Challenges to Biblical Credibility. Over the Carbon dating sample problems in genetics few decades, archaeology has come into its own as a scientific endeavor. Gone are the romantic images of gentlemen in pith helmets carting off treasures to the museums and estates of Europe. Gone, too, is the idea that archaeologists are always on the side of the Bible believer.
Modern interpretations frequently challenge biblical accounts. Further, dates generated by new techniques are often at odds with the timing of events given by Scripture. The purpose of this first article is to discuss problems with radiocarbon and tree-ring dating or dendrochronologywhich are the two most common direct dating techniques in archaeology.
Problems with relative dating by interpretation of material culture—arrowheads, pottery, tools—will be the subject of the next article. In the s, researchers began to study the effect of cosmic radiation on the upper atmosphere.
They found that it could transform common nitrogen 14N into a radioactive isotope of carbon called carbon 14Cor radiocarbon. Both radioactive and nonradioactive 12C,13C forms of carbon can react with oxygen to form carbon dioxide, which becomes part of the atmosphere. From here it can enter plants by respiration, animals by feeding, and the oceans by exchange with the atmosphere Figure 1.
Early in these studies, Willard F. Libby and his coworkers realized that they could use this process as a tool for dating objects containing carbon. Take, for instance, a piece of charcoal from an ancient campsite. While the wood was alive and growing, it was in carbon dioxide. Its ratio of common carbon to radioactive carbon closely matched the ratio in the surrounding air.
But after that ancient camper cut it for firewood, it no longer took in carbon dioxide. The carbon slowly decayed, while the amount of carbon stayed the same.
Theoretically, if we know the ratio of these two isotopes, and the decay rate, we can calculate the radiocarbon age of the charcoal. The decay rate for carbon, expressed as a half-life, is years e. Until the last few years, laboratories measured carbon content indirectly by extracting all the carbon a sample and then counting its radioactive emissions. Unfortunately, many of these systems required relatively large samples to obtain accurate results.
Archaeologists faced the dilemma of either preserving or dating their precious finds. The application of accelerator mass spectrometry AMS to carbon isotope analysis has changed this picture dramatically. An AMS system has the advantage of counting individual carbon atoms.
However, being able to measure tiny amounts of carbon is not the same as proving that objects are thousands-of-years old. Like other radiometric methods, radiocarbon dating faces technical problems and operates under some questionable assumptions. The radiocarbon method has a less convenient, but senior partner in the form of tree-ring dating. This
Carbon dating sample problems in genetics science began in the early part of the twentieth century when A.
Douglass was looking for a way to investigate the historical relationship between solar activity and climate. He noticed variations in the width of annual growth rings in yellow pine trees growing around Flagstaff, Arizona. The year-to-year variations were the result of changes in rainfall, while the larger patterns were perhaps the result of some longer-term trend. Douglass used a cross-identification system to match patterns in trees of the same age.
He later extended his work to the giant redwoods of California. Eventually he had a chronology going back more than three thousand years. In the mids, Douglass began to apply tree rings to dating in archaeology. His idea was to match ring patterns in the timbers of Native American structures, with the ring patterns in yellow pines. This is a relatively simple matter if the ruins are only a few hundred years old. But if they predate the living trees, then it is necessary to use indirect methods.
Douglass bridged the gap by overlapping patterns of successively older timbers. This classic technique is called cross dating. From this longest-living of all trees, they have constructed a chronology going back almost ten thousand years.
For example, say we wanted to date a piece of German oak furniture. We could
Carbon dating sample problems in genetics to match a pattern of rings on the furniture, with a pattern of rings in living oaks from a forest near to where it was made.
Using our tree-ring chronology for German oaks, we might get a date of A. In contrast, if we radiocarbon dating, all we could say is that the piece dates to sometime in the seventeenth century. The most questionable assumption in dendrochronology is the rate of ring formation. General principles of biology and climate suggest that trees add only one ring each year.
Individual bristlecone pines, which grow very slowly in arid, high altitude areas of western North America, will sometimes skip a year of growth.
This might make a tree appear younger than it really is, but dendrochronologists fill in the missing information by comparing rings from other trees. However, trees would appear too old if they grew more than one ring per year. Most dendrochronologists, drawing on an influential study by LaMarche and Harlanbelieve that bristlecone pines do indeed add only one ring per year.
Yet not all scientists accept this study. According to Harold Gladwinthe growth patterns of the bristlecone trees are too erratic for dating.
Lammerts found extra rings after studying the development of bristlecone saplings. He suggested that the existing chronology should be compressed from 7, to 5, years. Computers can provide an important tool for some of this analysis. But researchers must still judge the statistical significance of an apparent match. Also, they must consider variables like local climate and aging, which Carbon dating sample problems in genetics the width of the rings.
The stories of these two dating methods converged when researchers realized that they did not always give the same answer. However, we do not know the ratio at the time of death, which
Carbon dating sample problems in genetics we have to make an assumption.
In other words, the system of carbon production and decay is said to be in a state of balance or equilibrium. Yet this assumption is questionable, even for an old Earth. The problem is akin to a burning Carbon dating sample problems in genetics cf.
Without stretching the analogy too far, let us imagine that the wax represents carbon We could take a ruler and measure the length of the remaining candle. We could even measure the rate at which the candle is burning down.
But how can we know when the candle was lit? We simply cannot answer this question without knowing the original length of candle. Perhaps we could make a guess from a nearby unlit candle, but it would only ever be a guess.
In the old-Earth model, the process of making carbon began billions of years ago. The evolving atmosphere filled rapidly with carbon, but this rate slowed as carbon found its way into the oceans and the biosphere.
Eventually, the carbon would break down into nitrogen, thus completing the cycle. Geologists freely admit that this process has not always been in equilibrium, but they maintain that this will not affect the radiocarbon method in any practical way.
He settled on a specific decay rate SDR of Libby never seriously questioned the discrepancy between these two numbers. He felt that his method was accurate, and that the numbers were close enough.
These problems encouraged a systematic study in which researchers used the radiocarbon method to date tree rings. Two levels of error emerged. One was a small-scale, short-term variation that can make a given radiocarbon date appear up to four hundred years older or younger than expected Taylor,Figure 2.
Much of this error
Carbon dating sample problems in genetics be the result of sunspot activity, which in turn affects solar radiation and the production of carbon A second error comes from Carbon dating sample problems in genetics S-shaped, long-term trend Figure 2. One bend of the curve peaks in the middle of the first millennium A.
Radiocarbon ages during this period over estimate dendrochronological ages by up to a hundred years. The curve switches direction B.
The discrepancy grows as we go back in time, so that by the fifth millennium B. Major trend in the plot of dendrochronology vs. Dates above dashed zero line overestimate tree-ring ages; dates below underestimate tree-ring ages after Taylor,Figure 2. No one can explain this major trend adequately on the assumptions of an old Earth or an equilibrium system. Several creationists believe that the radiocarbon method may still be of some use, but only if we recognize that the Bible and nature record an instantaneous Creation and a cataclysmic Flood.
Not only are these the most significant events to have ever affected the physical world, but they occurred over a relatively short time span of only a few thousand years. In a world with such a history we would expect non equilibrium conditions. Production of carbon began only 6, years ago—the approximate time of Creation.
Roughly 1, years later, the Flood upset the entire carbon cycle. Further, we know from the radiocarbon dating of tree rings that as we go back in time, we find less and less carbon If there was less carbon in the past, then there has been less decay in our samples than the equilibrium model assumes.
And if there has been less decay, then the samples are not as old as they may seem. The nonequlibrium approach attempts to apply this information to radiocarbon dating. The rate of decay is such that half the atoms of carbon in a sample decay to reported may not invalidate all isotopic dating, they raise questions about the.
In addition, contamination of a sample by modern carbon, introduced The problem is particularly acute for samples that antedate 30, y ago because Here, we describe a genetic approach for dating ancient samples. 2. What are the units of evolution? a. Genes. b. Individuals. c. Populations. d. Species Radioactive dating indicates that the Earth is over 4 billion years old.