A1. Woodmorappe's Collection of Bad Dates
Eat one of those and your tummy will curl right up! Seriously speaking, a favorite attack on radiometric dating involves dangling "horror stories" about gross errors before the reader, thus giving the impression that radiometric dating is totally unreliable. Woodmorappe (1979), with his collection of some 350 bad radiometric dates, must surely be the master of that technique.
Upon being presented with claims that radiometric dating is totally erroneous, a question naturally arises:
If radiometric geochronology is half as bad as Woodmorappe's list suggests, then how in the world did geologists ever arrive at a tight consensus for the official dates? Look at the various radiometric tables in use over the last 20 years or so and you will find, at least for the fossilbearing strata, a remarkably tight agreement. ... Did the geochronologists throw darts to determine the accepted dates?
Either we have a worldwide conspiracy among geologists, which no sane person believes, or else the numerous radiometric dates were consistent enough to allow that kind of close agreement. In fact, Dr. Dalrymple, an expert in radiometric dating with lots of handson experience, puts the percentage of bad dates at only 5-10 percent.
Thus, we clear away the first illusion spun by creationism, namely that most of the dates are bad, that the radiometric picture is totally chaotic. In fact, it is not at all unusual for several different radiometric methods to agree within a few percentage points on a date. When you consider that each radiometric method is subject to different types of error, that the different "clocks" run at different speeds, such an agreement would be extremely rare on the basis of pure chance. In a number of instances, more than one might imagine, dates are further corroborated by methods which have nothing to do with radioactivity. Thus, the big, statistical picture painted by radiometric dating is excellent. Today, we have some 100,000 radiometric dates, the vast majority contributing sensibly to the overall picture.
Woodmorappe's main theme, minus the diplomatic wording, is that geologists are cheating like so many schoolboys to make their dates come out right. But even schoolboys need to know what the right answers are in order to cheat, and there was no absolute age list when radiometric dating was first applied to the strata.
Anyone can make up a list of bad cars, bad people, bad neighborhoods, or bad radiometric dates. What does that prove? Is it unsafe for you to drive a car, to meet new people, or to live in a neighborhood? Of course not!
The thing that is lacking in Woodmorappe's argument is statistical balance. He is very good at showing the many ways that things can go wrong; he has not shown that things normally go wrong.
To be sure, Woodmorappe isn't claiming that his table is a normal sample of radiometric dates. His is a table of discordant dates. However, in order to make his case against radiometric dating he must, at the very least, show a high percentage of bad dates among the credible radiometric candidates. This cannot be done by merely citing the numerous ways in which one can get a bad date; nor is it achieved by concentrating on atypical cases. Such information is certainly interesting, a healthy reminder of what can go wrong, but it is no threat to the radiometric dating methods which, after all, measure their successes on a statistical basis.
Thus, Woodmorappe is acting more like a mechanic who informs a car owner of the many ways that her car can break down, who quotes numerous horror stories to illustrate his points. Even if those horror stories were true, the mechanic has failed to prove that the lady's car needs repair, let alone junking.
How different it would be if the mechanic pulled out a statistical study done by a consumer magazine to show that the particular make and year for the lady's car was unreliable, due to certain parts, after so many miles. That kind of balanced statistical study is the very thing Woodmorappe's paper lacks.
An eyeopener awaits anyone who closely examines Woodmorappe's list of bad dates. Some of the dates involved minerals that even Woodmorappe admits are unreliable. No geologist would normally use such minerals.
Some of the dates were experimental! Since when do we count experimental work? The idea of experimental dating is to see if a given radiometric method can be applied to certain materials or under certain conditions.
A great many dates, perhaps most, were rejects. That is, they were rejected because of internal indicators (such as a bad isochron) rather than on the basis of the final date produced. If the radiometric method is to be indicted, it must be indicted by dates which were counted as good but shown, by other means, to be bad. Rejects don't fall into that category. They can't be used against the radiometric method.
All of the dates lacked the investigator's personal, detailed interpretation. That's no way to make a case for a bad date! Again, one must demonstrate that each bad date would have been counted as good had no contradiction by outside data occurred. Given a proper interpretation, a number of gross "errors" listed in Woodmorappe's table turn out to be no errors at all! A spectacular example showcased by Woodmorappe, though not actually listed in his table, dealt with an example from California.
The Pharump diabase from the Precambrian of California yielded an RbSr isochron of no less than 34 b.y., which is not only 7 times the age of the earth but also greater than some uniformitarian estimates of the age of the universe. This superanomaly was explained away by claiming some strange metamorphic effect on the Sr.
Sounds pretty grim, huh? The unsuspecting reader would assume that here is a real disaster which geochronologists were trying to cover up with some phoney explanation! In fact, the 34billionyear figure is the result of an incompetent reading of the data, an attempt by Woodmorappe to see an isochron where none exists!
The data do not fall on any straight line and do not, therefore, form an isochron. The original data are from a report by Wasserburg and others , who plotted the data as shown but did not draw a 34billionyear isochron on the diagram. The "isochrons" lines were drawn by Faure and Powell  as "reference isochrons" solely for the purpose of showing the magnitude of the scatter in the data. ... The scatter of the data in Figure 6 shows clearly that the sample has been an open system to Sr87 (and perhaps to other isotopes as well) and that no meaningful RbSr age can be calculated from these data. This conclusion was clearly stated by both Wasserburg and others  and by Faure and Powell . The interpretation that the data represent a 34billionyear isochron is solely Woodmorappe's  and is patently wrong.
Whatever the reasons may be for the scatter, the fact remains that these data were clearly a "discard" case. Thus, this example cannot be used against the RbSr method. That Woodmorappe would see an isochron where none could possibly exist, by misinterpreting one of the lines Faure and Powell had drawn, this in spite of the fact that those authors stated that the data cannot be used, strongly suggests that Woodmorappe's search for discordant dates is superficial. One wonders how many other obvious discards are hiding in his table.
Perhaps, by now, you can understand why long lists of bad dates do not, in themselves, impress scientists. The success of such an attack on radiometric dating hangs on a detailed, case by case analysis as well as a clear demonstration that the sample is representative of the whole to some meaningful degree. In my paper (1993) I listed about 10 conditions which must be examined in any meaningful study of bad dates.
Last updated: Thursday, 10-Mar-2011 15:58:19 CST
|Top of Page|