Human Evolution: Key Fossils, Species, and Dating Methods

Piltdown

A fake early-human skull planted in England that tricked scientists for decades.

Taung

Site in South Africa where the Taung Child fossil was found.

Australopithecus africanus

Early human relative that walked upright and still climbed trees.

Ardipithecus ramidus

Very early human ancestor ("Ardi") that walked upright but also lived in trees.

Paranthropus boisei

Robust early hominin with huge jaws and teeth for chewing tough plants.

Features that were believed to link the Taung Child with modern humans

Small canines, upright posture, and a human-like brain shape.

Evidence for bipedalism in South African australopiths

Bowl-shaped pelvis, angled femur, arched feet, and the foramen magnum (skull base hole) underneath.

Features that might indicate that australopiths spent a good deal of time in trees

Curved fingers, long arms, flexible shoulders, and some grasping toe ability.

lesser gluteals

Hip muscles that keep the body balanced during upright walking.

Australopithecus afarensis

Species of "Lucy"; walked upright but still climbed well.

Laetoli

Site in Tanzania with 3.6-million-year-old footprints showing upright walking.

Paranthropus robustus

South African robust species with strong jaws and large teeth.

Australopithecus anamensis

Early bipedal species older than A. afarensis.

Orrorin tugenensis

Very early possible human ancestor with leg bones suggesting upright walking.

Sahelanthropus

One of the oldest possible human ancestors; skull suggests upright posture.

size dimorphism in australopiths

Males were much larger than females, showing strong male competition.

Homoplasy

Similar traits that evolve separately, not from a common ancestor.

Homology

Traits shared because they came from a common ancestor.

Cladistics

Method for grouping species based on shared ancestry.

Monophyly

A group including one ancestor and all of its descendants.

Paraphyly

A group including an ancestor but leaving out some descendants.

Polyphyly

A group that does not share a recent common ancestor.

Radiocarbon dating

Dates once-living things up to ~50,000 years old using carbon-14.

K/Ar dating

Dates volcanic rock using potassium and argon; good for millions of years old.

Palomagnetism (Paleomagnetism)

Dating rocks by how they record Earth's ancient magnetic field flips.

Ur/Pb dating (U/Pb)

Very precise dating using uranium turning into lead in rocks.

Intraspecific and interspecific variation

Intraspecific = differences within one species; interspecific = differences between species.

Carbon isotopes of chimp and hominins

Chimps eat C3 forest foods; hominins ate more C4 open-grass foods and meat.

Olduvai Gorge

Important site with early Homo fossils, tools, and animal bones.

Lomekwi

Site with the oldest known stone tools (~3.3 million years old).

Ledi-Geraru

Site with the earliest known Homo jaw (2.8 million years old).

Occlusal relief and diet

High tooth relief = cutting tough foods; low relief = grinding softer foods.

Incisor size and diet

Big incisors = fruit eating; small incisors = less fruit.

Dental microwear

Tiny scratches/pits on teeth showing what foods were eaten right before death.

Early Homo's differences from Australopithecus

Bigger brains, smaller teeth, flatter faces, more tools, more meat.

The Expensive Tissue Hypothesis

Humans got bigger brains by shrinking their guts and improving diet quality.

KNM ER 1470

Large-brained early Homo skull, often linked to Homo rudolfensis.

Hadar Homo

Early Homo fossils from Hadar showing a mix of primitive and advanced features.

Possible evidence for persistence hunting

Long legs, sweating ability, endurance running traits.

Reasons to think early Homo may have

Cut marks on bones, stone tools near animal remains, body built for long distance movement.

Carbon isotope analysis of pedogenic carbonates

Soil chemistry used to identify ancient plant types (C3 vs. C4).

Homo rudolfensis

Early Homo species with big brain and a broad, flat face.

The Black Skull

Dark fossil of Paranthropus aethiopicus with strong robust traits.

Turkana Boy

Nearly complete Homo erectus skeleton; shows tall body and long legs.

Dmanisi

Site in Georgia with early Homo fossils showing lots of variation and early migration.

Homo erectus

First fully upright, long-legged human species; first to leave Africa.

Human skin color

Evolved from balancing UV protection and vitamin D needs.

Lice in humans

Their evolution shows when humans lost body hair and when clothing appeared.

Tapeworms

Show humans got parasites by eating meat early in evolution.

The original A. afarensis knee fossil

First strong fossil proof that Lucy's species walked upright.

The Burtele foot

Fossil foot with grasping big toe showing another species still climbed trees.

Features of Australopithecus afarensis that suggest good arboreal capabilities

Curved fingers, long arms, flexible shoulders, and climbing-friendly anatomy.

The new hand of Paranthropus boisei

Shows strong grip muscles, possibly used for tool manipulation.

New ways to determine sex of ancient teeth from enamel

Uses enamel proteins (like amelogenin) to identify male vs. female.

What is found in savannas?

There can be 40,000 kg of tubers per square kilometer.

How many fingers do humans possess compared to horses?

"Primitive" or ancestral compared to the number found in horses.

What is Orrorin tugenensis known for?

Has an obturator externus groove.

What does the fauna associated with early hominins suggest?

Australopithecus was associated with more grass-eating herbivores than was Paranthropus or Homo.

What features link the Taung Child with modern humans?

Both anterior foramen magnum and flatter face/higher forehead.

What characteristic do South African australopiths have?

Spines with lumbar lordosis.

What features indicate australopiths spent time in trees?

Their more cranially oriented scapulae.

What is uranium/lead dating used for?

Useful to date speleothems at sites without volcanic material.

What does paleomagnetism rely on?

Identifying changes in earth's magnetic pole orientation.

What are derived mammal traits?

Both mammary glands and hair.

What is an example of analogous traits?

Wings used for powered flight by bats and eagles.

What is the half-life of Potassium-40?

1.3 billion years.

What are whale flippers and human forelimbs examples of?

Homologous structures.

What do South African australopith bodies lack?

None of the above.

What is the age of the Laetoli footprint tuff?

About 3.6 million years ago.

What hindered the acceptance of the Taung child?

Both it was a juvenile and the belief brain enlargement came first.

What does a monophyletic group include?

An ancestor and all of its descendants, living and extinct.

Which species do we know the least about?

Orrorin tugenensis.

What evidence supports bipedalism in Australopithecus afarensis?

Includes a projecting lateral lip of the patellar notch.

What does the medial cuneiform of Ardipithecus suggest?

It used its big toe differently than Lucy.

What is Australopithecus anamensis known for?

All of the above (4 Ma, Kenya, expanded lateral condyle).

What is the species name of the Taung Child?

Australopithecus africanus.

What factors contributed to the initial evolution of bipedalism?

All of the above.

What are convergent-evolution structures?

Analogies or homoplasies.

What are important abductors during bipedal walking?

Lesser gluteals.

What does the savanna hypothesis argue?

Hominization occurred due to decreasing African forests.

What dating method is used for volcanic eruptions near hominin fossils?

K/Ar dating.

What can radiocarbon dating be used to date?

Bone.

What evidence supports bipedalism in South African australopiths?

A femur that deviates toward the midline.

What does morphological variation within a species indicate?

May be the product of male/female differences.

Which hominins were NOT found at Swartkrans?

Australopithecus africanus.

What was Piltdown Man?

All of the above.

What do paraphyletic groups include?

All of the above.

What is notable about the "Little Foot" skeleton?

Was argued to have a partially divergent hallux.