Introduction to Archaeology and Palaeoanthropology:
Humanity's Journeys
Dr. Kathryn Denning
Anth 2140, Sept 2005 - Apr 2006
8 Nov 2005... Welcome!
Plan for the day
1 Course business/ announcements...
2 Evolution, primates and early hominids - mostly review
Schedule
For today/tomorrow, catching up and reviewing: KIT: Macroevolution and the Early Primates, Something New and Different, and Cat in the Human Cradle. FAGAN Ch 8 Human origins.
Previous tutorial, Nov 2: Video: The Story of Lucy (about palaeoanthropology and Australopithecus afarensis) - if you missed it, pick up a handout.
See revised reading schedule. Next week: more human ancestors.
Quiz 2 will be held in tutorial tomorrow, on Weds Nov 9: Review guidelines are posted here. NOTE! This is Quiz 2 of 6. The best 4 of 6 quizzes will count. It's a good idea to try to do as well as possible on every quiz.
The big picture: where do humans and primates fit in the biological world?
Basic terms
| GENE Portions of DNA molecules that direct the synthesis of specific proteins |
| ALLELE Alternate forms of a single gene |
| GENOME The complete structure sequence of DNA for a species |
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POPULATION In biology, a
group of similar individuals that can and do interbreed
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| MUTATION Chance alteration of genetic material that produces new variation |
| GENETIC DRIFT Chance fluctuations of allele frequencies in the gene pool of a population |
| GENE FLOW The introduction of alleles from the gene pool of one population into that of another |
| NATURAL SELECTION The evolutionary process through which genetic variation at the population level is shaped to fit local environmental conditions OR the evolutionary process through which some factors in the environment exert pressure, favoring some individuals over others to produce the next generation |
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| CONVERGENT EVOLUTION process by which unrelated species develop similarities to one another |
ADAPTIVE RADIATION A burst of evolution, when a single species fills a number of ecological niches, resulting in several new forms
REMEMBER, on the macroevolutionary scale:
The video, Extinction! - on course of evolution over the last 250 million years, including significant extinction events (major moments in evolutionary history).
- significant interruptions to the development of life
- pattern of extinctions and then adaptive radiations
Timeline: Brief history of Life:
Flash: http://www.pbs.org/wgbh/nova/link/history.html
NonFlash: http://www.pbs.org/wgbh/nova/link/hist_nf.html
Fun link: Play the evolution game, here - demonstrates how environmental changes affect population survival http://www.pbs.org/wgbh/nova/link/evolution.html
History of Life on Earth... the anthropocentric version!
n.b. dates are approximate... but not too approximate! Extinctions in yellow.
| ERA | PERIOD | EPOCH | EVENT |
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Paleozoic Era
570 - 225 mya |
Cambrian | late Cambrian extinction | |
| Ordovician | first fishes (ext) | ||
| Silurian | first jawed fishes | ||
| Devonian | first amphibians | ||
| Carboniferous | first reptiles | ||
| Permian | mammal-like reptiles end Permian extinction - 96% | ||
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Mesozoic Era 225 - 65 mya |
Triassic | egg-laying mammals [ext] | |
| Jurassic | Great Age of dinosaurs | ||
| Cretaceous | placental mammals*,
first modern birds [end - ext, 85%] |
* Mammals generally differ from reptiles in these ways: bigger brain (more flexible behaviour, learning), slow growth, live young (not eggs), with lots of development in utero for the placental mamals, heterodont dentition (incisors, canines, premolars, molars, lots of functions), endothermic (maintain body temp through metabolism, not just behaviour)
| ERA | PERIOD | EPOCH | EVENT |
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Ceno-zoic Era 65 mya - now |
Tertiary | Paleocene 65 mya | |
| Eocene 55 mya | earliest definite primates * [ext] | ||
| Oligocene 34 mya | anthropoid (monkey) radiation | ||
| Miocene 23 mya | hominoid (ape) radiation | ||
| Pliocene 5 mya | hominids (human-like)
including:
Older genera 7-4.4 mya: Sahelanthropus Ardipithecus Orrorin
Early Australopithecines A. afarensis 4.2-3 mya
Later Australos 2.5-1.4 mya A. africanus, robustus, garhi
Early Homo 2.4-1.8 mya H. habilis
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| Quat-ernary | Pleistocene 1.8 mya | Homo erectus (leaves
Africa)
Homo ergaster Homo sapiens Homo sapiens neanderthalensis |
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| Holocene 0.01 mya = 10 000 ya |
[ext]
Homo sapiens sapiens (us) |
* Primate radiation - at the earliest emergence of primates, the environment may have favoured those with good vision and mobile hands because of visual predation, arboreality, association with angiosperms (flowering plants)
Taxonomy: remember, taxonomy is trying to organize diversity, but also show evolutionary relatedness. Taxonomies are often debated as new evidence (DNA or anatomical or fossil) comes to light.
Taxonomic category Category to which humans belong
Kingdom ................. Animalia
Phylum ................. Chordata
Subphylum ................. Vertebrata
Class ................. Mammalia
Order ................. Primates
Suborder ................. Anthropoidea
Superfamily ................. Hominoidea
Family ................. Hominidae
Subfamily / tribe ................. Homininae
Genus ................. Homo
Species ................. sapiens
Suborders: prosimians and anthropoids
Infraorders: lemurs, lorises, tarsiers, platyrrhines (NW), catarrhines (OW)
Superfamilies: ceboids, cercopithecoids, hominoids
Families: cercopithecids (OW monkeys), hylobatids (gibbons), pongids (apes), hominids (us)
Genus: Pongo (orangutan), Gorilla (gorilla), Pan (chimpanzees and bonobos), and Homo.
Note the suffixes: oid, id, ine.... ine being the most specific. So we're hominoids, hominids, and hominines
So, we are.... Primates, anthropoids, catarrhines, hominoids, and hominids
Reviewing key points about our primate cousins -- i.e., the extant nonhuman primates
- are found in Old World and New, but apes are only in the Old World - Africa and SE Asia
- main features include
Limbs/Locomotion - tendency toward erect posture;hands and feet prehensile with five digits, opposable thumb, nails, and tactile pads; a flexible/generalized limb structure permitting different modes of locomotion, e.g. brachiation, arboreal, quadrupedal, vertical clinging/leaping... each of these has skeletal specializations
Diet and teeth - not too specialized (compared to, say, a cow), generalized dentition; but n.b. though omnivorous and will eat anything, primate species do tend to rely on fruit or leaves or bugs or seeds
Senses and brain - heavily visual, decreased sense of smell, most with colour vision, all with stereoscopic vision (good depth perception), expansion and increased complexity of brain
Maturation, learning, behaviour - small numbers of offspring, long gestation, delayed maturation, long life span; greater dependency on flexible, learned behaviour; tendency to life in social groups including adult males; tendency to diurnal activity
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Characteristics of primates, compared to
other mammals Tendency towards erect posture Flexible, generalized limb structure (allowing varied locomotion) Hands / feet: prehensile, with five digits, opposable thumb, partially opposable big toe, usually nails instead of claws, tactile pads Lack of dietary specialization Generalized dentition Senses: heavily visual – most have colour vision and stereoscopic vision, decreased sense of smell, large and complex brain Maturation/learning/behaviour: long gestation, small number of offspring, dependence on flexible/learned behaviour, live in social groups with adult males, tend to be diurnal |
Traits of anthropoids (monkeys/apes/humans), compared to prosimians Larger body size Larger brain size Reduced sense of smell More reliance on vision More colour vision Back of eye socket formed by a bony plate Blood supply to brain different Fusion of two sides of the mandible at the midline Less specialized dentition Female reproductive anatomy different Longer gestation and maturation, more parental care More mutual grooming
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Traits of hominoids, compared to monkeys Larger body size Absence of a tail Shortened trunk Shoulder joint adapted for suspensory locomotion More complex behaviour More complex brain and cognitive abilities Increased period of infant development and dependency
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The four criteria generally used to assign a
fossil to the genus Homo
absolute brain size of 600 cc possession of some language, identified from casts of the brain patterns on the inside of the braincase the possession of a modern, humanlike precision grip and an opposable thumb the ability to manufacture stone tools
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Reviewing key points about primate behaviour and what it can teach us
- behaviour is tremendously diverse
- can teach us about primates for their own sake
- can teach us about our own general primate heritage -- but beware of 'shopping' for primate evidence to support theories about human behaviour. (e.g. that we're naturally aggressive, naturally peaceful, naturally in nuclear families, that males naturally do this while females naturally do that, etc.) The evidence must be weighed very carefully. No easy answers.
- also be aware if searching for specific characteristics that make humans different from other primates -- for most, there are exceptions! Usually a matter of degree. (e.g. language, culture)
- ethical issues include rights/protections in captivity and research, severe endangerment in the wild
Some key points about evolution in general
- genes can have more than one version [alleles] which account for much variation in a population. Some traits are Mendelian, i.e. the result of different alleles at one gene location. Some traits are polygenic, i.e. resulting from the action of more than one gene.
- genetic variation is produced and redistributed by mutation, gene flow, genetic drift (including founder effect), and recombination.
Then natural selection, sexual selection, etc. act upon that variation.
- we can trace inheritance through studies of mitochondrial DNA (mother) and nuclear DNA (both sides)
- overall, evolution works through many mechanisms, not just natural selection... e.g. macroevolutionary processes involve extinctions
- beware of simple evolutionary explanations for behaviour. It isn't always straightforward. In primates, behavioural plasticity is a result of genes/anatomy. Dependence of young is a result of anatomy. But there are a lot of different ways behavioural plasticity can be expressed, and many different ways to handle the dependence of young. Huge variability.
To proceed with studying hominid evolution, we need to know our way around the skeleton.
Orienting ourselves anatomically
Some key features on a human skeleton: frontal, parietal, mandible, maxilla, occipital, clavicle, ribs, humerus, femur, foramen magnum, incisors, canine, premolars, molars
A few key principles about hominoid & hominid evolution
challenges include these:
When we’re studying fossils: We have to contend with infrequent fossilization, fragmentary remains and the challenges of taphonomy (the changes that occur to organisms or objects after being buried or deposited), including scattering of remains, exposure to the elements, etc. Have to consider why things are found together (deliberate deposition, accidental coincidence, etc.)
- fragmentary, damage, infrequent fossils, often without a population for comparison
- this means there's a lot of room for differences of opinion (and ego), and different names for the same fossil
- dating can be a challenge
- new finds rewrite the taxonomies, quite often
Becoming Human (Flash) http://www.becominghuman.org/
(Anatomy... hominid profiles)
Hall of human ancestors (QVTR) http://www.mnh.si.edu/anthro/humanorigins/ha/ances_start.html
Human evolution: the fossil evidence in 3D - Shockwave
http://www.anth.ucsb.edu/projects/human/#
Hominid Timeline.... from Fagan book see pp 219.....