Human Evol. Final Concepts to Know

changes to the human diet over time

Human diet has evolved from high-fiber, foraged plant foods and raw meat in the Paleolithic era to calorie-dense, processed diets in the industrial age, driven by technological, cultural, and environmental shifts. Key transitions include cooking (increasing energy intake), farming (introducing dairy and grains), and the recent explosion of ultra-processed foods, which have outpaced human evolutionary adaptation

Difference between forensic anthropology and bioarchaeology

Similarities:

– Focus on human remains

– Use of same methods

– Biocultural approach

Differences:

– Focus

Bioarch → population level

– How does this individual fit into the wider cultural context?

Forensic → individual

– Who is this individual?

components of the biological profile

Estimation of:

– The age of the individual

– The sex of the individual

– The stature of the individual

– The geographic background or ancestry of the individual

Always use as many points of reference as possible

Oldowan tools

Oldowan tools are the oldest known stone tool industry, dating back roughly 2.6 to 1.7 million years, characterized by simple, crudely flaked pebbles and cores (primarily choppers) alongside sharp-edged flakes. Used by early hominids like Homo habilis for butchery, wood processing, and smashing bones for marrow, this industry represents a major cognitive leap in human evolution

Acheulean tools

Hand Axes

Found all over the Old World

Distribution of Acheulean tools is that of H. erectus and its variations

Dispersed out of Africa

Had regional variations

Mousterian tools

Smaller, lighter, and thinner than Acheulean hand axes

Hafted onto handles - spears

Mousterian tools vary site-to-site

Different tool-making traditions between communities?

Disappeared from archaeological record with the extinction of Neanderthals

Models for modern human origins:

Multi-regional

The diagram shows many regions connected over time.

The red lines between populations represent continuous gene flow (interbreeding).

Fossils in different regions gradually change into modern humans.

👉 Meaning: Humans evolved in multiple places at once, staying connected through interbreeding.

👉 Labeled in image as: “Overall Regional Continuity”

Models for modern human origins:

Recent African Origins

You see a strong origin in Africa, then movement outward.

The blue lines represent older human species dying off.

The red lines show modern humans spreading and replacing them.

👉 Meaning: Humans evolved only in Africa, then spread out and completely replaced other human species.

👉 Labeled as: “Complete Replacement”

Models for modern human origins:

Assimilation

Starts like the African model (origin in Africa).

But now there are some connections (mixing) with other populations.

Not full replacement—some older populations contribute genetically.

👉 Meaning: Humans came from Africa but interbred with others (like Neanderthals).

👉 Labeled as: “African Origin + Admixture”

Fossilization

the rare, complex geological process by which biological remains (bones, shells) or traces (footprints) are preserved, usually turning into stone over thousands or millions of years, typically requiring rapid burial in sediment.

Difference between absolute and relative dating

and examples of each

Relative Dating

The law of superposition: in undisturbed stratigraphic sequences, objects that are in lower Strata are older than objects in upper strata.

Absolute Dating

Giving things a date. This is 100 years old

general anatomical characteristics of pre-australopithecines

Primitive (ape-like) traits

• Very small brains (chimp-sized)

• Strongly prognathic faces (face sticks out)

• Large canines (often with honing complex)

• Ape-like teeth (U-shaped dental arcade)

• Long arms, short legs (arboreal adaptations)

• Curved fingers and toes (tree climbing)

🔹 Early bipedal traits (limited)

• Some evidence of bipedalism, but:

  • Not fully efficient or obligate

  • Still spent significant time in trees

👉 Big idea: Mostly ape-like, with the first signs of walking upright

Pre-Australopithecines = “mostly ape”

general anatomical characteristics of earlyaustralopithecines

Primitive traits (from your notes)

• Small brains

• Large, prognathic faces

• Small bodies

• Long arms

• Relatively large canines

• Ape-like dental formula (2.1.2.3)

🔹 Derived (more human-like) traits

• Clear bipedalism (habitual/obligate)

  • Knee valgus angle

  • Pelvis and leg adaptations

• Reduced canines (compared to earlier hominins)

• Larger posterior teeth (molars)

• Non-divergent big toe (in later forms like afarensis)

• Foot arch & heel strike (Laetoli footprints)

Early Australopithecines = “walking ape”

general anatomical characteristics of robust australopithecines

• Very large, broad face

• Extreme cheek flare (wide, dish-shaped face)

• Sagittal crest present (for large chewing muscles)

• Huge molars and premolars (back teeth)

• Small incisors (less emphasis on front teeth)

• Highly specialized for heavy chewing (tough plant foods)

Key Similarities (Important!)

• Postcranial skeleton nearly identical

• Fully bipedal

• Both have large back teeth (robust = larger)

• Brain sizes similar (ape range)

  • Robust: ~500 cc

  • Gracile: ~450 cc

general anatomical characteristics of gracile australopithecines

• Large face, but not as extreme as robust forms

• Moderate cheek flare (less wide face)

• No sagittal crest (no big chewing muscle ridge)

• Large incisors (front teeth)

• Less specialized teeth overall

• Molar microwear suggests a more varied diet

Key Similarities (Important!)

• Postcranial skeleton nearly identical

• Fully bipedal

• Both have large back teeth (robust = larger)

• Brain sizes similar (ape range)

  • Robust: ~500 cc

  • Gracile: ~450 cc

anatomical signs of bipedalism

Non-divergent big toe

Heel strike

Well-developed arch

Lucy and why she is so important

“Lucy” (aka AL 288-1)

A. afarensis dating to ~3.2 mya

Hadar, Ethiopia

40% of skeleton complete

Female due to wider more rounded pelvic opening

Third molars erupted → adult

Arm and leg bone lengths → 3’3” and about 60 lbs.

Pelvic bones and femur indicate bipedalism

Riverine forest at the time

Proof of Early Bipedalism: Lucy’s pelvis and leg bones closely resemble those of modern humans, providing, at the time of discovery, the earliest definitive evidence that hominins walked on two legs, even while retaining some tree-climbing abilities.

Filling the Evolutionary Gap: As one of the most complete, oldest hominin skeletons ever discovered at the time, she filled a massive gap in the fossil record between apes and early humans.

"Missing Link" Icon: She became a "celebrity fossil" that made paleoanthropology accessible, highlighting that our origins began in Africa.

Redefining Ancestry: Her discovery supported the understanding that human evolution was a gradual process, placing A. afarensis as a key ancestor in our lineage.

Homo erectus and why they are so important (fire, leaving Africa, etc…)

Homo erectus (approx. 2 million to 117,000 years ago) is a pivotal human ancestor, recognized as the first to possess a modern body plan, use fire, and disperse out of Africa into Asia and Europe. Their ability to adapt, hunt, and create, particularly using Acheulean stone tools, enabled them to survive for nearly 2 million years—longer than any other species in our genus.

Why Homo Erectus is So Important:

Leaving Africa (First Human Migrant): H. erectus was the first hominin to leave Africa and populate vast areas of the Old World, reaching regions like Java (Indonesia) and Georgia by roughly 1.8–2 million years ago.

Mastery of Fire: They are likely the first human relative to control fire, possibly dating back over 1 million years. This allowed for cooking food (increasing protein intake), protection against predators, and warmth in colder climates.

Technological Advancements: They developed the Acheulean stone tool industry, creating sophisticated bifacial tools like handaxes and cleavers for butchery and other tasks.

Modern Body Plan: They were the first hominins with human-like body proportions: shorter arms and longer legs for long-distance walking/running, adapting to varied environments.

Brain Expansion: They displayed a significant increase in brain size compared to earlier ancestors, suggesting increased cognitive abilities

Neanderthals and their relationship to modern humans

• Neanderthal genes found only in non-Africans

  • Interbred with modern humans AFTER they left Africa – likely soon after

  • Neanderthal genes detected in modern populations in W. Europe, E. Asia, and S. Pacific

• Suggests the last common ancestor of Neanderthals and modern humans between 700 and 516 kya

• Denisovan DNA also present in modern populations and in some Neanderthal individuals

• Neanderthals and Denisovans likely both incipient species

• Not fully distinct from H. sapiens

Evidence for Neanderthal culture

• Brain is large and complex, and they likely needed speech to hunt.

• Recently, a gene (FOXP2) related to speech in humans was identified in Neanderthal specimens, and it contained the same mutations we have, suggesting Neanderthals might have shared some basic language capabilities with modern humans

• Mousterian tools

• Smaller, lighter, and thinner than Acheulean hand axes

• Hafted onto handles - spears

• Mousterian tools vary site-to-site

• Different tool-making traditions between communities?

• Disappeared from archaeological record with the extinction of Neanderthals

Arboreal adaptation

Arboreal adaptation refers to the evolutionary, structural, and behavioral specializations of animals for living and moving within trees. These adaptations, crucial for survival in forest canopies, include grasping hands/feet, long limbs for balance, specialized claws, and enhanced vision to navigate complex 3D environments, often leading to reduced predation risks

Chimp and Gorilla locomotion

Opposable thumb/big toe

Nails instead of claws; tactile pads on ends of digits

Generalized skeletal structure

Tendency towards erect posture (vertically oriented)

vertebral column allows great range of motion

Lemur “Sunning” itself

Divergent thumb & big toe (opposable)

Nails on digits (instead of claws)

Grasping hands, dermal ridges

cost and benefits of being social (primates)

Costs? • Compete with group members for resources • Competition=>injury , death, more energy expenditure

Benefits? • Safety in numbers (predator defense) • Can outcompete smaller neighboring groups • Males attracted to groups of females • Females will tolerate familiar males

language in non-human primates (how we do define human language- 8 ways)

1. Displacement

Human language can refer to past and future times and to different locations.

• What does a mermaid look like? A werewolf?

• What does love feel like?

2. Arbitrariness

No natural connection between linguistic form and its meaning.

• E.g. in English word for “flower” , when written or spoken neither looks, smells, nor feels like a flower.

3. Productivity/creativity

Humans learning a language can form and produce utterances never heard before. Open-ended.

E.G. “on fleek” “Savage” “Netflix and chill”

4. Cultural transmission

Acquire language from listening to other speakers and participating. Passed on from one generation to the next.

5. Discreteness

Sounds in language are meaningfully distinct.

/pin/ vs. /bin/

6. Duality

Language is organized on two levels, the physical level and in our ability to produce sounds. And at the level of meaning, when we produce sounds in combination.

/c/, /t/, /a/

Can be organized into different words with different meanings. CAT, ACT, TACT, TACIT….

7. Semanticity

Language carries meaning.

The cats sing negatively.

Hay leche?

“Oh great. The cat threw up on our bed”

What does the word “crash” mean?

8. Structure dependence

Language is dependent on structure, syntactical rules.

The cats sing negatively.

Syntax/structure is correct- subject, verb, adverb- but does not make sense.

Primitive and derived primate characteristics

Primitive traits

Small brains

Large faces (prognathic and wideset)

Small bodies

Long arms and long curved fingers

Big canines

Ape-like configuration of teeth (2.1.2.3)

Derived traits

Diverse – varies by species

Some human-like, some not

Reduced canines and molars

Pelvic and leg morphology = biped

basic traits of the Strepsirrhines

Rhinarium - wet nose

Dental comb

basic traits of the haplorrhines

Anthropoidea: Monkeys, apes, humans

Diurnal

Vision

Often terrestrial

Social- more parental care, mutual grooming, etc.

Herbivorous and omnivorous

Difference between old (catarhines) and new world monkeys (platyrrhines)

Platyrrhini: New World Monkeys (NWM)

• Cebidae

  • (e.g. Squirrel monkeys, Capuchin, marmosets, tamarins)

• Atelidae

  • (e.g. howler monkeys, spider monkeys, uakaris, bearded sakis)

• Pygmy Marmoset- smallest NWM

• Example of the hairless patch of skin that enhances the grip of the prehensile tail. This tail is seen some of the New World Monkeys!

New World Monkeys:

Seven species of NWM inhabit different ecological levels of the Suriname tropical rain forest

Catarrhini: Old World Monkeys (OWM), Apes, Humans

Cercopithecoidea: OWM

• Colobinae

  • E.G. colobus monkeys, langurs

• Cercopithecinae

  • E.G. macaques, baboons, mandrills, vervets

Chimp vs. Bonobo behavior

Bonobos and chimpanzees exhibit strikingly different behaviors despite being closely related. Bonobos are generally peaceful, matriarchal, and utilize social sexual behavior to manage conflict, while chimpanzees are patriarchal, highly territorial, and prone to violent, lethal aggression. Bonobos show high tolerance toward strangers, whereas chimps are xenophobic

Tool use and culture in primates

Tool Use

• Primates use objects to solve problems or obtain food.

• Not just humans—seen in chimpanzees, capuchins, etc.

Examples:

• Chimpanzee:

  • Use sticks to fish for termites

  • Use stones to crack nuts

• Capuchin monkey:

  • Use rocks as hammers and anvils

• Orangutan:

  • Use leaves as sponges or gloves

👉 Key idea: Tool use shows problem-solving and intelligence

🧠 Culture in Primates

• Culture = learned behaviors passed socially, not genetically

Characteristics:

• Learned through observation/imitation

• Varies between groups of the same species

Examples:

• Different chimp groups use different tools for the same task

• Some populations have unique grooming rituals

👉 Key idea: Culture means “they learn from each other”

Primate reproductive strategies (infanticide, female reproductive strategies, etc…)

Infanticide

• Killing of infants (usually by males)

Why it happens:

• Brings female back into estrus faster

• Male can pass on his genes

Seen in:

• Lion (classic example, though not a primate)

• Hanuman langur

👉 Key idea: It’s about reproductive advantage

👩 Female Reproductive Strategies

Females evolve behaviors to protect offspring and maximize survival

Strategies:

• Paternity confusion

  • Mate with multiple males → reduces risk of infanticide

• Form alliances

  • Social bonds with other females or protective males

• Mate choice

  • Prefer strong/high-status males

• Concealed ovulation (in some species)

  • Males can’t tell when fertile → stay around longer