Humans

[P] Homo #

Thursday, March 12, 2020 1:25 PM

Early Homo #

• 2.5 – 1.8 mya
  • Kenya, Tanzania, Ethiopia
• E/S Africa
  • S Africa, Malawi
• River margin ecology
• More diverse and spread out

Homo: “human” #

• habilis: handy man
• ergaster: workman
• erectus: upright
• antecessor: explorer
• heidelbergensis: Heidelberg, Germany
• neanderthalensis: Neander Valley, Germany
• sapiens: wise

Homo rudolfensis #

• 2.5 – 1.7 mya
• Koobi Fora, Malawi
• Orthognathic, broad face
• Smaller back teeth, larger front teeth — similar to humans

Homo habilis “handy man” #

• Also 2.5 – 1.7 mya
• Koobi Fora, Olduvai, Hadar, Sterkfontein
• Very similar to H. rudolfensis

Differences #

• Smaller face, teeth, brain
• Postcrania is more like Australopithecus but still clearly bipedal

First fossils found with Oldowan tools, but garhi now known to use tools

Homo naledi #

• Found in S Africa very recently (2014)
• 236k – 335k ya
• Modern hands + feet, but hands are like climbers
• Mix of traits b/tw humans, primitive hominids
• Rising Star cave system (strange site)
• Modern teeth, postcrania
• Brain size of chimp, prognathic face

Significance #

• Small brained humans could have complex behavior
• Many humans lived at the same time

Homo ergaster and erectus #

stay in Africa leave Africa

• First hominids of broadly modern aspect
  • Obligate bipeds
  • Complex tool assemblages
  • First to leave Africa

Environment of H. erectus #

• 1.85 mya – 10 kya
• Ice Age – extreme climate change, sea level change
  • Sunda Shelf: now ocean near Indonesia
  • English Channel: previously connected

Homo ergaster — left Africa and became erectus #

• 1.75 mya
• Africa
• Similar sexual dimorphism to humans
• Supraorbital torus – bone over eyes
• Modern teeth
  • Modern small jaw
  • Smaller teeth
  • Small canines
• Larger brain — occipital torus: football shaped brain
  • Larger temporal lobes: memory
  • Larger parietal lobes: integration
• Slender bone structure → adaptation for warm climates
• Barrel shape rib cage
• Broad short pelvis

Homo erectus #

Differences to ergaster: #

• robust crania
• shorter
• lower brain cases
• found in Asia
• 1.7 mya – 25 kya (longer lived)

Variation: #

• accumulated over time
• geographic differences / isolation
• migrations occur over millions of years
• Dmanisi: very similar to erectus but wrong date, huge canines

Why are erectus/ergaster important? #

• much more modern anatomy
  • increased brain size – very close to human size
• changes in behavior
  • track prey over long distances: nomadic
  • spread out to a variety of habitats
  • varying strategies based on habitat
  • more generalized, flexible → innovation
• use of tools: Acheulian Stone
  • better material choice
  • standardized axes, choppers, flakes
  • multi-step production process
  • useful to many different environments, prey
  • replacing teeth as main method of processing food (reduced size in teeth, reduced sexual dimorphism)
  • ability to control fire → less stress on anatomy, survival in harsh environments, protection against predators, illumination (1.5–1.3 mya)
    • starting to lose ability to eat raw meat
• some evidence of cultural sophistication
• intentional, artistic carving / art

Significance of tools #

1. evolutionary adaptations:
   • lower sexual dimorphism
   • more communication / cooperation
   • larger brain size
2. ability to generalize and adapt to new environments

Timeline: #

Environment Change → Bipedalism → Tools → Larger brain size

• more time to think
• increased social cooperation and symbolic communication

Pre-Modern Humans #

800 kya – 30 kya #

• long lived, variable

Should know: #

• Homo heidelbergensis – Europe, Africa, 450 to 200 kya
• Homo sapiens ssp. Denisova – 50,000 – ?
• Homo neanderthalensis – Europe, Western Asia, 250 to 29 kya
• Homo denisova – Siberia, East Asia, New Guinea, 200 kya – 20 kya
• Homo sapiens – Worldwide, 190 kya to present
• Homo floresiensis – Flores Island, 800 kya?? – 50k

Overlap in time w/ erectus, modern human

H. Heidelbergensis #

• Africa, Asia, Europe

• 600–200 kya

• very similar to H. erectus (but more robust)

• Africa, Asia, Europe

• 600–200 kya

• Very similar to H. erectus (but more robust)

  • large brow ridges, thick face

• indication of social complexity: injuries that received care

• large brain size

Technology #

1. Levallois technique: chipped at perimeter, one final blow to create sharp edge. Very reproducible

2. Later Mousterian technology

   • first shelters
   • fire pits
   • efficient, predictable flakes
   • wooden spears for coordinated attacks

H. Neanderthalensis #

• Europe, West Asia

• 130–30 kya

• Very large brains (1500cc vs 1350 humans)

• Small teeth

• large body size

  • occipital bun: football shaped skull
  • M-shape brow
  • large nasal cavities

• adapted for living in cold environment

  • barrel shaped chest
  • large lungs
  • short but robust limbs

• fossils found in Europe, Middle East

  • frequently had pathologies (not healthy) – suggests longer lifespan

• tools have evidence of retouching

  • Châtelperronian technology: aesthetic, nonfunctional tools (necklaces, etc)

• language: hyoid bone very similar to humans, ability to make human sounds

  • FOXP2 gene – speech regulation

• elaborate/deliberate burial

• art – 50kya, music: bone flute

• lots of population overlap/interbreeding w/ humans

• extinct 40–30 kya due to decreasing temperatures

H. denisova #

• Denisova cave 200 kya – 20

• different DNA to humans/neanderthals

• fossils suggest multiple species coexisted, even lived together

• first species to be named solely by genome

• “cousins” of humans — able to interbreed

• Common ancestor: 350 kya based on mitochondrial DNA

• All modern humans share 99.3% of DNA originating from Africa

Evolution and Spread of H. Sapiens #

Out of Africa Theory #

1.8 mya, H. erectus leaves Africa and splits into new species

• the group that stays becomes H. sapiens (doesn’t make sense because does not include interbreeding)
• second wave of H. sapiens leaves ~50 kya

Multiregional Theory #

1.8 mya, H. erectus leaves Africa new species move around and interbreed freely

probably a hybrid model

H. Sapiens #

Traits: #

• large brain / cranial capacity, globular (not elongated)
• small teeth
• gracile

Unique:

• true forehead (from eyes to top of skull)
• chin

Early Homo Sapiens #

• Herto, Ethiopia

• 160 kya

• supports hypothesis of African origin

• Jebel Irhoud, Morocco

• 300 kya

• found with flint tools ← upper paleolithic / middle stone age

• suggests H. sapiens is older than we thought

• suggests large network of trade/transportation

More genetic variation in Africans than other humans. First human is African.

Technology #

• Very diverse regional tools in upper paleolithic (100-30kya)
• 70-50kya: middle Stone age
• Increasing sophistication over time
• Functional specialization
• Evidence for skill specialization

Art #

• 10,000 years ago — after Neanderthals die out
• Cave paintings/imagery in Europe
• Carvings in Australia, South Africa (60-75kya)

The Spread of Homo sapiens — first wave, second wave.

H. floresiensis #

• Found in island Flores, near Java
• 100–60kya (H. erectus time period)
• “hobbit” fossils — very small body size
• Very small brain size (chimp size)
• Similar anatomy to H. erectus
• Complex tools 190-50kya
• Evidence of tools as old as 1mya

Why so small? #

• Not pathology
• “Insular dwarfism”: an adaptation where small size is favored
  • Limited resources (less energy)
  • Limited predators (no need to be big)

Significance #

• Ability to make tools/have intelligence with small brain size
• Coexistence w/ modern humans: didn’t get replaced at the same time as other populations
• Reminder that humans are still subject to forces of evolution