Predictions - Is Evolution Science?

Original at -

Philosophers of science such as Popper and Kitcher say that it is. Scientists such as Mayr, Dobzhansky, and Ridley agree. Many organizations have passed resolutions to this effect. However, the important question is whether these authorities can back up what they say with evidence.

The following list gives a few of the predictions that have been made from the Theory of Evolution:


  • Darwin predicted that precursors to the trilobite would be found in pre-Silurian rocks. He was correct: they were subsequently found.


  • Similarly, Darwin predicted that Precambrian fossils would be found. He wrote in 1859 that the total absence of fossils in Precambrian rock was "inexplicable" and that the lack might "be truly urged as a valid argument" against his theory. When such fossils were found, starting in 1953, it turned out that they had been abundant all along. They were just so small that it took a microscope to see them.


  • There are two kinds of whales: those with teeth, and those that strain microscopic food out of seawater with baleen. It was predicted that a transitional whale must have once existed, which had both teeth and baleen. Such a fossil has since been found.


  • Evolution predicts that we will find fossil series.


  • Evolution predicts that the fossil record will show different populations of creatures at different times. For example, it predicts we will never find fossils of trilobites with fossils of dinosaurs, since their geological time-lines don't overlap. The "Cretaceous seaway" deposits in Colorado and Wyoming contain almost 90 different kinds of ammonites, but no one has ever found two different kinds of ammonite together in the same rockbed.


  • Evolution predicts that animals on distant islands will appear closely related to animals on the closest mainland, and that the older and more distant the island, the more distant the relationship.


  • Evolution predicts that features of living things will fit a hierarchical arrangement of relatedness. For example, arthropods all have chitinous exoskeleton, hemocoel, and jointed legs. Insects have all these plus head-thorax-abdomen body plan and 6 legs. Flies have all that plus two wings and halteres. Calypterate flies have all that plus a certain style of antennae, wing veins, and sutures on the face and back. You will never find the distinguishing features of calypterate flies on a non-fly, much less on a non-insect or non-arthropod.


  • Evolution predicts that simple, valuable features will evolve independently, and that when they do, they will most likely have differences not relevant to function. For example, the eyes of molluscs, arthropods, and vertebrates are extremely different, and ears can appear on any of at least ten different locations on different insects.


  • In 1837, a Creationist reported that during a pig's fetal development, part of the incipient jawbone detaches and becomes the little bones of the middle ear. After Evolution was invented, it was predicted that there would be a transitional fossil, of a reptile with a spare jaw joint right near its ear. A whole series of such fossils has since been found - the cynodont therapsids.


  • It was predicted that humans must have an intermaxillary bone, since other mammals do. The adult human skull consists of bones that have fused together, so you can't tell one way or the other in an adult. An examination of human embryonic development showed that an intermaxillary bone is one of the things that fuses to become your upper jaw.


  • From my junk DNA example I predict that three specific DNA patterns will be found at 9 specific places in the genome of white-tailed deer, but none of the three patterns will be found anywhere in the spider monkey genome.


  • In 1861, the first Archaeopteryx fossil was found. It was clearly a primitive bird with reptilian features. But, the fossil's head was very badly preserved. In 1872 Ichthyornis and Hesperornis were found. Both were clearly seabirds, but to everyone's astonishment, both had teeth. It was predicted that if we found a better-preserved Archaeopteryx, it too would have teeth. In 1877, a second Archaeopteryx was found, and the prediction turned out to be correct.


  • Almost all animals make Vitamin C inside their bodies. It was predicted that humans are descended from creatures that could do this, and that we had lost this ability. (There was a loss-of-function mutation, which didn't matter because our high-fruit diet was rich in Vitamin C.) When human DNA was studied, scientists found a gene which is just like the Vitamin C gene in dogs and cats. However, our copy has been turned off.


  • In "The Origin Of Species" (1859), Darwin said:
    "If it could be proved that any part of the structure of any one species had been formed for the exclusive good of another species, it would annihilate my theory, for such could not have been produced through natural selection."
    Chapter VI, Difficulties Of The Theory
    This challenge has not been met. In the ensuing 140 years, no such thing has been found. Plants give away nectar and fruit, but they get something in return. Taking care of other members of one's own species (kin selection) doesn't count, so ants and bees (and mammalian milk) don't count.


  • Darwin pointed out that the Madagascar Star orchid has a spur 30 centimeters (about a foot) long, with a puddle of nectar at the bottom. Now, evolution says that nectar isn't free. Creatures that drink it pay for it, by carrying pollen away to another orchid. For that to happen, the creature must rub against the top of the spur. So, Darwin concluded that the spur had evolved its length as an arms race. Some creature had a way to reach deeply without shoving itself hard against the pollen-producing parts. Orchids with longer spurs would be more likely to spread their pollen, so Darwin's gradualistic scenario applied. The spur would evolve to be longer and longer. From the huge size, the creature must have evolved in return, reaching deeper and deeper. So, he predicted in 1862 that Madagascar has a species of hawkmoth with a tongue just slightly shorter than 30 cm.

    The creature that pollinated that orchid was not learned until 1902, forty years later. It was indeed a moth, and it had a 25 cm tongue. And in 1988 it was proven that moth-pollinated short-spurred orchids did set less seed than long ones.


  • A thousand years ago, just about every remote island on the planet had a species of flightless bird. Evolution explains this by saying that flying creatures are particularly able to establish themselves on remote islands. Some birds, living in a safe place where there is no need to make sudden escapes, will take the opportunity to give up on flying. Hence, Evolution predicts that each flightless bird species arose on the island that it was found on. So, Evolution predicts that no two islands would have the same species of flightless bird. Now that all the world's islands have been visited, we know that this was a correct prediction.


  • The "same" protein in two related species is usually slightly different. A protein is made from a sequence of amino acids, and the two species have slightly different sequences. We can measure the sequences of many species, and cladistics has a mathematical procedure which tells us if these many sequences imply one common ancestral sequence. Evolution predicts that these species are all descended from a common ancestral species, and that the ancestral species used the ancestral sequence.

    This has been done for pancreatic ribonuclease in ruminants. (Cows, sheep, goats, deer and giraffes are ruminants.) Measurements were made on various ruminants. An ancestral sequence was computed, and protein molecules with that sequence were manufactured. When sequences are chosen at random, we usually wind up with a useless goo. However, the manufactured molecules were biologically active substances. Furthermore, they did exactly what a pancreatic ribonuclease is supposed to do - namely, digest ribonucleic acids.


  • An animal's bones contain oxygen atoms from the water it drank while growing. And, fresh water and salt water can be told apart by their slightly different mixture of oxygen isotopes. (This is because fresh water comes from water that evaporated out of the ocean. Lighter atoms evaporate more easily than heavy ones do, so fresh water has fewer of the heavy atoms.)

    Therefore, it should be possible to analyze an aquatic creature's bones, and tell whether it grew up in fresh water or in the ocean. This has been done, and it worked. We can distinguish the bones of river dolphins from the bones of killer whales.

    Now for the prediction. We have fossils of various early whales. Since whales are mammals, evolution predicts that they evolved from land animals. And, the very earliest of those whales would have lived in fresh water, while they were evolving their aquatic skills. Therefore, the oxygen isotope ratios in their fossils should be like the isotope ratios in modern river dolphins.

    It's been measured, and the prediction was correct. The two oldest species in the fossil record - Pakicetus and Ambulocetus - lived in fresh water. Rodhocetus, Basilosaurus and the others all lived in salt water.

The point is not that these prove evolution right. The point is that these were predictions that could have turned out to be wrong predictions. So, the people who made the predictions were doing science. The Theory of Evolution was also useful, in the sense that it suggested what evidence to look for, and where.
Last modified: 5 August 2001