BISC 120 - Lecture 16: Cenozoic & Human Evolution

Comprehensive vocabulary deck covering the transition from therapsids to mammals, Cenozoic primate evolution, hominin genera, anatomical adaptations, cultural milestones, and evolutionary timelines from Lecture 16.

Therapsid-to-mammal jaw transition

An evolutionary transition in advanced cynodonts where the dentary formed the jaw joint while older jaw bones shifted toward hearing.

Articular and quadrate bones

Former jaw bones that became the malleus and incus of the middle ear in mammals.

Mammalian lower jaw

A lower jaw reduced to one main bone: the dentary, called the mandible in humans.

Mammalian teeth

Teeth differentiated into distinct types: incisors, canines, premolars, and molars.

Cretaceous mass extinction ($65\text{--}66\,\text{mya}$)

An asteroid impact in Mexico that ended the Mesozoic and began the Cenozoic, evidenced by iridium layers.

Cenozoic climate trend

Climatic conditions that were warm and humid in the early Cenozoic, later becoming cooler, drier, and more variable with glaciations.

Primates

The mammalian group that includes lemurs, monkeys, and apes.

Primate adaptations

Traits adapted for tree climbing and fruit eating, characterized by opposable thumbs and relatively large brains.

Primate origins

An evolutionary emergence for which molecular clocks suggest a Mesozoic origin, while the fossil record indicates a later appearance.

Darwinius ($45\,\text{mya}$)

A nearly complete early primate fossil called 'Ida'.

Human-chimp last common ancestor

The ancestral point at which the human and chimpanzee/bonobo lineages split about $6\text{--}8\,\text{million years ago}$.

Hominin

A species more closely related to Homo sapiens than to chimpanzees or bonobos.

Hominin evolution

The evolutionary pathway after the human-chimp split that branched into several species rather than forming a straight line.

First typically human trait

Bipedalism, which was the first typically human trait to appear.

Bipedalism

Habitual upright movement on two legs.

Foramen magnum

The opening where the spinal cord enters the skull; an underside position supports upright posture.

Ardipithecus

An early East African hominin that was at least partly bipedal but still climbed well.

Ardipithecus chronological range ($4\text{--}5\,\text{mya}$)

The timeframe approximately $4\text{--}5\,\text{million years ago}$ during which two Ardipithecus species lived in East Africa.

Ardipithecus evidence for bipedalism

Anatomical features including a foramen magnum under the skull and a human-like pelvis that indicate upright posture.

Australopithecus

An African hominin genus from about $2\text{--}4\,\text{mya}$ that definitely walked on two legs.

Australopithecus chronological range ($2\text{--}4\,\text{mya}$)

The interval during which several African Australopithecus species lived.

Lucy

A famous fossil specimen belonging to the genus Australopithecus.

Laetoli footprints

Footprints preserved in volcanic ash that provide evidence of bipedal walking.

Australopithecus tool use

Evidence noted in lecture indicating some stone-tool use by members of Australopithecus.

Paranthropus

A robust australopith side branch characterized by a powerful jaw and robust skull.

Paranthropus chronological range ($2\text{--}3\,\text{mya}$)

The period approximately $2\text{--}3\,\text{million years ago}$ when robust australopiths lived in Africa.

Paranthropus evolutionary outcome

A hominin side branch that eventually went extinct.

Genus Homo emergence ($\sim 2\,\text{mya}$)

The evolutionary emergence of the genus Homo around $2\,\text{million years ago}$.

Homo habilis

An early Homo species with a noticeably larger braincase than Australopithecus and strong evidence of stone-tool use.

Homo habilis chronological range ($2.5\text{--}1.5\,\text{mya}$)

The time interval during which Homo habilis lived in Africa.

Homo erectus / Homo ergaster

Long-distance-running hominins with larger brains, active hunting, hand axes, and possibly cooking with fire.

Homo erectus / Homo ergaster emergence ($\sim 1.8\,\text{mya}$)

The appearance of Homo erectus/ergaster in Africa and their subsequent spread into the Middle East, Asia, and Europe.

Homo erectus / Homo ergaster persistence

The chronological duration of H. erectus/ergaster, which persisted until about $200{,}000\,\text{years ago}$ according to the lecture.

Homo erectus / Homo ergaster tools

Hand axes and other implements used by these active hunters.

Later hominin branches

Lineages descended from H. erectus/ergaster, including Neanderthals, Denisovans, and other Homo groups.

Homo floresiensis

A small-bodied island hominin from Flores, nicknamed the 'hobbit'.

Denisovans

An Asian hominin group closely related to Neanderthals, originally known mostly from DNA, teeth, and finger bones.

Homo longi

A taxonomic name used in the lecture in connection with Denisovans and the 'Dragon Man' skull.

Neanderthals appearance ($\sim 350{,}000\,\text{ya}$)

The emergence of cold-adapted Homo neanderthalensis in Europe and the Middle East.

Neanderthal anatomy

Morphological traits including modern brain size, a robust skeleton, and short limbs adapted to cold climates.

Neanderthal culture

Behaviors and toolkits including wooden spears, stone tools, fire, and the burial of their dead.

Neanderthal extinction ($\sim 30{,}000\,\text{ya}$)

The disappearance of Neanderthals occurring around $30{,}000\,\text{years ago}$.

Homo sapiens emergence ($\sim 200{,}000\,\text{ya}$)

The origin of anatomically modern humans in Africa around $200{,}000\,\text{years ago}$.

Out of Africa hypothesis

The evolutionary model proposing that Homo sapiens originated in Africa, spread outward, and replaced many older hominin populations.

Modern Homo sapiens anatomy

Physical traits characterized by a high forehead, a large braincase around $1300\,\text{cc}$, and usually a pronounced chin.

Modern human culture

Cultural attributes consisting of advanced stone tools, extensive fire use, and more symbolism and art than earlier hominins.

Hominin interbreeding

Genetic admixture between spreading Homo sapiens and other archaic groups, including Neanderthals and Denisovans.

Homo sapiens + Neanderthal interbreeding

Admixture events between modern humans and Neanderthals that occurred in the Middle East and Europe.

Homo sapiens + Denisovan interbreeding

Admixture events that occurred as modern humans spread through Asia.

Possible African admixture

DNA evidence suggesting that Homo sapiens may have mixed with unknown hominins within Africa.

Human evolution pattern

A phylogenetic structure represented as a branching tree with side branches, rather than a straight ladder.

Human evolution sequence

The lineage sequence: $6\text{--}8\,\text{mya}$ split $\rightarrow$ Ardipithecus $\rightarrow$ Australopithecus $\rightarrow$ Homo habilis $\rightarrow$ H. erectus/ergaster $\rightarrow$ later Homo branches.

Cenozoic human-evolution timeline

The chronological sequence of major events: $45\,\text{mya}$ Darwinius; $6\text{--}8\,\text{mya}$ split; $4\text{--}5\,\text{mya}$ Ardipithecus; $2\text{--}4\,\text{mya}$ Australopithecus; $\sim 2\,\text{mya}$ Homo; $1.8\,\text{mya}$ erectus; $200{,}000\,\text{ya}$ sapiens.