Radioactive decay dating

14 Apr

Gregory Brennecka of Arizona State University and colleagues measured the relative amounts of Uranium 238 to Uranium 235 from several samples taken from the large Allende meteorite, named for the village in Mexico near where it landed in 1969.With the more sensitive instrument, they detected small differences in isotope ratios from different inclusions within the same meteorite..For organic materials, the comparison is between the current ratio of a radioactive isotope to a stable isotope of the same element and the known ratio of the two isotopes in living organisms.Radiocarbon dating is one such type of radiometric dating.Even the solar system has been dated using one of these systems, by measuring the amount of a decaying element and comparing it to the amount of its stable (decayed) daughter material in meteorites.However, a recent analysis using state-of-the-art equipment found that a basic assumption underlying one of these clock systems needs to be re-evaluated.It could be another nail in the coffin of the stereotyping of Neanderthals as “dumb,” Zilhão says.

Part 1 (in the previous issue) explained how scientists observe unstable atoms changing into stable atoms in the present.There's a small amount of radioactive carbon-14 in all living organisms.When they die no new carbon-14 is taken in by the dead organism.In three cases, the art was dated to between 35,600 and 40,800 years ago.Neanderthals were definitely present in Europe during this era, whereas modern humans likely appeared around 41,000 to 42,000 years ago, says João Zilhão, a Neanderthal expert at the University of Barcelona, who was involved in the study.