Davescot on Darwin and eugenics

In a post at the Uncommon Descent blog, Davescot has an excellent summary of the connection between Darwin and eugenics. The article is A complete Darwin quote with a brief translation (20 April, 2008). Davescot's article is simple, accurate, and straight to the point.

For those who follow these debates, this may come as a surprise. Normally I find little of value at Uncommon Descent, and I'm very surprised to see this one. But credit where it is due; Davescot's post is excellent, and needs no modication or qualification to get my full recommendation.

The article has a full quote from Descent of Man, including the second paragraph traditionally omitted by those who want to link Darwin to the holocaust. He follows this with a couple of very simple and straightforward observations.

Paraphrasing briefly, Darwin notes that we humans are animals in the body, and that the same selective breeding applied to farm animals for generations would work in the same way if it was applied to humans. Immediately after this, Darwin also notes that the attempt would degrade the noblest part of our nature, the very part which distinguishes humans from other animal species.

Quoting Davescot's concluding paragraph.

If there’s any real case to be made for Darwin and the holocaust it’s the opposite of what’s messaged in Expelled. The holocaust resulted from a failure to heed Darwin’s warning that eugenics could only be practiced by sacrificing the noblest part of our nature, the very part and only part that separates us from other animals. Those responsible for the holocaust, beginning with the eugenics movement in America, were the true animals. Those opposed were nobler than the animals.

Hat tip to Wes Elsberry at the Austringer for alerting me to Davescot's post. Flunked, Not Expelled: Not Even David Springer Buys the Darwin-Leads-to-Hitler Rhetoric.
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Non Sequitur on Birds and Dinosaurs

Non Sequitur by Wiley Miller is one of my favourite comic strips. This one is May 17, 2007; but read the whole sequence from May 14 through to May 19, as Jeffery goes back in time to get a DNA sample from T-Rex, taking a chicken along as his interpreter.

(PS. Wiley is pretty clued up. I am sure he is well aware that T-Rex was not actually a direct ancestor of birds. It was a Theropod; a distinct member of the group from which birds are descended.)
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Teach the controversy

Evolutionary biology is a vibrant field of science, and full of active dispute and uncertainty and new discovery. Science education ideally gives students the basic background so that can find their way around popular descriptions of what is going on at the bleeding edge of research.

Here are some of the controversies that could easily be part of a lesson even in high schools.

1. The Cambrian Explosion. About 530 million years ago, and over a period of some 10 million years or so, there was a dramatic diversification of animal life, the like of which has never been seen before or since. There are a host of unanswered questions and hypotheses about what is involved. When it occurred, how long it lasted, what are the antecedents, what changes took place, what mechanisms were involved. It is seen as an artefact of sampling, giving limited insight to a much more spread out period of change, or as a comparatively abrupt phase shift in the biosphere. It's seen as driven by evolution of exoskeletons, or of vision, or of predation, or of HOX genes. It is seen as driven by oxygenation, or warmer temperature, or changes in the sea floor. On going investigations continue to shed light on this fascinating period, but it's still wide open for new research and ideas.

2. Horizontal transfer verses variation through descent. For the most part, we carry within our bodies the genetic heritage of our ancestors; but there are also possibilities for genetic information to become incorporated into the genome from other organisms or a virus. This is particularly common in bacteria, but it can also occur for more complex organisms. The extent and importance of this is an open research question.

3. Particulars of lineage and relationships. There are many cases in which scientists are uncertain as to the relationships of different organisms. A classic example is the whole dinosaurs to birds issues, though this one is now all but resolved. There are plenty more that remain wide open. One example would be relationships between insectivores (insect eaters -- shrews, hedgehogs, moles, tenrecs, etc). There are many other examples.

4. Drift verses positive selection. It's a common misconception to think of evolution as a kind of continuous progress in improved fitness. Recent decades have given strong support for a notion of neutral drift, and the development of characteristics that are not adaptive, but simply a consequence of accumulated neutral change. What features of an organism actually are adaptive, or a result of positive selection? There are ways to measure this when we have access to a DNA sequence. With fossils and paleospecies it gets more difficult.

5. Target of selection. People often think they understand selection; but what is selected? Is it genes? Individuals? Populations? Species? All of these have been proposed as targets for selection, and the debate continues as to their relative importance.

6. Evolution and behaviour. We are more than our physical forms; we also have tendencies and predilections for different kinds of behaviour. To what extent is behaviour subject to evolution? This is a very difficult and contentious dispute!

7. Physical details of microevolution. There's still a lot we don't know about how development works, and how variation accumulates from generation to generation. What kinds of change can arise in the genome? Genes are far more than a coded protein sequence. They come with promoter regions and splicing points, and ways of encoding multiple proteins depending on how exons are combined. Evolution can duplicate whole genes, or combine them, or alter the regulatory promoters. Some parts of the genome are much more subject to variation than others. What kinds of variation are possible? What is their relativity frequency and importance? What proportion of variation is deleterious? How important is the piggyback effect where selection for one variation carries along other consequences? I'm only touching on the huge range of active research questions here.

I'm not a biologist. If you can educate me further in any of these or add some more, please leave me a comment!

(Disclaimer: this post is a repeat with minor revisions of something I wrote sometime ago in a discussion forum.)

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Update: I omitted to say why I wrote this. It was originally given in the context of creationist notions about teaching the controversy. I intended to contrast what genuine scientific controversy looks like, as opposed to the screwy notions of creationists.
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Does Darwinian evolution support conservative values?

In a recent article, conservative USA blogger and writer Dinesh D'Souza suggests conservatives should recognize that Darwinian evolution "has a lot of evidence going for it [with] the added merit of being politically congenial" (Why Darwin Scares Conservatives, When He Shouldn't.)

In my previous blog article, I suggested that D'Souza's article is a positive step, in so far as it recognizes the validity of conventional evolutionary biology. In this followup, I propose that recognizing the validity of Darwinian evolution does not give the easy support to conservative values that D'Souza proposes.

Dinesh notes that Christian conservatives in the USA sometimes come across as yahoos, because of their rejection of Darwinian evolution. They do indeed! It's a startling comment on the failure of science education that so many people can't tell the difference between straightforward well established discoveries of science, and breathtakingly inane pseudoscience.

The major impediment to education is religious. Far too many people accept on faith certain religious beliefs that have long since been decisively refuted. For such folks, progress in basic science education requires them to revise those beliefs.

Does this require them to drop their religion altogether? Actually, no. That is one way forward, and many have taken it. There are also others who have reconciled their religious beliefs with the findings of conventional science. In the latter case, there will continue to be debate and dispute between believers and unbelievers; addressing the consistency and parsimony of their views; but it's no longer a dispute on the underlying empirical facts about how evolution proceeds.

I'm fine with that. I do debate religion, and will be posting here some positive arguments for unbelief. But I don't think this has the same urgency as basic science education. Many people find it much easier to revise their beliefs rather than to abandon their religion altogether and so Christians who accept science (like Ken Miller, for a prominent example) have an especially important role in the fight for science education.

Just quietly, I also think this is a slippery slope. It seems to me that Christians who switch away from a position of crude fundamentalism and historical inerrancy and into a more "liberal" faith are particularly prone to keep going and in time lose their faith altogether. It's not a universal rule; but once your beliefs start to move even a little bit, there seems to be some momentum involved. But I digress. I truly don't mind when Christians find a stable reconciliation, and am much more concerned to help people break free from pseudoscience than to persuade them away from religion altogether.

Dinesh proposes an interesting point of leverage. It's not merely religion that breeds rejection of science. This is especially true of politically conservative religion. But Dinesh suggests that political conservatives could, if they recognized the validity of evolutionary biology, employ that as a new basis for argument in support of conservative ideals.

If this worked, it would be a powerful tactic. Being "scientific" is impressive. A "yahoo" is less persuasive. So in this article, I'll look briefly at Dinesh's three chosen examples.

Tough Foreign policy

D'Souza considers that Darwinian evolution provides a justification for "tough foreign policy".

First, Darwin gives a dark and selfish view of human nature, which is why we need a tough foreign policy to deal with bad guys who cannot be talked out of their badness--even if U.N. cocktails are served.

This is, of course, a classic example of a superficial misunderstanding of evolutionary biology. This could be cited as a refutation of my previous blog entry, to say that D'Souza really is "redefining" evolution. I think it is better seen as a common limited understanding of evolution.

In fact, evolution can perfectly well select for altruistic and social behaviours, as well as for selfish ones. Humans are "naturally" social beings, and there's good reason to see that as a characteristic that has evolved under natural selection.

We co-operate, but we also act to "punish" those who don't co-operate with us. There has been quite a deal of research on this, and some fascinating papers. Humans are willing to make significant personal sacrifices for the sake of inflicting "punishment" on someone else who breaks norms of social co-operation; and we are also inclined to altruistic behaviours – up to a point. Both of these convey no immediate benefit to the individual; but they can indirectly contribute to the fitness of an individual within the social context of human society.

There are lots of papers on this. One example of many is "Costly punishment across human societies", by Henrich et. al., in Science 2006;312(5781):1767–70. Here's the abstract:

Abstract
Recent behavioral experiments aimed at understanding the evolutionary foundations of human cooperation have suggested that a willingness to engage in costly punishment, even in one-shot situations, may be part of human psychology and a key element in understanding our sociality. However, because most experiments have been confined to students in industrialized societies, generalizations of these insights to the species have necessarily been tentative. Here, experimental results from 15 diverse populations show that (i) all populations demonstrate some willingness to administer costly punishment as unequal behavior increases, (ii) the magnitude of this punishment varies substantially across populations, and (iii) costly punishment positively covaries with altruistic behavior across populations. These findings are consistent with models of the gene-culture coevolution of human altruism and further sharpen what any theory of human cooperation needs to explain.

The appropriate way to use any theory of human behaviour as a guide to policy is certainly not to decide what is natural and then do that. We need to estimate the probable response of others to our various policy possibilities, and use that to estimate whether or not the policy is likely to have the effects we want.

That is, any model of human behaviour is a description, not a prescription. We have the capacity to reflect and decide actions, on whatever basis we choose. The role of a behaviour model is an aid to estimating the probable effects of actions, so that we can use that to help make a wise choice.

D'Souza suggests that people are bad, and cannot be talked out of bad behaviours; and so force is a better option. But in fact, evolution does not mean simply that people are bad.

I suggest that a genuine scientific investigation of human behaviour reveals a bad downside to "tough" foreign policy. If we take actions that others perceive as "unfair", then they are likely to make considerable personal sacrifices in order to punish us. But if our actions are perceived as fair, then we have a better hope of tapping into the natural human capacity for social co-operation. It's not a simple question; because there are also costs associated with actions that others might perceive as fair, and that needs to be weighed in the balance. But it's just not a valid inference of evolutionary theory to infer that "tough" policy is likely to be the most effective.

Capitalism

D'Souza says:

… the selfishness in human nature warrants a system called capitalism which channels this self-orientation toward the material betterment of society.

This is a massive begged question. It may be that Darwinism gives an explanation for human selfishness; but as noted above it is also consistent with altruistic behaviours. The fact is, evolution does not give a simple prediction for either selfishness or for altruism. It rather predicts that behaviour will tend to increase reproductive fitness; but what behaviour has that effect depends on the environment and interactions of the organism.

More seriously, what really needs to be argued here is that capitalism does actually channel self-orientation toward the material betterment of society, as claimed. That's what is really required for a support of the conservative position. Sorting out the causes of behaviour is not all that important; since we have the behaviours in any case, regardless of causes. Evolution does nothing to support the notion that capitalism is actually effective at channeling self-interest into material betterment of society. It's pretty clear that unrestrained unregulated capitalism has some major negative effects on society as individuals accumulate sufficient power to manipulate circumstance to their personal benefit.

Family values

D'Souza says:

Darwinian theory supplies the reason [that children are safest with their natural parents]: the real parent shares the same genes as the child and this forms a bond that dispels sexual attraction and discourages abuse. "Family values" are supported by modern evolutionary biology.

I agree that children tend to be safest in the care of their own parents; but that is a general tendency rather than a universal rule. Evolutionary theory means that there is variation in behaviour; and we see that in any case. Good parents have better evolutionary fitness; but some children nevertheless end up with the rare examples of abusive natural parents.

But more seriously, this has little to do with the wide ranging set of policies that come under the umbrella of "family values" for political conservatives.

For example, supporters "family values" typically oppose homosexual marriage. That has nothing to do with children. They oppose adoption of children by homosexuals. But the argument as given is actually against adoption altogether – except that adoption is invariably in a case where natural parents are simply not an available option. The advocate adoption as an alternative to abortion. If anything, the argument presented should suggest that adoption is NOT a good alternative; except of course that someone who insists on a right to life for the unborn will see adoption as better than death. But D'Souza's argument sheds no light there.

One feature of evolutionary theory is that there is always potential for far more children to be born than can possibly survive. So in "saving" one unborn child from abortion, one is in fact contributing to population pressure that will contribute to subsequent potential lives never being realized. This applies also on the small scale. A girl or young single woman who opts for abortion in response to an unwanted pregnancy is often likely to mature and form a stable relationship in the future where children are safer and wanted. That potential may be lost if the first pregnancy proceeds to birth. Of course, this is unpersuasive to those who only recognize potential in the context of an actual physical conception; but the Darwinian argument does not work for that position.

In brief; I'm glad to see a religious conservative speak up on the validity of conventional Darwinian evolution. I don't agree that this gives the easy support to conservative values as D'Souza understands them. But at least one level of irrationality has been (hopefully!) removed from consideration as we engage such issues.
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Is D'Souza really redefining evolution?

Conservative USA blogger and writer Dinesh D'Souza isn't afraid of Darwin. According to D'Souza, this is not because Darwin can be easily refuted; but because actually Darwin is perfectly compatible with Christian belief in design. He says:

I know many on the right, especially the Christian right, are scared of Darwin. Even intellectual magazines like Commentary seem to have adopted an anti-Darwin position. This has enabled many on the left, as well as the professional atheists like Richard Dawkins and Sam Harris, to portray conservative Christians as yahoos. Sometimes we do come across that way.

In my forthcoming book "What's So Great About Christianity" I will show why, contrary to the claims of Dawkins and company, Darwinian evolution does not undermine the design argument for God. On the contrary, the latest findings of modern science have greatly strengthened that argument. Paley was right and Dawkins is wrong.

This has been picked up by a number of prominent bloggers. Pharyngula is unimpressed, at The rebranding of Intelligent Design. He says:

The new strategy is to embrace the word "evolution". Ask them if they believe in evolution, and they will happily declare that "Yes, I believe in 'evolution'!" Unfortunately, what they call "evolution" is not evolution as evolutionary biologists understand it. If they're willing to redefine science, what's to stop them from redefining mere evolution to suit them?

Pharyngula's title got it right. D'Souza is trying to rebrand design, but without letting on that this is what he is doing. But is D'Souza actually redefining evolution? Not that I can see.

Paley's notion of design

D'Souza is playing fast and loose with the notion of design. Paley's arguments on natural theology dealt specifically with the forms of living things. His famous book, first published in 1802, is Natural Theology, Or, Evidences of the Existence and Attributes of the Deity. This includes the notorious "watchmaker" argument, which is the argument that has been picked up by the modern intelligent design movement. Put simply, anything that complex needs a designer. This argument was exploded by Darwin's insights on the origin of species.

The modern Intelligent Design movement picked up the shreds of this now useless argument, and by virtue of reeking incompetence at elementary science they tried to prop up the corpse with a lot of claims about new scientific theories. No science was actually involved, of course; just lots of bafflegab, and repackaging of conventional creationist arguments. This charade has been thoroughly exposed for anyone with the wit to see it.

D'Souza thinks Paley got it right. But Paley does much more than propose design. He gives an actual argument for design, and he speaks specifically of design of the forms of living things themselves. And in this, Paley got it wrong.

For instance, on page 468 (12 ed) of his book, Paley considers some difficulties with his view.

The TWO CASES which appear to me to have the most of difficulty in them, as forming the most of the appearance of exception to the representation here given, are those of venomous animals, and of animals preying upon one another. These properties of animals, wherever they are found, must, I think, be referred to design; because there is, in all cases of the first, and in most cases of the second, an express and distinct organization provided for the producing of them. Under the first head, the fangs of vipers, the stings of wasps and scorpions, are as clearly intended for their purpose, as any animal structure is for any purpose the most incontestably beneficial. ...

The remainder of the chapter makes fascinating reading. Paley gives some mitigating considerations, and a look at the whole problem of evil, and also, interestingly, a consideration of a role for chance and contingency along with design.

The critical point to bear in mind is this: Paley is looking at the specific organs and adaptions of living things. In Paley's view, the form of such organs can only be explained by design. Darwin showed that this is wrong; finely adapted organs can also be explained by natural selection.

The modern intelligent design movement is perfectly correct to see evolution and design as being two radically different explanations for the finely adapted forms of living complexity. They can't both be right, and this design argument is most certainly wrong.

Another view of design

At this point, we come to a subtle distinction. Darwin certainly exploded the line of reasoning used by Paley, but he did not explode the conclusion that the natural world is established by the design of a deity. Darwin left in smoking ruins the best positive argument from the natural world to a deity. He did not actually proceed to refute the deity itself.

It seems hard for many atheists to get their head around this point: but there are many Christians actively at work in scientific research into the natural world, and who accept without quibble or distortion all the basic empirical facts of evolutionary biology as conventionally understood by mainstream science. Christians are a minority amongst working scientists, but there are still a substantial number.

Christians invariably have some kind of notion whereby the natural world is God's creation. For Christians active in conventional science, this usually means that evolution itself is an intended consequence of how the designer set up the cosmos. An interesting example of this perspective is the famous evolutionary biologist Theodosius Dobzhansky. Dobzhansky's well known essay,
Nothing in Biology Makes Sense Except in the Light of Evolution is actually about science and religion, and it expresses basically a kind of theistic evolution. He says:

The organic diversity becomes, however, reasonable and understandable if the Creator has created the living world not by caprice but by evolution propelled by natural selection. It is wrong to hold creation and evolution as mutually exclusive alternatives. I am a creationist and an evolutionist. Evolution is God's, or Nature's method of creation. Creation is not an event that happened in 4004 BC; it is a process that began some 10 billion years ago and is still under way.

This is a variant of a common theme amongst Christians who are active in science. They hold that the entire natural world is established by design, and that any study of natural processes is study of that design.

This perspective is, of course, not provable and (usually) not falsifiable. It is not a scientific model. This is invariably recognized by its advocates. It may not be a good fit with popular religion, but Christianity is extremely diverse in any case. Dobzhansky, for example, was a devout Russian Orthodox Christian, but he was by no means conventional in his beliefs.

Whether this perspective is a fit with traditional religion is debatable. My own feeling is that we can see this much, at least... it has been a traditional belief all down the centuries that all natural processes are established by God. This foundational belief has been maintained many many Christians even as our understanding of those processes has developed.

Don't Redefine Evolution

We don't have to agree with Dobzhansky. But it would be rash to say that his view was inconsistent with evolution, or that he redefined evolution! As one of the major developers of the "New Synthesis" of evolutionary biology with genetics in the 1960s, Dobzhansky has an excellent claim to being one of those who established the definitions of evolution that we use today!

D'Souza recognizes that taking an explicit anti-Darwin position makes you look like a yahoo. As far as I can tell he's recognizing Darwinian evolution as it is conventionally defined. I see no flagrant errors in the details of evolutionary biology involved; and no redefinition.

The explicitly anti-Darwin position of the modern Intelligent Design movement so popular with D'Souza's fellow religious conservatives is a position of breathtaking inanity, fostered by culpable ignorance and calculated dishonesty in its public defenders. The real risk from attempts to rebadge intelligent design is the problem of the big tent. The risk is that they'll say one thing to one audience and another for a different audience, and try slide anti-Darwinian design of specific forms into the arena under the cover of a vague belief in a creative design underlying the whole cosmos.

D'Souza is, as far as I can tell, recognizing the validity of evolution, but arguing that it's a part of the whole design. That's a position that can and should be argued. But let's not argue it by redefining evolution ourselves!

This has nothing to do with wanting atheists to keep silence, or with rolling over and accepting the validity of religion, or with avoiding offense to believers who happen to be allies in the fight against creationist pseudoscience.

Evolutionary biology makes no mention of plans, or designs, or Gods. We have no need of that hypothesis. The same is true of meteorology, geology, physics, chemistry or any other science. There is not even an additional clause to say "there's no God who set this up". To argue for or against God's existence can use arguments relating to empirical science, but they have to go further than this and into some metaphysics.

Distorting science to insert our own metaphysics is bad because it distorts science. It is bad when done by believers, and it is bad when done by unbelievers.
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The Evolution of Wings

Image of Archaeopteryx and Microraptor by Jennifer (Jenna) Bolen, UC Santa Cruz.

This is a sequel to my earlier blog entry on an exhibition of Chinese dinosaurs, with a PhD student in attendance giving visitors some free lessons in paleontology and dinosaur evolution.

The thing I found most interesting was his discussion of the probable evolutionary development of wings.

Background: what use is half a wing?

It's a common argument from anti-evolutionists that evolution of specialized structures like a wing is impossible, because the initial stages would serve no useful function and so could not possibly be selected. As creationists sometimes ask: "What use is half a wing?". This is number CB921.2 in the Index to Creationist Claims.

The index provides answers -- there are many things that a "half wing" could be good for.

The question incorporates a misconception. Individual organs don't evolve in isolation. They are part of a complete living organism, and the whole organism evolves together. At any point along a successful lineage, you are bound to have effective fully functional organisms, well adapted to their particular lifestyle. There may be positive selective pressures giving some direction to the changes that accumulate along the lineage, but successful variants are those that incorporate changes with an immediate benefit. Just grafting a wing that is complete for an eagle onto a Velociraptor dinosaur would not work; because the rest of the Velociraptor's body is adapted for a different lifestyle to that of the soaring eagle. If a particular organism has "half a wing", than that is most likely pretty much the right kind of wing for that organism.

Another consideration is functional shift. The ancestral forms of any organ may have been adapted for quite different purposes, and over time their primary function shifts from one role to another. If you could replace "half a wing" with a "full wing", then you may actually make matters worse, since the change removed some other other important function that is vital to the ancestral form.

A common argument from the evolutionist side, in attempting to fill out an entire hypothetical picture of evolution, is that even the tiniest fraction of a wing might give at least SOME benefit, perhaps in breaking a fall, and so this is leverage for evolution. This response runs the risk of contributing to the misunderstanding of thinking that the original form is properly understood as a half-wing.

Natural selection is, for the most part, a conservative force, acting to weed out damaging mutations and to retain existing function. You can have positive selection for a gradual change, but this really only works if there is also a strong selection against losing change in the reverse direction.

Functional shift

The relevance of this to wings is that if an organism has some proto-wing which has only the tiniest contribution as a wing, then this is not likely to be a sufficient explanation for how a wing can evolve. You might think that even 1% of a wing still gives some leverage to evolution. Actually, it quite probably does not.

This point is well argued in the context of insects by Kingsolver and Koehl, Selective Factors in the Evolution of Insect Wings (Annu. Rev. Entomol. 1994.39:425-5). It was found that the tiny contribution of the earliest proto-wings to flight was not able to account for the kinds of selective pressures that could plausibly explain wings. The solution is found in functional shift: wings originally were selected for a different function – thermoregulation. In this case, the initial thermo-regulators could still give a substantial benefit to a well-adapted organism, despite being too small for aerodynamic qualities to be of much importance. This allowed leverage for evolution to drive to greater surface areas for more effective thermoregulation; and co-incidentally this was just the kind of change that gave them also the quality of aerodynamic function.

Furthermore: at small sizes, an increase in size of wings had a significant effect on thermoregulation but little effect on aerodynamics. But as the wing size became larger, further increases in size had little further impact on thermoregulation but a substantial impact on aerodynamics. This is illustrated in the following figure.

"The thermoregulatory (upper curve) and aerodynamic (lower curve) Advantages for increasing wing length in insects. Note that thermodynamic benefits accrue rapidly when the wing is very small (too small for flight), but scarcely increase at all for wings of larger size. Aerodynamic advantages, on the other hand, are insignificant for small size, but increase rapidly at larger wing dimensions, just as the thermodynamic benefits cease." (Reproduced from Not Necessarily a Wing, by Stephen Jay Gould.)

Back to dinosaurs: Sinornithosaurys millenii

One of the fossils recently found in China is Sinornithosaurus milleni. Sinornithosaurus is a dromaeosaur, part of a family of agile meat eating dinosaurs. Another famous dromaeosaur is the Velociraptor, which had a starring role in Jurassic Park. In fact the models in the movie were based on Deinonychus; and since then we have learned that these animals had feathers. A fossil Deinonychus is illustrated below, and an artist's impression for Sinornithosaurus graced my earlier blog article on the subject.

Sinornithosaurus was not a bird, and it could not fly. Its forearms are not wings; but the fossil shows two crucial "preadaptions" for bird wings. Sinornithosaurus has feathers, or proto-feathers. It seems probable that these structures developed mainly for insulation. The feathers were not adapted for flight, but would have been more like a kind of soft coat of down. Such a coat can help trap a layer of air next to the skin. We can't prove definitively the various stages, but it is plain that selection for a capacity to give insulation will lead to structures that trap air, and this in turn gives an increased capacity to push on air, or develop an aerodynamic effect.

The other significant preadaption are the long forearms, and their range of movement. Many dinosaurs had very small forearms; Tyrannosaurus Rex being a classic example. Such forearms could not possibly give rise to wings, and small changes in a stunted forearm will have no selective advantage for wings.

However, there may be selective advantage for a longer forearm in dinosaurs that use their arm for an attack. Sinornithosaurus had very long arms, and furthermore they had an extended range of movement. This was a matter of special interest to the PhD student at the Chinese Dinosaurs exhibition. The skeleton indicates that this dinosaur was able to move its arms above the head, and would have been able to bring them down for a slashing attack on their prey. This movement needs to be in place before there can be selection for wings; but the selection force for developing this movement is a capacity to attack. They had long legs, and were probably well suited to run down and leap on their victims.

Dinosaur dreaming

Fossils of Buitreraptor (foreground) and Deinonychus (background) at the Field Museum of Natural History in Chicago, Illinois. Photo by C. Horwitz, available at wikipedia.

We don't know all the stages in the ancestry of birds, but the transitional fossils we see indicate how the initial dinosaur form merges into that of birds. Sinornithosaurus, and many other fossils from the Yixian formations in Northern China and elsewhere, give an insight into now extinct forms of life. It's not possible to prove how selection worked on these creatures; but that they were as subject to selection as any other living thing is plain.

The relationships between these dinosaurs and birds have been emerging as we continue to find fossils of bird-like dinosaurs, and dinosaur-like birds; all fully functional living organisms in their own right, but with a mix of characters that make them splendid examples of "transitional" fossils. Precisely how the various processes of evolution worked out, and the full details of lineage, will never be given as a complete finished picture.

The glimpses we have do show the kinds of forms that gave rise to modern birds, and they show ample scope for selection to apply by small changes in form as an arm becomes longer, and with a wider range of movement, and with a coat of feathers, and with a benefit to a sudden spurt of speed to jump and leap out at prey. It may not have been exactly like that; and maybe other processes and effects will be found; and quite possibly there are significant contributory factors that will never be revealed.

Imagination and speculation are important qualities for a scientist. These ancient forms are thrilling and fire the imagination all the more for being based in reality. Children love dinosaurs, and the best scientists (IMO) continue to be driven by a child-like wonder at the ancient world they explore, combining an active imagination with detailed and rigourous study of all evidence available.

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Update. This post is part of the Tangled Bank blog carnival #79. Check out all the other posts available.

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Chinese Dinosaurs

A while ago I had the good fortune to see an exhibition of Chinese dinosaur fossils, and now that I have a blog I'll repeat some comments I recorded at the time.


The exhibition was fairly small, and the information available was limited, but appropriately geared towards the general public. There were a number of reconstructions of skeletons, and some models of what the dinosaurs might have looked like in real life, and some of the fossils themselves (copies, I suspect).

The best feature of the exhibition was a PhD student from the University of Queensland, who was there in an official capacity to talk to anyone who was interested, and was able to go into much more depth than was available in the small bits of text on the exhibits. He gave me and a few others a very clear discussion of the major classification of dinosaurs into "lizard hipped" and "bird hipped" forms. He also did a great job of conveying to some other visitors the complexities of relationships between various forms, and how evolutionary change and in particular the rise of birds does not simply involve progressive change in one lineage, but a range of forms with the development and loss of various characteristics in different lineages. For example, birds are descended from the lizard hipped dinosaurs; not the bird hipped.

His own work is on biomechanics, and in particular on birds and dinosaurs.

One striking thing about dinosaurs is the way they can capture the enthusiasm of young people. There was a little boy there, about five years old, who nevertheless knew the names of many dinosaurs, and pronounced them better than I can manage. His mother said that he gets irritated with plastic toy dinosaurs that have anatomical errors. He was talking with the PhD student about the velociraptor model, because the model was given with feathers; a plausible hypothesis not confirmed by direct fossil evidence, but based on the close relationship of the velociraptors to other dinosaurs which have been found with feathers.

The dinosaur finds from China over the last decade have been a revelation on the close association to birds, and the spectacular preservation has revealed fine details of the life of an ancient world.

I'll have more to say about this in another post! In the meantime, what you see at the head of this post is an artist's impression of Sinornithosaurus milleni based on these fossils. Artist is James Reece; image available in the feathered dinosaurs photo gallery of the link above.

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