ANTHRO Final Exam

Ma

Millions of years ago.

Ky

Thousands of years ago.

Molecular clock

Method that estimates evolutionary divergence times by measuring how mutations accumulate in DNA over time at a relatively constant rate.

Last common ancestor (LCA)

Most recent shared ancestor between humans and chimpanzees, estimated to have lived about 5–7 million years ago.

2% human-chimp DNA difference

Humans and chimpanzees differ by about 2% of their DNA, supporting a divergence around 6 million years ago.

Sahelanthropus tchadensis

Early possible hominin from Chad dating 7–6 Ma that may show early bipedal traits.

Orrorin tugenensis

Early possible hominin from Kenya dating about 6 Ma with possible evidence of bipedality.

Ardipithecus kadabba

Early hominin species from Ethiopia dating about 5.8 Ma.

Ardipithecus ramidus

Early hominin from Ethiopia dating 4.4 Ma with primitive bipedalism, reduced canines, and climbing adaptations.

Bipedality

Habitual upright walking on two legs, one of the defining features of hominins.

Center of gravity

Point through which body weight is balanced; in humans it is positioned over the legs.

Foramen magnum

Opening at the base of the skull where the spinal cord enters; positioned underneath the skull in bipeds.

Shock-absorbing spinal curves

Curves in the vertebral column that help distribute body weight and absorb impact during walking.

Short broad pelvis

Pelvic shape that helps stabilize body weight during upright walking.

Sacrum

Triangular bone at the base of the spine positioned close to the hip joints in bipeds.

Pelvic balancing mechanism

Human adaptation where gluteal muscles stabilize the body while balancing on one leg during walking.

Femur angled toward midline

Adaptation in bipeds where the thigh bone angles inward to improve balance.

Expanded knee joints

Enlarged femur and tibia joint surfaces for efficient weight transmission during walking.

Non-opposable big toe

Human foot adaptation where the big toe aligns with the others instead of grasping.

Foot arches

Curved structures in the foot that absorb shock and help propel walking.

Canine-honing complex

Sharpening system between upper canines and lower premolars found in apes but reduced in hominins.

Primitive bipedality

Early less efficient form of upright walking seen in Ardipithecus.

Stiff midfoot

Foot adaptation in Ardipithecus helping push the body forward during walking.

Pan-sized brain

Brain approximately the size of a chimpanzee brain.

Knucklewalking features

Skeletal wrist and hand adaptations seen in chimpanzees and gorillas but absent in Ardipithecus.

Australopithecus

Genus of gracile australopithecines closely related to humans that lived 4.2–2 Ma.

Australopithecus anamensis

Early australopithecine species from East Africa.

Australopithecus afarensis

East African australopithecine species dating 3.8–3.0 Ma including “Lucy.”

Australopithecus africanus

South African australopithecine species dating about 3–2.4 Ma.

Australopithecus sediba

Late South African australopithecine species dating about 2 Ma.

Australopithecus garhi

Late East African australopithecine species.

Lucy

Famous Australopithecus afarensis skeleton discovered at Hadar, Ethiopia.

Laetoli footprints

Fossil footprints in Tanzania showing early evidence of bipedal walking.

Primitive skull traits

Ape-like characteristics retained by australopithecines such as projecting faces and small brains.

Derived traits

Newly evolved characteristics distinguishing species from ancestors.

U-shaped dental arcade

Ape-like tooth row shape seen in australopithecines.

Parabolic dental arcade

Rounded human-like tooth row shape.

Diastema

Gap between teeth associated with larger canines.

Asymmetrical premolars

Primitive ape-like premolars not fully adapted for grinding.

Broad cranial base

Primitive skull feature seen in australopithecines.

Flat jaw joint

Primitive jaw structure found in australopithecines.

Canine reduction

Evolutionary decrease in canine size.

Bicuspid premolars

Human-like premolars with two cusps for grinding.

Cheek teeth

Molars and premolars specialized for chewing.

Thick enamel

Adaptation protecting teeth during chewing of hard foods.

Sexual dimorphism

Physical size differences between males and females.

Intrasexual competition

Competition between members of the same sex for mates.

Multimale polygyny

Social system with several males and multiple females.

Australopithecus male size

Average male A. afarensis was about 4’11” and 99 pounds.

Australopithecus female size

Average female A. afarensis was about 3’5” and 64 pounds.

Mixed woodland habitat

Environment combining forests and more open areas used by australopithecines.

Underground storage organs (USOs)

Tubers and roots eaten by australopithecines.

Late Pliocene environmental change

Climatic cooling and drying between 3–2.5 Ma affecting hominin evolution.

Global cooling and drying

Climate changes reducing rainfall and increasing seasonality.

Habitat seasonality

Changes in food availability across seasons.

Paranthropus

Genus of robust australopithecines adapted for intensive chewing.

Paranthropus boisei

East African robust australopithecine species.

Paranthropus robustus

South African robust australopithecine species.

Robust australopithecines

Hominins with massive jaws, large teeth, and strong chewing muscles.

Sagittal crest

Ridge on top of skull for attachment of powerful chewing muscles.

Molarized premolars

Premolars shaped like molars for grinding.

Dish-shaped face

Broad flat facial structure in robust australopithecines.

Temporalis muscle

Large chewing muscle attached to sagittal crest.

Tiny incisors and canines

Dental adaptation in Paranthropus emphasizing grinding over slicing.

Bone tool use

Possible use of bones as tools for digging termites by Paranthropus.

Limestone cave deposits

South African fossil sites preserving robust australopithecine remains.

Predator accumulation hypothesis

Idea that some fossils were accumulated by predators like leopards.

Earliest Homo

First members of genus Homo appearing about 2.8–1.6 Ma.

Homo habilis

Early Homo species likely associated with Oldowan tools.

Homo rudolfensis

Large-faced early Homo species with bigger brain.

Oldowan technology

Earliest simple stone tool industry based on cores and flakes.

Core tool

Stone tool from which flakes are removed.

Flake tool

Sharp stone fragment used for cutting.

Large mammal butchery

Evidence of animal carcass processing using stone tools.

Energetic efficiency hypothesis

Idea that bipedalism evolved because it used less energy.

Knucklewalking

Quadrupedal ape locomotion supported on knuckles.

Chimpanzee hunting model

Use of chimpanzee behavior to infer australopithecine hunting and food-sharing behavior.

Food sharing

Distribution of food among social group members.

Chimpanzee dietary sex differences

Male chimpanzees obtain more fat and protein from hunted animals while females obtain more from nuts and insects.

Adaptive strategy

Survival approach used by hominins in response to environmental pressures.

High-quality diet

Nutrient-dense foods such as meat and tubers associated with Homo evolution.

Homo erectus

Hominin species existing from about 2 Ma to 120 Ky with larger brains and human-like body proportions.

Cranial capacity

Brain volume measured in cubic centimeters.

Homo erectus brain size

600–1200 cc with an average around 900 cc.

Supraorbital torus

Thick continuous brow ridge above the eyes.

Occipital torus

Thickened ridge of bone across the back of the skull.

Nasal prominence

External projecting nose aiding thermoregulation.

Turkana Boy

Nearly complete Homo erectus skeleton from Kenya dating 1.6 Ma.

Turkana Boy age at death

About 8–9 years old.

Turkana Boy development

Had faster growth and shorter childhood than modern humans.

Age of first reproduction in H. erectus

Estimated around 14.5 years.

Gona pelvis

Female Homo erectus pelvis from Ethiopia showing larger birth canal.

Birth canal enlargement

Pelvic adaptation for birthing larger-brained infants.

Reduced gut hypothesis

Idea that nutrient-rich diets allowed smaller digestive systems and larger brains.

Thermoregulation

Regulation of body temperature.

Allen’s Rule

Animals in colder climates evolve shorter limbs.

Sweating adaptation

Human cooling mechanism through perspiration.

Endurance running hypothesis

Idea Homo erectus hunted by chasing prey until overheating.

Human sweating ability

Extreme adaptation allowing activity when other animals overheat.

Long stride walking

Efficient walking adaptation in Homo erectus.