Option D – Evolution

D.3 – Human Evolution

http://www.youtube.com/watch?v=ErgdpG_N9vQ

http://phet.colorado.edu/en/simulation/radioactive-dating-game

http://www.elucy.org/

Species of hominid (chronological order): (A) Ardipithecus ramidus, (B) Australopithecus afarensis, (C) Australopithecus africanus, (D) Homo habilis, (E) Homo erectus, (F) Homo neanderthalensis, and (G) Homo sapiens.

Ardipithecus ramidus: 5.8 million years ago; split between organisms that are more human like and more chimpanzee like; the fossils of this organism consist mainly of teeth, so physical features are uncertain; similar to chimpanzee; the length of the molars are greater than the width; canines are shorter; bipedalism may have been possible (uncertainty of fossil record)

Australopithecus afarensis: between 4 and 2.5 million years ago; Example: Lucy, remains are 3.5 million years old; large molar teeth; higher cranial capacity

Australopithecus africanus: between 3 and 2.5 million years ago; bigger lower jaw; protecting face; higher cranial capacity

Homo habilis: between 2.4 and 1.6 million years ago; flat face; large molars; cranial capacity that allowed for simple stone tools, fire; some lived in caves

Homo erectus: between 1.8 million years ago to 100 000 years ago; smaller jaw; receding forehead; brow ridges; small molars; very large cranial capacity

Homo neanderthalensis: between 200 000 and 300 000 years ago; survived ice ages; small jaw; low forehead; small brow ridges; small molars; larger brains than modern humans

Homo sapiens: between 140 000 and 70 000 years ago; high forehead; no brow ridges; flat face; small molars; small jaw; cave paintings; tools and weapons; large cranial capacity; similar to modern humans

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

Several species of hominid may have co-existed at the same time:

Homo habilis may have co-existed with various species of AustralopithicusHomo neanderthalensis likely co-existed with Homo sapiens

http://en.wikipedia.org/wiki/Homo_floresiensis

Incompleteness of the Fossil Record- Fossilisation is an exceptionally rare occurrence that requires an unusual combination of special conditions- Most living things tend to decompose rapidly (or be scavenged) following death- Fossilisation tends to favour hard body parts (bone, teeth, shells, etc.) and exposed fossils will soon be weathered / destroyed- Only a small percentage of fossils have been discovered - fossilisation favours species that were long-lived and widespread

Significance of Incompleteness of the Fossil Record- Individual fossils may not be representative of species (e.g. Homo floresiensis - 'Hobbit' man)- Very few complete skeletons have been discovered, and so paleoanthropology is an inductive (data-poor) science- Many conclusions have been drawn on limited data and are frequently re-interpreted in the light of new discoveries

So, overall, to put it in “plain terms”…

A change in habitat in Africa ~2.5 million years ago may have prompted the emergence of Homo species from forest to savannah

This necessitated a change of diet to include meat (more protein), which increased the skull capacity and brain size of hominids

Improved diet quality provided energy to support greater brain function and learning capacity (positive correlation)

Activities resulting from improved cognition (such as group hunting and cooking food) enabled hominids to eat a wider variety of food

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

Changes in genotype (genetic evolution via natural selection) have lead to cultural evolution in humans by promoting intelligent behaviour:

Larger brain sizes have promoted increased learning capacity / greater cognitive ability

Prolonged gestations have promoted social interaction / familiy networks

Bipedalism has promoted extensive migration and improved socialisation tendencies

Shorter finger bones and reduced reliance on forelimbs for locomation have promoted increased tool manipulation

Evolution of culture (e.g. art, science, language) has been more rapid and recent than genetic evolution (which requires many generations)

Further cultural evolution (through genetic engineering) may hasten changes in our genetic evolution

Certain products of cultural evolution (e.g. medicines) may reduce genetic evolution via natural selection

Other products of cultural evolution (e.g. pollution) may increase genetic evolution (increased mutagenic rate)