One radioisotope used for the dating of rocks and fossils
The half-lives of several radioactive isotopes are known and are used often to figure out the age of newly found fossils.
Different isotopes have different half-lives and sometimes more than one present isotope can be used to get an even more specific age of a fossil.
This technique relies on the property of half-life.
Half-life is defined as the time it takes for one half of a radioactive element to decay into a daughter isotope.
erectus: .4 - 1.8 million years – more complex tools so meat significant part of diet and changed teeth. neanderthensis .5 million years – larger brains and bones, larger teeth and jaw, shorter limbs for the cold H. If q = frequency of t allele, q squared = .288 so q = .537 If p = frequency of T allele, p = (1 - q) = .463 The frequency of homozygous dominants (TT) and heterozygotes (Tt) can be calculated.
By measuring the ratio of the amount of the original radioactive element to the daughter isotope, scientists can determine how many half-lives the element has undergone and from there can figure out the absolute age of the sample. afarensis: 3 - 3.9 million years – ape-like face A.