Does the cosmic ray impact on carbon-14 isotopes, given their half-life of 5730 years, support evolution?

Answer 1

Creationist statement of evidence for a young earth...
(Slusher) "The radioactivity of carbon-14 is very weak and even with all of its dubious assumptions the method is not applicable to samples that supposedly go back 10,000 to 15,000 years."

The counter-argument...
This was written in 1973. Laboratories were then performing [14]C dating to either 35,000 years or 50,000 years (the latter required cosmic ray shielding). Today, new experimental methods can reach 80,000 years, and 100,000 years may soon be reached.

Another creationist denial...
Carbon dating is based on the atmospheric C-14/C-12 ratio, but that ratio varies. Thus the carbon dating method is not valid.

The rebuttal...
The variability of the C-14/C-12 ratio, and the need for calibration, has been recognized since 1969 (Dickin 1995, 364-366). Calibration is possible by analyzing the C-14 content of items dated by independent methods. Dendrochronology (age dating by counting tree rings) has been used to calibrate C-14/C-12 ratios back more than 11,000 years before the present (Becker and Kromer 1993; Becker et al. 1991). C-14 dating has been calibrated back more than 30,000 years by using uranium-thorium (isochron) dating of corals (Bard et al. 1990; Edwards et al. 1993), to 45,000 yeas ago by using U-Th dates of glacial lake varve sediments (Kitagawa and van der Plicht 1998), and to 50,000 years ago using ocean cores from the Cariaco Basin which have been calibrated to the annual layers of the Greenland Ice Sheet (Hughen et al. 2004).

The repeated creationist mantra is that C14 dating is innaccurate, but any tool will give bad results when misused. Radiocarbon dating has some known limitations. Any measurement that exceeds these limitations will probably be invalid. In particular, radiocarbon dating works to find ages as old as 50,000 years but not much older. Using it to date older items will give bad results. Samples can be contaminated with younger or older carbon, again invalidating the results. Because of excess 12C released into the atmosphere from the Industrial Revolution and excess 14C produced by atmospheric nuclear testing during the 1950s, materials less than 150 years old cannot be dated with radiocarbon (Faure 1998, 294).

In their claims of errors, creationists do not consider misuse of the technique. It is not uncommon for them to misuse radiocarbon dating by attempting to date samples that are millions of years old (for example, Triassic "wood") or that have been treated with organic substances. In such cases, the errors belong to the creationists, not the carbon-14 dating method.


Radiocarbon dating has been repeatedly tested, demonstrating its accuracy. It is calibrated by tree-ring data, which gives a nearly exact calendar for more than 11,000 years back. It has also been tested on items for which the age is known through historical records, such as parts of the Dead Sea scrolls and some wood from an Egyptian tomb (MNSU n.d.; Watson 2001). Multiple samples from a single object have been dated independently, yielding consistent results. Radiocarbon dating is also concordant with other dating techniques (e.g., Bard et al. 1990).

Carbon-14 is produced in the upper layers of the troposphere and the stratosphere by thermal neutrons absorbed by nitrogen atoms. When cosmic rays enter the atmosphere, they undergo various transformations, including the production of neutrons. The resulting neutrons participate in the following reaction:

n + 14N → 14C + 1H
The highest rate of carbon-14 production takes place at altitudes of 9 to 15 km (30,000 to 50,000 feet), and at high geomagnetic latitudes, but the carbon-14 readily mixes and becomes evenly distributed throughout the atmosphere and reacts with oxygen to form radioactive carbon dioxide. Carbon dioxide also dissolves in water and thus permeates the oceans.

Carbon-14 can also be produced in ice by fast neutrons causing spallation reactions in oxygen.

Most of man-made chemicals are made of fossil fuels, such as petroleum or coal, in which the carbon-14 has long since decayed. Presence of carbon-14 in the isotopic signature of a sample of carbonaceous material therefore indicates its possible biogenic origin and relatively recent geologic age.

Answer 2

The Chernobyl incident of 1986 is very important here, as imods said. Though it may depend where the Carbon 14 sample that you are asking about came from, as the different places that the Carbon 14 sample came from may have an affect on the amount of Carbon 14 that is remaining. Carbon 14 is affected different in different places around the globe - for example, if the sample were to be taken from around Chernobyl, the result may in fact turn out to be about 120 grams. However, if the sample turned out to be from California, the mass may be varying due to outside factors and end up with a value of approximately 145 grams. The location of the Carbon 14 may also affect the way that it has affected human skin, and the amount of people it has been handled by can also change the mass.

Answer 3

Carbon-14 is not the best isotope. Techniques are limited to about 10 half lives. This gets to about 50,000 years back. It's useful for anthropology, but most fossils of significance in studying evolution do not fall into this time frame. Alternate techniques are preferable.

Answer 4

In and of itself, carbon dating has very little if anything to do with evolution. It only determines approximately how old something was if it was alive years ago, and that does not prove or disprove evolution's statement that we all came from a common ancestor. I think evolution's statement needs to be modified because it now appears that there are multiple pathways to life.

Answer 5

No