Lecture 11

Bipedality

Advantages

• more energetically efficient than quadrupedal locomotion

• frees hands for other uses

• allows for improved long-distant vision

• upright primates dissipate heat better than quadrupeds

Disadvantages

• bipedal hominins are slower than their quadruped relatives

• terrestrial living makes primates vulnerable to predation

• early hominins would not seem to have had the size, intelligence, or cultural attributes to consistently offset this advantage

• likely arose in a forest environment

• early hominins likely would have needed to ascend trees at night to survive

Darwin on Bipedalism

• believed it emerged as hominins shifted from fruit and leaf-based diets to one based around meat

• saw the small canines of hominins as evidence that they were eating far fewer foods that need to be sliced and shredded

• hominins adopted a hunting lifeway that created selective pressures for freeing up hands for creating tools

  • turned out to be wrong as data now shows that hominins only began regularly hunting and creating tools much later in their evolution

    • small brain sizes of the first hominins also show they likely lacked the cognitive abilities to be successful hunters

• Stated that Africa was likely homeland to the first hominins

  • views were based on anatomical similarities between modern humans and African apes

  • reasoned that if our closest common living ancestors are Africa, so are our last common ancestors.

Forest Landscapes

Patchy Forests

• forests would have been reduced in size and density during dry periods

• forest primates would have a selective advantage

Standing Feeding

• arboreal mammals have difficulty feeding while gathering food in the trees so they often take their food to more stable branches or the ground

  • it has been hypothesized that bipeds in arboreal situations could be more comfortable eating in these areas

• could have improved their energy allocation

Owen Lovejoy

Provisioning Hypothesis

• proposed that bipedality may have emerges as part of an adaption where males provisioned females

• males bringing them food improved energy allocation and allowed them to have more than one offspring at a time

  • implies monogamous relationships between males and females

  • also implies that there are selective advantages for males

• these early hominin groups likely had social mechanisms that monitored behavior and promoted such male-female relationships

Canine Reduction

• canine reduction is evidence of pair-bonded relationships

• canines in all modern and fossil male apes are quite large and protruding and are used for fighting with or intimidating other males over sexual access to females

• the earliest known hominin fossils show a marked reduction in canine size, compared to apes

Estrus Loss

• modern female apes features an estrus cycle

  • refers when their genital region becomes swollen and discolored during ovulation

  • generally the only time when they are sexually receptive

• modern humans have lost this estrus cycle

  • Lovejoy hypothesizes that this loss occurred at the beginning of hominin evolution to help promote pair-bonding

Great Rift Valley

• located in Africa

• the result of faulting which has exposed millions of years of geologic strata

• has featured regular volcanic activity for millions of years

  • allows for the application of Potassium-Argon dating methods

Early Hominins

Sahelanthropus tchadensis

• found in the northern desert of Chad

  • today this area is a grassland but data shows it was a swampy forest 7-6 MYA

• holds some hominin features and some ape-like ones

• was about the size of chimp and has a 350cc brain (small brain)

• features a large supraorbital torus (brow ridge)

• foramen magnum seemed to be positioned like that of a biped but could have been moved due to the skull being crushed and reformed

• small canines and thick enamel on its molars

• lack of shearing complex

• flat face suggests it is not on the direct evolutionary lien to modern humans

Orrorin tugenensis

• found near Lake Turkana, Kenya, in the Rift Valley

• thick enamel on the molars

• relatively large, ape-like canines

• length and curvature of its femurs consistent with hominins

Ardipithecus ramidus

• found in the Middle Awash river valley of Ethiopia (upper Rift Valley) by a team led by Timothy White

  • likely lived in a dense woodland but this area is now a desert

  • seems to have been both terrestrial and arboreal

• 45% of an individual skeleton has been found

• about the size of a chimpanzee

• brain in the low 400cc range

• jutting lower face

• grasping big toe (hallux)

• foot has less-flexible muscularity typical of bipeds

• hands and wrists are not anatomically designed for knuckle walking

• does not feature evidence of brachiator anatomy

• ape-like thin molar enamel

• reduced canines

  • not much a shearing complex

  • lacking canine dimorphism between sexes

  • teeth feature thicker enamel than apes, but thinner than other hominins

Ardipithecus ramidus kadabba

• found in the same region as the former and was likely its ancestor by a team led by Johannes Haile-Selassie

• featured canine reduction but not to the same degree as A. ramidus

• remains show a strong overall affinity with A. ramidus

Australopithecines

• term coined by South African anatomist Raymond Dart

  • means “Southern Ape”

• genus first discovered in the early 1920s in South Africa

  • numerous species have since been discovered in eastern and southern Africa though have never been found outside of Africa, like earlier hominins

• all roughly within the size range of modern chimpanzees and bonobos

• feature considerable sexual dimorphism

• brain sizes range from the low to mid-400cc range

• their feed do not have opposable big toes — closer to modern human feet than those of apes

• still feature the following ape-like traits:

  • long, curved finger phalanges

  • shoulder joints still designed for suspensory locomotion

  • significant brow ridges

  • long arms

  • large teeth

  • ape-like hyoid bones

  • pyramid-shaped trapezoids

• may have been regional creatures that spent time in the trees

• exploited both forested and more open environments

  • practiced a mixed strategy likely of plant gathering, scavenging, and hunting of small game

• likely made tools — most of which were made with materials, such as wood, that have not survived archaeologically

• stone tools have been found dating back as far as 3.4 MYA+ which seem to have been used for digging and food processing as opposed to hunting

Australopithecus anamensis (4.0 MYA)

• found in Kenya (Lake Turkana) by Maeve Leakey

• Tim White believes it is a direct descendant of A. ramidus

• has strong affinities with Au. afarensis

• lived in a woodland environment

• large molar with thick enamel

• large canines and a slight shearing complex

• ape-like u-shaped mandible

• potentially featured canine dimorphism

• sexual dimorphism in regard to body size

Australopithecus afarensis

• discovered in 1974 by Don Johanson’s team at Hadar in Ethiopia

• about the size of a chimp

  • avg. height for females is 3.5 and 4.9 feet for males

• males potentially weighed twice as much as females

• brain was in the 400cc range

• features pronounced lower-face prognathism

• lack opposable big toes and have very human-like feet

• dental palate is less u-shaped compared to earlier hominins

• large mandibles and teeth

  • thick enamel on molars

  • small canines and little canine dimorphism

  • except in regard to their size, teeth are more like later hominins than apes

• first hominin species that lived in areas other than forests

  • seem to have occupied patchy woodlands, and open savannas

• their teeth show a wide variety of wear patterns, indicating broad diets

  • large tooth and mandible size might have developed to eat hard foods found outside of forests

Australopithecus deyiremeda(3.5 - 3.3 MYA)

• discovered by Yohannes Haile-Selassie in the Afar region of Ethiopia

• strong affinities with Au. afarensis

• very small teeth, which fall far outside the range of any other member of its genus

• lived in woodlands and open areas

Australopithecus africanus ()

• first reported by Raymond Dart in 1925

  • only found in southern African

• potentially a direct descendant of Au afarensis

• likely gave rise to other australopithecine species

• may not be on the direct evolutionary line of humans

• similar in size to A. afarensis

• weighed between 65-95 lbs.

• seems to be sexually dimorphic in regard to size

• larger brains than earlier australopithecines (the mean being 454 cc)

• less prognathic than A. afarensis

• smaller, less specialized teeth than A. afarensis

• “Taung Child” / Adult Au. africanus

Robust Australopithecines (2.5 - 1.3 MYA)

• alternate genus = Paranthropus

• found in southern and east Africa

• arose from and have strong affinities with Au. africanus

• roughly the same size as other australopithecines

• brain size is in the 450cc range

• extremely anatomically specialized

• feature highly developed muscles of mastication

• postorbital constriction, flares zygomatic arches; pronounces sagittal crests

• chewing apparatus might be an adaption to harder, more fibrous foods

  • tooth-wear patterns in some individuals support this hypothesis

  • C4 analysis shows that at least one species (Au. boisei) specialized in eating grass

• includes three difference species (that have been discovered)

  • Au. (P.) aethiopicus (2.6-2.5 MYA)

  • Au. (P.) boisei (2.3-1.2 MYA)

  • Au. (P.) robustus (2.0-1.5 MYA)

• Au. aethiopicus and Au. boisei have only been found in eastern Africa whereas Au. robustus has only been found in southern Africa

Kenyanthropus platyops (“Flat face” — 3.5 MYA)

• found by Maeve Leakey’s team in the region west of Lake Turkana (Kenya) in the late 1990s

• seems to have lived in a woodland environment

• small teeth and relatively flat face suggest that it is not an australopithecine

Australopithecus sediba (2.0-1.5 MYA)

• found in the Malapa cave site in South Africa by American anthropologist Lee Berger in 2008

• share features with both A. africanusand members of the genus Homo

• features a 420cc-sized brain

• tooth size similar to Homo, but design is more like A. africanus

• pelvic shape similar to Homo, but foot structure similar to A. africanus

• does not seem to be closely related to Au. robustus

• Berger believes Au. sediba to be a link between the A. africanus and the genus Homo

  • others simply see parallel evolution at work and believe this species as another evolutionary dead end and their south African location relatively recent position in time would seem to go against their being a direct ancestor to our genus

Australopithecus garhi (“Surprise” — 2.5 MYA)

• found in Ethiopia in 1999 by Ethiopian anthropologist Berhane Asfaw

• upper limbs resemble those of A. afarensis, while lower limbs look like those of later hominins

• leg and arm ratios are similar to later hominins

• large premolars and molars (larger than the robust species)

• large incisors

• shares primitive facial and palate traits with Au. afarensis — large molars with thick enamel, relatively large canines, prognathic face, etc.

• has 455cc brain size

• primitive stone tools and animal bones with cut marks dating to the same period of Au. garhi have been in the region where this hominin lived

  • no other hominin find has been made in this region

  • early members of the genus homo made stone tools in this area

  • it’s geography, timing, and potential tool use make Au. garhi a strong candidate for a direct ancestor to the genus Homo

Lecture 12

Pliocene-Pleistocene Boundary

Climate

• Ice sheets at the north and south poles (3 MYA - The Pliocene).

• The Earth in general was cooling and drying at this time.

• Glacial conditions become severe around 2.5 MYA.

• The beginning of the Pleistocene (1.8 MYA) was a time of great climatic change. Yearly temperatures often fluctuated considerably, as did seasonal patterns.

  • Created unstable mosaic environments, which featured forests, patchy woodlands, savannas, and deserts.

  • Many species went extinct and new ones appeared — including primates/hominins.

  • Created strong selective pressures for intelligence and therefore increased socio-cultural abilities. The advantage would have gone to thsoe who could consistently live in multiple types of environments. Efficient longer-distance mobility may have been a key component.

Homo habilis

• Discovered in the early 1960s by Louis and Mary Leaky.

• First found at Oldulvai Gorge in Tanzania, remains of a hominin dating to 2.5. MYA.

• There are great differences in size within the members of this classification.

  • Certain very “robust” individuals have been found.

• Some researchers believe these individuals are of a different species and have been classified as Homo rudolfensis. Others see this as an example of sexual dimorphism.

  • Remains are very fragmented and some researchers believe they are the remains of late-occurring members of a robust australopithecine species.

General Traits | Anatomical Changes (Compared to earlier hominins)

• Males on average were 4.3 feet tall and females averaged 3.2 feet (similar to bonobos).

• Males weight averaged 81 lbs. and females 70 lbs.

• Brain sizes range form 503-661 cc, with a mean of 601 cc.

• Still featured traits associated with autralopithecines (such as their general lower-body design).

• Hand anatomy suggests that they had a more precise grips and greater manual dexterity.

• Larger, more rounded brain-case.

• Smaller, less jutting face.

• Smaller post-canine teeth and large incisors.

• Smaller chewing muscles

• More efficient in their bidpedalism.

• Seem to display greater intelligence.

Stone Tools | Olduwan Industry

• Consist of flakes, cores, and hammer stones,

  • Flakes were used for slicing hides, butchering meat, and processing plant foods.

  • Cores are the stone from which flakes are “knocked off".”

  • Hammer stones were used to crack bone and to knock flakes off of cores.

• Do not seem to be significantly specialized. They are used for roughly 2 MYA and change little throughout this period.

  • Some regional variation eventually develops within the industry. These tools will eventually be used by later hominin species.

H. habilis Lifeways — Hunters?

• Meat becomes more important in hominin diets — evidence shots that early Homo butchered animals, often large ones.

• Olduwan tools do not seem to be designed for hunting and appear to primarily be primitive processing tools.

• Cognitive abilities and social structures also may not have been sufficient for them to live entirely by a hunting lifeway.

• Behavioral ecology models show the most optimal lifeway would have been a mixed strategy of:

  • Hunting

  • Plant gathering

  • Scavenging

    • This would be efficient and evolutionarily stable.

Homo erectus

• First appears in Africa around 1.8 MYA.

• Most likely evolved from H. habilis/rudolfensis.

• May be the result of adaptive responses to harsh environmental conditions

• Marks a major turning point in hominin evolution.

• Brain sizes range from 727 cc-1251 cc, with a mean of 800 cc.

• Endocasts suggest its brain was much more like a modern human’s than those of an earlier hominin or apes.

• Feature pronounced supraorbital torii (brow ridges).

  • Some skulls features a sagittal keel.

• Features considerable lower-face prognathism.

• Smaller post-canine teeth and a more generalized dental pattern.

• Larger body than previous hominins.

• Much longer legs than arms.

• Longer legs in ratio to body size.

• Long, straight finger bones.

• Greater bone density compared to modern humans (more robust).

• Males averages 5’9'“ in height and weighed 145 lbs., whereas females averaged 5’3” and 112 lbs.

  • Moe sexual dimorphism in earlier members of the species than later ones.

• Great anatomical variation amongst their populations.

• Likely the first hominin to leave Africa.

• Survived in large numbers until at least 300,000 years ago. Relic populations existed in Indonesia until as recently as 40,000-25,000 YA.

  • Most geographically successful hominin before the rise of modern Homo sapiens.

• Possibly the first homin to use fire and cook food.

  • No unequivocal “hearth” (fire pit) has been found.

  • Deposits consistent with controlled fire have been discovered at a handful of sites.

• Thousands of fossils have been found from many locations in Africa and Asia. Most of which have been skull fragments and teeth. Three partial skeletons have been found.

  • More H. erectus material than any earlier hominin.

Homo ergaster

• Some early H. erectus individual in Africa seem to feature more primitive traits than later individuals and because of this, some scientists want to divide these hominins into two species:

  • Homo ergaster (Africa)

  • Homo erectus (Asia)

    • Others believe that H. ergaster is a regional variant of H. erectus. The regional variation has been argued to be no greater than that found amongst modern humans.

Nariokotome Boy

• Found in 1984 in Lake Turkana, Kenya by Richard Leakey’s team.

  • A nearly complete skeleton of an adolescent male Homo erectus (Homo ergaster).

  • Age estimates are from 8-12 years. If he would have grown to full stature, he would have been around 6" feet tall.

  • His brain capacity was roughly 900 cc.

Homo erectus Dispersal

• Seems to leave Africa by at least 1.8 MYA

  • Made it to western China by 1.6 MYA.

  • They appear in southern Indonesia (Java) by perhaps as early as 1.7 MYA.

  • Among the earliest finds outside of Africa are those in the Republic of Georgia, near the village of Dmanisi.

Dmanisi

• Finds seem to represent a small colony of hominins.

• Body and brain size of these individuals are very small by H. erectus standards. Some scientists see these as being transition figures between H. habilis and H. erectus. Others believe they should be classifies as H. habilis.

• Region would have been quite old much of the years during this period. This implies these hominins had the cultural abilities to adapt to such conditions. Perhaps they had rudimentary clothes and/or dwellings. They may also have had the use of fire.

• Only Olduwan-type tools have been found at this site.

Leaving Africa

• As H. erectus are evolving, the African climate is both cooling and drying. Grasslands are expanding and forests contracting. These changes are stoking population increases in large grazing animals.

• H. erectus is well-adapted for long distance travel.

• Likely intelligent enough and had the technology to be at least part-time big-game hunters. There is evidence for meat growing in dietary importance. H. erectus may have been following food resources onto the vast Asian grasslands.

• Lowered sea-levels meant there were more potential land routes from Africa to Asia than today.

Homo antecessor

• Stone tools have been found in Europe dating to 1.2 MYA.

• Oldest sites are Sima del Elefante (1.2 MYA) and Gran Dolina (900,000 YA.), both in Spain.

• Some of these Spanish remains show evidence of cannibalism.

• Many scientists argue these early European hominins carry modern traits.

Acheulean Toolkit

• For the first 300,000 years H. erectus’ existence, they used Olduwan tools. Between 1.7-1.5 MYA the Acheulean tool tradition begins in Africa and lasts until around 250,000 YA.

• Used for butchering large animals, hunting tools, weapons used for the processing of plant foods.

• Dominated by biface tools researchers call hand axes and cleavers.

• NOT FOUND IN ASIA

• Unlike Olduwan tools, Acheulean tools seem to be made for specifc uses.

Boxgrove

• Site found in England and dates to about 500,000 YA.

• Likely created by H. antecessor.

• Most complete example of archaic lifeways.

• Seems to not have been a home base but a massive butchering area. It features the remains of many large and small game animals in association with many stone.

  • Animal bones show stone-tool cut marks underlying tooth marks of other animals.

• Site features horse scapula that has a clear projectile wound.

• A single tibia is the only hominin remain found at the site.

• Earlier stone tools have been found in England dating 780,00 YA.

Homo naledi

• Found by American anthropologist Lee Berger in 2013 at Rising Star Cave, South Africa.

• There are over 1,600 fossil remains representing at least 18 individuals of both sexes and various ages.

• Shares many traits with early members of the genus homo.

• Its cranial design has strong affinities with H. erectus (large brow ridges, a saggital keel, and reduced tooth size). However, post-cranially it features australopithecine-like traits.

• Likely shares a common ancestor with H. erectus.

• This find shows that relatively primitive hominins in Africa were living side-by-side with derived ones until quite recently.

• No stone tools have yet been found attributable to this species.

Wallacea

• The Flora and Fauna of Southeast Asia and Australia-New Guinea are radically different from each other.

• Deep underwater trenches, produce powerful currents that keep most plants and animals from crossing them.

Ancient Island Tools

• It was long believed that modern humans were the only hominins ever to reach islands south of the “Wallace Line.” However, in the 1990s, stone tools dating back to 900,000-700,000 YA were found on the island of Flores. More recently, stone tools of a similar age have been found on the nearby island of Sulawesi.

Homo florensiensis

• Found in the early 2000s by New Zealand archaeologist Mike Morwood’s team.

• Discovered at Liam Bua Cave on Flores Island remains of extremely small hominins. They are roughly 3 feet tall and have brain sizes only in the high 300cc range.

• Feature some traits associated with H. erectus.

• Also have primitive australopithecine-like post-cranial traits.

• Their teeth feature and unusual back-to-front compression to fit their small jaws.

• The Liam Bua site also features primitive stone tools.

• There is evidence there of butchered pygmy stegadons and the use of fire for cooking.

• Recently at Mata Menge on Flores, remains of 700,000 YA hominins that strongly resemble those at Liam Bua have been found.

Homo luzonensis

• A small hominin species found recently at Callao Cave.

  • This island does not connect to the mainland during glacial periods.

• So far only seven teeth, two hand bones, three foot bones, and one thigh bone have been found, thought to belong to two adults and one child.

Lecture 13

Archaic Lineages

• Highly varied hominins began appearing between 500,000-350,000 YA. First in African then shortly after in Europe and Asia.

  • They feature traits associated with both H. erectus and later members of the genus Homo. They feature a great deal of anatomical and cultural diversity.

  • Some scientists have defined individual species (as many as 8) from these lineages, while other lump them under the single category Archaic Homo Sapiens.

  • Anatomical features include:

    • Larger brains (1,000cc-1,4000cc).

    • Taller, less angular cranial vaults.

    • Arching instead of straight supraorbital torii.

    • Same have wider nasal apertures.

    • Greater chin developments (in some groups).

    • Lower cranial vaults.

    • Larger, more robust faces.

    • More prognathic faces.

    • Thicker-walled, lower cranial vaults.

  • They used Levallois tools and techniques.

    • More specialized flake tools.

    • Stone was used much more efficiently

      • Smaller average brain size (in most cases).

      • More robust (thicker bones, more heavily muscled).

      • In some groups, there are significant dental issues.