Predictions of Evolution

While finishing up the content for the article I intended for this week, I realized that I wanted to scrap the whole thing.  So this week's entry is actual a re-post (and slight edit) of a 2010 entry on my other blog which I was reminded of recently. It's about predictions based on evolutionary theory. Not, of course, of what path evolution will take. Rather, things we should find based on the path evolution seems to have taken.

The original pointers for most of these was found on other sites (especially talk.origins here and here and here). Talk origins have tons more of these predictions, I just picked the ones I found particularly interesting and fleshed them out with additional explanations and sources.

Jaw to Ear Transition

In 1837, C.B. Reichert (who was a Creationist, but pre-Darwin most everyone was), observed that when pig fetuses were growing, there was a point at which a portion of the jawbone detaches to become the tiny bones of the middle ear, which he found quite remarkable.  Once we had a theory of evolution, one of its early predictions was that there should exist a fossil between reptiles and mammals that essentially has two separate jaws, one of which was smaller and near the ear. When fossils of early cynodonts were found, specifically the Diarthrognathus (“two-jointed jaw”), this prediction was found to be true.  This is described better by Stephen Jay Gould in his book Eight little piggies: reflections in natural history.

Long-tongued Moth (1862-1903)

This is one of my absolute favorites. Darwin predicted in 1862, from observation of the Madagascar Star orchid, that there should exist a species of moth with a tongue a bit less than 30 cm (specifically “between 10 and 11 inches”) (Darwin 1862 ^[3]). At the time, no moth with a tongue that long had been discovered. However, natural selection predicts a battle between the orchid and moths in an “arms race” to get/deny nectar without proper “payment” (in the form of pollination in this case). In 1903, A hawk moth with a tongue around 300 mm was discovered, from the species known as Xanthopan morgani (the one pictured below only has a 7 inch tongue, but demonstrates the point I think) (Wikipedia 2010 ^[4])

Archaeopteryx Teeth (1872-1877)

When the first Archaeopteryx (a sort of intermediary between reptiles and birds) fossils  was found, the head was not in good shape and had no teeth. Then when Ichtyhornis and Hesperornis were found in 1872, they were determined to be seabirds, but they retained teeth (Huxley 1872 ^[5]). The early evolutionists of the time, specifically Henry Woodward of the British Museum, predicted that that the archaeopteryx should also have had teeth since reptiles had teeth, and birds descended from them. Woodward recognized the controversy of his proposal, putting words to it (Woodward 1875 [6]):

But, it may be urged, ‘your proposition that the Archaeopteryx had teeth is a pure assumption. Show me some evidence of a fossil bird whose head and skeleton are in juxtaposition so as to leave no reasonable doubt of their unity’).

But if the Archeopteryx didn’t have teeth, that was a problem for evolution.

In 1877, more intact Archaeopteryx fossils were found... with teeth. It is now accepted (even among Creationists) that the Archaeopteryx had teeth. And Archeopteryx would have had teeth whether or not we thought it should. The point is, evolutionary theory virtually demanded that it did, and the prediction held out.

Antarctica, and its fossils (1893-1982)

Believe it or not, we didn’t always knows Antarctica existed. In 1893, H.O. Forbes presented a paper at the Royal Geographic Society in which he discussed his findings in the Chatham Islands. He (and other naturalists) predicted that there should have existed a large sub-tropical southern continent (Editors 1893 [7]):

Taking these fresh facts into consideration, he marshals all the data which he considers prove a strong case for the probability of the existence of a former southern continent, and he sketches on a map of the Southern Hemisphere what he believes was the configuration of Antarctica, as he has named that vanished continent. He believes that it followed nearly what is the 2,000-fathom line, and extended northward from a circumpolar area, by broad extensions, one to join an old New Zealand continental island (including the Antipodes, the Maquarries, New Zealand, the Chatham, Lord Howe, Norfolk, the Kermadec, and the Fiji Islands); another to East Australia with Tasmania; another to the Mascarene and surrounding islands (the Lemuria of Sclater); perhaps one to South Africa, and, lastly, one to South America. The form of this continent would not interfere with the opinions expressed by many authorities in the permanence of the great ocean basins.

Viewing the article, you can see that it was not just about a single bird, but actually a wide variety of species whose distribution only made sense in light of there being this continent. At this time Antarctica had been spotted, but was seen as just being ice shelves. Additionally, at this time scientists were just starting work on the idea of prior large connected continents that broke up over millions of years.

One of his examples was “Marsupials - Nototherium, Diprotodon, Thylacoleo, Thylacinus in Australia ; Prothylacinus, Amphiproviverra in Patagonia.” Obviously there are no longer marsupials living in the current Antarctica, but it stood to reason that there should be fossils from the Mesozoic era.

These were found in 1982, with Polydolops. It was a 9-foot marsupial (Woodburne 1984 ^[8])

No doubt you can find papers for all the other fossils that were predicted to exist.

Flying Insects with Hemocyanin (2003)

The theory of evolution held for a long time that flying insects evolved from gilled crustaceans (Burmester 1996 ^[9]). Those crustaceans use a protein known as hemocyanin to circulate oxygen. Evolutionary theory would hold that there should be still be remnants of that in some flying insects, but none had been found. In 2003, scientists discovered a type of stonefly (generally considered to be some of the most “primitive” of insects, which makes sense) which still had functional versions of that protein (Hagner-Holler 2004 ^[10]). This is discussed more fully in an article by James H. Marden where he talks about the evolution of flight in aquatic insects (Marsden 2008 ^[11]).

Ancestral whale with teeth and baleen (-2008)

Currently there are two types of whales: those that have teeth, and those that have baleen to filter their food. None exist currently that have both. On the assumption that all whales must have descended from a common ancestor, it was predicted (I could not track down a date however) that there must have existed a whale that had both teeth and baleen at the point in time when the two diverged. Even today, baleen whales start with tooth buds that disappear (evidence that the toothed whale was first).  Well,  in 2008 this transitional form was found to have existed  24-28 million years ago, when baleen whales where splitting from toothed whales (Coyne 2010 ^[12]).

“Junk” DNA fingerprinting

“Junk” DNA can actually be used to predict (coming from a retrovirus) whether two seemingly-unrelated animals shared a common ancestor. Or, to put it another way. When we know that two species are related, we can predict whether or not they will share certain sequences of “junk” DNA. For example, There is a particular sequence found in hippos, whales  and cows but not in humans, mice, kangaroo, elephants or horses. This would lead to the conclusion that there was a common ancestor (after the split that led to humans and mice) shared by hippos , whales and cows (which is true). And based on this theory, they should be able to find this  same set of “junk” DNA in deer, but not in monkeys. Incidentally, finding this particular “junk” DNA in monkeys would actually be a point against evolution, since the retro-virus that caused it came after the ancestor to primates. (Lindsay 2010 ^[13])

As another example, both guinea pigs and humans have a specific defect in the gene that encodes for Vitamin C processing, meaning that any species in the line "between" guinea pigs and humans* should have that mutation (the math works out that that genetic divergence would have occurred approximately 20 million years ago) (Nishikimi 1988 ^[14]). If this exact same “typo” (of the same sequence) were found outside of the primate line from guinea pigs to humans, that would be a problem for evolution.

* This is not suggesting that humans descend from guinea pigs. They are as evolved as we are. Rather, guinea pigs and humans both descend from some ancestor which had this defect. So any ancestors we encounter as we go "back" from both humans and guinea pigs will have the defect until reaching that common ancestor. Richard Dawkins' The Ancestor's Tale illustrates this idea beautifully.

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