PrintMore Insight to Evolution
Many very good sources are available on evolution. The interested reader may wish to start with Teaching About Evolution and the Nature of Science (1998), National Academy of Sciences, National Academies Press, Washington, DC.
What follows, in question-and-answer format, is a synopsis of some of the objections that the author, Dr. Alley, has heard or read against evolution, together with brief answers. The author expresses some opinions toward the end on teaching of science, but they are quite in line with the broader scientific view and with materials already discussed in class. The author really believes that science is a tremendously useful way for humans to find out how the world works to help us stay fed and clothed and housed and healthy so that we can address big questions. The author also includes quotes from two noted people (Pope John Paul II and US President James Earl Carter) that tend to promote religion as well as science.
Question: Is evolution anti-religious, or religion anti-evolution?
Answer: They don’t have to be. The author is religious, and is convinced of the overwhelming scientific evidence for evolution. When the author wrote a commentary on the subject for Pennsylvania newspapers, the pastors at the author’s church (a mainline Protestant denomination) approved of the piece. Most of the religious people in the U.S. belong to groups that have accepted evolution. Pope John Paul II added the Catholic Church to those groups accepting evolution (“Truth cannot contradict truth;” Address of Pope John Paul II to the Pontifical Academy of Sciences, October 22, 1996).
Perhaps the most famous Sunday-School teacher ever in the U.S., former president James Earl (“Jimmy”) Carter, said in January, 2004 that “he was embarrassed by the Georgia Department of Education proposal to eliminate the word ‘evolution’ from the state’s curriculum” (CNN story). He went on to say, “The existing and long-standing use of the word ‘evolution’ in our state’s textbooks has not adversely affected Georgians’ belief in the omnipotence of God as creator of the universe. There can be no incompatibility between Christian faith and proven facts concerning geology, biology, and astronomy. There is no need to teach that stars can fall out of the sky and land on a flat Earth in order to defend our religious faith.”
There surely are people who believe in evolution and who dislike or even attack religion, and there are many religious people who dislike or attack evolution. But, evolution is not anti-religious in any way. The author is of the opinion that most leaders of evolutionary research wish to coexist with religion, and that most religious leaders wish to coexist with evolution.
Question: Doesn't evolution lead to Hitler, or ethnic cleansing, or killing of innocent misfits?
Answer: Very often, “what is” becomes entangled with “what ought to be”—“Letters to the Editor” on the subject frequently include the worry that science displacing religion inevitably leads to a lack of divine authority for moral codes, which leads to lack of morality. As noted above, this just doesn’t make sense—the morality of evolution-accepting Jimmy Carter or of the late Pope John Paul II has not been seriously in question. (But, the author suspects that questions of morality are more important than questions of science to many of the critics of evolution.)
In regard to racial purity or some similar such nonsense, consider for a moment the case of the author. He peers out from behind thick glasses, and his daughters both wear corrective contact lenses. It is likely that he has a genetic predisposition causing near-sightedness in individuals who, while still young, use their eyes for much close-up work such as reading. This genetic predisposition seems to be hereditable—he has passed it on. (There is still medical debate about genetic roots of bad eyesight, but the interpretation here is probably correct.) Leaving the author in the gene pool may “weaken” it a little bit. How should the author be dealt with in a world that recognizes evolution? Should he have been sterilized as a youth, or killed, or forbidden to mate? Or, should he be recognized as suffering from a handicap for which he should receive affirmative action? The government could have subsidized lessons for him during his youth on how to be attractive to a potential mate while peering through thick glasses. (Fortunately, he was successful in marrying a wonderful woman, but maybe there are other downtrodden thick-glasses wearers who should have been helped by outreach efforts.) Or, should we just recognize that glasses (and now, contacts) work just fine, and why worry about it? The reality of evolution in no way dictates one’s morality! Evolution is what is, not what ought to be—we have to decide how to use the scientific information about evolution.
Question: Don’t the gaps in the fossil record prove that evolution did not occur?
Answer: No. We covered this one in the text at some length; the fossil record is beautifully consistent with evolution. The gaps present are the gaps expected based on the nature of speciation and the incompleteness of the fossil record, and the gaps are filled by transitional forms in those groups that are commonly fossilized and for which you would expect to find transitional fossils. Even a little consideration shows that not every creature is fossilized, and that big and relatively rare land creatures will have somewhat sketchy fossil records whereas small and relatively common shelly shallow-sea creatures will have rather complete fossil records. This is observed. One can look at the likelihood of fossilization, and then generate predictions on how complete the fossil record will become as more fossils are collected, and these work.
Question: Aren’t there lots of problems with age dating, showing that the world is really young?
Answer: Again, this was discussed a lot in the text. There are commentators who make arguments against science that might seem sensible to those who don’t know the field, but those arguments can be shown to be completely wrong with just a little care.
Consider one that the author has been shown several times. The author has helped count over 100,000 annual layers in a Greenland ice core, and to do all of the careful testing using fallout of historically dated volcanoes and other time markers to show that the results are reliable. The “counter-argument” from the young-Earth supporters was that a flight of World War II planes that was forced to land on the ice sheet had been buried a couple of hundred feet in only 50 years, so a couple of thousand feet would be 500 years, and the 10,000 feet of ice thickness in central Greenland would be about 2,500 years, so the ice sheet started safely after Noah’s flood. Seems perfectly reasonable, doesn’t it?
But, when we discussed glacier flow back a few chapters, we noted that a glacier is a bit like pancake batter, spreading across a griddle under the influence of gravity. If you put a dollop of pancake batter in the middle of a griddle and watch, the layer thins as it spreads. Put another dollop on top, and both spread and thin. Keep putting dollops on top, and letting the batter drip off the end of the griddle, and eventually you’ll have a whole pile of layers. The one at the bottom will have been spreading and thinning the longest, and will be the thinnest.
An ice sheet is similar, spreading and thinning as more snow is piled on top. Very crudely, an annual layer will become half as thick and twice as long while it is moving halfway from wherever it is toward the bed. Friends of the author have directly measured the motion and spreading of the ice, and it fits this pattern beautifully. (These measurements show a little extra downward motion associated with squeezing snow to ice, but glaciologists usually speak in terms of ice-equivalent thickness—the air already mathematically squeezed. And very deep, the halfway-to-the-bed-thins-by-half breaks down, because the ice sheet had to form sometime so the first layers weren’t thinned while flowing through the ice sheet, and because the flow over bumps in waffle-iron fashion also complicates things a little). The fact that Greenland makes icebergs, hence is spreading, means that deeper layers are thinner, and the simple airplane burial calculation is completely wrong.
At the time the author was writing this, a quick search of the Web found numerous sites that slightly improved the young-Greenland calculation while still getting it completely wrong. These sites noted the thinning of layers with increasing depth, picked a place near the edge of the ice sheet where the ice was relatively thin, picked a thickness of annual layers at the surface, picked an erroneously thick annual value at the bottom, and suggested using the numerical average of the surface and bottom thickness in the calculation to get the age of the ice sheet. Fourteen inches thick at the top, less than two inches thick at the bottom, call it two inches, take the average of 14 and 2 inches and get 8 inches per year, and a few thousand feet of ice in the thin margin of the ice sheet still squeaks in after Noah’s flood—the scientists must be confused. Seems reasonable, right?
Absolutely not. Try this very simple equivalent, that you can do in your head. Suppose that the ice sheet is two feet thick, or 24 inches, that the top annual layer is 12 inches thick, and the bottom has twelve annual layers each 1 inch thick. A scientist would count the annual layers and find 13, giving a 13-year age for the ice sheet. But the technique advocated by the young-Earth websites would average the top and bottom thicknesses (6.5 inches per year), and then calculate that fewer than 4 years were required to build up the two feet of ice, not the actual 13 years. The mathematical error made on the websites is a very simple one, and one that most students will have learned to avoid while still in middle school. (The author doesn’t know whether the mistake on these young-Earth websites represents stupidity or deliberate misrepresentation, but the mistake is so flagrant that it is not easy to think of a third option.) Do the calculation right for Greenland, and you end up with a very old ice sheet. If you count the annual layers, or calculate the age using the flow of the ice sheet, or estimate the age by identifying abrupt climate changes and using the ages from tree-ring or other layer counting of those abrupt changes elsewhere, or use any of the other dating techniques, you’ll get the same Answer: Greenland’s ice is much older than written history.
The scientific community is continually improving age-dating techniques, arguing about them, working on them, and thus far, no serious problems have been found with the old age of the Earth. The arguments presented against the old age, such as the buried planes or the 5,000-year-old living clam (see the Enrichment from the Grand Canyon) prove not to be problems after all.
Question: Doesn’t the second law of thermodynamics, or the “law of conservation of information,” prove that evolution cannot have occurred?
Answer: No. The second law of thermodynamics says that entropy increases in a closed system; the law of conservation of information is something promoted by the intelligent-design supporter William Dembski in his writings arguing against evolution, and appears to be basically a special case of the second law of thermodynamics, although there is no scientifically recognized “law of conservation of information.” In fact, order can emerge out of chaos, and does so all the time—a snowflake does form from randomly oriented water molecules, for example. The second law summarizes a great number of observations showing that, in growing the snowflake, heat must be removed, which causes an increase in disorder of the surroundings. Some creationist websites have suggested that followers not use this second-law argument because it is completely wrong.
An interesting note is that a whole field of Evolutionary Computing now exists (linked to genetic algorithms, artificial intelligence, etc.). In trying to “teach” computers to solve complex and difficult problems, computer scientists have found it useful to mimic evolution and natural selection—have the computer start with a possible answer, see if it works, then tweak the answer and see if that works better, throwing away ones that work worse and keeping ones that work better. If, for example, you’re trying to improve the routing of airplanes to fly the shortest distance while carrying the most passengers, you could start with the current route map, and then randomly “perturb” it a little, to see if that works better. You need to define “better” (how many more miles of flying is it worth to allow you to sell another passenger ticket?), but then the technique is successful. Usually, many small perturbations are used in sequence, but occasionally a slightly larger one may be useful; huge ones usually fail. The approach obtains order—a useful optimization of the flight plan—from the chaos of reality by random adjustments followed by selection of those that work better. Selection doesn’t require intelligence, but simply telling the computer to save the coordinates if the cost is lower. In biology, this selection is achieved by survival—if you survive to have kids, you have been selected. The lessons of biological evolution thus have been used to help computer scientists solve hard problems—science works. And the idea that somehow the second law of thermodynamics prevents evolution is just silliness.
Note that, in the absence of the “selection” step, randomly generating new options is almost guaranteed to fail in finding an optimal answer. Many of the anti-evolution websites and other anti-evolution materials point to how incredibly unlikely it is for random processes to generate something useful. These sites are completely correct, but completely misrepresenting evolutionary theory. The step of randomly generating lots and lots of new “experiments” is followed by the step of picking “successful” ones—in evolutionary computing, the successful ones meet some criterion such as saving the airline money; in evolution by natural selection, the successful ones promote survival to have kids.
Question: Isn’t evolution restricted to the “micro-evolution” that we can see (such as breeding tiny white dogs from larger, grayer dogs), and cannot include “macro-evolution” of new types?
Answer: This one takes a bit of discussion; it seems common-sensical, but turns out not to make sense.
To many biologists, evolution is defined as something like “change in gene frequencies over time,” with genes being the basic inherited instructions for making and running living things. There is no “micro” or “macro” in this; the distinction is simply not meaningful in the modern theory of evolution. “Macro” is just more of “micro”; they are not separate things.
A different way to view this question is that, biologically, there is a division between species (either things interbreed, or they don’t, or they do somewhat, as discussed next). All of the other divisions that we draw between different living types (kingdom, phylum, class, order, family, genus) are human constructs to help us understand the world. If different people with well-developed science had named all of the creatures, those people likely would have picked the same species, but may have picked different ways to group the species. “Macro” in this sense presumably is used by the evolution-skeptics to refer to changes between the larger groupings (there are wolves and coyotes and domestic dogs, but these people claim that there is a fundamental difference between “dogness” and “catness”). But larger groupings are primarily conveniences for us; evolutionary biology addresses whether creatures interbreed and exchange genes, or not.
“No, no, no” a skeptic might say, “We don’t care about what biologists think; we care about the reality, and we know that there is ‘dogness’ and ‘catness,’ these are different types or sorts.” This is harder to answer; such people presumably are postulating some unknown barrier that somehow prevents genetic “experiments” beyond pre-defined boundaries—evolution can bring about new types of dogs, or new types of cats, but only to some boundary and not beyond. But what forms such a boundary? Where is the ‘police officer’—biochemical or otherwise—that would check after two dogs had sex to make sure that the potential offspring did not include a genetic experiment that went one DNA base pair outside of the defined limits of ‘dogness’? An omnipotent deity could of course do such a thing, but there exists no scientific evidence for this—make another base substitution in DNA, and you have another experiment. Let nature choose the “good” experiments (those that lead to lots of surviving kids) and evolution happens. “Macro” evolution really means “evolution that takes long enough to occur that humans in their lifetimes won’t see much change in large animals (although plenty of such changes are happening to disease organisms).”
Dogs and cats really are different, because many successful evolutionary experiments have accumulated over tens of millions of years. Evolution really is gradual, and “hopeful monsters” (a dog gives birth to a cat, for example) do not happen. But, given the observed rates at which variability is produced by reproduction, and the rates at which natural selection is observed to function, mathematical modeling shows that there has been more than enough time in geological history for all of evolution to have occurred. There is no problem, for example, in going from the known damage that happens to cells in the bright sun (sunburn), to cells that are a bit more sensitive to light to help a creature know where the light is and avoid it, to groupings of those cells, and on to an eye. The question is not whether evolution could have happened in that much time, but why evolution ran as slowly as it did—most of the time, not a lot of change has been occurring, probably because creatures had found pretty good evolutionary solutions to problems and tend to stick with those solutions.
An additional note is that the species with us today are really not as separate and distinct as some people might have you believe, but have blurry edges, overlaps, etc., as you would expect from the scientific understanding of evolution. For example, “ring complexes” of animals are observed—species A interbreeds with B, which interbreeds with C, but A and C don’t interbreed. Are A and C the same species? Would they be if B became extinct? (Imagine what would happen if we had nothing but miniature poodles and Great Danes—could they ever “get it on”?) The messy world of biology shows that the world is not populated by “types” but by evolving populations with greater or lesser degrees of gene exchange.
Question: What about “Intelligent Design”?
Answer: “Intelligent design” is a resurrection of a very old idea. Proponents of “intelligent design” argue that there exist “irreducibly complex” parts of plants and animals, such that these parts would not have been useful while they were evolving but only after they evolved, and thus that they could not have evolved. If evolution made a useless something that later became part of an eye, that something wouldn’t help the creature and might hurt it, and so wouldn’t be saved and experimented upon to generate the rest of the eye—the intermediate steps usually should be useful for evolution to work.
In decades gone by, the eye was often cited as an irreducibly complex structure—without all of the parts of your eye, you wouldn’t be reading this. But it is very easy to find successful creatures on Earth with no eyes, and others with rudimentary eye spots, and others with slightly more complex eyes, and so on—gradual improvements on the slight sensitivity of all cells to light can lead to an eye. Because each step in the evolution of an eye has utility, the eye is not “irreducibly complex”. (Ask someone whether they would prefer to be completely blind or to be able to discern light and darkness, or vague shapes, and that person is not likely to opt for blindness—less-than-perfect eyes are still valuable.) As their eye-argument failed, intelligent-design advocates have switched to other arguments, such as the flagellum or the clotting of blood, but scientists working on these topics are not finding these structures to be irreducibly complex, either.
Scientists working in many fields related to evolution have been vocal through their leading organizations, such as the National Academy of Sciences, and the American Association for the Advancement of Science, in noting that “intelligent design” is not science, even if it happens to be stated by people with scientific training. Scientists after all can say all sorts of things that are not science. (And yes, you can find a few scientists saying anti-religion things, but those are not science either.) The leading hypothesis of “intelligent design” seems to be that there are some things that evolutionists cannot explain. This hypothesis does not lead to useful predictions that can be tested and falsified, so it just isn’t science. Notice, by the way, that successful scientific explanation of one so-called irreducibly complex item such as the eye has not falsified “intelligent design” to its supporters, who can always propose that something else is irreducibly complex. In a widely watched court case in Dover, Pennsylvania in 2005, a federal court stated these results very clearly: “intelligent design” is not science. (See the Kitzmiller case (.pdf) at uscourts.gov if you’d like 139 very interesting pages on this topic.)
After the author wrote a newspaper column advocating the teaching of science in science classes, he received communications (e-mail, phone, letter) from numerous interested people, including many intelligent-design supporters. Aside from a couple of unpleasant “You’re going to burn in Hell” e-mails from the fringe, the exchanges were respectful, interesting, and informative, from a broad spectrum of beliefs. Notice that these are not the leaders of the “intelligent design movement”, but mostly-Pennsylvanian newspaper readers responding to a column. Two observations are:
1) None of the “intelligent design” supporters seemed to seriously consider the possibility that the “intelligent designer” was a flying spaghetti monster or a space alien; where it could be determined, the correspondent identified the “intelligent designer” as God as worshipped in the Judeo-Christian tradition, and the correspondent came from a fundamentalist, conservative, or traditional Christian background.
2) None of the “intelligent design” supporters seem to have come to their religious beliefs based on the perceived difficulty of evolutionary biochemists in explaining blood clotting, flagellae, or eyes. Awe and reverence for the glory of nature did seem to figure in some religious beliefs, but supposedly irreducibly complex items were not in the forefront.
This leads to some additional, important points. The broad umbrella of “intelligent design” allows an old Earth and allows evolution to have occurred, except at those moments when an unspecified intelligence tinkered with the process, so if you are a true sacred-book literalist, “intelligent design” may give you scant comfort. And many religious people object to “intelligent design” based on the argument that it is lousy theology—if an unspecified “intelligent designer” is introduced to high-school biology students based on a claimed difficulty that scientists are having in explaining intermediate steps in blood clotting, might future success in explaining blood clotting raise questions in the minds of those students about the validity of belief in the “intelligent designer”? The pastors at the author’s church seemed remarkably uninterested in getting high school biology teachers to take over religious instruction based on explanations of flagellae.
Question: But shouldn’t we be fair, teach both sides, and let kids decide?
Answer: This is a hard one, because we so strongly believe in fairness and in hearing a diversity of ideas. But, if you present “both sides” in science class, it isn’t science class any more. Science is the human search for ways to make accurate predictions, and that means setting aside the ideas that don’t work (the Earth is flat, the Earth is the center of the universe) and keeping the ones that do. Teaching the controversy over evolution in science class would be akin to teaching the controversy over whether the Earth or the Sun is more nearly the center of the solar system. Students are not really equipped to answer such a question (it took bright people, telescopes, calculations, and observations over centuries to figure out that the Earth does most of the moving in the Earth-Sun system). Teaching “intelligent design” is not good science and does not stimulate good science. “You biology students will fail in explaining and predicting some things” is not an especially motivational approach to teaching. Imagine if you did the same thing for math homework—“Do problems 1-24, but a few of them are impossible, so if you hit a hard one, just skip it”—what kind of motivation would that give to students?
The scientific controversy over evolution by natural selection is similar to the controversy over gravity. We don’t have a complete understanding of gravity yet. The grand unified theories of physics have not succeeded in explaining the quantum world and gravity through one set of equations, gravitational waves have not been observed, and other research frontiers await. But we have a pretty good idea that if you knock your pencil off your desk, the pencil will fall down. There are limits to predictability—although gravity causes things to fall down, and gravity keeps the atmosphere near the Earth, gravitational attraction is weak enough compared to thermal energy that you can’t easily keep track of the position of an air molecule, for example. But, scientists can hit a tiny meteorite with a spacecraft from across the solar system, and can deliver a small exploding device to a particular window in the palace of a particular former dictator, using gravitationally based calculations. In the same way, there are lots of evolutionary questions, things we don’t know, and fascinating research frontiers, but the basic idea that kids are mostly like parents, differences affect success, and this leads to evolution, is very well established with very little uncertainty.
Discussions about “intelligent design” surely can be included in school—a school that does not recognize the reality of religion in the world is not preparing its students for that world. But “intelligent design” is not science, and the author believes that science classes should teach science.
Petrification - How is the Bone Turned to Stone?
No magic is involved in petrification of bone, or wood or other materials. The chemical environment inside organic materials is very different from the chemical environment outside. All groundwaters carry minerals, and when those mineral-carrying groundwaters encounter a change in chemical conditions, some chemicals usually are picked up while others are put down. Remember that water can poison people by picking up lead and other chemicals from old pipes and that water can clog old pipes by putting down scum and hard-water deposits—picking up some chemicals and putting down others is the usual behavior for water. Water softeners work by pulling calcium out of water and putting sodium back in.
When organic material is buried in mud, if enough adding and subtracting of chemicals occurs before the material is eaten by worms or fungi or bacteria, then the organic material can be “turned to stone”. This petrification is rare—most organics are recycled—but occurs often enough to give us plenty of fossils to study.
For example, silica is very common, and is relatively insoluble in acidic solutions but very soluble in basic solutions. Groundwater in dry environments often is basic and so carries much silica. When this silica-carrying groundwater meets the organic acids in a buried tree or bone or other formerly living thing, the silica may precipitate. Actual chemical processes are typically a little more complicated than explained here, but the principle is the same. Materials scientists are even succeeding now in using wood as a template for “growing” ceramics, replacing the wood by zeolites, silicon carbide, or other materials to make useful things by human-accelerated petrification.
Extinction and Absorbing Boundaries
If you go to a casino to gamble, you are likely to lose. This is partly because the games are stacked against you—the odds on all casino games favor the house. (The odds on state lotteries typically are even more in favor of the house, by the way.)
But, you also lose at a casino because you are poor and the casino is rich. Suppose that you start off with $10 and the casino starts off with $999,990. Together, you have $1,000,000. Suppose further that this is a bizarre casino with a perfectly fair game—you and the casino are equally likely to win. If you win $10, then you have $20 and the casino has $999,980. But, there is slight catch—if you lose $10, you are at $0 and the casino will show you the door. If you stay and gamble for a while, the outcome is almost guaranteed; you will hit $0 before the casino does, the casino will have all of your money, and you will go home broke. The $0 mark is an absorbing boundary—you can’t bounce off of it (the casino won’t give you your money back), nor can you go negative and then return (well, you might go take out a loan, but your ability to get loans to cover gambling losses is much smaller than the casino’s ability to get loans, so you’ll eventually reach the point of no return—your money will have been absorbed by the casino).
Extinction works the same way. Once a species is gone, it is gone. You can’t have a negative number of tigers and then later have a positive number. So random fluctuations eventually kill off species. But, at certain times, such as when the meteorite hit at the end of the Mesozoic, or now as we humans spread across the surface of the planet and squeeze others out (more on this coming soon!), extinctions go a whole lot faster than normal.