Does evolutionary biology make predictions?

A commenter on my other blog at ScientificBlogging (basically a subset of posts from this one) seems to have objected to the claim that evolutionary science makes predictions.

gimme 5 examples of predictions, i mean real predictions: not fit the model hogwash

Here’s a list that I put together in around 10 minutes.

1) That a transitional fossil linking fishes and tetrapods would be found in rocks of a specific age (from the Devonian) and formed in freshwater environments. CONFIRMED.

2) That human chromosome 2 would show clear signs of fusion of two chromosomes that are separate in other apes when examined at the level of DNA sequence. CONFIRMED.

3) That genes for producing features thought to have existed in ancestors but absent in descendants will still be found when genomes are examined in detail or even through atavism. CONFIRMED (see also the paper mentioned in the original post).

4) That proteins in the bacterial flagellum will turn out to be similar to proteins with other functions. CONFIRMED.

And a classic…

5) Darwin predicted that the evidence would show that humans evolved in Africa based on similarities to other apes. CONFIRMED.

Others have put together some decent videos about this as well.

Want to share your own favourite examples?


15 comments to Does evolutionary biology make predictions?

  • robert d

    For fun I will play devil’s advocate

    1. Evolution always celebrates the finding of a transitional fossil between 2 different groups with great fan fare. At best this supports the case for punctuated evolution. There has yet to be found a successive sequence of fossils that demonstrates the gradual divergence of one group from another.

    2. How was it known ex ante that it would be chromosome 2? Was it also known which of the 2 chimpanzee’s chromosomes would be the linked pair? The real problem here is the amount of time between the occurrence of chimpanzee 24 to human 23. This is all suppose to have been brought about by gradual random mutation.

    3. I really don’t have any objection to the spirit of the example. However, I find the use of the word thought to have existed confusing.

    4. Wow! Proteins turn out to be like other proteins.

    5. This is very interesting. Somehow there was this place in Africa and only Africa were first Homo Erectus came from, and then Neanderthal, and final Homo Sapien. What was it about this special place in Africa that differed so much from the rest of the planet. It was almost as if there was an experiment being conducted. Wind up Homo Erectus and see what he does. Do some more tinkering and release upgrade 2.0. Finally upgrade 3.0, Homo Sapien was released from this exact same area.

    I know it is a very strange story. What makes it even stranger is that we are making up all these great stories based on perhaps 15-20 skeletal remains.

    Life is good,

    d

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    • Leao

      For fun I’ll reply:

      1 – Punctated evolution is gradual in every meaningful way, because the time lapses indicated by different layers of sediment deposition are huge. The stasis periods ares imply longer than the gradual change ones.

      2 – Actually, no. Cytogenetic, that is, chromosomal mutations can take place in a  single a genration leading to instantaneous speciation. This does not, in absolute, falsify non-teleological biological evolution.

      4. proteins do differ quite a lot 

      5. except there is no evidence whatsoever poiting to the experimenters’ existence. 

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  • The other Jim

    How about the entire fields of molecular evolution / phylogenetics / phylogenomics being predicted to be plausible after the marriage of genetics to classical Darwinian evolutionary thought?

    A handful of science journalists kept calling my PhD lab to try to get quotes when they finally figured out that these fields were independent confirmation of evolution and common descent, and something Darwin had never thought of himself.

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  • T Ryan Gregory

    Robert D,

    I think you've missed the point entirely. The question was about predictions made by evolutionary theory that were tested and confirmed. To reiterate,

    1) Based on previous fossils and the expectation of common descent, researchers predicted what age of rocks (~365-380 Mya) and type of habitat (freshwater) would hold the transitional fossil between fishes and tetrapods. They consulted geological maps to see where late Devonian rocks are exposed, went to the high Arctic to dig, and they found the fossil.

    2) Humans have 23 pairs of chromosomes, the other apes have 24. This looks like a problem for common descent, except that people noticed similar banding patterns on human chromosome 2 and two chromosomes in non-human apes. Once genome data became available, the exact fusion site was identified, along with remnants of telomeres and centromeres within chromosome 2.

    3) Confusing sentence structure aside, the point is that common descent would expect some genes that were active in ancestors but not in descendants to still be present. And they are.

    4) The issue isn't that proteins are like other proteins. It's that specific proteins within the flagellum can be identified as similar to other proteins in the cell that serve other functions because they are modifications of them, rather than being independent and exclusive to the flagellum.

    5) Darwin did not have any information about fossil hominids. He predicted an African origin on the basis of morphology in living apes. Then fossils were discovered (but note that Neanderthals were not from Africa, they evolved in Europe). And then DNA data confirmed this. So, Darwin's prediction was made on the basis of one sort of data, and it was then confirmed with two independent kinds of data.

    You're welcome to explain how your particular understanding of the history of life would have made these predictions.

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  • robert d

    I appreciate your comments.

    Recently, actually, yesterday, at the library I obtained Only A Theory – Kenneth R. Miller and The Edge of Evolution – Michael J. Behe, to do a compare and contrast.

    First impressions

    My name is Kenneth R. Miller. I am very important because I teach at Brown University and have been on lots of committees. I just don’t teach any class at Brown, I teach Cell 4. I have also published a high school text book on biology. Although I teach cell biology I sometimes have problems getting to the point. I like to quote Mathew Arnold, Disraeli, and others because it makes me seem more well rounded and well, intelligent.

    Miller may eventually make some good points but his beginning is awkward.

    Behe to his credit gets to the point in the 2nd paragraph –

    “-it is a mixture of several unrelated, entirely separate ideas. The three most important ideas to keep straight from the start are random mutation, natural selection, and common descent.”

    I have not thought about it enough to decide for myself if the ideas are entirely separate but his plain statement of the troika of the neo evolutionary synthesis is seminal.

    1. With more detail provided I appreciate your point. However, this could also support a punctuated evolutionary scenario. Most impressed that the time period predicted was correct. There are many cases of newer time studies finding more recent times for many events.

    2. I am extremely interested in the 24 to 23 transition. Is this an example of Ohno’s Paleopolyploidy Hypothesis? They looked and saw banding and then predicted that if they looked closer they would still find banding. Wow!

    In general I am unopposed to common descent. My concern here is if whether there was enough time, based on the geological record, for this change to have happened by random mutation? In the spirit of Ohno’s Hypothesis, there seems to be many times when very large changes happened over relatively short time spans.

    3. OK

    4. OK

    5. Thanks for the Neanderthal correction. Still, there is a lot being deduced from a relatively small sample size.

    I think the neo evolutionary synthesis is a good theory, but still a theory. My concern is that participants in this field are becoming increasingly myopic. More succinctly, nothing I am aware of prevents occasional periods of punctuated evolution. The mystery being the causes of these unpredicted events.

    Life is good,

    d

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  • T Ryan Gregory

    Hi Robert,

    I appreciate your interest, and given the polite tone you have taken and your apparent sincerity in contemplating the subject, I am happy to carry on in the discussion.

    I think it would be productive to separate "evolution" into its three major components or definitions.

    One, the "fact" of evolution. This is the idea that species are related through common ancestors by descent with modification. This is considered a "fact" in the scientific sense that it is supported by a wide range of independent types of evidence.

    Two, the "theory" of evolution. This is the series of mechanisms that have been put forth to explain the fact of evolution. This includes mutation, natural selection, genetic drift, gene flow, and other components.

    Three, the "path" of evolution. This is the historical route that lineages have followed over time. This would also cover patterns like whether evolution has occurred gradually or in bursts.

    It is important not to mix these. "Punctuated evolution" would be about the path, and perhaps would raise questions about the mechanism, but it has no bearing on the fact. (And, for the record, I am a proponent of punctuated evolution as a common phenomenon).

    As to your specific statements,

    1) You may be expecting a very gradual change depicted in the fossil record, which is almost certainly impossible to find. Fossils are rare in most groups. For vertebrates, we have examples showing the major intermediate stages (but note a difference between lineal and collateral ancestors), but not change in minute steps. However, in some invertebrates or protists that leave hard cases, the record can be remarkably detailed.

    2) Banding is based on the arrangement of DNA, specifically whether it is compacted (heterochromatin) or less so (euchromatin). This is quite different from whether the DNA sequences are the same. So, the observation is a discrepancy in chromosome number, which was proposed to be explained by chromosome fusion and supported initially by banding data. Then, when genome sequences were available, it was possible to confirm not only that a fusion occurred, but to identify the exact site of it.

    As to paleopolyploidy, no, a chromosome fusion would not be part of that. Paleopolyploidy under Ohno's hypothesis is that entire genomes duplicated 2 or 3 times in the history of vertebrates/bony fishes. A fusion of chromosomes is a different process.

    5) You're right that there aren't enough specimens to be sure about the overall range of Neanderthals (new discoveries have expanded it), but it is pretty clear that they did not originate in Africa. Nor are they ancestors of ours, rather they would be cousins. We now have DNA from Neanderthal fossils, so we can be sure that they were very closely related.

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  • Zen

    Birds appear to be descended from therapod dinosaurs. But the earliest fossil with feathers, Archaeopteryx, is older than therapod dinosaurs, leading to the prediction that feathered dinosaurs will be found that are older than Archaeopteryx.

    CONFIRMED TODAY!

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  • Mike Flynn

    No one doubts that genetics is a hard science, nor that evolution is a fine metaphysics for just plain making sense out of a mass of empirical data. Sometimes it is difficult to separate the metaphysical assumption from the empirical fact; but that is a hazard in any science. [e.g., gravity is not an empirical fact; falling bodies are an empirical fact. Gravity is a story we tell to make sense of the motion of bodies. We've had stories by Aristotle, Buridan, Newton, and Einstein — each giving an essentially different "take" of the nature of gravity.]

    To a physicist, a lot of those predictions may seem a little thin, and broad enough to be fulfilled in a great many ways. I think what some folks may mean by "predictions of evolution" is in Dr. Gregory's second layer: the theory. For example, Newton's theory of gravitation enabled him to predict planetary positions and motions with great precision (if after laborious calculations). In that spirit, Darwin's theory of natural selection via the struggle for existence ought to enable us to "calculate" the "trajectory" of species in some way. (I know there are no Darwin's Equations. The language is analogical.)

    The dog-bear seems to be more or less ancestral to dogs and to bears (arising in two distinct habitats over the ancestor's range), possibly a "collateral" ancestor. Given the dog-bear, can we predict the dog and the bear? IOW, does natural selection predict forward the way mechanics or electromagnetism does?

    Just to be clear: Species either poof into existence or they emerge from other species; and they don't poof. Therefore, they emerge from other species. So the fact of evolution [Level 1] is quite solid. The question is whether the theory/mechanism [Level 2] makes adequate predictions of the path [Level 3]. I don't expect evolutionary theory to be any more immutable than gravitational theory, after all, and sometimes it's useful to know at what points the theory breaks. [E.g., Newtonian mechanics at the very small and the very fast.]

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  • T Ryan Gregory

    What physicists consider predictions is not really relevant to biologists. Physics deals with simple phenomena, biology with extremely complex ones. Can you predict the exact outcome of long-term evolution? Of course not, because there are way too many factors.

    That said, I think there is still confusion regarding "fact" vs. "theory" vs. "path". My post was about predictions based on assuming the fact of common descent. I think predictions about path in a major sense are simply not possible given the number of influences. However, the notion that the theory can't make predictions is clearly incorrect, given that there are mathematical models specifically developed to predict the effects of natural selection, drift, gene flow, etc., within populations, and these can be and have been investigated experimentally and through observation of natural systems.

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  • Zen

    Mike Flynn asked: "(D)oes natural selection predict forward the way mechanics or electromagnetism does?"

    Yes, in the sense that you can make detailed predictions only for simple situations. You can only make predictions in broad strokes for complex situations.

    In physics, predicting the motion of just three idealized interacting bodies was fiendishly difficult (cf. "three body problem").

    If classic Newtonian physics has a hard time predicting three simple objects following strict, simple rules, image the difficulty of making detailed predictions involving millions of entities following probabilistic rules. In other words, biology.

    Biological prediction is far from hopeless, though. For instance, companies now anticipate that antibiotics or pesticides will lose their effectiveness as control agents after several years, due to the strong selection pressure for resistance that the chemicals apply to the "bugs" they are meant to control.

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  • Anonymous

    Ummm, how about one of the most famously successful predictions of all time?

    E.O. Wilson predicted a number of characters that an ancestral ant would have based on the assumption that it shared a common ancestor with wasps. Fossil species Sphecomyrma freyi turns up dating to around the age that was predicted for the divergence of wasps and ants, and it has all of Wilson's characters except for two.

    And one from more recent memory:

    Neil Shubin opens an old geography textbook and sees there's a bunch of exposed old rocks on Ellesmere Island that no one has ever searched before. They're rocks in which, according to evolutionary theory, we're likely to find "fishapods"–they date to the age when fish first moved out onto the land. He decides to go on a dig. All hail Tiktaalik.

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  • Mike Flynn

    The Wilson one is pretty good, although it was based on genetics rather than natural selection. How repeatable was it, or was it the intuition of an insect expert? What we don't know (as skeptics point out regarding psychic experiences) is how many species were "postdicted" unsuccessfully. IOW, is it better than dowsing?

    One cannot hope for the sort of quantification one finds in the hard sciences. But if it could be quantified by objective algorithms and applied across the board, I think such postdictions would make up for the impossibility of predictions. There is too much contingency to successfully extrapolate forward; but interpolation ought to be easier.

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  • Shinka

    Theoretical pop. genetics makes plenty of predictions about evolution, and many of them have been confirmed since the development of molecular evolutionary biology.

    I guess we tend to show evolutionary biology as some sort of proto-science only interested in describing the universe and accumulating tons of data, perhaps because its how biology is born, but anyone who take a look at journals like "evolution" will see evolutionary biologists are very much interested in theory and predictions.

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  • Michael Le Page

    I wrote about this for New Scientist here:

    http://www.newscientist.com/article/dn13677-evolution-myths-evolution-is-not-predictive.html

    Including this nice example:

    Perhaps the most striking prediction in biology was made in 1975 by entomologist Richard Alexander. After studying the evolution of eusocial insects such as termites, he predicted that some burrowing rodents in the tropics might have evolved the same eusocial system – as later proved to be the case with the naked mole-rat.

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