2 methods dating fossils
Once multicellular organisation became possible as atmospheric oxygen levels rose, the early multicellular organisms rapidly diverged into many adaptive forms.
Mass extinction events and an organism's unique adaptations mark the history of evolution, both of which may lead to adaptive radiation.
Carbon combines with other elements in complex ways to form the molecules that make up our bodies.
Most carbon on Earth is not radioactive, but a very small percentage is.
Thus, as living things take in carbon, they inevitably will take up a small amount of radioactive carbon into their bodies.
When these lifeforms die, they stop taking in new carbon.
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I have integrated this web page on human evolution into an electronic text, " Nature's Holism - Holism.
Ernst Mayr reduced all the hominid (human ancestor: (see hominid books)) fossil records to three species, A.
The carbon in their bodies at the time of their death will remain in their bodies until they decompose, or if they become fossilized, then forever. This allows scientists to look at the amount of decay in a fossil’s radioactive carbon and determine a relative date.
Radiocarbon dating is only effective for objects and fossils that are less than 50,000 years old.
 Natural selection, gene flow and random genetic drift (the random change in gene combinations with each generation) drive evolution, resulting in a change in gene frequencies within populations .
 Adaptation is genetically based and so leads to phenotypic changes that accumulate over time;  Speciation (species formation) evolves through reproductive isolation and (genetic) divergence of populations;  Genetic changes through natural selection lead to new species and eventually new taxa .