Example of Scientific Prediction

I've been reading Hen's Teeth and Horses Toes by Gould and in essay 29, he discusses the issue of whether zebras are black with white stripes or white with black stripes. In the process, he discusses the question of body morphology and introduces a hypothetical method for the three species of zebra and why they have the stripes they do. Forgive me for not using specific species names because I don't have the book handy and I'm being lazy in looking it up.In one species, the stripes are numerous throughout the entire body...lots of little stripes across the torso, over the rump, and down the legs.In the second species, the stripes are numerous on the torso, but when you get to the rump you get three really big stripes that lead down to the legs.In the third species, the stripes are smaller again, but the rear stripes reach much more forward on the torso than they do on the other two species.This is a wonderful example of how science is a predictive work. The proferred explanation is that the method of striping is identical for each species of zebra but the timing of when the stripes get laid down in the developing embryo varies. For one species, they would be laid down at three weeks. For another, four weeks. For the last, five weeks.If we take the back ridge of the zebra's spine and put stripe markers every so often, we would expect that a larger embryo would get more stripes than a smaller one. Too, if the body changes its rate of growth, the resulting pattern will vary depending on when the stripe got laid down.For the first species, the stripes would come down in the fifth week when the embryo is fairly large with the torso and hind quarters having been filled out...a fairly uniform striping pattern.For the second species, however, the striping happens in the fourth week. The torso has expanded but the hind quarters have lagged behind. Thus, we get lots of stripes on the torso but just a few on the hind quarters which then expand, carrying the stripes with them.For the third species, the striping would happen at the third week when the embryo is small, the torso hasn't expanded, and thus the stripes from the hind quarters are closer to the ones on the torso so that when that area expands, the stripes are pulled all the way across.At the time the hypothesis was presented and the time Gould wrote, nobody had done the requisite embryological analysis to determine if this was actually the case. How would one go about showing it? This is the prediction part of science. It isn't enough to make a model that conforms to known data...you have to predict data you don't have yet.What predictions can we make from this? What would we expect to see? One thing, for example, is that the ratio of number of stripes to size of embryo should be consistent. And sure enough, it is. The zebra with lots of little stripes has a size-to-stripe ratio (assuming a stripe lay-down time of five weeks gestation) of 0.4 mm in that you can fit about 80 stripes along the body at a spacing of one every 0.4 mm and the adults have about 80 stripes. The ratio of one stripe per 0.4 mm of embryonic body length fits for the other species, too.Also, we should think that striping patterns would be altered in hybrids of zebras with other equines. And we see that, too: A zebra/horse hybrid has a different number of stripes than the parent reflecting the different size of the embryo.So the ultimate prediction is that if we were to do the requisite embryological examination, we should see the cellular laydown of stripe-forming cells about every 0.4 mm along the body of the zebra at specific times that differ for each species of zebra. We've taken our observations, analyzed their components, and come up with a synthesis that tells us what we ought to expect regarding a piece of data we don't know. The model we have seems to work...but now we have to test it against something we don't know to see if it matches.As far as I know, I don't know if anybody has done this, but I hope the point is made: The work behind science is to gather information, process it, and make predictions. It is not sufficient to simply create a model that fits the data. That is why creationism continually fails. It seeks to create models that fit the biblical story but cannot do the next step: Given that model, what should we expect to see that we don't know? When we try to apply that, we find the model fails miserably. For example, the claim that the fossils we see are the result of the flood. If that were the case, then we should expect to see one of two things: Fossils jumbled together with no order to their position or fossils sorted by their density such as what you see in a bag of potato chips or cereal where the biggest ones are on top.We see neither. Instead, we see a clear layering pattern that continually varies in body density: Big animals below little ones and that particular big animal always appears below that particular little one (which always appears below that other big animal which always appears under that other little animal, etc.)Oh, and the question of black-on-white or white-on-black? Gould points out some evidence from the author he's referring to that they are black with white stripes: Every now and again you get zebras with mutated stripe patterns: Black fields with white dots or splotches. It seems that striping patterns are an inhibition of melanin production rather than an over-expression of melanin.Me? I claim that zebras are pink animals with black and white stripes. When you look under all that hair, they seem pink to me.

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Rrhain
WWJD? JWRTFM!

Thread moved here from the Proposed New Topics forum.

I'm not real sure where you want this to go, Rrhain, but let me offer another example of what you're telling about.Back around 1950, a couple of astronomers named Jan Oort and Gerard Kuiper put some serious thought into the observations that had previously been made of comets. These observations were only from the portions of orbits fairly close to the Sun - telescopes and photographic plates then could only see moderately faint objects, so comets had to start cooking off gases to be observable at all. In any case, Oort hypothesized that there had to be a reservoir of objects far outside the orbit of Pluto to supply comets that we see, specifically non-periodic comets - ones whose orbits indicate that they're coming through for a one-time show.Kuiper very quickly hypothesized a subset of out-there comets, as his analysis suggested that a good many comets were on slightly less extreme orbits than Oort's were - about a hundred to a maybe a thousand years per orbit, and very roughly in the plane of the planets' orbits. (Oort comets were at all angles.) Observations after these predictions confirmed that these predictions were reasonable, and the putative reservoirs were named the Oort Cloud and the Kuiper Belt.But nobody had seen any of these objects at home, so to speak. The creationist organization Answers in Genesis went so far as to publish a little article that said "there are no Kuiper/Oort objects there, so the universe is only 6000 years old." Then, in the early 1990's, technology began to catch up. Jewitt's group in Hawaii, and then others, began using bigger telescopes with sensitive electronic detectors to look for Kuiper Belt Objects - and they started finding them! At least 700 are now known, with precise orbits calculated in the region where Kuiper predicted. Mechanisms have been worked out for how they can get "bumped" into comet-like orbits, and size distributions of the (bigger) ones observable from Earth look like size distributions of main-belt asteroids - in other words, there are bunches and gobs of five-mile-across ones to make "normal" sized comets.Observations. Hypotheses. More observations. A hypothesis or two confirmed. That's science. (AiG still says "We don't see any little ones. The universe must be 6000 years old.")

That's pretty much it, Coragyps: The process of making observations from known data, working it over (quite often coming up with a new way of looking at the old data), and then coming up with a test that will help determine if the synthesis is pointing in the right direction.One of the big questions in science is how we go about confirming something. It isn't enough to feel good about the work and having an internal understanding that the world ought to work like that. What kind of test could be developed in order to verify that feeling?The question of zebra striping would require examination of embryos. The distant objects required the development of more powerful telescopes. Even Einstein's relativity theory required the development of atomic clocks and supersonic jets (remember, he developed it before the advent of aviation.)The fact that we cannot perform the test right now given the technology that we have does not mean that there is no test.What I'd love to see out of creationists is some examples of how one would go about testing their claims. Suppose god did it. What would we expect to see? What sort of test could be carried out? What results from that test would need to happen in order to lead to a conclusion that god did it?And on the other hand, examples of how evolutionary biology has tested itself. Suppose life evolved. What would we expect to see? What sort of test could be carried out? What results from that test would need to happen in order to lead to a conclusion that life evolved?And in the end, if one can understand that the test would lead to such a conclusion, why would this process need to be altered when it comes to questions of how life diversified?

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Rrhain
WWJD? JWRTFM!