Jan 29 2009
Dinosaur Fossils and Evolution
Leading up to the 200th anniversary of Darwin’s birth on February 12th, and the 150th anniversary of the publication of the Origin of Species, I will be covering more evolution-related news items. It has long been a favorite scientific topic of mine anyway, so it’s a good enough excuse to focus on evolution.
One of the strongest lines of evidence for the fact that life on earth arose through evolution is the fossil record. I do not think this is the strongest line of evidence, not because it is weak but because the genetic evidence is so remarkably strong. Statistically speaking, the genetic evidence speaks to common descent through branching speciation of all life on earth to such a degree that it approaches certainty.
But the fossil evidence is also impressive, and much more visceral – walking into a museum full of gigantic fossil dinosaurs (or at least their casts) has a coolness factor with which a string of base pairs cannot compete.
Creationists, of course, deny the implications of the fossil evidence. At the extreme end are some young-earth creationists who claim that Satan put the fossils there to test our faith. That unfalsifiable notion is not worth further comment.
The less extreme evolution-deniers simply fail to grasp the history of science and the methods by which we test scientific theories. When Darwin published The Origin of Species in 1859 the fossil record was extremely sparse. Geologists had discovered enough fossils to see that different geological layers tended to contain different assortments of fossil species. This is what led originally to the notion that life has changed through geological time. Fossils led to the evolution hypothesis even before Darwin.
But the fossil record that Darwin had access to was more gaps than anything else – provocative specimens scattered about the history of life without any patterns yet emerging, like a vast jigsaw puzzle with only a few pieces present, and with no picture as a guide to where the pieces went.
The theory of evolution made a very strong prediction, one that could potential falsify evolutionary theory completely. Evolution depends upon common descent – that all life is related through a series of branching events. Evolution therefore predicts that as we discover more fossils (more pieces to the puzzle) the picture that will emerge will be one of branching descent. Evolution requires this.
Branching descent has two main components – morphology and temporal sequence. The sequence of fossils should show morphological relationships in a branching pattern. One branch will have a set of morphological features that define the branch, and within that branch species will emerge with variations on those features. Occasionally a branch may give rise to a significant morphological change leading to a new branch.
In other words, evolution predicts that as we lay out fossil species morphologically they will fit into a branching pattern of relatedness. We will not see, however, random morphological features without a clear pattern. We will not see impossible hybrids, or entirely new complex structures arising without plausible antecedents, or the same specific derived characteristics in unrelated lines.
Further, the morphological branching pattern must simultaneously exist in a proper temporal sequence in the fossil record. Ancestors must come before descendants. We won’t find horses amid Cambrian fossils.
Over time these two related predictions of evolution have been validated spectacularly, and increasingly. The more fossils we find, the better they fit into a morphological and temporal sequence compatible with evolution. Gaps are slowly filled, and we find generally what we expect to find. We have not found the equivalent of a horse in Cambrian strata. The fossil record has created thousands of opportunities to falsify evolution, and evolution has survived every one.
Creationists desperately try to deny the undeniable significance of the fossil record by various tactics, all logically dubious. One tactic is to focus on a snap-shot of the fossil record as it exists today, ignoring the progress of discovery over time. At any moment in history there will be gaps in the fossil record. Creationists point out those gaps as if they call into question evolution. But when those gaps are filled, they just move on to other gaps or just point to the smaller gaps remaining.
They will also focus on the noise in the fossil record. A tiny percentage of living individuals will eventually be fossilized and discovered. Therefore the fossil record is a very low-res picture of the history of life. It is easy, therefore, to point to apparent discrepancies at below the resolution of the fossil record as if it calls into question the bigger picture that the fossil record can paint.
A proper scientific assessment of the fossil record, however, in terms of whether or not is supports evolutionary theory and common descent, is to look at how it is changing over time. What we see is that the more fossils we find the better the resulting picture matches predictions from evolutionary theory. If evolution were not true, then we would predict the opposite.
As a side note – I am not talking about predicting what species evolved into what. The specific course of evolution is not something that is predictable, and evolutionary theory is not dependent upon any specific history of life. That is entirely a separate question.
A new study published by researchers at the University of Bath and London’s Natural History Museum provides more evidence for the success of evolutionary theory in predicting the pattern of the fossil record. They conducted a systematic survey of fossil dinosaurs. Evolutionary theory predicts that a morphological pattern and a temporal pattern of dinosaur fossils should overlap, and this is exactly what the researchers found. This adds statistical rigor to what was already apparent.
The researchers added that the tightness of overlap is dependent upon two things: the correctness of evolutionary theory, and the completeness of the fossil record. Therefore this study strongly suggests that not only is evolutionary theory correct, but at present we have a pretty complete picture of dinosaur evolution.
That’s cool. It’s also not surprising. Hunting dinosaur fossils has been a priority for paleontologists for over a century. And, dinosaur fossils are generally big. I assume this makes them easier to find.
It’s also a bit sad in that the evidence implies there are no major groups of dinosaurs in the mix waiting to be discovered. We have the big picture of dinosaur evolution pretty well sketched out. There are probably still many individual species waiting to be discovered, but not major groups. I suppose there can still be side branches that were regionally isolated, but if so then we do not have any individual specimens from these groups that do not fit into the bigger picture we already have. If there are any missing groups, they are completely missing.
When Darwin was alive and publishing his theory of evolution, we had only a smattering of dinosaur fossils. Now, 150 years later, we have a fairly complete picture of a temporal and morphological sequence of branching dinosaur evolution. Scientific theories are judged primarily on how well they make predictions about future discoveries. By that criterion Mr. Darwin’s theory is a resounding success.
31 Responses to “Dinosaur Fossils and Evolution”
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Thanks, Dr. Novella. You wrote:
Relating the broad topic of evolution to the question of intelligent (technologically capable) life in the universe, I have often wondered why life on Earth took so long to make humans, the only such intelligent species to have existed here. The dinosaur fossil record (and the animal fossil record in general) stretches back hundreds of millions of years, and it is said that dinosaurs ruled the earth for much of that time. Yet, no dinosaur species or any other prehistoric animal species ever evolved to develop technology. In a very real sense, we owe our existence, and that of the only known technologically advanced civilization in the universe, to a cosmic accident that killed the dinosaurs.
Given tens or even hundreds of millions of years, why didn’t the dinosaurs evolve to technological capability, when it took humans less than a million years to do it? Or maybe the real question is, if life on Earth got along fine for hundreds of millions of years without evolving a technologically intelligent species, what are the chances that other planets in our galaxy have produced such intelligence?
I think the course of life on Earth may support the idea that even if life is common in the universe, intelligent life may be exceptionally rare. Creationists may see this situation as proof that they are so special that their existence must have been directed by a god. The way I see it, though, the fortuitous circumstances that finally resulted in human evolution on Earth are more consistent with an undirected natural process. Intelligence is not an evolutionary imperative. The universe doesn’t really want us. We are an accident, just like every other species.
Jim — technology requires intelligence, and intelligence is but one of (infinitely?) many possible adaptations to increase survivability (and therefore be selected for). While technology and intelligence certainly would have given them a competitive advantage, they just happened to go the route of bigger teeth and better armor. (Hmm, looking back on that last sentence, I realize it also applies to some people I know…)
Perhaps whenever and wherever you might find intelligence in the cosmos, the most intelligent there will have tended to assume they are also the most intelligent in the cosmos. Except somewhere there was and or/is an entity so intelligent that it makes no such assumptions.
I think it was a Vonegut book that told the story that basically large human brains were an evolutionary accident that eventually was selected out. It ended with a small remaining population semi-aquatic, web-footed humanoids living like otters in the Galapagos – much less intelligent, but happy and not busily killing the planet.
Jim Shaver,
LarryCoon put it pretty well. Evolution doesn’t necessarily lead to more advanced (or intelligent) forms of life, just to forms of life better suited to survival.
Dinosaurs ruled the Earth fairly successfully until (supposedly) their environment changed faster than they could adapt to and less specialized species expanded and evolved to take over.
If I had to guess, I would say that intelligent life is far rarer in the universe than regular complex life. Intelligent life is not the necessary endpoint or target of evolution. (Evolution doesn’t have a target other than survival)
I’m amazed (well, not really, not anymore) at how the ID/ creationists point to gaps in the fossil record as the damnation of evolution rather than one of its strongest supports, that is, for them to get it exactly wrong.
Devils’:
Come on now, I’ve read enough of your comments over the years to know that you aren’t the least bit amazed at the contortions through which creationists will go to demonstrate their utter lack of comprehension! Forget about the shock, that emotion is long gone. Just keep telling it like it is.
“when it took humans less than a million years to do it?”
But it didnt, it took us since the dawn of life to get where we are today, our ancestors were not on pause during the age of dinosaurs.
Karl’s comment leads to an interesting question — had it not been for the K-T extinction, would mammals have been able to gain the evolutionary foothold which eventually resulted in intelligence being selected for? Or to put it another way, had the dinosaurs not died off and left a void, would they have always outcompeted other adaptations through bigger teeth & better armor? Would intelligence ONLY have developed over their dead bodies?
To the extent that intelligence of some sort is necessary for any organism to survive, it will tend to drive that organism’s evolution, and in the aggregate, be a significant evolutionary force. So we can’t really say that evolution has NOT “created” one of its purposive goals as an increase in its aggregate intelligence.
mannik5000,
That’s a good point, but I’ve always wondered whether evolution needed 4 billion years to produce intelligent life, or if that’s just how long it took on our particular planet for intelligent life to develop. If various circumstances had been different, could intelligent life have evolved hear tens of millions of years ago?
cwfong, could you give us a definition of what you mean by “intelligence”. The way you seem to be using it, any hypothesis you make using your definition is ill formed so as to be not even wrong.
I googled to this site, http://dinosaurs.about.com/od/dinosaurbasics/a/dinosmarts.htm, and found this question:
“what if at least some dinosaur species had survived the K/T extinction 65 million years ago? Dale Russell, the curator of vertebrate fossils at the National Museum of Canada, has caused a stir with his speculation that Troodon–a human-sized dinosaur about as smart as an opossum–might eventually have evolved a human-sized brain if it had been left to evolve for another few million years.”
So there seems to exist among some scientists an underlying assumption that evolution of a species tends to include an increase in its “intellectual” capacities.
daedalus: I said “intelligence of some sort.” That simply requires the simplest of calculative mechanisms fashioned to achieve the simplest of purposes and fulfill the simplest of expectations.
In any case I’m going to refuse to explore the issue with you further.
Steve you should pick out specific pieces of evidence, and provide blog entries that focus in much more detail. Perhaps you can choose which piece of evidence to blog about based on latest discoveries in the news about that aspect. So for example if some sort of genetic evolutionary news is published, you could start with talking about the article, and then give a more thorough detailed entry of the knowledge we already had about the topic.
Also people can shoot me if they want, but celebrating Darwins birthday in my opinion gives creationists the idea that Darwin is some sort of cult leader that we all worship.
Great article on Darwin’s motivations:
http://www.prospect-magazine.co.uk/pdfarticle.php?id=10581
empiricalgod2: Yes, the Creationists will yell that we are “worshiping” Darwin but they’d say that anyways. I say screw ‘em and let’s do what we want to do. Science should be celebrated every once in awhile just to remind us how far we’ve come in such a short time. We can’t let the Fundamentalists take something like that away from us.
-Also people can shoot me if they want, but celebrating Darwins birthday in my opinion gives creationists the idea that Darwin is some sort of cult leader that we all worship.-
They would believe that anyway…they do this so that in their minds we are playing by the same rules, but then they have the upper hand because our ‘great ruler’ is clearly false.
Unfortunately for them we have better things to do than play the knowledge equivelant of ‘tiddlywinks’.
Despite the ridiculous cover, the New Scientist article about HGT and its role in evolution fleshed out the idea that evolution is best described as a web rather than a tree. The tree signal is still strong, I guess the next frontier in evolution is determining just how much evolution was driven by hybridisation – gene transfer among different species.
As a side issue, this HGT happens so often that anti-GM activists ought to realise gene transfer between species happens naturally anyway (usuall via viruses)
cwfong, your reply about intelligence defined it to be “fashioned” and doing calculation to “achieve purposes” and “fulfill expectations”. Whose purposes are being achieved and whose expectations are being fulfilled?
“Fashioned” implies a “Fashioner”, which I can interpret to be the Intelligent Designer of the creationists. Perhaps you were speaking metaphorically and didn’t mean to imply an ID.
Achieving purposes and fulfilling expectations only relate to the plans and schemes of self-aware entities as I understand the terms. Non-entities don’t have purposes and non-self-aware entities don’t have expectations. As least that is my understanding of the terms as they are commonly used. If you are meaning them in different ways and you want us to understand what you are meaning, you need to explain how you are meaning them.
Thinking about Life
The History and Philosophy of Biology and Other Sciences
10.1007/978-1-4020-8866-7_15
Paul S. Agutter and Denys N. Wheatley
Living organisms act purposefully, and their individual parts — organs, cells, organelles, molecules — fulfil purposes for the whole. Those purposes ‘come from within’; animals, for example, seek food and mates for themselves. In contrast, the purposes of technological products such as drawing pins, hat-stands and washing machines ‘come from outside’; they are defined by their makers and users. A washing machine does not wash clothes for itself.
Ever since the Scientific Revolution it has been agreed that the inanimate world of rocks, rivers, stars, clouds etc. does not act purposefully. It is to be understood in mechanistic not teleological terms. An inanimate object is not for anything or anyone; whatever it does is a consequence of antecedent causes. That implies a basic difference between biology on the one hand and physics and chemistry on the other. If biology is to be wholly compatible with physics, that difference needs to be resolved. We must be able to make complete mechanistic sense of purpose in biology.
and if you look at the next paragraph in what you cited:
But that is not a straightforward matter; ‘purpose’ is a slippery concept. We can propose (for example) that the purpose of a flower colour is to attract pollinating insects, but the proposal is not testable; it is not a hypothesis. We may be able to show experimentally that if the colour is changed then the flower fails to attract the insects, but that only demonstrates an effect of the colour. Can we legitimately equate ‘effect’ with ‘purpose’? We argue in this chapter that we cannot.
An untestable proposal is not a hypothesis.
You can’t equate effect with purpose. That’s a logical and philosophical position best attributed to Hume. Who also pointed out that you CAN equate purpose with effect.
As to expectations, I’m still working on the following proposal:
Abstract:
Reflecting the nature of biologically generated decisions, the error correction mechanism (ECM) in the error-correction representation of a system of co-integrated variables may arise from forward-looking behavior. In such a case, the estimated ECM coefficients may misleadingly appear to be insignificant or to have the opposite-than-expected sign if the variables in the error-correction representation do not adequately capture short-term expectations. This paper explores the nature of this problem with a theoretical model for consumption and demonstrates how severe the problem can be with microbes and fungi. Because the conditions for similar erroneous inferences are likely to apply to many other settings, the paper also recommends a reexamination of the evidence in cases where the ECM appears to be insignificant or to display the wrong sign.
Apropos to this discussion is the little known realization that virtually all calculative systems were invented and fashioned to develop expectations. 2+2=4 is not so much a truth as a prediction of what can be expected from the use of that formula.
This then is the calculative system’s function, from which all organisms both acquired and fulfilled their initial purpose. Which was to solve the ongoing problem of acquiring energy to survive. And the reason life has expectations and inert items don’t is simply that it was during the formation of life that the calculative process was fashioned
by those very forms to continue what we refer to as living.
Do such forms need self-awareness to have expectations? No, bunky, they need expectations to eventually become aware of anything at all.
A mix of particles of particles of different sizes of a soluble material such as salt is not “inert”. The effect is that the largest crystals grow and make themselves bigger at the expense of the smaller crystals which shrink and eventually disappear as they are consumed. The large crystals gain material (NaCl) by processing energy (the surface energy of the crystals). The large crystals are calculating where the Na+ and Cl- ions go into its lattice to minimize energy and make it bigger. The effect of these calculations is a larger size crystal with the same crystal lattice.
In that sense the “purpose” of the NaCl crystals is to get bigger. The crystals “expect” to get bigger and by getting bigger they fulfill their “expectations”. The NaCl is acting “intelligently” by fulfilling its “purpose” and “expectations” and by doing the “calculations” necessary to fit the ions into the right sites in the lattice. In that sense the NaCl is “intelligent” and “alive.”
Did I get that right? Am I using the terms in the way that you are meaning them?
No.
I think he meant that ‘The very condition of a dinosaur may be at work in the work, within the system to be desaurized. It may already be located there, already at non-work. Not at the center, but in an eccentric orbiting center, in a corner whose eccentricity assures the solid concentration of centers of the system, participating in the construction of what it, at the same time, threatens to dedinosaur. One might then be inclined to reach this conclusion: dinosauria is not an operation that supervenes afterwards before, from the outside inside, one fine day. It is always already at work in the non-work. Since the destructive force of sauriscia is always already contained within the very bones of the work, all one would finally have to do to be able to dedinosaur, given this always already, is to do memory work. Yet since I want neither to accept nor to reject a conclusion formulated in precisely these terms, let us leave this question suspended for the moment.’
Slightly tweaked Derrida
Sorry, could not resist the temptation…
/S
I do believe, however, that deconstruction is enlivening, productive, and affirmative, and that it does not “undermine” norms but rather places them within contexts that reveal their developmental and affective features.
Derrida was ultmately stymied by his failure to deconstruct the internal assumptions that sustained what he considered to be the deliberate nature of ignorance.
[...] the 150th of his book being published, approaches. Here’s one from the good Dr. Novella on Dinosaur Fossils and Evolution. One of the strongest lines of evidence for the fact that life on earth arose through evolution is [...]