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OPTION D3: Human evolution [6h]
SL/HL—CORE
SYLLABUS OVERVIEWMEN

D.3.5 Outline the trends illustrated by the fossils of:

Ardipithecus ramidus,

Australopithecus including A. afarensis and A. africanus, and

Homo including H. habilis, H. erectus, H. neanderthalensis and H. sapiens.

Knowledge of approximate dates and distribution of the named species is expected.
Details of subspecies or particular groups (Cro-Magnon, Peking, and so on) are not required.


D.3.6 State that, at various stages in hominid evolution, several species may have coexisted.

An example of this is H. neanderthalensis and H. sapiens.

D.3.7 Discuss the incompleteness of the fossil record and the resulting uncertainties about human evolution.

Reasons for the incompleteness of the fossil record should be included.

TOK:
Paleoanthropology is an example of the diverse aspects of science, in that it is a data-poor science with largely uncontrollable subject matter. Paradigm shifts are more common in a data-poor science. The discovery of small numbers of fossils has caused huge changes in theories of human evolution, perhaps indicating that too much has been constructed on too little. Conversely, discoveries such as those made in Dmanisi, Georgia provide examples of falsification of earlier held positions, indicating why paleoanthropology can be considered a science.

D.3.8 Discuss the correlation between the change in diet and increase in brain size during hominid evolution.


D.3.9 Distinguish between genetic and cultural evolution.


D.3.10 Discuss the relative importance of genetic and cultural evolution in the recent evolution of humans.


TOK:
This is an opportunity to enter into the nature/nurture debate. There is clear causation when a genetic factor controls a characteristic. Cultural factors are much more complex, and correlation and cause are more easily confused.

 

D.3.1 Outline the method for dating rocks and fossils using radioisotopes, with reference to 14C and 40K. Knowledge of the degree of accuracy and the choice of isotope to use is expected. Details of the apparatus used are not required.

D.3.2 Define half-life.


D.3.3 Deduce the approximate age of materials based on a simple decay curve for a radioisotope.
D.3.4 Describe the major anatomical features that define humans as primates.


PRIMATE DIAGNOSTIC FEATURES


Generalist mammals adapted to arboreal life.
Nails on hands and feet rather than claws.
Trend towards a flatter face as vision becomes more important than olfaction.
Stereoscopic (binocular) and color vision.
Trend towards holding torso upright.
Comparatively large brain.
Comparatively long gestation, infancy, childhood and lifespan.
Social.

Sensitive, manipulative hands with some thumb opposability.

 

Human Origins at the Smithsonian

The BBC on Neanderthals

New York Times artcle on DNA and Neanderthals

TED talk by Robert Sapolsky on Human Uniqueness

 

 


CACTUS VS. BUSH

The late American palaeontologist Steven Jay Gould wrote a classic essay in 1977 in which he predicted that the hominid family tree would prove to be “bushy.” Today, it is common to see lists of more than 25 different hominid species, and Gould’s prediction is often declared to be fulfilled.

Not so fast. Many of these species are “chronospecies,” which evolve from one to the other, such as the earliest two Australopithecus species, A. afarensis and A. anamensis. These names are merely arbitrary divisions of a single evolving lineage. not a bush but something like a saguaro cactus, with only a few branches or species lineages.

Indeed, the greatest diversity among hominid species appears to be at around 2 million years ago, when as many as four different lineages “briefly” co-existed in Africa. The key question turns out to be not how many species there were per se, but rather why species diversity has been so limited on our branch of the evolutionary tree compared with other mammals like fruit bats or South American monkeys? The reason is probably that our ancestors’ niche kept broadening, as a woodland omnivore 6 million years ago expanded ecologically into more open environments, and then again as technology further extended its capability and horizons.

 

 

 

Reconstruction of the “gracile” A. afarensis [left]and the “robust” A. boisei [right]

HUMAN DIAGNOSTIC FEATURES AND TRENDS

PRIMATE ROOTS at the Homo discens website

  1. Bipedalism: evidenced by angle of femur and downward position of the foramen magnum at the base of the skull
  2. Reduced canines and tooth enamel. Crescent shaped rather than parallel arrangement of teeth in the mandible
  3. Increased cranial capacity
  4. Neoteny: the retention of child-like primate features
  5. Technology, hunting, fire-use, culture, ritual and language

 

ROBUST FEATURES—Australopithecus boisei
“ARDI”—Ardipithecus ramidus found in a woodland habitat

Homo neanderthalensis

Debate about whether Neanderthals were ancestors or cousins persisted for decades, but fossil discoveries and genetics have finally solved this problem. Early anatomically near-modern and modern people lived in Africa long before the Neanderthals perished about 35,000 years ago. Genomic studies suggest that there was possibly slight interbreeding between them, with leakage--of at most a few per cent--of genes from Neanderthals into human populations.They were our evolutionary close cousins, but the equivalent of a separately evolving species.

 

BECOMING HUMAN: INTERACTIVE TIMELINE AND DOCUMENTARY FROM THE UNIVERSITY OF ARIZONA
NAMED SPECIES APPROXIMATE DATES CRANIAL CAPACITY UPRIGHT
POSTURE
DISTRIBUTION TECHNOLOGY
Ardipithecus ramidus          
Australopithecus afarensis
         
Australopithecus africanus          
Homo
habilis
         
Homo
erectus
         
Homo neanderthalensis          
Homo
sapiens
         
Pdf. TABLE AND SOLUTION