Amino Acid Dating

10—AMINO ACID DECOMPOSITION—In 1955, *Philip Abelson reported on a new dating method, and immediately a number of researchers began exploring its possibilities.

Amino acids are the building blocks of proteins. At the death of the creature that they were in, amino acids begin decomposing at varying rates.

A major difficulty in applying this dating method is that, of the twenty amino acids, some decompose much more rapidly than others. Scientists can only try to estimate the age when an animal died by the amount of decomposition it has experienced since death. Gradually more stable compounds remain while others decompose in varying ways.

Accompanying this is the problem that various organisms have different ratios of amino acids. Each type of plant and animal has its own special amino acid ratios. Because of this, trying to analyze their later decomposition to establish the dates when they died is risky business. Because there is a wide variation in decomposition time among different plant and animal species, researchers who have worked with this dating method have written several reports stating that amino acid dating, on the basis of comparative decomposition, can only yield broad ranges of fossil age. In other words, it is not a useful dating method.

NO ANCIENT FOSSILS—One worthwhile discovery that scientists made when they applied amino acid dating methods (both amino acid decomposition and amino acid racemization) out in the field—was that traces of amino acid still exist all through the fossil strata! This means that none of the fossils are ancient!

Although we cannot accurately date with amino acid methods, yet we can know that, when amino acids still exist in the field,—they are not very old! We will discuss this more in a later chapter (Fossils and Strata).

ii—RACEMIC DATING—This is a different dating method based on amino acid remains from once-living creatures. It is also called racemization. A leader in re search in both amino acid dating methods has been the Carnegie Institute of Washington, D.C.

Of the twenty amino acids, all but one (glycine) can be formed in one of two patterns: the L (left-handed) and the D (right-handed). The chemical structure of the L and D are identical to one another. The difference lies only in their shape. Imagine two gloves: a left-handed glove and a right-handed one. Both are made of the same materials, but they are mirror opposites. The L and D amino acids are both identical in every way; except, in the L form, some molecules stick out on the left side and, on the D form, some protrude on the right side. (In two later chapters, Primitive Environment and DNA, we will discuss L and D amino acids again.)

ONLY L—Only the L (left-handed) amino acids ever occur in animal tissue. The D (right-handed) ones are never found in the protein of animals that are alive.

When man makes amino acids in a laboratory, he will always get an equal number of both L and D. Only very complicated methods are able to separate them so the experimenter can end up with only L amino acids. There is no way to synthetically make only L amino acids. This is a marvelous proof that living things could not form by chance. More on this in chapter 8, DNA and Protein.

SEEKING A RACEMIC MIXTURE—This brings us back to racemization as a dating method: At death, the L amino acids begin converting to the D type. The changeover in animal remains is completely random, with Ls changing into Ds, and Ds changing back to Ls. Gradually, over a period of time, a "racemic mixture" is the result. The amino acids become "racemic" when they contain equal amounts of both L and D types.

Scientists much prefer racemic dating to amino acid decomposition dating. Analyzing for a racemic mixture can be done more quickly and with less expensive equipment than the amino acid decomposition method.

In addition, the starting point will, with the exception of glycine (the simplest amino acid, which is neither L nor D), always be 100 percent L amino acid content.

But there are serious problems in trying to use race-mic activity to date ancient materials:

TEN RACEMIC PROBLEMS—Many different factors can affect the accuracy of racemic dating methods; and, as with problems accompanying radioactive and radiocarbon dating analysis, for any given specimen no one can know which factors are involved or to what degree. Why? Because the person would have to be there studying the specimen since its clock first started thousands of years ago, at its death, and its L amino acids began their journey toward racemization.

The rate at which racemization occurs is dependent on at least ten different _factors:

(1) What have been the surrounding water concentrations? (2) What amount of acidity and/or alkalinity has been nearby at different times? (3) What has been the varying temperature of the specimen since death? (4) To what degree has there been contact with clay surfaces in the past? (Clay is highly absorbent.) (5) Could aldehydes—especially when associated with metal ions—have contacted the sample at some past time? (6) What buffer compounds have contacted it? What were their concentrations? (7) To what degree in the past has the amino acid specimen been "bound" (isolated from surrounding contamination)? (8) If bound, what was the location of the tested specific amino acid, in relation to the outer membrane or shell of the specimen? (9) How large was the specimen it was in? Have changes in size occurred in the past? (10) Were bacteria present at some earlier time? Because bacteria can produce one of the amino acids (D-alanine), test results can be thrown off by this one factor.

CONTAMINATION FACTOR—Soft materials are the most easily contaminated. Using this method, amino acids in very hard materials, such as bone, tend to produce dates up to 20,000 years. But amino acids in more easily contaminated materials, such as sea shell meat, will run to long ages of time, peaking out about 150,000 years.

TEMPERATURE CHANGE—Just a one degree increase in temperature at 23° C. [73.4° F.]—just one degree—will produce a nearly 16 percent increase in the rate at which racemization occurs. So any temperature change will significantly affect the racemic clock within the amino acid mixture.

Interestingly enough, the only time when racemic dating agrees with the theorized long-ages dating of radioactive materials is when the racemization has been done in the laboratory with very high temperatures!

Thus, as would be expected, samples from out in the field reveal ages that are far less than those acceptable to evolutionary conjectures.

THE COLD STORAGE PROBLEM—Another problem lies with the fact that "cold storage" slows down racemization and give an appearance of a longer age span since death. After the Flood, intense volcanic activity spewed so much dust into the air that the earth cooled and glaciers spread from the poles southward for quite some time. Since then, the climate has gradually been warming up. Thus, if an animal died in A.D. 500, and if it was free from various contamination factors, it might yield a date of 1,500 years. But an animal dying in 2200 B.C., shortly after the Flood, might yield an age of 150,000 years.

The Racemic researchers themselves admit that their dates can only be tentative at best. The fact is (as they know all too well), there is no characteristic racemization rate that is reliably constant.

MOISTURE: A DOUBLE PROBLEM—*Wehmiller and *Hare have suggested that racemization can only occur during the hydrolysis of the protein. In other words, moisture has to be present all during the time that the amino acids are racemizing. But that moisture, coming from outside and flowing in and through the specimen, will bring with it contamination of various kinds.

In contrast, amino acid samples from extinct dinosaurs, from the La Brea tar pits in southern California, indicate that they died only yesterday! This is because tar sealed water away from the samples. Yet scientists can have no way of knowing the temperature and other factors of the water and air that earlier contacted any given sample.

pH FACTOR—If the water moistening the amino acids had a higher pH (if it was more alkaline), then racemization would occur in only a fraction of its normal time, giving the impression of great age to the sample. But who can know the pH of the contaminating water at various times in the past?

A SAMPLE TEST—One example of racemic dating problems is the dating of a single Late Pleistocene Mercenaria shell, which, when several tests were run on it, produced a variety of dates ranging from 30,000 to 2 million years for its various amino acids! Other examples could be cited (see the radiodating section on our website).

ANOTHER RADIODATING PROBLEM—Efforts have been made to confirm racemization dating by radiocarbon dating, but this has failed also.

Because of the very low dates it produces, racemic dating has cast yet another shadow over the integrity of the high-age dates produced by the various radioactive dating methods.

0 0


  • markus
    How can dating be done using amino acids racemic mixture?
    7 years ago

Post a comment