STUDY GUIDE 3B for EXAM No. 3

SECTION 10 - PRIMATE EVOLUTION

See pp. 82-83; 92-95; 100-103; 106-113 in Stringer and Andrews

Continental Drift and its Effects on Primate Evolution (see also examples in Course Materials in Blackboard)

gear.gif (333 bytes) 200 mya All continents in one landmass, Pangea
(see 1st map below)
  165 mya Madagascar begins to separate from Africa. One or two lemur species raft over from Africa and thrive without competition from monkeys which evolve later.
gear.gif (333 bytes) 125 mya Pangea (all continents) has begun to split apart into northern (Laurasia) and southern (Gondwanaland) land masses (see 2nd map below)
gear.gif (333 bytes)  ca. 90 mya South America and Africa moving apart; India begins to drift toward Asia from Africa.
gear.gif (333 bytes) 65 mya Continents at beginning of Cenozoic,  (see 4th map below)
gear.gif (333 bytes) 55 mya Australia drifts away from Asia allowing marsupials to develop and diversify without competition from placental mammals
  45 mya North America and Eurasia begin to separate
gear.gif (333 bytes) 37-35 mya South America & Africa are hundreds of miles apart, but a proto-monkey ancestor "rafts" from Africa to S. America.
gear.gif (333 bytes) 17-18 mya Northeast Africa docks with Asia (Arabian Peninsula)  esp. after 15 mya -- hominoids begin radiating into Eurasia. (See maps on p. 100 in Stringer and Andrews)
gear.gif (333 bytes) 3 mya Isthmus of Panama formed -- changes ocean currents (creates the Gulf Stream) and world climates; affects hominid evolution, i.e., origin of genus Homo 2.5-3.0 mya.

Continental drift led to climatic change as ocean currents changed direction and land masses, especially Laurasia, drifted northward into cooler latitudes. The appearance of flowering plants led to a proliferation of insects and new species of insectivores.  Birds and mammals diversified to exploit the increase in both edible plant parts and insects. The primate order branched off the insectivore evolutionary line, perhaps as a result of the proliferation of insects. 

PALEOCENE (65-56 MYA):  1) Plesiadapids from late Cretaceous and Paleocene -- have been variously classified as early primates or insectivores, but generally viewed as primates now.   2) Altiatlasius, found in the Atlas Mountains of Morocco, North Africa -- no consensus it was actually a primate.

eocene (55-34 mya):  Prosimian Adaptive Radiation – Age of Prosimians

Abundant and widely distributed prosimians; 4 times as many genera as today, but mostly extinct by end of Eocene.  Some are lemur/loris-like, others tarsier-like, but none can be clearly linked to modern forms.  Found in North America, Europe and North Africa.

The Eocene prosimians of North America and Europe go extinct during the Oligocene (see below) due to cooler, drier climatic conditions which eliminated suitable prosimian habitat (subtropical forest) from the temperate latitudes (Klein, 1999, p. 109).  Prosimians survived in tropical Asia and Africa but did not compete well with the evolving monkeys who are almost all diurnal (day feeders); as a result those that did survive became nocturnal (night feeders) via natural selection or were isolated like the lemurs in Madagascar.


Early Transitional Fossil between Prosimians and Anthropoids in the Old World

Recent new discovery -- Fossil Ida found completely preserved in Germany -- dates to 47 million years ago!

 

The Fayum Depression is located south of Cairo, Egypt; its deposits date to the late Eocene and early Oligocene, i.e., 36-33 mya.    Early anthropoids are present in the late Eocene.


 NEW WORLD MONKEYS (NWM) -- Late Eocene/Early Oligocene

Except for NWM, most primate fossils found after the Eocene are from Africa.

Ca. 35 mya or somewhat later, an early monkey form made it from Africa to South America and eventually underwent adaptive radiation resulting in 70 species of New World Monkeys.  Why is it difficult to trace the early evolutionary heritage of New World Monkeys?  because only a few bone fragments have been found from the late Eocene to late Pleistocene in South America, with the oldest dating only to 27 mya in Bolivia.

What points to an African origin of the New World Monkeys?

RedDiamond.gif (232 bytes) "Rafting" of animals from one land mass or island to another has been documented in SE Asia/South Pacific.
RedDiamond.gif (232 bytes) NWMs have a 2-1-3-3 dental formula and there exists an extinct African ancestor with such a formula: Apidium.
RedDiamond.gif (232 bytes) An African rodent also made it to Africa during the Oligocene.
RedDiamond.gif (232 bytes) DNA studies indicate that New World Monkeys are genetically closer to Old World Monkeys than they are to prosimians.

One could argue that New World Monkeys came from North America, but the fossil links are not there and any such ancestor would also have had to raft over to South America. The Panama link between North and South America was not created by Continental Drift until ca. 3 million years ago.


OLIGOCENE (34-22.5 MYA):  Era of the Anthropoids

Why is Apidium's 3-1-3-3 dental formula of interest? See above.
  
Aegyptopithecus is an important fossil found at the Fayum site; it represents a probable transitional fossil between anthropoids and hominoids, i.e., between monkeys and apes.


 Miocene hominoids (22.5-5 mya)

The Miocene was a period of climatic instability which may have favored speciation events.

The transition from monkeys to apes remains obscure in part due to a major gap in the fossil record during the late Oligocene in Africa.  Most scholars believe hominoids evolved in Africa and later migrated out to Europe and Asia ca. post-17 mya when a land bridge was created by continental drift between Africa and the Middle East. 

The evidence is growing that while climatic change led to the extinction of apes in Europe,  some European apes migrated BACK TO AFRICA ca. 9-10 mya to become the ancestors of the gorilla and chimpanzees and ultimately the hominids [see Cameron and Groves,' Bones Stones and Molecules, Elsevier Academic Press, London, 2004, pp. 47-58.  See also Richard Dawkins, The Ancestor's Tale, Houghton Mifflin, New York, 2004, pp. 115-118; Stringer and Andrews, Thames and Hudson, London, 2005, pp. 110-113]

Dryopithecus and/or Graecopithecus are the likeliest candidates as ancestors of living apes.  BUT Cela-Conde and Ayala's Human Evolution: Trails from the Past, Oxford University Press, 2007, pp. 76-80) dispute this conclusion saying there is not enough evidence to make a determination due to the major fossil gap in Africa during the late Miocene.

African Miocene Fossil Hominoid Forms (23-14 mya; 13-7 mya few to no fossils)

NOTE:  Gap in late Miocene fossil record of Africa, ca. 13-7 mya, poses problems for the resolution of hominid evolution.
Earliest Miocene apes found in Africa beginning at least 23 mya; Continental Drift would lead to Africa docking with Eurasia about 17 mya; this allowed the adaptive radiation of apes out of Africa into Eurasia for the first time.  Data also suggest that some of the European apes would eventually return to Africa as conditions became colder in Europe and that one or more of these genera was ancestral to gorillas, chimps, and ultimately hominids.

European Hominoid Fossil Forms (15-7 mya)

South and Southeast Asian Forms (16-7 mya)

Most Miocene hominoids from East Africa, Europe, and Asia display marked sexual dimorphism. They were also very numerous, as many as 100 different species.

SECTION 11 -- PALEOANTHROPOLOGY and DATING TECHNIQUES


Definition of a Hominid

Bipedalism distinguishes all hominids from other primates.     HYPOTHESES ABOUT THE ORIGIN OF BIPEDALISM (see table below)

1  Owen Lovejoy's male provisioning female theory leading to all-year-round female sexual availability and pair-bonding beahvior. 
2  Permitted greater thermoregulation of body temperature in tropical heat
3  Developed because of sexual selection (female choice) which selected for male sexual displays standing on two legs 
4  Allowed early hominids to see greater distances which helped it find food and avoid predators especially in the savanna

 

What is mosaic hominid evolution? -- see below

1 hominid bipedalism with Orrorin tugenensis 6 mya
2 hominid stone toolmaking and larger brain, early Homo 2.6-2.5 mya
3 first use of fire by Homo ergaster/erectus at Swartkrans Cave, South Africa (controlling fire, not starting a fire) 1.4-1.5 mya
4 earliest hominid hunting -- small game with wooden clubs, etc., early Homo and Homo ergaster/erectus 1-2 mya??
5 possible early big game hunting with wooden spears found in England and Germany, Homo heidelbergensis 400,000 ya
6 clear evidence of big game hunting, early Neandertals 250-200,000 ya
7 fluid spoken language with Homo sapiens, possibly Neandertals ca. 100-150,000 ya

NOTE:  Archaeology recovers only artifacts made of stone and other durable material; thus, early
tools made of other materials, such as wood or bamboo, are rarely recovered.


PALEOANTHROPOLOGY as a Multidisciplinary Science -- See pp. 24-25 and pp. 46-61 in Stringer and Andrews


Paleoanthropology is a costly, multidisciplinary enterprise.   Some subdisciplines of paleoanthropology include:

stratigraphy -- see below
archaeology -- the study of sites and artifacts left behind by hominids (see Study Guide No. 1A)
 geomorphology -- study of how rocks and landforms are created; the study of ancient landforms
 paleontology -- the study of animal fossils
 taphonomy -- study of decay processes, especially of bone
 palynology -- study of fossil pollen


DATING TECHNIQUES -- See pp. 30-33 in Stringer and Andrews; pp. 13-18 in Evolution and the Fossil Record
Relative Dating ="older or younger than", e.g., stratigraphy and Principle of Superposition
Chronometric Dating = yields calendrical time period or dates


 Radiocarbon Dating (radioactive carbon dating):
Some Useful Terms:  atoms and molecules; isotope

·         H2O, CO2 = molecular formulas for water and carbon dioxide

·         Elements in the periodic table are defined on the basis of the number of protons in the nucleus.  Elements often come in several forms called isotopes which differ in their atomic weight due to variable numbers of neutrons, e.g., carbon exists in three isotopes, 12C and 13C (stable isotopes) and 14C (unstable or radioactive isotope).

·         12C = 98.89% (6 protons & 6 neutrons);  13C = 1.11% (6 protons & 7 neutrons); 14C = 0.0000000001%!! (1 C14 atom or every trillion C12 atoms;   6 protons & 8 neutrons)

Terms: atoms and molecule; isotope

Cosmic Ray bombardment of the gaseous atoms in the upper atmosphere (Nitrogen, Oxygen, Carbon Dioxide) produces C14 in the atmosphere day and night

 

C14 eventually works its way into all living things:

Important Points to Remember about Radiocarbon Dating:

1

How C14 gets into life cycle: 1) cosmic rays split nitrogen atoms in upper atmosphere CREATING free neutrons (n); 2) neutrons strike 14N atoms CREATING 14C  [14N + n (neutron) = 14C + displaced p (proton)]; 3) 14C + O2 = 14CO2;  4) plants use CO2 for photosynthesis; 4) then from plants and animals to humans as food.

2

During life, organism's C14 is replenished daily; at death, C14 begins to decay at a rate based on its half-life of 5,730 ± 40 years.

3

Dating based on comparing known atmospheric ratio of C14 to C12 (stable isotope of carbon) to C14/C12 ratio in dead organic sample.

4

Dates organics: charcoal, shell, wood, bone, peat, leather, pictographs, organic remains in pottery, ice cores, slag/iron, and hearth or humus-rich soils

5

Cost: $345/date (conventional date); $595/date (date using linear accelerator)

6

Good for dating objects 30 to 40,000 ya (conventional); up to 60-70,000 ya (accelerator technique or AMS dating)

7

Good for dating later Homo sapiens and Neandertal sites; not early history or evolution of these species which go back 200,000 years.

8

Subject to errors due to changes in earth's magnetic field over time, but calibration (correction) curves have been developed:
a) back to 9,000 years ago (since 1972) – Ferguson bristlecone pine calibration;

b) back to 22,000 years ago (since the late 1990s) – using coral reef data;

c) back to 50,000 years ago (since 2004) – comparing dated marine layers to annual layers in Greenland ice core.

9

Sample lab date:  500 ± 50 B.P., which translates to A.D. 1400-1500.  [1950 - 500 = 1450 ± 50 BP (B.P. = Before Present which is set by convention at A.D. 1950). 

10

C14 dating can date an artifact or site to the approximate century or so.

 

Example of C14 Decay Process

14C decays into 14N + β particle

No. of Half-lives

Years Passed

% C14 Remaining

0
 (death of organism)

0

100%

1

5,730

50%

2

11,460

25%

3

17,190

12.5%

4

22,910

6.25%

5

28,640

3.125%

6

34,370

1.5+%

7

40,100

<1%

 

Importance of East African Rift Valley for Finding and Dating Fossils

1 Presence of large freshwater lakes for last 5 million years that were very favorable for human settlement.
2 Large lakes with tributary streams and rivers favored rapid burial and fossilization.
3 Tectonic movement (uplift) force rivers to downcut into strata creating river valleys and gorges; they also create titled strata  -- all provide exposures of fossils through surface erosion.
4 Numerous volcanoes associated with rift in Earth's crust have produced many  volcanic layers (tuffs and ash) that can be dated with potassium-argon dating.


Important Points About Potassium Argon Dating

1 A radiometric dating technique.
2 Based on decay of radioactive potassium K40 or 40K; decays into argon, Ar40 or 40Ar.
3 Half-life of K40 = 1.25 billion years
4 Dates volcanic sediments and tuffs only
5 Good for dating from ca. 150,000 ya to the Age of Earth or 4.6 bya.
6 Subject to error due to argon leakage in some rocks:  best to cross-check using fission track dating, paleomagnetism and faunal correlation (also known as biostratigraphy)
7

Good for dating hominid sites if volcanic sediments are present.
8 Derived technique: argon argon laser fusion dating -- involves measuring the ratio of 39Ar to 40Ar.  Can date very small samples and often samples that are less than 50-100,000 years old.   If large volcanic crystals are available, dating can be done into the historic period [e.g., dated the A.D. 79 eruption of Mount Vesuvius (Pompeii) to within 7 years!]

Cross-checking potassium argon dating

Faunal correlation or biostratigraphy uses dated paleontological sequences to cross-check other dates (e.g., the KBS tuff at East Lake Turkana) or to cross-date hominid finds (e.g., hominid remains in South African caves)

Paleomagnetism = dating method based on the shifting polarity of earth's magnetic fields, i.e., flipflopping of north and south magnetic poles

FYI:
        Brunhes Normal Polarity Chron:              780,000 ya to present
        Matuyama Reversed Polarity Chron:       2.6 mya to 780,000 ya
        Gauss Normal Polarity Chron:                   3.6 - 2.6 mya
        Gilbert Reversed Polarity Chron:              5.3 - 3.6 mya
        [These periods and dates are FYI; not needed for exam]

Fission Track Dating = based on fission tracks left behind when the uranium isotope, U-238, decays [used to confirm potassium-argon dates].

ADDITIONAL TECHNIQUES WHEN RADIOCARBON AND POTASSIUM-ARGON DATING CANNOT BE USED:

Dating Technique Dates
TL or Thermoluminescence pottery, hearth stones, heated stone tools
ESR or Electron Spin Resonance dental enamel on teeth
Ostrich Eggshell (AAR) ostrich eggshells in Africa


NEW RADIOMETRIC TECHNIQUE:  based on the effects of cosmic rays on aluminum and beryllium isotopes in miniscule quartz grains.  Used to date to sedimentary sand grains and sandstone stone tools in Zhoukoudian cave, thus redating the Peking Man fossils (2010).

 

SECTION 12 --  EARLY HOMINID EVOLUTION -- BIPEDAL APES AND EARLY HOMO

See pp. 124-135 and 208-209 in Stringer and Andrews


Basal Hominids:  Sahelanthropus tchadensis, Orrorin tugenensis, Ardipithecus ramidus

Early Australopithecines:  Australopithecus anamensis, A. afarensis (Lucy), & A. bahr-el-ghazali? AND Kenyanthropus platyops

Later Australopithecines:  A. africanus and A. garhi

Robust Australopithecines:  Paranthropus aethiopicus, P. boisei, and  P. robustus

Early Homo:  Homo habilis and Homo rudolphensis


Summary of Early Man Discoveries, 1856-2011 (for reference only)

1856 Discovery of Neandertal (formerly Neanderthal), in Neander Valley in Germany  – dismissed by some as remains of a Mongolian Cossack who died in Napoleonic Wars.
1868 Discovery of Cro Magnon site in France. Homo sapiens.
1891 Discovery of Java Man by Eugene Dubois – rejected by scientific community. Homo erectus.
1912 Piltdown Man fraud – fit preconceptions about early human – ape-like face + big brain. Not until 1953 that fraud was clearly revealed. Perpetrated by disgruntled curator of zoology, Martin Hinton.
1924 Raymond Dart discovers & names Taung baby in South Africa – Australopithecus africanus. Find rejected as not a hominid & on wrong continent. Everyone "knew" humans evolved in Asia. Brain seen as too "small".  Bipedalism before large brain did not fit then current theories of hominid evolution. 
1929 Peking Man discovered by Pei Wenshong at Zhoukoudian cave near Beijing. Homo erectus. Davidson Black was primary excavation leader in 1920s.
1930s-
1940s		 Robert Broom makes many discoveries in South Africa, at Swartkrans, Sterkfontein, and Kromdraai limestone caves, including what was to be known as Australopithecus (now Paranthropus) robustus.
Early 1940s original Peking Man & Zhoukoudian cave fossils lost! but excellent plaster casts remain.
1946 Dart vindicated – Australopithecines recognized as hominids.
1959 Discovery of Zinjanthropus (Paranthropus boisei) at Olduvai Gorge by Mary Leakey; named by Louis Leakey. Dated by potassium argon dating: 1.75 million ya!  Astonished the world.  Led to well-funded early man studies.
Early 1960s Discovery/naming of Homo habilis found at Olduvai Gorge by Louis Leakey. Violated taxonomic tradition by using behavioral criteria (presumed to make stone tools) and lower (630 cc) than generally accepted brain size (750 cc) for the genus Homo.
1960s-
1970s		 Many important discoveries made by Richard Leakey near Lake Turkana.
1970s: ---Skull 1470 (775 cc) found by Richard Leakey near Lake Turkana (Kenya). Homo rudolphensis.
---"Lucy" discovered in Hadar (Ethiopia); named A. afarensis by D. Johanson T. White.
---First Family found by Don Johanson’s team in Ethiopia
---Hominid footprints of "Lucy"-type found at Laetoli (Tanzania) by Mary Leakey.
1980s: ---Discovery of Turkana Boy by Kimoya Kimeu,R. Leakey, A. Walker. Homo ergaster.
 ---Discovery of Paranthropus aethiopicus.
1990s: ---Discovery of Ardipithecus ramidus by Tim White and Ethiopian scholars. New hominid genus.  White's relatively complete skeleton study finally published in 2009 in Science.
---Discovery of A. anamensis by Meave Leakey’s team near Lake Turkana
---Discovery of A. bahrelghazali ("River of the Gazelles") fossil by Michael Brunet in Chad, Central Africa.
---Discovery of complete A. africanus skeleton at Sterkfontein Cave, South Africa
---Discovery of two more limestone cave sites with hominid remains in South Africa:
   Gladysvale and Drimolen -- the latter produced Paranthropus robustus including the most complete female skull of this species; remains indicate it is very sexually dimorphic (males larger than females); early Homo remains have also been found.
2000-
2002		 ---Discovery of 2.5 mya remains of Australopithecus garhi in Ethiopia by Berhane Asfaw and Tim White with nearby broken animal bones and stone tools discovered by J. Desmond Clark
---Discovery of 6.2-5.6 mya hominid remains of Orrorin tugenensis in Tugen Hills, Kenya (French-Kenya team).  More hominid-looking than Lucy.
---Discovery of 3.5 mya skull of Kenyanthropus platyops ("flat face") by Meave Leakey on east side of Lake Turkana. Contemporaneous with Lucy but more hominid-looking.
---Discovery of 5.8-5.2 mya teeth & bones of Ardipithecus kadabba by Yohannes Haile-Selassie of Ethiopia.
---Discovery of 6-7 mya Sahelanthropus tchadensis (Toumai) in Chad by Michael Brunet. Its hominid status is uncertain; it may be a female gorilla.
2002-2011 ---Discovery of early Homo sapiens skulls (2 adults, 1 child) in Herto, Ethiopia dating to 160,000 ya; fills gap between earlier pre-Sapiens skulls & Homo sapiens remains dating to after 120,000 ya in Africa. Skulls slightly larger, longer and with more pronounced brow ridges than modern Homo sapiens.
---Discovery of possible new dwarf species on Flores Island in Indonesia tentatively dating to 35, 000 to 18, 000 ya; a dwarf Homo erectus-like species, Homo floresiensis.
---3.3 mya Lucy's baby -- skull and much of skeleton preserved; helps understand developmental history of A. afarensis or Lucy.
---1 mya old fossil homind jaw in Europe --oldest ever found!
---47 mya completely preserved fossil "Ida" -- transitional fossil beween prosimians and anthropoids (monkeys)
---Publication in Science about Ardipithecus ramidus as non-knuckle walker early biped with splayed big toe like an ape, yet it was bipedal
---Discovery of Australopithecus sediba in Malapa Cave in South Africa
---Discovery of mtDNA from a finger bone of a new species that was neither Homo sapiens or Neandertal, yet lived in central Asia 40,000 ya   DENISOVANS

Chronology of hominid species  -- FYI; test will emphasize points made in class.

Before hominids chimp/hominid split 6-7 mya
Set IA: Basal Hominids
 Sahelanthropus tchadensis
Orrorin tugenensis		 7-5.6 mya
 
Set IB: Basal Hominids
 Ardipithecus ramidus &
Ardipithecus kadabba		 5.8-4.4 mya
Set IIA:  Early, Primitive Australopithecus Australopithecus afarensis (Lucy) includes A. anamensis (Kenya &, A. bahrelghazali (Chad). 4.2-2.9 mya
Set IIB: Kenyanthropus Kenyanthropus platyops 3.5 mya
Set IIIA: Later, More Derived Australopithecus early gracile form:  A. africanus 3.6-2.5 mya
  later gracile form:  A. garhi 2.5 mya
Set IIIB:  Paranthropus early robust form:
Paranthropus aethiopicus		 2.5-2.4 mya
  later robust forms:
P. boisei and P. robustus		 2.3-1.0 mya (or less)
Set IV:  Early Homo
 Homo rudolphensis
&  Homo habilis		 2.5-1.45 mya
  earliest stone tools 2.5-2.6 mya
Set V:  Maturing Homo Homo ergaster
Homo erectus		 1.8 mya--600,000 ya (Europe & Africa)
1.7 mya?- <50,000 ya (Asia)

Note:  The data in this table were updated based on Klein's (1999) The Human Career, 2nd Edition, University of Chicago Press; and especially, Physical Anthropology by Stein & Rowe (2003), 8th Edition, published by McGraw Hill.  Other sources were also used.


Cranial capacities -- FYI -- test will emphasize points made in class

Chimpanzees (including bonobos) ca. 400 cc (average)
(bonobo - ca 350 cc)
Gorillas and Orangutans ca. 500 cc (average)
(orangutan - ca. 410)
Homo floresiensis ca. 380 cc (one skull); 3' tall female
Sahelanthropus tchadensis ca. 350 cc (only 1 skull available)
Ardipithecus ramidus, Orrorin tugenensis unknown
Kenyanthropus platyops ca. 350 cc (only 1 skull available)
All Australopithecines ca. 400-550 cc; up to 10% larger then apes for robust types
A. afarensis, africanus (gracile forms) & aethiopicus (early robust form) low to mid-400s cc
A. robustus, boisei (later robust forms) 500-545 cc (mean 520 cc)
Early Homo:  25% (Homo habilis) to 40% (Homo rudolphensis) larger than Australopithecines after correction for body size generally in the 600s to 700s cc; habilis is the smaller of the two


Know the FOUR hominid species found in South and Central Africa (2 each); all others are from East Africa.

What problem does the Late Miocene fossil gap in Africa (13-5 mya), especially 8-5 mya, pose for understanding early human evolution?

What are the peculiarities of the South African limestone cave sites which make them difficult to date and to interpret?

1 hominid fossils were introduced mainly by carnivores, raptors, hyenas and by erosion
2 thus, the caves are generally not sites of human activity
 3  the dissolution of the limestone by water and the subsequent collapse of cave walls and roofs has created a very complicated stratigraphy that is difficult to interpret and date;
4 much of the fossils are trapped within a cement-like limestone breccia that takes years to excavate
5 there are no volcanic deposits to date the bones; only biostratigraphy can be used, i.e., cross-dating the hominid bones by looking at the associated animal bones

 

DIVERGENCE BETWEEN CHIMPANZEE AND HOMINID LINEAGES:

The latest genetic data indicates that the Hominid lineage split from the common ancestral lineage leading to both chimps and hominids about 6.3 mya.  However, the evidence also indicates that there was interbreeding between chimps and bipedal apes until about 5.4 mya.  After that, the genetic differences between ancestral chimps and ancestral hominids was too great to permit hybridization.


 Set IA:  Basal Hominids -- see pp. 114-117 (top) in Stringer and Andrews

1 The earliest hominid's immediate ancestor was probably NOTa knuckle-walker based on the published remains of the feet of Ardipithecus ramidus in 2009.
2 Early bipedalism was probably an adaptation to the forest, not the savanna grasslands; recent data show that Orrorin tugenensis probably lived within generally forested environment 6 mya
3 Earliest hominids were probably tool users (made of wood or stone), not tool makers.  There is evidence of using animal horns or animal long bone shafts as "digging tools", especially at South African caves sites, to obtain tubers and other roots.
4 Appearance of thick dental enamel in hominid line (as opposed to thin enamel in chimps and gorillas) may be associated with eating such tubers and roots.


Sahelanthropus tchadensis (Toumai)(Central Africa: Chad), 6-7 mya.

1

New genus from Central Africa -- based on skull

2

 Some have suggested it might be a female gorilla instead of a homind.
  3  Some evidence suggests location of the foramen magnum was toward center indicating it was a hominid.  Scientists wish to find evidence from the pelvic region, leg bones and/or feet to clinch its status.  No full consensus yet.


Orrorin tugenensis (East Africa: Kenya), 6.0 mya.

1 New genus found along ancient watercourse in Tugen Hills, north central Kenya; Tugen Hills contain strata for much of the fossil gap of 13-5 mya. 
2 Orrorin is from local African language and means "ancient one" or first human. Found by Pickford and Senut in 2000.
3 A bipedal hominid based on shape of the femur, slot for muscle attachment, and variable thickness of the femur bone.  Pelvis more like human pelvis than Lucy's pelvis. Molars are  small and square like humans, whereas Lucy's molars are bigger and more elongated.
4 Presence of impalas and Colobus monkeys in the same deposit suggest bipedal Orrorin represents evolution of bipedalism in the forest or mostly forested environment.
5 Arm bone (humerus) and curved finger bones indicates it was a tree-climber like later Australopithecines.
6 Carnivore teeth marks in humerus; probably killed by a leopard
7 Back teeth are human-like teeth, whereas front teeth are more like chimp teeth. Teeth have thick enamel.  Shape of molars suggest it was an omnivore, not a folivore.
8 OVERALL, it is more modern-looking than early Australopithecines suggesting "Lucy" is not ancestral to the genus Homo as has been thought since 1970's.
9 Dated by potassium argon dating between 5.65 and 6.2 mya; the use of paleomagnetism and faunal correlation narrow it down to ca. 6 mya.
10 Film shows that bipedalism emerged with straight legs and knees, not a bent-hip, bent-knee gait; orangutan is a good model for this development.


Set IB:  Basal Hominids Cont'd:

Ardipithecus sp. (East Africa: Ethiopia), 4.4 mya and 5.2-5.8 mya

1

age determined by argon argon laser fusion dating cross-checked with paleomagnetism and faunal correlation
2 Bipedal?: yes based on location of foramen magnum, shape of pelvis, and foot bones.  Splayed big toe shows it had an ape-like big toe, but it could walk bipedally, and also quadrupedally by walking on its hands like a monkey (wrist could bend backward) -- and not like a chimp which walks on its knuckles.
3 Thin dental enamel
4 Very apelike, more primitive than "Lucy".
5 Fossil pollen & presence of Colobus monkey fossils indicate it was a forest dweller.
6 Striking in its reduced canine and splayed big toe, yet it walked bipedally.


The Australopithecines -- see pp. 68-71 and 117-129 in Stringer and Andrews

If we exclude Ardipithecus which precedes them, and include the genus Paranthropus (the robust australopithecines), there are eight species of australopithecines:  anamensis, afarensis (including bahrelghazali which is probably not a separate species),  africanus and P. aethiopicus, boisei, and robustus.  As described by Klein (1999:190-193):

"The australopithecines were all bipedal ... [which] guarantees their hominid status.  As a group they are distinguished from [the genus] Homo by small cranial capacity (roughly 400-550 cc); relatively large, prognathic (projecting) faces with apelike noses rather than typically human external ones; large posterior teeth (premolars and molars), usually with very thick enamel; and aspects of the [skeleton] that suggest an apelike ability to climb. . .

The australopithecines differed from later people not only in their morphology [form], but also in their pattern of growth and maturation and in their shared tendency to very small body size, particularly for females [e.g.,] the first permanent premolar erupted at roughly three years of age versus an average of six years in living people . . . [and] individual australopithecines probably reached sexual maturity at a much younger age than later people, and they probably did not live beyond fifty years, the approximate life span of the great apes. . . .

australopithecine females, like great ape females, did not enjoy a significant post reproductive life span.  A decade or more of female post reproductive life is a uniquely human trait that may have appeared first in Homo ergaster at roughly 1.7 my ago, in H. sapiens after 500 ka ago, or perhaps or perhaps [somewhere in] between the two. . . .

. . . . strong sexual dimorphism in the australopithecines implies an apelike social organization in which males compete vigorously for females and the sexes did not cooperate economically. . . ."

Note:  the robust australopithecines -- now placed in the genus Paranthropus -- are distinguished by a more robust skull, face, and chewing apparatus specialized for eating hard seeds, tubers and nuts.

Note: a recent study (Cameron & Groves 2004) strongly suggests that the Australopithecines probably should not be in the same genus as they are too varied in their form; the study also suggests Australopithecus africanus is the most likely candidate to have evolved into the genus Homo, but there is considerable disagreement over this.


SET IIA:  Early, Primitive Australopithecus and Kenyanthropus

Australopithecus anamensis:  4.2-3.9 mya (East Africa: West Lake Turkana), 

1 Thick teeth enamel (like Lucy) vs. thin teeth enamel of Ardipithecus ramidus
2 Not all agree it should be classified as a separate species from A. afarensis (Lucy)

Video: In Search of Human Origins, Part II (Johanson) [if time]

Australopithecus afarensis ("Lucy"):  3.9-2.9 mya  (East Africa: Laetoli,
Tanzania and Hadar, Ethiopia)

1 Very sexually dimorphic:  Males averaged 4' 10" (142 lbs), Females 3' 3" (66 lbs)!!!!
2 Apelike:
 ----Large, often pointed canines (semisectorial lower premolar)
----Parallel (U-shaped) tooth rows
----Compound sagittal/nuchal crest (cranial-neck crest)
4 Has longest arms relative to legs of any known hominid; curved hand phalanges with relatively long toes suggest climbing abilities
5 May have had strolling rather than striding walk, possibly with bent-hip, bent-knee gait; some insist it walked fully upright. Foot bones are human-like, whereas ankle-bones are chimpanzee-like
6 Left hominid footprints at Laetoli 3.5-3.7 mya (discovered by Mary Leakey); individuals were about 4' 9" and 4' 1" in height.


Australopithecus bahrelghazali:   3.5-3.0 mya  (Central Africa, Chad)

1 First early hominid found outside of East & South Africa
2 May not be separate species from Lucy


SET IIB: Kenyanthropus platyops, 3.5 mya

1 New genus as it is more human-like with flatter face & less of a brow ridge than Lucy -- suggests separate lineage leading to genus Homo, i.e.,  we did not evolve from "Lucy".
2 Strikingly similar to Skull 1470 (Homo rudolphensis), yet 1.5 million years earlier.


Set IIIA: Later, Derived Australopithecus (gracile type)

Australopithecus africanus:  South Africa, "Dart's Boy"

1 Taung baby had small brain, 405 cc, but when adult = 25% larger than bonobo.
2 Less ape-like than Lucy; less robust than later robust forms (see below); small sagittal crest in some individuals
3 Its divergent big toe and long arm length relative to leg length, indicates it was even a better tree climber than Lucy.
4 However, its slightly larger brain and reduced canines suggest it may be ancestral to Homo, but no stone tools have ever been found with its fossils.
5    Potentially complete australopithecine skeleton found embedded in cave wall; dates from ca. 3.6-2.5 mya.

What clues suggested to Dart that the Taung baby (3-4 yr old child) was a hominid? Why were Dart's explanations of the Taung baby rejected until 1946?

NOTE: Early hominids were not fully-oriented toward bipedalism: A. afarensis (Lucy), A. africanus, and Homo habilis, all show evidence for tree-climbing ability.   Longer hands, long arms, and a divergent big toe (in A. africanus skeletons) all indicate adaptations for tree climbing.


 Australopithecus garhi:   2.5 mya (East Africa, Ethiopia).

1 projecting face, fairly large front teeth and very large back teeth
2 long forelimbs (like ape) but also quite long hind limbs (like human)
3 KEY POINT: found close to animal bones butchered with stone tools-- a tool maker????


Australopithecus sediba:  1.98-1.75 mya  or ca. 2.0 to 1.75 mya, from Malapa Cave, South Africa (published in 2010)
1 Two partial fossil skeletons: an 8-13 yr old boy and a 30 yr
old woman who apparently fell to their deaths in a pit containing corpses of saber-toothed cats and other predators.
2 "sediba" means "wellspring" in the Sotho language
3  Probably descended from Australopithecus africanus
4 Height ca. 4 feet, but it is not clear if sexual dimorphism present was important.
5  Has transitional features between the Australopithecines
and the genus Homo, e.g., small teeth and modern nose; long legs and humanlike characteristics in the pelvis, but still has traits suggesting climbing in trees.
6  The researchers (L.R. Berger et al.) believe that it is
 ancestral to Homo erectus; others disagree
7    What is problematic is that it is contemporaneous with
  Homo habilis, Homo rudolphensis and Homo
  ergaster/erectus! -- so how can it be ancestral to them?

 

CLIMATIC CHANGE (3-2.5 mya)  -- this was a major period of climatic change where climates became cooler and drier in East and South Africa, leading to a mosaic of forest and savanna grasslands.  It is associated with the earliest glaciation in the Northern Hemisphere and well as the gradual creation of the isthmus of Panama land bridge between North and South America which changed ocean currents which in turn affected global climate.  Interestingly, the following occurred by about 2.5 mya:


SET IIIB: Later Derived Australopithecines = Genus Paranthropus (ca. 2.5-1.0 mya) [robust types].

Paranthropus aethiopicus (Black Skull): 2.5-2.4 mya (East Africa, Ethiopia)

1 Mosaic of primitive features of Lucy + derived features of later robust forms (see below)


Paranthropus boisei:  2.3-1.4 mya  (East Africa)
 Paranthropus robustus: 1.9-1.0 mya (So. Africa)

1 Both species have very large, broad face with massive back teeth & lower jaws with sagittal crest (males); robustus somewhat less massive than boisei.
2 Facial architecture due to specialized diet of hard seeds and nuts (large molars and microwear patterns on teeth).  Have much bigger, broader head with much larger back teeth than do the Australopithecines.
3 P. robustus MAY have had an opposable thumb needed for the manipulative skills required to make stone tools, but the thumb bone could be from a Homo erectus skeleton.  Evidence this species used bone as digging tools, perhaps to dig up tubers.
4 No evidence P. boisei ever made stone tools; P. robustus may have made bone tools.


SET IV:  Early Homo -- see pp. 130-135 in Stringer and Andrews

Early Homo: Homo habilis (2.4 - 1.45 mya) and Homo rudolphensis (2.5-1.8 mya)  East & South Africa)

1 Homo habilis  seen as tool makers at Olduvai Gorge, although "Zinj" (Zinjanthropus) found at same site
2 Homo habilis -- mean cranial capacity of 612 cc, a small body size (3-4 ft), australopithecine-like body proportions and feet adapted to climbing; however, its teeth are more like later hominids.
3 Homo rudolphensis -- mean cranial capacity of  781 cc, a larger body (up to 5 ft tall), some foot and thigh features more like later hominids; however, it had grinding teeth more like Paranthropus. Resembles Kenyanthropus platyops of 3.5 mya.
4 Those who emphasize brain and body size see H. rudolphensis as the most likely ancestor of Homo erectus (textbook's view).  Those who focus on the teeth see H. habilis as the most likely ancestor (Campbell and Loy 2000:289, 293). 
5 Early Homo: [grouping both species]:  more developed frontal lobe and no sagittal crest; less sexually dimorphic; as much as 40% larger cranial capacity than australopithecines
6 Early Homo (especially H. habilis) retains some of the climbing abilities of A. afarensis and A. africanus


Olduvai Gorge -- see pp. 68-71 in Stringer and Andrews

Olduvai Gorge has a very well documented 2 million year old geological, archaeological, paleontological, and hominid sequence developed by Louis Leakey.

Louis Leakey discovered Zinjanthropus = Africa Man.  It will later be reclassified as Paranthropus boisei. [see below]

Types of sites found at Olduvai Gorge associated with Homo habilis and/or Homo erectus: meat processing sites, quarry sites, and possible camp sites (multipurpose sites), some as old as 1.7 mya.


Diet of Early Hominids:

1 probable vegetable foods: berries, fruits, nuts, buds, shoots, shallow roots and tubers
2 probable animal foods: most terrestrial and small aquatic reptiles, eggs and nesting birds;  some mollusks, insects, and smaller mammals.


Omo River Basin in Ethiopia north of Lake Turkana: F. Clark Howell's well-dated, paleontological sequence used for cross-dating other areas.  Hominid remains mostly isolated teeth; no skulls have found.


CONTEMPORANEOUS HOMINID SPECIES (reference)

Ca. 3.5 mya A. afarensis (Lucy), Kenyanthropus platyops, A. bahrelghazali?, A. africanus? 2-4 species
Ca. 2.5 mya A. africanus, A. garhi, P. aethiopicus, and early Homo 4 species
Ca. 2.0 mya P. boisei, P. robustus?, H. habilis, and H. rudolphensis 3-4 species
Ca. 1.5 mya P. boisei, P. robustus, Homo ergaster, and Homo erectus 4 species
Ca. 130 to 30,000 ya Homo neandertalensis, Homo sapiens, the Denisovans, Homo erectus & Homo floresiensis 4 species
 (KNOW THIS)

Who is perhaps the most successful African fossil hunter of the last 30 years? Answer: Kimoya Kimeu, who works for Richard Leakey. He found the 195,000 year old Omo 1 fossil in Kibish, Ethiopia; the Turkana Boy near Lake Turkana; the tibia from A. anamensis; and many other major finds.