From Hominoid to Homo Sapiens: The Evolution of our Family Tree

Hominoid… Homonin…Homo Sapiens What’s the difference?• When scientists characterize a creature as a hominin, what we mean is that they are

classified with humans in the “tribe” Hominini . The tribe is a taxonomic unit between the family and the genus. Humans belong to the family Hominidae, which includes all of the great apes and the genus Homo.

Non-Human Primates and the Roots of Human Culture

• Primate characteristics • Vary in size from several ounces – to over 400lbs. • Have flat faces and reduced snouts in comparison with other mammals• Very reliant on vision for dealing with their environment and social interactions• Have 5 digits on their hands and feet. • Opposable Thumbs, can grasp with both their hands and feet• Have large brains in comparison to their overall body size• Take longer to mature than other mammals

• Extended developmental/juvenile period • Most primate species are highly social, provides a context for the social

molding of primate behavior• Modern humans are closely related to the great apes with whom we share a

LCA(Last Common Ancestor).

Non-Human Primates• Most primates live in low-altitude area of the tropics or

subtropics. ( A few live in the high altitudes of Africa, Nepal and Japan.)

• Most primate species are arboreal, quadrupedal and diurnal like humans.

• Most primate species are highly social and prefer to live in groups and interacting with others of the same species.

• provide for their food needs via foraging or obtaining food available in nature through gathering, hunting or scavenging.

• Species vary in terms of what food preferences they have: frugivores, folivores, insectivores, gumnivores, and omnivores.

Brachiation

The Evolutionary Spark… Climate Change.• Miocene Epoch (23 mya-5mya)

This geological time frame was important in that it was witness to extreme climatic changes both globally and on the African continent.

During this time period the ambient temperature cooled. This cooling led to the proliferation of woodland/savanna and drastically limited the area of semi-tropical forests.

The spread of woodland and savanna led to the evolution of the first hominins about 6 mya.

• Approximately 6 mya, hominins begin to appear in the fossil record.

• Between 4-2 mya, the hominin lineage diversified becoming a community of several hominin species that ranged from Eastern to Southern Africa.

• A number of shared derived characters distinguish modern humans from other living hominoids…

• Bipedal locomotion• A larger brain• Slower development • Several features of dental morphology• Cultural adaptation

Derived Traits that distinguish modern humans from contemporary Apes

• 1. We habitually walk bipedally.• 2. Our dentition and jaw musculature are different from those

of apes for example; we have a parabolic dental arcades, thick enamel, reduced canine teeth and larger molars in relation to the other teeth.

• 3. We have much larger brains in relation to our body size.• 4. We develop slowly with a long juvenile period. • 5. We depend on an elaborate, highly variable material and

symbolic culture, transmitted in part through spoken language.

Evolution of Modern Homo…

Sahelanthropus tchadensis (7mya-4.9mya)• Discovered 2002, in Torros-Menalla Chad.• Discoverer: Michel Brunet of University of Poitiers, France• The Fossil consisted of a nearly complete cranium, 2 fragments

of the lower mandible, and several teeth. • The face is very flat, the foramen magnum is located at the

base of the cranium and a massive brow ridge over the eye orbits. These are 3 features of much later (4-2mya) hominin species.

• On the other hand…It has a very small brain case only (320cc-350 cc), the teeth are very primitive, and the back of the cranium is extremely ape-like

Orrorin tugenensis (6 mya- 4.9mya)

• Discovered: 2001, in Tugen Hills Kenya• Discoverer: French-Kenyan team led by Brigitte Senut of

National Museum of Natural History, Paris and Martin Pickford of the Kenya Paleontology Expedition.

• Fossil(s) consisted of 12 hominins. These fossils included parts of the thigh and arm bones, a finger bone, 2 partial mandibles, and several teeth.

• The incisors and canines look more chimpanzee-like. The arm and finger bones have features showing an adaptation for climbing.

• On the other hand…• Tugenensis’ molars are much smaller than in A. Ramidus and

have thick enamel similar to what we find in humans.

The fossils of Orrorin Tugenensis includeParts of the femur, lowerJaws, fingers and teeth

Ardipithecus (6mya-4mya)• Discovered: 1992, Aramis in the Middle Awash Basin of Ethiopia south

of Hadar.• Discoverer: Team led by Dr. Timothy White of University of California,

Berkeley.• Fossil(s): First fossil dated to 4.4mya and subsequent fossils fell into

range date of (5.8-5.2mya) and consisted of teeth, jaws, the lower part of the skull and parts of the upper arms.

• The genus Ardipithecus includes 2 species– A. ramidus and A. kadabba. Both species have similarities to humans as well as chimpanzees.

• Hominin-like: “Ardi”- 1.)has a foramen magnum located forward under the skull; this is generally associated with bipedalism. 2.)Fossil also contained small incisor-like canines that have not been sharpened by the lower premolars as found in chimpanzees. 3.) Additional features of the teeth and upper arm bones are very human-like.

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Ardipithecus (continued)• 1.)Ardipithecus’ canines are fairly small in comparison to its

overall body size. • 2.) Thin enamel layer on the teeth. • 3.) The deciduous molars and jaw joint are very similar to those

of apes. • 4.) The base of the skull is more pneumatized (filled with air

pockets) than in hominins. • 90 more fossil specimens have be been recovered including – a

pelvis, hand/foot bones, arm, leg and skull making up 45% of the overall skeleton.

• Johannes Haile-Selassie (a member of Tim White’s Team) has discovered an earlier fossil sub-species of Ardipithecus known as A. kadabba. A. Kadabba shows many features that are more ape-like and dates back earlier than A. ramidus.

Ardipithecus ramidus

Hominin community: Diversifies• A number of hominin species lived in Africa between 4-2 mya. They have been divided into 3

genera: Austrolapithecus, Paranthropus, and Kenyanthropus• Austrolapithecus

• Includes 6 species: A. anamensis, *A. afarensis, A. africanus, A. garhi, A. habilis, and A. rudolfensis.

• The australopithecines were small bipeds with teeth, skull and jaws adapted to a generalized diet.

• Australopithecines share derived traits characteristic of both modern humans and contemporary chimpanzees. • A. afarensis • Discovered in the 1970’s by Maurice Taieb and Don Johanson in Hadar,

Ethiopia. Further discoveries were made by Mary Leakey at Laeotoli , Tanzania.

• Afarensis fossils have been found at several sites throughout eastern and southern Africa.

• Based on A. afarensis fossils they probably spent a good deal of time in the trees, were sexually dimorphic, had small more ape-like brains, V-shaped dental arcade, and human-like bipedalism.

• Reconstructions of the environments at these sites indicate that A. afarensis lived in habitats ranging from woodland to dry savanna between the 4-3mya.

• Paranthropus• Includes 3 species: P. aethiopicus, P. robustus, and P. boisei. (2.2-1.3

mya)• Discovered by Alan Walker of Penn State University in 1985 on the

western shore of Lake Turkana, Northern Kenya• The paranthropines were similar to the australopithecines from the neck

down.

• Paranthropines featured massive molars and jaws adapted to the heavy chewing of tough plant materials.

• The skull in turn was modified to the enormous temporalis muscles needed to power this chewing apparatus. Other features of many paranthropines are sagittal crests (more apparent in males) and flared cheekbones that caused the face to be flat or even pushed in.

• Kenyanthropus• Includes only 1 species: K. platyops (3.5-3.2mya)• It has features such as a flattened face, a small chimpanzee-like brain case

and small molars that distinguish it from other hominins. Lived in a mixed woodland and savanna environs.

• Discovered in 1999 by Justus Erus part of Meave Leakey’s Team near Lake Turkana, Kenya.

From Hominin to Homo• The Lower Pleistocene, 1.8 mya saw a fluctuation in global temperature and then

ultimately leading to a cooling of the world’s climate.

• Homo ergaster vs. Homo Erectus ( 1.8-0.6 mya) • These 2 species are very similar save for some morphological differences in

their skulls. • H. erectus’ skull is thicker, the brow ridges more pronounced, sides of the

skull slope more steeply, the occipital torus is more pronounced, and there is a distinct sagittal keel.

• Appears in the African fossil record 1.8 mya. H. ergaster fossils have been found in Tanzania, Ethiopia, Kenya, and South Africa.

• Richard Leakey, 1976, Lake Turkana Kenya- found a nearly complete skull that resembles H. erectus.

• H. ergaster migrated out of Africa and into Eurasia around 1.7 mya. • H. ergaster fossils are commonly associated with Oldowan-style tools. H.

ergaster brought their tool making skills along with them through Eurasia.

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H. ergaster skulls differ from both earlier hominin species and modern humans. H. ergaster has several more hominin like features Including- large brow ridges, receding forehead, and no chin. H. ergaster also has many human-like features including- a smaller less prognathic face, a higher skull, smaller jaws and teeth.Interesting Points on H. ergaster…1. H. ergaster grew to approximately the same size as modern

humans. However may have developed more rapidly than modern humans.

2. Their infants probably matured slowly and were dependent upon their mothers for an extended period of time.

3. Sexual Dimorphism was reduced.4. They may not have had spoken language.5. First hominin that could run for long distances.

H. ergaster (continued)6. Developed tools (Oldowan and Acheulean stone tools) for subsistence, hunting and/or butchering scavenged animals. 7. Ate meat and may have controlled fire.

________________________________________Middle Pleistocene saw the evolutionary transition from H. ergaster to modern humans. (0.6- 0.25 mya)Homo heidelbergensis (800-500 kya)

In many ways very similar to H. ergaster including their use of stone tools, good evidence for hunting and driving big game, used spears (nearly 2 meters in length).

Oldowan Stone Tools

H. ergaster

H. Erectus

Out of Africa Theory of Migration

Upper Pleistocene (300-50 kya) Homo Neanderthalensis lived in Europe and western Asia from (127 to 30 kya). Neanderthals’ Distinctive morphology: include large brow ridges, large brains/faces, rounded crania, small back teeth, large heavily worn front teeth, short/robust muscular bodies, long/thick femurs, load bearing knee/ hip joints, robust scapulae attachments, and low foreheads. A high larynx (voice box) probably did not allow for human like speech but perhaps ape-like vocalizations. Neanderthals made somewhat intricate (mode 3) stone tools, hunted big game, little evidence for shelters or organized camps, probably buried their dead, and seemed to live short/difficult lives (oldest being about 40-45 years) Genetic tests have revealed that this particular lineage was isolated and did not contribute to the human gene pool.

Homo Neanderthalensis

The Appearance of Homo Sapiens• H. Sapiens appear in Africa (200-100 kya) • H. Sapiens migrated out of Africa approximately 50 kya into

Europe, Asia, and the Middle East. • Between 40-30kya the archaeological record in Europe

undergoes a striking change… Neanderthals basically disappear and are replaced by Modern Homo sapiens (Cro-Magnon man).

• (Anatomically Modern Humans AMH) Morphologically characterized by a small face/teeth, pointed chin, high rounded cranium, and less robust post-cranium.

• Archaeological Evidence indicates that modern humans in Europe were able to accumulate complex adaptive and symbolic behavior in the same way as people living today.

• Exploited a wide range of prey, gathered plants, made very intricate stone tools, and built shelters/communities.

•Questions?