Uncertainties are well illustrated in the dating of Leakey's "Skull 1470" in Kenya, Africa. The first dating Leakey received back on his skull "gave the impossible date of 220 million years."[a] This clearly violated the understanding of where humans fit into the evolutionary time scale. In fact, it would erase the "Common Ancestor," and every identified descendant off man's presumed ancestral family tree! Subsequent dates ranged from 290 thousand years to 19.5 million. Leakey finally settled on the "reasonable" date of 2.6 million years, which he published. Even this date stretched evolutionary science. Over the next ten years, additional scientific studies by other researchers confirmed Dr. Leakey's original dating. Unfortunately, another date was also being confirmed by other studies, around 1.88 million years. Neither set of data had uncertainty bounds that would incorporate the other. However, the more recent dating had the weight of the paradigm,[b] and that eventually was sufficient to decide the controversy, where mere science was insufficient. Frequently, geologic events are assigned dates for which uncertainties are presumed to be very small in spite of great variability between methods. For example, Table 1 is an illustration of the variability of geological dating for the basaltic rocks of the Uinkaret Plateau on the lip of the Grand Canyon.
|American Indian Legend||few thousand|
|Potassium Argon||1.2 +/- 0.2 million|
|Potassium Argon||117 +\- 3 million|
|Stratigraphic Controls||low thousands to a few million|
|Ribidium-Strontium Isochron||1.34 +/- 0.04 billion|
|Pb-Pb Isochron||2.6 +/- 0.21 billion|
Table 1: Dates for Volcano on Grand Canyon Rim
The variation between methods used in Table 1 is quite large, but the uncertainty assigned to each method is quite small. For instance, the K-Ar uncertainty is 3% to 17%. But the small uncertainties stated are misleading: One experimenter in a radiometric dating lab privately stated that 50% of the K/Ar results are discarded (and never reported) in order to preserve the apparent accuracy of the method.[c] This was qualitatively confirmed by McDougall, also working on the Leakey skull: "The criterion for exclusion of a datum was that the calculated age differed by more than twice its error from that of the plateau." And, what else should be expected but small uncertainties when the uncertainties are calculated after the outliers are discarded, based upon the expected uncertainties?
A geologist can look at these dates and pick the "right" method because he "knows the approximate date." And that approximate date is based upon similar selection processes elsewhere, ad infinitum. For the most part, their conclusions tend to cluster, and they have ample reasons for throwing out any dates that don't conform to their expectations. But, subjectivity and circular reasoning are involved in this approach, and disagreements do arise. This may work well amongst peers, but such circular reasoning and subjectivity [should not be hidden from the public nor the students being fed this "certainty."]
In any scientific field, an instrument is not accepted unless it is periodically calibrated against a known. Radiocarbon dating is fairly well accepted because it can be calibrated against known historical dates. Yet, great disparity exists between this "calibrated" dating technique and other dating techniques (see Table 2).
|Object Dated||C-14 Date (years)||Date (Dating Technique)|
|Australopithicus - Ethiopia||15,500||1 to 2 million (KAr)|
|Zinjanthropus - Kenya||10,000||2 million (KAr)|
|Saber-toothed Tiger||28,000||100,000 to 1 million (geologic chart)|
|Natural Gas||34,000||50 million (geologic chart)|
|Coal||1,680||100 million (geologic chart)|
|Note: These C-14 dates are||based upon several issues||of Radiocarbon Journal|
Table 2: Dating Techniques Fail to Calibrate to Radiocarbon Standard
Potassium Argon (KAr) dating was tested on 22 volcanic rocks from various parts of the world, known to have crystallized in the last 200 years, yielding crystallization ages ranging from 100 million to 10 billion years. The explanation for this discrepancy is occluded argon that did not get released from the molten lava (so the "clock" was not reset). Yet, in spite of this calibration failure for KAr dating, great confidence is placed in it even when we have nothing to calibrate it against.
The obvious rejoinder is, KAr dating is not valid in the ranges of historical time (4,000 B.C. to present) or radiocarbon dating (50,000 B.C. to present). Then, the following questions must be addressed:
1) Since KAr dating can err a billion years either way, how do we know which is correct? For example, one reference noted that ages varied considerably throughout the entire pillow of lava, and recommended that the age in the center was most accurate because it had more time to outgas the argon. How do we know it had enough cooling time to completely reset the clock?
2) If radiocarbon dating cannot apply to such ancient dates (Table 2), why does it give a readable date, rather than "below detectable limits"?
3) Granted that it is impossible to calibrate KAr against knowns, why does it behave so poorly when calibrated against other dating methods that are also uncalibrated (Table 1)?
Excerpted from the technical article, "Problems with Distant Horizons," published at the ESREL'96 - PSAMIII Conference in Crete, 1996.
Leakey stated, "Either we toss out this skull or we toss out our theories of early man. It simply fits no previous models of human beginnings." -- R. E. Leakey, National Geographic, June 1973, 819.
Reynolds, S. J., et al., "Compilation of Radiometric Age Determinations in Arizona," Arizona Bureau of Geology and Mineral Technology Bulletin 197, 1986, p. 8.
P. E. Damon and others, "Correlation and Chronology of the Ore Deposits and Volcanic Rocks," U.S. Atomic Energy Commission Annual Report, No. C00-689-76, (1967), 82 pp. Olivine is not considered a suitable mineral for K-Ar dating.
Dr. Steve Austin, Editor, Grand Canyon: Monument to Catastrophe, ICR, 1994.
C. Alibert, "Isotope and Trace Element Geochemistry of Colorado Plateau Volcanics," Geochimica et Cosmochimica Acta, Vol. 50, 1986, pp. 2735-2750.
Ian McDougall, "40Ar/39Ar Age Spectra from the KBS Tuff, Koobi Fora Formation," Nature 294 (12 Nov. 1981): 123.
G. Faure, Isotope Geology, Wiley and Sons, 1986, is a popular textbook that gives a very good discussion of the weaknesses of each dating technique, including all the accepted reasons for throwing out displeasing results.
Excerpted from the technical article, "Uncertainties In Repository Modeling," presented at the Probabilistic Safety Assessment '96 Conference in Park City, Utah, by James R. Wilson.
3. S. Baker, Evolution: Bone of Contention, Evangelical Press, Phillipsburg, NJ, (1986).
4. Dalrymple, G. B., and J. G. Moore, "Argon-40: Excess in Submarine Pillow Basalts from Kilauea Volcano, Hawaii," Science, Vol. 161, p. 1132-1135, (1968).