Paleoanthropology: Human Evolution

Paleoanthropological Data Types

• Major paleoanthropological data types: fossil-bearing sites, fossils, and artifacts

Paleoanthropology as a Historical Science

• Paleoanthropology is considered a historical science because it generates testable hypotheses without relying on direct observation.

Key Features of Paleoanthropology

• Paleoanthropology studies human evolution through fossil, genetic, and anatomical evidence
• It uses archaeology, genetics, geology, and primatology to comprehend human evolution
• The field is ever-changing due to new discoveries reshaping existing theories
• Paleoanthropology discoveries often get exaggerated media coverage
• Fossil interpretations and evolutionary pathways are often debated

Hominins Defined

• A hominin is a bipedal member of the evolutionary line leading to modern humans
• Hominins are any species evolving after the human lineage split from the chimpanzee lineage

Diagnostic Traits of Hominins

• Bipedalism is the key diagnostic trait defining hominins

Fossils

• Fossils offer material evidence of past life, providing a glimpse into the past
• Fossils represent a small sample of past life
• Fossilization is rare, occurring under specific geological conditions
• Sample bias exists in fossil records; teeth/jaws are more likely recovered

Geological Context and Dating

• Relative dating uses rock strata to determine age; top layers are younger, bottom layers are older, and it is not absolute dating.
• Chronometric dating uses radioactive half-life to measure the ratio of radioactive to stable atoms, and it is absolute dating
• Half-life is the time it reduces radioactive atoms by 50%

Non-Fossil Based Inferences

• Four behavioral features that might be found in the common ancestor of humans and chimpanzees: culture, tool use, warfare, and hunting.

Unique Traits of the Human Lineage

• The unique traits evolving only on the human lineage include bipedalism, reduced canines, complex tool use, less sexual dimorphism, smaller face, larger brain, and language

Stone Tool Technology

• Most tools are modified flakes or cores
• Pressure flaking is a controlled technique using pressure to remove small flakes
• Direct percussion strikes a rock with a hammerstone to break off flakes

Bipedalism and Anatomical Regions

• The pelvis is comprised of the illium, ischium, and pubis
• The inominate is comprised of 2 os coxae and 1 sacrum
• Bowl-shaped pelvis efficiently transfers weight from torso to legs
• Broad curved illia and shorter pubic bones are biomechanical features of the pelvis
• Gluteus maximus, medius, and minimus stabilize the trunk during walking
• The human femur has a bicondylar angle to increase stride
• Humans have cervical and lumbar spinal curves
• The vertebrae are large in humans to support body weight
• The human foot has a longitudinal arch to absorb shock
• The spinal cord passes through a downward-facing foramen magnum on the skull base

Species from Australopithecines to Hominins

• The species are in order of relative appearance
• Australopithecus afarensis, found in East Africa, had a cranial capacity of 250-500cc, climbed, and had ape-like and later human traits
• Australopithecus Africanus, found in South Africa, had faster maturation than modern humans and an anterior foramen magnum.
• Homo Habilis/Homo Ergaster, found in East and South Africa, had a cranial capacity of 600-800cc, a larger brain, smaller teeth, a human-like face, used Oldwan tools, and had long arms
• Homo Erectus, found in Europe and Asia, had a cranial capacity of 900cc, a long, low skull, pronounced brow ridges, used Acheulean tools, controlled fire, and possibly built shelters
• Homo Heidelbergensis, found in Africa, Europe, and Asia, had a cranial capacity of 1100-1200cc, large brow ridges, was robust, and likely hunted big game with spears
• Homo Neanderthalensis, found in Europe and the Middle East, had a brain size of 1520cc, a short/stocky build, was cold-adapted, used complex tools, and buried the dead
• Homo Sapiens, from Africa, spread globally and has a brain size of 1400cc, a high/rounded skull, small brow bridges, a chin, and used language and art

Pre-Australopithecines

• Sahleanthropus tchadensis existed 6-7 mya and had a cranial capacity about 320-380cc, a sagittal crest, large brow ridges, and a somewhat anterior foramen magnum

Orrorin tugenensis

• Orrorin tugenensis existed 6 mya, had evidence of bipedality in the femur and chimp-like teeth with a sectorial premolar complex

Ardipithecus ramidus

• Ardipithecus ramidus lived 4.4 mya, had pelvis/toe bones suggesting bipedalism, an anterior foramen magnum, a widely divergent big toe, and also climbed

Australopithecines

• They had a cranial capacity of 450-500cc
• With bipedal adaptations, they also had adaptations for climbing
• Small brained creatures with size dimorphism, they reached sexual maturity quicker
• They showed up around 4.2 mya and disappeared around 1.2 mya
• All had bipedal adaptations and adaptations for climbing

Australopithecine Behavior

• Locomotion: bipedal adaptations and adaptations for climbing
• Sexual dimorphism implies a polygynous social system or multi-male/multi-female
• Development: reached sexual maturity more quickly and less infant dependency
• Gracile forms were more omnivorous and robust forms fed on herbivory and hard seeds
• Tool Use: sticks and bones were used by Australopithecus Garhi and Homo Habilis

Brain Size of Australopithecines

• Brain size: 450-500cc, a size that had no great increase over chimps

Gracile and Robust Forms

• Robust forms had large cheek teeth, reduced anterior teeth, and large molars with thick enamel
• Gracile forms did not have chewing adaptations like robust forms with larger muscle attachment sites
• Robust forms had a sagittal crest, broad flaring cheekbones, large infratemporal fossae, and postorbital construction
• Gracile forms were bipedal and climbed

A. afarensis

• A. afarensis, found in East and South Africa, exhibited a mix of ape-like and later human traits
• Ape-like traits: prognathism, small brain size, long arms relative to legs, curved fingers and toes, and a narrow birth canal.
• Human traits included a pelvis for bipedal walking, an angled femur, and a forward-placed foramen magnum

A. africanus

• A. africanus, the "Taung child" from South Africa, had a faster growth and development timeline

A. garhi

• A. garhi, found in East Africa, was significant for being found near animal bones with cut marks, suggesting it may have been among the first to use stone tools to butcher meat

Robust Forms

• Robust forms (Genus- Paranthropus), H. Habilis, H. Erectus, H. Heidelbergensis, and H. Neandertalensis had adaptations for chewing
• Basic adaptations for chewing inclued massive jaws, large molars, thick enamel, and flaring cheekbones

Homo habilis

• Homo habilis, found in East and South Africa, is known as "The Handyman" for its tool-making capabilities
• Bones of prey animals and stone tools were found with discovered fossils

Homo habilis as a Scavenger

• Homo habilis expanded its brain for observation, learning, and memory to learn large carnivore habits
• Skills for carrying tools and scavenged meat: bipedalism, terrestriality, and free hands
• Cranial features had an approximate brain size of 600-800cc, less prognathism, and a more rounded skull
• Smaller molars existed
• Lengthened legs and a robust heel bone helped with bipedalism
• They could climb as well as austrlopithecines
• Hands had a long strong thumb, short straight fingers, and broader fingertips with better blood/nerve supply
• Diet: Meat and vegetarian

Olduwan Tool Industry

• The basic type of Olduwan tool are hammers, choppers, and mostly core type tools

Taphonomy

• Raymond Dart was convinced A. africanus was a human ancestor and built a case based on A. africanus being aggressive and warring
• Dart argued that A. africanus had “bone-tooth-horn tool box”
• Dart said A. africanus was a blood-thirsty predator using bone tools to slay prey including other hominins

C.K. Brain Analysis

• CK Brain argues against Dart, stating bones, teeth, and horns weren't from animals killed by A. africanus or used as tools, but actually A. Africanus were the hunted

Homo Erectus

• Homo Erectus roamed outside of Africa
• This differs from prior hominins because it has a bigger and bigger brain, found in sites outside of Africa, used more advanced tools, and has features approximating modern human traits

Homo Erectus Brain

• Appoximate brain size was 900cc
• H. Habilis was more encephalized

Homo Erectus Cranial

• The cranium had large browridges and a broad skullbase

Homo Erectus Body Size

• The approximate body size was as tall as modern humans

History of Homo Erectus Discovery

• Eugene Dubois discovered fossils in Java in 1894, including a skull cap and femur.

Zhoukoudian Site

• Davidson Black, Franz Weidenreich, and Pei Wenshong excavated the site
• Over 100 fossils attributed to H. Erectus came from this site
• This site is noteworthy because there is evidence possible fire control, cooking, and hunting

Homo Erectus Fossils

• Two craniums were found uncovered at Koobi Fora, 1.6-1.8 million years ago.
• The “Turkana Boy,” was discovered to be 11-12 years old, it dates to 1.6 million years ago, and had a complete skeleton and cranium.

Acheulian Tool Industry

• Acheulian tools found Africa, Asia, and Western Europe, commonly found as tear-shaped hand axes

Comparing Acheulian Tools and Oldowan Tools

• The acheulian tools were larger, more symmetrical, and bifaced

Behaviors Inferred from Homo Erectus

• Homo erectus was the first widespread species, colonizing seasonal habitats
• They used and possibly controlled fire
• Tools were used for butchering big game
• They may have have “embraced culture” as an adaptive strategy

Homo heidelbergensis

• Homo heidelbergensis roamed Africa, Europe, and Asia overlapping with modern humans
• Homo heidelbergensis differed from modern humans, having a larger cranial capacity that overlaps with the cranial capacity of modern humans

Homo heidelbergensis Anatomy

• Homo heidelbergensis brain size overlaps with that of modern humans at 1100-1200cc, showing a larger cranial capacity and prominent brow ridges like H. Erectus, but the brow ridges are rounded

Heidelbergensis Technology

• Homo heidelbergensis used Levellois tools, controlled fire, built shelters and structures, exploited many food sources, and maybe hunted large game
• The Levellois Tool Industry design was more complex

Neanderthals

• Neanderthal regions are found only in Europe and the Middle East
• The approximate brain size was on average 1520cc
• Mid-face prognathism and a large nasal opening are unique to the neandertals

Neanderthal Anatomy

• Postcranial features included no chin, worn teeth, Taroudant tooth-roots in molar teeth, a short & robust body, barrel-chestedness, and thick long bones/large joints
• The anatomy suggests they were built for cold environments

Neanderthal Behavior

• Some bodies are regarded as burials due to positions and Animal bones/stones surrounding

Mousterian Tool Industry

• They used thinner blades and more complex tools with sharp edges
• Evidence shows halfted spear-heads
• Materials consist of glue to secure arrowheads, bone, wood, and ivory

Neanderthal Behavior and Diet

• There's Evidence for foresight and mental templates
• Incorporated quantities of meat and were hunters

Neanderthals sheltering behavior

• Neanderthals built hearths, cooked, made wind-breaks, clothing/skins
• Neanderthal women used their teeth as a tool

Neanderthal Language

• The general anatomy of langauge needs regulated breathing, a low larynx, and smaller oral cavity
• A "longer vocal tract" = Increased basicranial flexion
• Broca’s Area is for speech production and Wernicke’s Area is for Speech Comprehension

Neanderthal Evidence

• Neanderthals possessed possible basicranial flexion and their Hyoid bone are similar to modern humans
• The symbolic and related behaviors count as evidence of potential language skills
• Hypoglossal canal carries the cranial nerve through the brain to the tongue which plays a large role in speech production
• Neandertals and modern humans have large hypoglossal canals

Evolution of Homo gracileens

• Homo sapiens have a vertical forehead, small brow ridges, a chin, small incisors, and a cranial size of 1400cc

Herto discoveries

• This Herto specimen in Ethiopia serves as strong evidence humans evolved in Africa

Human Evolution Theories

• Humans did not interbreed
• Regional Continuity: Humans Interbred
• Humans partially interbred

Genetics and Neanderthals

• There is about 1-4% similarity between human and neanderthal

Homo floresiensis

• Homo floresiensis had features like a small brain, large feet, and resembled the australopithecine group
• Homo floresiensis was found in Asia

H. sapiens Migration

• H. sapiens migrated to the New World when sea levels were low during glaciation
• They arrived between 15-20 kya

Traveling by Sea

• Australia and New Guinea were settled by sea travel 50-66 kya
• Hawaii, New Zealand, and Easter Island settled by Polynesian seafarers with advanced canoes around 1.2-0.8 kya