This page is a reprint of the book "The Science of Evolution," by William D. Stansfield of California Polytechnic University. McMillan Publishing Company, New York. Copyright 1977 by William Stansfield. ISBN 0-02-415750-3. This section is from Chapter 4. Evidence of Evolution - Paleontology and Biogeography.

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Page 80 The Framework of Evolution

Several methods have been devised for estimating the age of the earth and its layers of rocks. These methods rely heavily on the assumption of uniformitarianism, i.e., natural processes have proceeded at relatively constant rates throughout the earth's history. Some estimates of geological age are derived from calculations based on the present average rate of sediment deposition in oceans, deltas, and lakes. Dividing the thickness of a rock layer (stratum) by the average rate of deposition for that kind of sediment gives an estimate of the length of time required for its formation. The rate of sedimentation, however, is known to vary widely from one locality to another, so that the use of an average rate would very likely lead to considerable errors of estimate. Probably no more than one percent of geological history can be accurately read in rocks. Furthermore, no single location contains the complete geological record. Gaps in the record can sometimes be pieced together using information from other localities that share strata. Certain fossils appear to be restricted to rocks of a relatively limited geological age span. These are called index fossils. Whenever a rock is found bearing such a fossil, its approximate age is automatically established.

This method is not foolproof. Occasionally an organism, previously thought to be extinct, is found to be extant. Such "living fossils" obviously cannot function as index fossils except within the broader time span of their known existence.

Geologists now assume that most of the water in the oceans was produced by volcanic outgassings. It has been estimated that seventy volcanoes the size of Mexico's Paricutin producing 0.001 cubic mile of water per year for 4.5 billion years of the earth's history could

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account for the 315 million cubic miles of water in the oceans today. There are now approximately 600 active volcanoes and about 10,000 dormant ones. Six hundred volcanoes comparable to Paricutin could account for the present oceans in approximately 0.5 billion years. Since volcanic activity presumably was much greater during early earth history than at present, creationists argue that the age of the oceans would appear to be considerably less than 0.5 billion years. By this methodology, creationists stand guilty of the "crime" they ascribe to evolutionists, namely uniformitarianism. Perhaps the earth is now experiencing greater volcanic activity than the average; there is no accurate way of knowing. How much water vapor was lost to space during the early warmer stages of geological history is also a big unknown.

Uranium salts presently appear to be accumulating in the oceans at about one hundred times the rate of their loss. It is estimated that 6 x 10^10 grams of uranium is added to the oceans annually. Under uniformitarian rules, the total concentration of uranium salts of the oceans (estimated at less than 10^17 grams) could be accumulated in less than one million years. Again there is no way of knowing if present rates have been operating constantly throughout geological time or if the estimates of rate and total uranium content are accurate.

The atmospheric content of helium-4 (the most abundant isotope of helium) has accumulated from the radioactive decay of uranium and thorium in the earth's crust and oceans, from nuclear reactions caused by cosmic rays, and from the sun. If the present rate of accumulation of helium has been constant throughout four billion years of the earth's history, there should be thirty times as much helium in our atmosphere as is presently there. Little is known about how helium escapes from our atmosphere. Until more light is shed on this problem, arguments of atmospheric age based on these kinds of calculations are highly suspect.

One estimate for the amount of meteorite dust settling to earth places it at 14.3 million tons annually. If this rate has been constant throughout five billion years of geological history, one might expect over fifty feet of meteorite dust to have settled over all the surface of the earth. Some creationists suggest that the failure to find a fifty foot layer of such dust in the geological record argues against a long earth history. It is obvious that as the dust settles on earth it would become incorporated with terrestrial materials into the geological strata and therefore would not appear as a discrete band. The average meteorite contains about three hundred times more nickel than the average earth rock. Perhaps our entire crustal content of nickel and iron could have a cosmic origin. If one assumes that the meteorite fallout rate was much greater earlier in the earth's history, one would argue for an earth considerably younger than five billion years. No meteorites have been found in the geological column. Creationists submit that evidence of meteorite showers should have appeared by now; their absence should be interpreted as support for the concept of a very young earth (perhaps only 5,000 to 10,000 years old). The rarity with which contemporary meteorites are found, however, makes it much less likely that ancient ones would be found by geologists.

It has been estimated that just four volcanoes spewing lava at the rate observed for Paricutin and continuing for five billion years could almost account for the volume of the continental crusts. The Columbian plateau of northwestern United States (covering 200,000 square miles) was produced by a gigantic lava flow several thousands of feet deep. The Canadian shield and other extensive lava flows indicate that volcanic activity has indeed

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followed an accelerated tempo in the past. The fact that only a small percentage of crustal rocks are recognizably lavas has been offered in support of the "young earth" concept. However, it is unlikely that the smaller lava deposits would escape extensive erosion, and many of them could have been largely weathered away.

Some geologists find it difficult to understand how the great pressures found in some oil wells could be retained over millions of years. Creationists also use this currently puzzling situation as evidence that oil was formed less than 10,000 years ago.

If humanity is really about 2.5 million years old (as claimed by Dr. Louis Leakey), creationists calculate from conservative population estimates (2.4 children per family, average generation and life span of forty-three years) that the world population would have grown from a single family to 10^2700 people over one million years. The present world population is about 2 X 10^9, an infinitesimal part of 10^2700. They conclude that humanity was created only a few thousand years ago. It was pointed out in the first chapter that although populations tend to have large reproductive potentials, the limiting factors of the environment prevent unlimited geometric increase. The size of a population may fluctuate over various lengths of time, but the long-term picture is one of stability. Populations need not continually expand in order to survive over long periods of time. Many more limitations to population growth were undoubtedly imposed on primitive humans than are faced by modern people. For one thing, primitive humans were gatherers and hunters. Scarcity of food was probably severely restrictive of human population growth until relatively recent times (a few thousand years ago), when humans learned how to raise their own crops and domesticate animals (the dawn of agriculture).

All the above methods for dating the age of the earth, its various strata, and its fossils are questionable, because the rates are likely to have fluctuated widely over earth history. A method that appears to have much greater reliability for determining absolute ages of rocks is that of radiometric dating. For some inexplicable reason, the nuclei of certain elements become unstable and spontaneously release energy and/or particles.

When atoms emit particles of alpha or beta radiation, they transmute (change or decay) into atoms of a different element. Gamma rays are the result of, rather than the cause of, transmutation. Each radioactive isotope (radioisotope) decays at a characteristic rate, measured in terms of its half-life. This is the time required for half of its atoms to decay. A radioisotope of carbon (C14) is produced in the atmosphere by the action of cosmic rays on nitrogen (14). The half-life for C14 is about 5730 years. If we start with ten grams of C14, in

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5730 years half its atoms would be expected to decay back to stable N14, leaving five grams of C14. After another 5730 years, only one quarter of the original amount of C14 would remain (i.e., 2.5 grams); at the end of three half-lives (17,190 years) there would be 1.25 grams C14 and 8.75 grams N14, etc. Carbon-14 reacts with oxygen-yielding radioactive carbon dioxide (CO2)and enters the carbon cycle worldwide. Plants take up carbon dioxide and thereby incorporate both carbon-14 and normal carbon-12 into their tissues in the same proportion as they occur in the atmosphere. Carbon-14 would pass along the various food chains to enter animal tissues. After death, C14 would cease to enter the organism through active processes and would begin to decay in the manner previously outlined. The age of a recent fossil (up to approximately 25,000 years old) can be estimated under the assumption that the C14 content of the atmosphere has remained constant during this time span. The fossil can be analyzed for the ratio of C14 to C12 and its age determined from the known rate of radioactive decay.

It now appears that the C14 decay rate in living organisms is about 30 per cent less than its production rate in the upper atmosphere. Since the amount of C14 is now increasing in the atmosphere, it may be assumed that the quantity of C14 was even lower in the past than at present. This condition would lead to abnormally low C14/C12 ratios for the older fossils. Such a fossil would be interpreted as being much older than it really is. Various correction factors have been calculated to take into account the disequilibrium between C14 production and decay. The correction is small for relatively young fossils, but amounts to about a 25 per cent reduction from an uncorrected age of 10,000 years. Creationists argue that since C14 has not yet reached its equilibrium rate, the age of the atmosphere must be less than 20,000 years old. It is possible that a greater concentration of water vapor existed prior to the Biblical flood (presumably about 5,000 years ago). This water vapor may have retarded neutron production by cosmic rays and consequently diminished the yield of C14. This would give early fossils a low C14/C12 ratio and therefore the appearance of great antiquity. On the other hand, if a lower concentration of water vapor existed, there may have been a greater amount of C14 produced; the increased C14/C12 ratio in the fossil would be interpreted as a relatively young age. The water-vapor content of the atmosphere has varied considerably in the past, thereby disturbing any C14 equilibrium that may have been attained. Because the C14 method is useful only for very recent fossils, it has been mainly used by archaeologists who have found it to yield ages in fairly good agreement with historically dated materials.

Radioisotopes with half-lives in the millions or billions of years are used in dating events in the geological column. For example, half of uranium-238 (U238) decays to its nonradioactive daughter isotope lead-206 (Pb206) in 4.5 billion years. If one gram of U238 produces (1.54 x 10^10)^-1 gram of Pb206 per year, then x grams of uranium in y years should produce (xy)/(1.54 x 10^10) gram of lead. Hence, y = (Pb206/U238)x(1.54 x 10^10). Suppose that the ratio of lead to uranium-bearing mineral was determined to be 6.5 x 10^-3. The age of the rock in which the crystal was found is estimated to be y = (6.5 x 10^-3)x(1.54 x 10^10)) = about 1x10^8 or approximately 100 million years. More precise calculations would apply correction factors for the gradual decrease in uranium content, for the production of thorium, and for other complicating factors, but the general outline of the methodology is straightforward.

If we assume that (1) a rock contained no Pb206 when it was formed, (2) all Pb206 now in

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the rock was produced by radioactive decay of U238, (3) the rate of decay has been constant, (4) there has been no differential leaching by water of either element, and (5) no U238 has been transported into the rock from another source, then we might expect our estimate of age to be fairly accurate. Each assumption is a potential variable, the magnitude of which can seldom be ascertained. In cases in which the daughter product is a gas, as in the decay of potassium (K40) to the gas argon (Ar40), it is essential that none of the gas escapes from the rock over long periods of time.

It is obvious that radiometric techniques may not be the absolute dating methods that they are claimed to be. Age estimates on a given geological stratum by different radiometric methods are often quite different (sometimes by hundreds of millions of years). There is no absolutely reliable long-term radiological "clock." The uncertainties inherent in radiometric dating are disturbing to geologists and evolutionists, but their overall interpretation supports the concept of a long history of geological evolution. The flaws in radiometric dating methods are considered by creationists to be sufficient justification for denying their use as evidence against the young earth theory.

In 1972 Jeffrey Bada introduced a new method of absolute dating that does not involve radioactive elements. His method is based on the following principle. Amino acids occur in two optical forms; the L (laevo) isomer rotates the plane of polarized light to the left (counterclockwise); the D (dextro) isomer rotates it to the right (clockwise). A racemic substance does not rotate the plane of polarized light, because it contains equal quantities of dextrorotatory and laevorotatory isomers. All living organisms possess only the L-amino acid isomers in their proteins (excepting glycine). After death, the L isomers are slowly converted to D isomers (racemized). By measuring the ratio of D to L forms, the age of a bone can be estimated (provided the environmental temperature is known and it has not varied greatly). Radiocarbon dating is of little use for fossils older than about 40,000 years. Racemization dating has been applied to Middle Stone Age artifacts (110,000 years old) as well as to middle Pliocene fossils (8.5 million years old). This method holds promise for dating Cenozoic fossils that are too old for dating by C14 and too young for accurate dating by U-Pb or K-Ar methods.

Francis Bacon (circa 1620) was one of the first to notice the striking complementarity between the eastern shoreline of South America and the western boundary of Africa. They would fit together like pieces of a puzzle if they could be moved. Benjamin Franklin speculated in 1782 that ". . . the internal parts (of the earth) might be a fluid more dense, and of a greater specific gravity than any of the solids we are acquainted with; which therefore might swim in or upon that fluid. Thus the surface of the globe would be a shell, capable of being broken and distorted by the violent movements of the fluid on which it rested. . . ." Franklin's idea was similar to the modern geological theory of continental drift or, as it is now called, plate tectonics.

Between 1915 and 1929 German meteorologist and theorist Alfred 1. Wegener (Figure

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