shoulder) and Homo-like (particularly in the hands and feet, and the size of its brain).
Homo sapiens
300,000 years ago to present
Lighter build of their skeletons compared to earlier humans. Modern humans have very large brains, which vary in size from population to population and between males and females, but the average size is approximately 1300 cubic centimeters.
Housing this big brain involved the reorganization of the skull into what is thought of as "modern" -- a thin-walled, high vaulted skull with a flat and near vertical forehead.
Modern human faces also show much less (if any) of the heavy brow ridges and prognathism of other early humans.
Our jaws are also less heavily developed, with smaller teeth.
H. Sapiens evolution traits:
Skull features
Skulls have a short base and a high braincase up to 1500 cubic cm. The bigger braincase alows room for a bigger brain which went from 450 cm in Australopithecus afarensis 7 mln yers ago, to 1350 cubic cm.
Rounded skull indicates reduction of neck muscles
Reasonably small face
Brow bridge is limited and tall forehead
Jaws are short which resulted in almost a vertical face
No retromolar gap
Shortened jaw with narrow arranged teeth in a parabolic shape.
Relatively small teeth especially in the front incisors and canine teeth
Limb bones are thinner and less robust and indicate a reduction of muscle size
Longer legs compared to the arms and have arches
Finger and toe bones don’t have the curvature topical for australopithecine ancestors
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The pelvis is narrower and deeper bowl shape. From front to back compared to the previous human species.
H. sapiens lifestyle
The use of tools
A wide range of materials is used such as bone, ivory, and anther.
Production of blades, spearheads.
The use of fire included complex pits, kilns. Survivability in cold regions.
In early hominids, both the sacrum and hip bones are relatively short compared to apes.
300,000 Years Ago: Fossils Found of Oldest Homo sapiens.
But fragments of 300,000-year-old skulls, jaws, teeth, and other fossils found at Jebel Irhoud- Morocco,a rich site also home to advanced stone tools, are the oldest Homo sapiens remains yet found (Handwerk, 2021).
100,000 to 210,000 Years Ago: Fossils Show Homo sapiens Lived Outside of Africa.
Fossils of a jawbone found inside a collapsed cave in Mount Carmel, Israel, show that modern humans lived along the Mediterranean 177,000 to 194,000 years ago.
The jaw and teeth are from Misliya Cave unambiguously similar to those seen in modern humans; they were found with sophisticated handaxes and flint tools. (Handwerk, 2021).
15,000 to 40,000 Years Ago: Genetics and Fossils Show Homo sapiens Became the Only Surviving Human Species
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Male Homo habilis
Bipedal walking was possible due to the changes in:
Reshaping the pelvis and lower limbs brings the feet and knees directly under the body’s center of gravity.
The pelvis became short and wide compared to tall and narrow
Femur and tibia became slant inwards compared to straight
Knees joint could lock to maintain a straight position
Feet and toes developed into a stable platform with a spring to push off the ground.
Modification in the skull backbone created the upright body with the head directly above the backbone.
The feet became curved with an arch.
Bones were short and straight compared t long and curved
The big toe was alight with other toes compared to opposable toes
The foramen magnum in the skull changed position under the skull compared to the back of the skull base.
The backbone is attached to the base of the skull.
The lower backbone is curved so the upper body sits Above the pelvis.
Over 3 million years ago yearly, humans started to use tools. The evidence from Dikika in Ethiopia shows cut marks on the fossil bones. Tools were used to remove flesh and possibly smash bone to remove the marrow.
Early tools included twigs, sticks, and other plant materials that were easily shaped. Unmodified stones were used to process nuts.
Control of fire provided a new tool with several uses—including cooking, which led to a fundamental change in the early human diet (Smithsonian, 2021).
Survival of the fittest. When humans migrated from Africa 60000 years ago, they encountered the Neanderthals, Denisovans, and hobbit people. DNA shows that humans interbreed with these people, but other evidence of encounters is lost in history. Despite all that, humans prevail over neanderthals. Although the Neanderthals had similar large brains as humans, the human brain had a larger frontal lobe. This is important as the frontal lobe is responsible for decision-making and social behavior. Although Neanderthals were broader and stronger than humans, with especially strong upper bodies and better adapted to cold climates, brainpower won the evolutionary race. Being smart helped humans adapt to various diets. Smaller teeth suggested superior thinking in food preparation, such as (such as pounding cooked yams), which could have been a great survival advantage. The more processing goes before the food is eaten, the more energy is saved. Processed food was used for children as well. Highly cognitive abilities allowed for the spread of information relevant to survival (Wolchover, 2012).
Reference: Blaxland, B. (2018). Sharing a common ancestor. The Australian Museum. Geraadpleegd op 7 april 2022, van https://australian.museum/learn/science/human-evolution/sharing-a-common-ancestor/Choi, C. L. Q. (2017, 10 augustus). Fossil Reveals What Last Common Ancestor of Humans and Apes Looked Liked. Scientific American. Geraadpleegd op 7 april 2022, van https://www.scientificamerican.com/article/fossil-reveals-what-last-common-ancestor-of-humans-and-apes-looked-liked/Handwerk, B. (2021, 2 februari). An Evolutionary Timeline of Homo Sapiens. Smithsonian Magazine. Geraadpleegd op 7 april 2022, van https://www.smithsonianmag.com/science-nature/essential-timeline-understanding-evolution-homo-sapiens-180976807/Smithsonian. (2021, 27 april). Human Evolution Interactive Timeline. The Smithsonian Institution’s Human Origins Program. Geraadpleegd op 7 april 2022, van https://humanorigins.si.edu/evidence/human-evolution-interactive-timelineThe Australian Museum. (2021). Homo neanderthalensis – The Neanderthals. Geraadpleegd op 7 april 2022, van https://australian.museum/learn/science/human-evolution/homo-neanderthalensis/Wolchover, N. (2012, 7 juni). Why Did Humans Prevail? Livescience.Com. Geraadpleegd op 7 april 2022, van https://www.livescience.com/20798-humans-prevailed-neanderthals.html
Mitochondrial Eve
Mitochondrial Eve -- the maternal ancestor of all living humans -- confirms that she lived about 200,000 years ago.