Notes for lecture given 2001.04.19 in Jonathon Lunine's undergrad class
Read chapter 20 in textbook. I found http://www.becominghuman.org and http://www.mnh.si.edu/anthro/humanorigins/faq/Encarta/encarta.htm helpful resources.
Recent Nature Article
http://www.nature.com/nature/archive/, select March 22, 2001 issue (use username "withers" and password "withers" if needed). Read the News and Views article about "Another face in our family tree." Full reference: Nature (2001) volume 410, page 419 - 420.
What is a human?
- Kingdom: Animalia
- Phylum: Chordata
- Subphylum: Vertebrata
- Class: Mammalia
- Subclass: Theria
- Infraclass: Eutheria
- Order: Primates
- Suborder: Anthropoidea
- Superfamily: Hominoidea
- Family: Hominidae
- Genus: Homo
- Species: sapiens
Keep it simple, stupid
- Order: Primates
Anything monkey-like
- Family: Hominidae
Modern humans, early humans and some monkeys
- Genus: Homo
Modern humans and some early humans
- Species: sapiens
Modern humans
What is a primate - Behaviour?
many generalized mammalian characteristics rather than specialized
adaptations to narrow niches; basic arboreal adaptation, especially to
tropical forests, although some species have become terrestrial;
excellent manual dexterity; well developed sense of sight; good hand-eye
co-ordination; cerebral cortex highly organized, involving a dependence
upon learned behaviour; long infant dependency periods; complex social
organizations.
What is a primate - Behaviour?
- Good with hands
- Good with eyes
- Good with trees
- Dumb kids
- Good at parties
What is a primate - Anatomy?
- hands: prehensile with opposable thumbs; tactile pads and nails on
fingers and toes;
- adapted for precision grip; facilitating feeding and locomotion in the
trees; mobile arms: posture frees arms and hands for grasping;
- eyes: binocular vision; colour vision; skull contains post-orbital bars
for protection of eyes; development of visual organs is achieved at the
expense of olfactory organs;
- face: large eyes and brain and reduced snout area;
- large brains: especially in cerebral cortex;
bear single offspring.
What makes a human human?
Grossly summarizing, a human is a primate that walks on its hindlimbs. I
shall call any ancient, extinct primate that walked on its hindlimbs
human. Our species, Homo sapiens, are humans. There are other extinct
human species, but no others that are alive today.
Where do we fit in?
http://www.umanitoba.ca/anthropology/courses/121/pritax.gif from http://www.umanitoba.ca/anthropology/courses/121/taxonomy.html
We share 98% of our DNA with gorillas and chimps. This makes us as similar as grizzly/polar bears or horses/zebras. DNA mutation rates suggest that humans, gorillas, and chimps had a common ancestor 5 - 10 Mya.
Geological Time
http://www.kingston.ac.uk/~kx08126/gifs/timescale.gif from http://www.kingston.ac.uk/~kx08126/tscale.htm
The Earth 5 Mya
http://www.ucmp.berkeley.edu/cenozoic/tertiary.gif from http://www.ucmp.berkeley.edu/cenozoic/cenozoic.html
- No large movement of tectonic plates.
- Ice ages, mile-high ice sheets, changing sea levels, ocean and
atmospheric circulation, rapid changes in environments.
Family Tree
http://www.mnh.si.edu/anthro/humanorigins/ha/images/bigtree2.GIF from http://www.mnh.si.edu/anthro/humanorigins/ha/a_tree.html
The first human
- Appears in Africa 4.5 Mya, when Earth is 99.9% as old as it is today.
- Several species of the genus Australopithecus live and die in Africa. And
Africa alone. An offshoot genus, Paranthropus, did much the same. The
genus Homo, to which we belong, first appears in Africa about 2.5 Mya.
What's going to change by next semester?
- Lots!
- Fossils will get reclassified into different species or genera
- New species will be discovered
- Which species is descended from which other species
- Exactly where and when species lived
- Exactly which species we are descended from
What's not going to change by next semester?
- There were several apelike human species a few Mya
- Old species died, new species appeared
- Some lucky Australopithecus species became the first Homo species
- Several Homo species existed, one of which became us.
Africa and the Great Rift Valley
http://users.hol.gr/~dilos/prehis/Mpafrica.jpg from http://users.hol.gr/~dilos/prehis/prerm3.htm
Australopithecus
Fossils of several species of this genus have been found. A few hundred
people in all. We shall skip over the differences between all these
species. They are classified as early humans rather than apes due to
their small canine teeth and thick leg bones and other adaptations for
walking. Species are distinguished by properties such as size of earhole,
development of molars and cheek muscles (grinding, chewing, cutting),
enamel coating on teeth
Lucy
- The most complete (40%) Australopithecus skeleton
- Found November 30, 1974, in Ethiopia by someone now at ASU
- About 3 feet tall, 65 pounds, fully grown
- Walked upright
- Named after "Lucy in the Sky with Diamonds"
Lucy's Bones
http://www.wsu.edu:8001/vwsu/gened/learn-modules/top_longfor/timeline/afarensis/images/afarensis-three-skeletons.jpeg from http://www.wsu.edu:8001/vwsu/gened/learn-modules/top_longfor/timeline/afarensis/afarensis-a.html
Lucy 2
http://www.angelfire.com/mi/dinosaurs/images/afar/lucyfarside.jpg from http://www.angelfire.com/mi/dinosaurs/lucy.html. This looks like a Larson Far Side cartoon of Peanuts's Lucy fossilized in rock, the link is unreliable.
Laetoli Footprints
http://www.getty.edu/conservation/resources/newsletter/10_1/images/p15.jpg from http://www.getty.edu/conservation/resources/newsletter/10_1/laetoli.html
Footprint closeup
http://www.mnh.si.edu/anthro/humanorigins/ha/images/laetoli1.jpg from http://www.mnh.si.edu/anthro/humanorigins/ha/laetoli.htm
Human Footprints
3.6 Mya a volcanic eruption in Tanzania covered the landscape with
volcanic ash. Rain fell, cooling the ash and making it like plaster.
Animals walked across this gooey plaster, which later solidified into
volcanic cement, preserving their footprints. Humans (Australopithecus)
walked here. They walked upright.
The genus Homo
- A good marker for apemen turning into men
- Appears 2.5 Mya in Africa
- Brain volume larger than a pint, larger than 500 cc
- Possible first toolmaker (but story is complicated)
- Beginning of the Stone Age
Skulls
http://abcnews.go.com/media/science/images/hominid_timeline.gif from http://abcnews.go.com/sections/science/DyeHard/dye990113.html
Also good images of skulls at http://www.umanitoba.ca/faculties/arts/anthropology/courses/121/fyde/session8.html, http://www.anth.ucsb.edu/projects/human/, and http://cgi.pbs.org/wgbh/aso/tryit/evolution/
Why does Homo appear?
- Environmental change in Africa, becoming cooler and drier
- Environmental fluctuations increase
- Sophisticated tool users are better equipped to survive changes in food
supply
- All this is speculation
Homo Habilis and Tools
- Eastern and southern Africa 1.5 - 2 Mya
- Made tools by hitting rocks together
- Used tools to cut, bash, and whittle
- Cut meat from carcass, bash marrow from bones, whittle sticks into
digging tools
Homo erectus
- Appears in Africa 2 Mya and spreads into Asia and Europe within a few
100,000 years
- One mile every generation
- Large (two pint) brain size
- Well adapted for walking
- Why the migration?
What happens next?
- Limited genetic interaction between continents
- Regional differences appear in the species (race?)
- Are the different groups evolving into different species, or are the
regional differences being passed into other groups quickly enough to
keep a single species?
Multiregional Theory
Separated groups of Homo erectus developed over 1 My into Homo sapiens
with just the right amount of mixing to stay a single species but
maintain regional differences (ie race). Racial differences between
present day humans originate more than 1 Mya. Helps explain physical
similarities between East Asian Homo erectus and East Asian Homo sapiens.
Doesn't fit the (currently favoured) punctuated equilibrium model for
evolution.
Replacement Theory
- Homo sapiens appeared relatively recently in a geographically small
region, then took over the world from Homo erectus. Racial differences
date from the (recent) appearance of Homo sapiens.
- Favoured by DNA evidence (and the professor)
DNA Evidence
- Mitochondrial DNA comes from mother and mother alone
- Only change from mother to child is due to copying mistakes and other
mutations
- More diverse mtDNA in a group implies longer since a common mother
- Homo sapiens mtDNA has a common mother about 200,000 years ago
Homo sapiens
- Us
- Distinguished from other Homo species by some skull characteristics.
- First strong evidence of language, art, and religion is in this species
(about 50,000 years ago)
- Appears in southern and central Africa 130,000 years ago then spreads
around the entire globe
- Has even been to the Moon