Overview of Fossil Hominids

Alan R. Rogers

March 14, 2011

Geological Time Scale

AgePeriod Epoch (myr) Events

Quarternary Recent 0.01–0 agriculture, complex societiesPleistocene 1.7–0.01 genus Homo

Tertiary Pliocene 5–1.7 genus AustralopithecusMiocene 23–5 genus Sahelanthropus

Hominin sites of the Pliocene andearly Pleistocene

Early middlePleistocene.

ArchaicH. sapienscolonizedEurope.

Early upperPleistocene137–10 kya

Miocene hominins

Species Age EA SA CA

Sahelanthropus tchadensis 6–7 mya *

CA: Central Af; mya: millions of years ago.

The Toumai skull

I 6–7 mya

I Central Africa

I Sahelanthropus tchadensis

I brain: 320–380 cc

I Ancestral to humans? to chimps?

Gracile hominins of the Pliocene

Species Age EA SA CA

Ardipithecus ramidus 4.4 mya *Australopithecus anamensis 4.2–3.9 mya *Australopithecus afarensis 3.9–2.8 mya *Australopithecus africanus 3.5–2.3 mya * *

EA: East Af; SA: South Af; CA: Central Af; mya: millions of years ago

Ardipithecus ramidus

I Ardipithecus ramidus

I 4.4 mya

I East Africa

I Small brain

I Intermediate between hominins andearlier apes

Ardipithecus ramidus

I Ardipithecus ramidus

I Small brain

I Small canines

Ardipithecus ramidus

I Ardipithecus ramidus

I Opposable big toe, flexible wrist

I Walked upright; also climbed on branches

The “Lucy” skeleton

I 3.2 mya

I East Africa

I Australopithecus afarensis

I most complete australopithicine skeleton

Mrs. Ples

I Australopithecus africanus

I 2.3–2.8 mya

I Sterkfontein, S Africa

Robust hominins of the Pliocene

Species Age EA SA CA

Australopithecus aethiopicus 2.7–2.3 mya *Australopithecus boisei 2.2–1.3 mya *Australopithecus robustus 1.8–1 mya *

EA: East Af; SA: South Af; CA: Central Af; mya: millions of years ago

E African robust australopithicine

I Australopithecusboisei

I 1.5 mya

I E Turkana, E Africa

I massive jaw muscles

I huge molars

I A. afarensis and H. sapiens

I afarensis walked like we do(bipedal locomotion)

I had a chimpanzee-sizedbrain

Africanus had big teeth.

I Australopithecus africanus

I 3.0–3.3 mya

I S Africa

I Thick molars

I Thick enamel

I Short canines

Boisei had even bigger teeth.

I Australopithecus boisei

I 1.5 mya

I Lake Natron, Tanzania

I huge molars

I extremely thick enamel

I massive cheekbones

I enormous jaw muscles

I especially on robust forms

On robust forms, jaw muscles reached to top of head.

I big molars

I thick enamel

I small diastema means small canine

The genus Homo

A E A A OSpecies Age f u s m z

Homo habilis 1.9–1.6 mya *Homo erectus 1.8–0.4 mya * * *archaic Homo sapiens

(incl Neandertal) 400–40 kya * * *a.m. Homo sapiens 90–0 kya * * * * *

Af: Africa; Eu: Europe; As: Asia; Am: Americas; Oz: Australia; mya: millions

of years ago; kya: thousands of years ago.

I the old Homo habilis is now2 species

I H. rudolphensis (on left):large brain; large teeth

I H. habilis (on right): smallbrain; smaller teeth

Homo habilis (sm brain & teeth)

Homo rudolfensis (lg brain & teeth)

I early African Homo erectus

I restricted to Africa;1.8–0.6 mya

I also called Homo ergaster

I larger brain (900 cc)

I small gut

I smaller cheek teeth

Homo ergaster (↑ brain, ↓ teeth) The Nariokotome skeleton

I early African H. erectus

I 12 years old

I 5’4” tall (like a modern human)

I body proportions like ours

I small teeth

I powerful muscles

I Asian Homo erectus

I Between 800 and 500 kyathere appeared homininswith higher, more roundedcrania and larger brains

I archaic Homo sapiens

I includes Neanderthals

Shanidar, Iraq

I Neandertal

Jebel Irhoud

I archaic H. sapiens or earlymodern

I 90–190 kya

early modern Homo sapiens

Tiny hominins of Flores Island, Indonesia

I Homo floresiensis

I Stood about 1m high.

I Brain 380 cc.

I 18 kya

I Genetic deformity?

I Island dwarfism?

Summary

I Hominins are the bipedal apes in that portion of theevolutionary tree that includes humans but not chimpanzees.

I Sahelanthropus was a Miocene ape that may have beenancestral to humans, to chimps, or to both. Not clear whetherit walked upright.

I In the Pliocene, there was a variety hominin species. Theywalked upright but had chimp-sized brains.

I Larger brains began to appear at the end of the Pliocene, withthe advent of Home habilis and Homo erectus.

I In the early Pleistocene, Homo erectus expands out of Africaand throughout Europe and Asia.

Summary (cont)

I The species called archaic Homo sapiens appears about 400kya. It retains the strong brow ridges and receding chin of H.erectus, but has a larger brain.

I Anatomically modern Homo sapiens appears about 100 kyaand spreads throughout the world about 50 kya.

I erectus/ergaster’sribcage less conical

I implies a smaller gut

I implies a high-qualitydiet