INVESTIGATING GENESIS SERIES ©2002  by Gerard Wakefield    http://www.creationism.org/wakefield/ (This article may be copied for educational purposes only.)

Old-earth evolutionists consistently state that their methods of dating the ages of fossils are practically incontrovertible. This forms one of their most formidable weapons against the Biblical model of a young earth, since their conclusions are held as unarguable facts established by objective, scientific data.
 
Closer investigation reveals a different story. Many of the dating methods which claim to provide unarguable evidence for ancient fossils are deeply flawed or based on assumptions rather than facts. One example is the method of measuring the absorption of uranium (U) into fossil human teeth and bones. As archeologists Chen Tiemei and Yuan Sixun of Beijing University found out, the “main difficulty of fossil dating” with this method is that the process by which uranium is absorbed into teeth and bones “has not been fully understood.” They point out that many bones and teeth suffer from a continuous drain of uranium after fossilization takes place, “so the apparent ages might deviate from the true ages. It is very difficult prior to analysis to predict whether a bone or tooth sample is a closed system” (Tiemei & Sixun 1988: 60).

A. G. Latham of the University of Liverpool similarly comments: “[O]ften we do not know when, or for how long, the bone has absorbed U from its environment” (Latham 1997: 218). He goes on to note that the results of many studies show that the absorption of uranium is dependent upon many factors, including the type of sediment in which the fossil was found, the acidity of the soil, ground water history, “as well as on its [the fossil’s] own changing physical and chemical properties” (Latham 1997: 218).
 
Latham admits that the only way for this method to work “is to adopt simple assumptions” about uranium absorption. He also points out that age estimates are usually made by assuming that uranium absorption began immediately after burial, and that uranium continued to be absorbed at an unchanging rate from burial to present (Latham 1997: 218). The problem with this technique is self-evident: it is based on two unfounded assumptions that can never be proven.
 
Dating the famous Swanscombe skull has also produced difficulties. Found in England many years ago, this human skull has defied scientific dating techniques. Two scientists, J. C. Barton (Birkbeck College, London) and C. B. Stringer (Natural History Museum, London), measured three separate pieces of the skull using a low-background germanium spectrometer, which dates objects by comparing the ratio of two uranium isotopes found in them. These isotopes were supposed to have come from radioactive ground water that seeped into the skull fragments over time.

Barton and Stringer reported that the results of the three samples “were inconsistent, showing that their exposure to radioactive ground water must have been very different, although they were found close together” (Barton & Stringer 1997: 205). Other problems included uncertainty in the ratio of the two isotopes in the ground water and a lack of knowledge of when the bones actually began absorbing the isotopes. These two problems “prevented the deduction of any reliable dates for these specimens” (Barton & Stringer 1997: 205).

Sifting through the technical wording, it is clear that the scientific dating methods mentioned above are far from perfect, to the point where only assumptions and estimates can be reached, rather than hard facts.

References:
Barton, J. C., and C. B. Stringer. 1997. “An Attempt at Dating the Swanscombe Skull Bones Using Non-Destructive Gamma-Ray Counting.” Archaeometry 39, no. 1.
Latham, A. G. 1997. “Uranium-Series Dating of Bone by Gamma-Ray Spectrometry: Comment.” Archaeometry 39, no. 1.
Tiemei, C., and Y. Sixun. 1988. “Uranium-Series Dating of Bones and Teeth from Chinese Palaeolithic Sites.” Archaeometry 30, no. 1.