ANTH 201 Final - UofC

FILM: DISCOVERING ARDI

Where was Ardi found?

Ethiopia

How old is Ardi? How old is Lucy? How do we know? (2)

• 4.4 million years old, determined by radiometric dating of volcanic layers

• Lucy (first discovered Ardi) is 3.2 million years old

What parts of Ardi’s (Lucy’s) skeleton are preserved?

Pelvis, skull, teeth, hands, feet, one leg, and jaw

How do we know that Ardi (Lucy) was female and an adult?

Pelvis and skull showed female traits; molars were fully erupted, and canines suggested she was female

What challenges were involved in finding Ardi and fossils? (5)

• Hyena predation

• Fragile bones

• Flooding

• Scattered fragments

• Fossils deep in sediment

What techniques were used to study Ardi and reconstruct her morphology and behavior? (5)

• Radiometric dating of volcanic layers

• CT scans

• Digital 3D reconstructions

• micro-CT scanning

• Comparative analysis to other primate species

How did Ardi move? (4)

• Bipedal (walked upright)

• Grasping hands and feet

• Opposable toe

• Fossils suggested Ardi could likely climb as well

What kind of habitat did Ardi live in? How do we know?

A woodland environment; evidence from fossilized plants, seeds, animal remains, and isotopic analysis

LECTURE 15: EARLIEST HOMININS

What is a fossil?

A fossil is the preserved remains or traces of plants, animals, and other organisms from the remote past

What are the main types of fossils? (4)

• Bones and teeth

• Trace fossils

• Wood, leaves, etc.

• Subfossils (contain organic material)

How consistent is fossil preservation quality?

Fossil preservation quality is highly variable

What role did climate change play in evolutionary history?

Environmental changes due to climate caused major evolutionary shifts; human evolution occurred during a trend toward cooler, more variable climates

Continental Drift

Continents have moved considerably over the last 200 Ma (plate tectonics)

How does continental drift affect climate change? (2)

• It changes landmass size and orientation, which influences temperature and water circulation

• Larger landmasses tend to be colder

When did global temperatures start cooling significantly?

During the Cenozoic (66 Ma), especially after the mid-Miocene epoch (15 Ma).

What ecological factor is affected by continental drift and cooling?

Vegetation

The Order of the Geological Time Scale

Era —> Period —> Epoch (more specific period)

Cenozoic Era (2)

• ~66 million years ago

• Divided into tertiary and quaternary periods

Tertiary Period (2)

• ~66-2.6 million years ago

• Divided into Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene epochs (oldest epoch to most recent)

• Diversification of primates

Paleocene and Eocene Epochs (2)

• Paleocene (66 Ma): Early adaptive radiation after the dinosaurs' extinction

• Eocene (54 Ma): Major diversification and emergence of primates

Miocene Epoch (3)

• ~23 million years ago

• First appearance of hominins

• Dominance of land by angiosperms, mammals, birds, and insects
  

Pleistocene Epoch (2)

• ~2.6 million years ago

• Appearance of Homo sapiens

Quaternary Period (2)

• ~2.6 million years ago to present

• Divided into the Holocene epoch (recent)

Holocene Epoch (2)

• ~0.01 million years ago (10,000 years ago)

• Marked by the rise of agriculture and complex societies

Mesozoic Era (3)

• ~136 million years ago

• Cretaceous period (136 MYA)

• Rise of angiosperms, disappearance of dinosaurs, second great radiation of insects

Two types of Dating Methods: (2)

• Absolute dating

• Relative dating

What is absolute dating?

• A method that provides an estimated age in years for a fossil

• A method using radioactive isotopes to estimate a fossil's age in years

What is relative dating?

A method that gives a fossil’s age compared to another, helping establish sequence and complementing absolute dating

How do radioactive isotopes help date fossils?

They decay at a known rate into other isotopes, allowing age estimates based on isotope ratios (known rate and proportion of
Isotopes = can get time)

What are two examples of absolute dating methods and their applications?

• Potassium-argon dating for volcanic layers (>500kya)

• Carbon-14/12 dating for organic matter (<40kya)

What kind of material is typically dated using potassium-argon dating?

Volcanic ash or rock layers

What does relative dating tell us in fossil analysis? (2)

• It tells which rock layers are younger or older based on their position

• It supplements radiometric methods, which aren't always possible

What is biostratigraphy?

A method to date rocks by looking at the fossils and comparing with other dated sequences (i.e. African pigs)

According to genetic analysis, who is our closest living relative? (2)

• Chimpanzees (genus Pan)

• Split from common ancestor approximately 6–8 million years ago

What defines a hominin?

A hominin is any member of the human clade that evolved after the split with chimpanzees—everything more closely related to humans than to chimps

What is the difference between a hominid and a hominin?

Hominid: includes all great apes (humans, chimps, gorillas, orangutans)

Hominin: includes only humans and their closest relatives

Shared Derived Traits of Hominins (5)

1. Dental characteristics

2. Larger brain-to-body size ratio

3. Slow maturation and development

4. Complex symbolic and material culture (i.e. language)

5. Habitual (committed) bipedalism

Do the first hominins have all the derived traits that separate humans from chimps?

No, not all traits are expected to be present in the first hominins

Which trait is most commonly used to determine hominin status?

Bipedalism (standing and walking on two feet fully)

1. Dental Changes (4)

• Reduction in size; canines no longer interlock

• Upper canine no longer hones (sharpens) on 1st lower premolar

• Dental arcade (tooth row) changes from U-shape to parabola (refer to diagram)

• Enamel got thicker

2. Brain Size (5)

• Apes have brains ~2× larger than expected for body size

• Humans have brains 7–8× larger than expected

• Chimpanzee brain size: ~320–350 cc

• Human brain size: ~1350 cc

• Size matters, but cognition and life history also play roles

3. Slow Maturation (4)

• Humans have slower life histories than apes

• Life history = timing of key life events (growth, maturity, death), shaped by evolution

• Humans show longer gestation, juvenile period, growth, and menopause

• Fossil evidence includes tooth eruption and bone/enamel development

4. Culture (3 + 3 subpoints)

• Apes have basic cognition and tool use, but not as advanced as hominins

• Hominins show:

  • Greater reliance on tools and technology

  • Adaptation to diverse environments

  • Use of fire, symbolism, art, and language

• Culture is partially preserved in the archaeological record, but many items (like wood tools, body decoration) don’t fossilize

5. Bipedalism (3)

• It's likely the most defining feature of hominins

• Clearly visible in fossil anatomy

• Evolved before larger brains in our lineage

What are key anatomical adaptations for bipedal walking in hominins? (6)

• Foramen magnum at bottom of skull (upright head position)

• Wide, flared pelvis supports hip abductor muscles

• Angled femur brings knees under the body

• Long femoral neck and cortical bone indicate upright weight-bearing

• Non-opposable big toe in line with others; arched foot for shock absorption

• Stiff ankle limits side-to-side motion for stability

What is the most altered bony anatomy in humans?

The pelvis

What evolutionary trade-off is reflected in the shape of the human pelvis?

The need to walk upright and to birth large-brained babies, requiring a wide birth canal

Where do hip abductor muscles attach, and what bone feature distinguishes humans and hominins from chimps?

Hip abductors attach to the iliac crest; humans and hominins have a wide, short ilium with a sciatic notch, which chimps lack

What is the functional role of hip abductor muscles in bipedalism?

They keep the pelvis level during walking and reduce side-to-side movement, making walking more efficient

Bipedalism: Chimpanzees vs Humans (3)

• Humans have an extended hip and knee, a lumbar curve, and a ventral foramen magnum, aligning the center of gravity (COG) with major joints for efficient, stable posture

• Chimpanzees walk with a bent hip and bent knee (BHBK), placing COG forward, requiring constant muscle use to stay upright

• Humans use only ~7% more oxygen than lying down, due to skeletal support. Chimps must actively engage their muscles to maintain balance

The Late Miocene of Africa (4)

• ~ 9 million years ago

• Drying and cooling

• Few fossil apes are known from 12–5 Ma due to poor fossil preservation and a lack of suitable rocks

• Because the human-chimpanzee split likely occurred around 6–8 Ma, and the transition is largely undocumented

Sahelanthropus tchadensis (4)

• Chad (2002), relative dating to 6-7 MYA (fauna)

• Woodland environment

• Primitive traits: chimp-like brain size (~350 cc)

• Derived traits: flat face, thick enamel, small canines. Position of foramen magnum suggests bipedalism

Orrorin tugenensis (4)

• Tugen Hills, Kenya (1999), dated to ~6 MYA

• Woodland environment

• Primitive trait: curved proximal phalanx

• Derived traits: small teeth with thick enamel; femoral neck shape and bone distribution suggest bipedalism

Ardipithecus kadabba (4)

• Middle Awash, Ethiopia, dated to ~5.2-5.8 MYA

• Limited fossil evidence: dental remains and a toe bone

• Primitive trait: upper canine hones against lower premolar (not reduced)

• Derived trait: toe bone resembles later hominins, suggesting possible bipedalism

Ardipithecus ramidus (4)

• Middle Awash, Ethiopia, dated to ~4.4 MYA (one MYA after A. kadabba)

• First material published in 1994 (dental only); major find in 2009

• "Ardi": nearly complete female skeleton (hands, feet, pelvis, skull, teeth)

• Woodland environment

What are the primitive traits of Ardipithecus ramidus?

Opposable big toe, long fingers, short thumb, thin enamel on molars, small brain (~300–350 cc)

What are the derived traits of Ardipithecus ramidus?

Anterior foramen magnum, bipedal pelvic adaptations, small canines, thick enamel

What did the original research team conclude about A. ramidus locomotion?

Bipedal on the ground; spent significant time in trees; moved arboreally using flat hands (palmigrade - on flat hands), not knuckle-walking

What does A. ramidus suggest about the last common ancestor (LCA) of humans and chimps?

LCA was likely not Pan-like (i.e. not a knuckle-walker), but a more generalized arboreal quadruped

What primitive traits are retained in early hominins? (2)

• Small brains in all species, chimp-like canines in some, and a unique mix of primitive and derived traits in each species

• It's debated whether they are true hominins, if bipedalism evidence is sufficient, and whether they are ancestors of later hominins or evolutionary dead ends

What suggests early hominins still spent time in trees?

Arboreal adaptations in the arms, such as length and curved phalanges

What do early hominins reveal about their geographic range?

They were more widespread than previously thought—not limited to East and South Africa

What are the first key derived features of hominins? (4)

• Bipedalism

• Thicker tooth enamel

• Reduced canines

• Not brain size or tool use

What environment did the earliest bipedal creatures likely inhabit?

Woodland environments, not just open savannah—challenging older assumptions about bipedal evolution

What do scientists emphasize is needed to better understand early hominins?

More fossil evidence

LECTURE 16: AUSTRALOPITHS

What is an Australopith? (3)

• A group of fossil hominins found from ~4 MYA to ~1 MYA, also known as Australopithecines

• Divided into two genera: Australopithecus and Paranthropus

• East Africa (older sites) and South Africa (discovered first)

Which australopith species is best known and why?

Australopithecus afarensis; most of what we know about australopiths comes from this species

What is notable about Kenyanthropus platyops?

Lived ~3.5–3.2 MYA and shows a mix of Australopithecus and Paranthropus features

Where was Sahelanthropus tchadensis found?

Koro Toro, Chad

Where were Paranthropus boisei and Homo habilis found?

Hadar and Konso, Ethiopia

What species were discovered in the Middle Awash, Ethiopia? (5)

• Australopithecus afarensis

• Au. deyiremeda

• Au. garhi

• Ardipithecus kadabba

• Ar. ramidus

What major species are found at Lake Turkana, Kenya? (7)

• Australopithecus anamensis

• Paranthropus aethiopicus

• P. boisei

• Kenyanthropus platyops

• Homo habilis

• H. rudolfensis

• H. erectus

Where was Orrorin tugenensis found?

Tungen Hills, Kenya

What fossils are found at Olduvai, Tanzania? (3)

• Paranthropus boisei

• Homo habilis

• Homo erectus

Which species have been discovered at Laetoli, Tanzania? (2)

• Australopithecus afarensis

• Paranthropus aethiopicus

Where was Homo rudolfensis found?

Uraha, Malawi

Which species are found in South Africa? (6)

• Australopithecus prometheus

• Au. africanus

• Au. sediba

• Paranthropus robustus

• Homo habilis

• Homo erectus

What are the key traits of Australopithecus anamensis? (5)

• Lived 4.2–3.9 Ma in Kenya/Ethiopia

• Oldest known australopith

• Derived traits: small canines, thick enamel, large molars, knee & ankle for bipedalism

• Primitive traits: box-shaped jaw, large canines (vs. later species), upper limb traits for arboreality

• Likely lived in mixed habitats (grasslands & woodlands)

What features of A. anamensis suggest both arboreal and bipedal adaptations? (2)

• Upper limb features indicate arboreality

• Knee and ankle suggest bipedalism

What are key facts about Australopithecus afarensis? (3)

• Lived 3.6–3.0 Ma in Ethiopia/Kenya (East Africa)

• Inhabited forests, woodlands, and savannahs

• One of the best-known early hominins

What are important Australopithecus afarensis fossil specimens? (4)

• AL 288-1 "Lucy" (40% skeleton, found in Hadar, 1974)

• AL 333 "First Family" (13 individuals)

• Selam (Dikika Child, 3-year-old female)

• Laetoli footprints (evidence of bipedalism)

What are some more interesting and notable traits of Australopithecus afarensis? (5)

• Prognathic face, medium canines, large molars with thick enamel

• Somewhat curved tooth rows

• Large chewing muscles

• Diastema and moderate canine dimorphism

• Ape-like brain size (~404 cc)

What does Australopithecus afarensis' body reveal about its locomotion? (3)

• Major anatomical shift for bipedalism

• Clear evidence of habitual bipedalism

• Changes seen in pelvis, femur/knee, and foot

Bipedal Adaptations: Hip/Pelvis (2)

• The ilium is flared and rotated to let hip abductors keep the body over the midline

• Enlarged sacrum-iliumjoint – more capacity for weight-bearing

Bipedal Adaptations: Femur & Knee (2)

• Valgus knee, when the femur angles inward (medially), placing body weight closer to the midline for efficient walking

• Reduces side-to-side motion and aligns the knee under the trunk

Bipedal Adaptations: Foot (3)

• Enlarged heel (absorbs forces at heel strike)

• Longitudinal arch (stiffens foot into propulsive lever and absorbs forces during stance)

• Big toe in line with the other toes (not opposable)

Arboreal Retentions (4)

• Relatively long arms (for climbing)

• Mobile shoulder joint oriented superiorly (greater shoulder mobility)

• Slender, curved fingers & toes (grasping branches)

• May have spent time in the trees (safe from predators)

What bipedal adaptations did A. afarensis (“Lucy”) show from the waist down?

Hip abductors, long femoral neck, carrying angle, large sacrum and femoral head, plantar arches, large heel, etc.

Was A. afarensis bipedalism as efficient as modern humans?

Possibly not—used a “bent-hip bent-knee” gait and had short legs, requiring more steps to cover distance

What do the Laetoli Footprints tell us about A. afarensis?

They are strong evidence of habitual bipedalism—dated to 3.4 Ma in Tanzania, made by 3 individuals walking in wet volcanic ash, with a footprint pattern similar to modern humans

What do 3D footprint analyses of Laetoli tracks suggest about A. afarensis gait?

Heel and toe depressions are equally deep—unlike BHBK gait—indicating A. afarensis (Lucy) had a more modern, efficient form of bipedalism

What are the key facts about Australopithecus africanus? (7)

• Lived in South Africa, 3 – 2.2 MYA

• First Australopithecine species found in Africa

• “Taung baby” was discovered by Raymond Dart in 1924

• Identified as a hominin due to foramen magnum position

• Initially rejected as too primitive with a small brain

• Postcranial skeleton similar to A. afarensis

• Dentition differs: smaller canines/incisors, larger molars (likely adaptations for powerful chewing)

Who are Taung Baby and Selam (Dikika Child)? (3)

• 3 year old juvenile australopith specimens

• Help us understand life history patterns in early hominins

• They grew fast, like apes (seen in dental eruption sequence and enamel growth rate)

What are the key facts about Australopithecus garhi? (5)

• Lived 2.5 MYA in Afar, Ethiopia

• Name means “surprise!” in Afar language

• Larger molars and premolars than A. africanus

• Found with cut-marked animal bones → possible butchery

• Stone tools found nearby (may indicate hunting or scavenging behavior)

What are the key facts about Australopithecus sediba? (6)

• Found in South Africa, dated to 2–1.8 Ma (discovered in 2010)

• Possibly descended from A. africanus; proposed ancestor of genus Homo

• Features: Homo-like face and teeth, small brain

• Two partial skeletons recovered

• Fully bipedal, but retained long arms → some arboreal traits

• Considered a possible “transitional species”

Paranthropus: the “Robust” Australopithecines (2)

• Separate line that diverged from early hominids

• Genus Paranthropus (disputed, ‘Australopithecus’ also used)

What postcranial traits do Paranthropus share with other australopiths?

They share the same bipedal adaptations as A. africanus and A. afarensis