Final Exam Flashcards
Fossilization Process
calcium/phosphate in bone -> rock forming minerals (iron/silica). 1. death and soft-tissue decay. 2. Skeleton is covered by lake sediments. 3. Rock-forming minerals from water begin to replace calcium-phosphate of bone. 4. Skeleton fossilizes as lake sediments continue to be deposited as layers. 5. Erosion exposes the deep strata in which fossil is located. 6. Excavation and analysis by physical anthropologists
Mineral Composition of bone
65-75% mineral
Mineral Composition of teeth
97% mineral
Ideal Environments for Fossilization
remains covered soon after death, protection from scavengers, oxygen-free environment limits decomposition, avoid acidic groundwater/soils that dissolve bone/teeth
Morphological species concept & how it’s used to group fossil species
Assuming that species look similar because they share genes. Gene exchange->species->similarity and vice versa.
Risks of defining paleospecies
allometry-study of the change in proportion of various parts of an organism as a consequence of growth. sexual dimorphism-morphologically different fossils may be male and female examples of the same species. interspecies variation- interbreeding-capable individuals may look different due to environmental adaptations, random variations, or trauma.
Gradualism
Darwin’s theory that species are constantly and slowly changing, and that these changes eventually “add up” to a new species. ex: human evolution
Punctuated Equilibrium
Stephen Gould’s theory that species are not changing very much. They rapidly evolve into new species in short periods of time. Species suddenly exposed to very different environment. Mutations for very different phenotypes are suddenly spread by natural selection. “The Cambrian Explosion”- huge increase in diversity in a short amount of time.
Law of Superposition
Nicolaus Steno- the lower the layer of rock, the earlier in time it was deposited. Lower fossils are older.
Disturbances to superposition
Erosion. Intrusion.
Relative Dating
what is the order of the fossils? Based on the relationship with fossils or other artifacts
Stratigraphic Correlation
Order of layers determined by looking at many sites. Paraconformity- a layer representing time was eroded away or not deposited at a site
Biostratigraphy
Index fossils- known dates. First and last appearance and/or morphological change. Rock containing an index fossil must fall within that range.
Cultural Dating
material culture produced by humans also has known date ranges. Rock contains artifact= falls within date range of that artifact.
Absolute Dating
What is the approximate age of a fossil? Does not require other fossils.
Radiometrics
isotope- atoms with a different number of neutrons (carbon 12, carbon 13). Half-life- how long it takes for 1/2 of the radioisotopes in a substance to decay
radiocarbon dating
Carbon-14 Dating. organic material absorbs carbon-14 by breathing small amounts of atmospheric C02. We know original C14 to C12 ratio at death: same ratio in atmosphere and living things. Compare specimen to original ratio and see how much C14 has decayed. Useful for dating materials 50,000 yBP to 1950 AD
potassium-argon dating
Potassium bearing minerals. Igneous rock= argon gas driven off by volcanic heat. All K-40 solid -> All Ar-40 gas: Proton -> Neutron, half life of 1.3 billion years, rocks older than 200,000 years
argon-argon dating
K-39 appears in same amount in igneous rock as K-40. Also 1.3 billion year half-life. Nuclear reactor bombards K-39 with neutrons, converts it to Ar-39, Measure Ar-40 to Ar-39 ratio. Advantages: less rock needed. Don’t need to measure potassium.
Fission track dating
Uranium 238 splits and leaves tracks on rock crystal. Uranium-bearing minerals. Laser measures uranium content. Equation with how much of this Uranium has split = age. Half-life of 4.5 billion years. Date rocks up to 3 mya
dendrochronology
temperature/cold regions. Growth stops in winter, leaves a ring. One ring= one year. requires excellent preservation of tree sections. Date between 12,000 to 8,000 years ago.
paleomagnetic dating
Random reversals of the Earth’s magnetic field. Normal vs reversed North-South polarity. Metal grains align with magnetic field as they settle into sedimentary rock. Banding pattern matched fossil collection. Date sedimentary rocks younger than 5 mya.
genetic dating
molecular clock- rate of mutation in DNA for a species. # base pairs mutated per 1 million years. Number of differences between a species- years since those species diverged.
radiometric techniques-
use radioactive decay
non-radiometric techniques
do not use radioactive decay
Hominidae
Great apes, humans, and ancestors
Hominini
humans and human ancestors. Different from apes: oblige bipeds, non-honing chewing complex, significant brain size increase, complex culture, speech
Origins of bipedalism
foramen magnum: more anterior (bottom of skull) on biped, more posterior (back of skull) on quadruped. Vertebral column: S-shaped in biped, C-shaped in quadruped. Vertebrae: Larger at bottom in biped, same size in quadruped. Angle of femur: biped has values knee with more than 90 degree angle, quadruped has varus knee with a 90 degree angle to femur. Acetebelum: larger in bipeds. Bipeds have short, wide pelvis, quadrupeds have a long narrow one. Bipeds have longer legs than arms, quadrupeds have arms slightly longer than legs. Bipeds have an adducted hallux, quadrupeds have an abducted (opposable) hallux. bipeds have double arched feet, quadrupeds only have a transverse arch.
Quadrupeds have more curved phelanges than bipeds.
Darwin’s hunting hypothesis
bipedalism was naturally selected so humans could carry tools and weapons for hunting. Problem: hunting and tools appeared much later than bipedalism
patchy forest hypothesis
savannah like environment at end of miocene caused loss of food. Bipedalism allowed humans to travel further and become more energy efficient.
thermoregulation hypothesis
stand upright= less exposure to solar regulation, wind blows heat off head. Regulation of body temperature. Problem: less useful in woodlands where humans first evolved.
male provisioning hypothesis
males provide food and resources for females. bipedal= male can carry food back to offspring while mother cares for children. Problem: assumes monogamous pairs occurred before bipedalism.
Brain evolution
larger brains evolved along with complex speech and fine motor skills