Evolution - Beyond the Popular Science

ny writes: "Patterns and Processes of Vertebrate Evolution is not popular science, but as a broad overview of the processes of evolutionary change it is reasonably accessible to non-specialists. I recommend it to anyone who has read Gould and Dawkins and Ridley and so forth and now wants something more substantial." This sounds like a book to interest anyone interested in current ideas in evolution -- read on below for Danny's complete review. Patterns and Processes of Vertebrate Evolution author Robert L. Carroll pages 448 publisher Cambridge University Press rating 9 reviewer Danny Yee ISBN 0-521-47809-X summary An uncompromising but accessable overview of modern evolutionary theory.

In Patterns and Processes of Vertebrate Evolution Carroll undertook an ambitious project - nothing less than to update George Gaylord Simpson's classic works from the 1940s and 50s, Tempo and Mode in Evolution and The Major Features of Evolution. The result is a "broad picture" overview of the processes of evolutionary change, centred on paleontology but attempting to integrate that with the rest of biology. Patterns and Processes is aimed at students of paleontology and specialists in that and related fields, but it should also be considered by general readers: while it goes into quite involved details, they are always used to illustrate broader ideas and there is solid motivation for persevering with them. It is especially recommended to those unhappy with the lack of substance in popular debates over the theory of punctuated equilibrium, which Carroll critically appraises. Patterns and Processes is effectively illustrated with line-drawings and figures and has a useful glossary.

Carroll begins with an overview of current problems in evolutionary theory and in particular of the "gap" between short- and long-term processes in evolution, and between paleontology and other disciplines. He also discusses the choice of the vertebrates as a testing ground (which is picked up at the end of the book in a brief comparison with invertebrate metazoa, prokaryotes, protists, and vascular plants). He then provides an overview of theories of evolution, at the level of populations and species, from Darwin through Dobzhansky and Mayr to Gould and Eldredge.

Two chapters present some essential background. The first looks at evolution in modern populations, in particular at rates of evolution among the Galapagos island finches, where significant directional change does occur and doesn't appear to be correlated with speciation. The second considers some of the limitations of fossil evidence, the irregularity of fossilization and other stratigraphic issues and problems with the dating of events and processes and the measurement of rates of evolution.

Next come two case studies. The rates and directions of change among late Cenozoic mammals are examined with an eye to testing theories of punctuated equilibrium and species selection. Many lineages exhibit stasis "of particular characters and character complexes," but in none is there stasis of all characters and phyletic evolution is common. And "no major trends involving a complex of character changes can be demonstrated as having resulted from species selection." In contrast, the rapid radiation of the cichlid fish of the East African Great Lakes provides some evidence for species level evolution, and a bridge between macroevolution and microevolution.

Four separate chapters focus on related disciplines, in an attempt to reunify different fields. Taxonomy influences our basic concepts of evolutionary patterns as well as providing tools for discovering them; phylogenetic systematics (cladistics) has been particular influential, offering "an objective way to compare patterns of large-scale evolution from group to group and within groups over time" and forcing reconsideration of traditional naming schemes in the vertebrates. With evolutionary genetics Carroll presents some basic models, focusing on quantitative traits; he touches on the enigma of low selection coefficients and on genetic constraints.

Turning to developmental biology, Carroll surveys heterochrony, homeobox and Hox genes, and the phylotypic stage. He then applies this to the origin of craniates and skull and axial skeleton development, but above all to tetrapod limbs, to their origins, developmental processes, morphogenesis, and evolution. He also considers the integration of developmental biology with the evolutionary synthesis and its possible connections with macroevolution. Other constraints are imposed by physics: Carroll considers vertebrate locomotion in water, in the air, and on land, and touches on membrane transport, heat transfer, and size scaling.

Three chapters then look at large scale structure and patterns in evolution. A chapter on "major transitions" focuses on movements between environments: the most detailed study is of the origin of birds, but others cover the origins of terrestrial vertebrates, mosasaurs, and whales. Critical periods saw rates of change exceeding those in ancestral and descendant groups, but not those observed in modern populations; more importantly, directions of change were sustained for long periods. Turning to radiations, Carroll treats at length the Cambrian explosion and the radiation of early Cenozoic mammals: occurring in intervals of 10 million years or less; these differ from other, slower radiations into already occupied environments and "can certainly be attributed to factors that were not considered by Darwin". At the largest scales, vertebrate evolution has been irregular, driven by "forces" that can't be extrapolated from those operating at the level of populations and species: among them sustained evolutionary trends, continental drift, and mass extinctions.

Among Carroll's overall conclusions:

"Evolutionary forces that can be studied in modern populations are sufficiently powerful to account for the amount and rate of morphological change throughout the entire course of vertebrate history."

and

"Transitions between environments governed by major differences in physical constraints do not necessarily require special evolutionary processes."

but at the same time

"Large-scale patterns of evolution cannot be fully explained by processes that are directly observable at the level of modern populations and species.

... the patterns, rates, and controlling forces of evolution are much more varied than had been conceived by either Darwin or Simpson."

And macroevolution is essentially historical, with each major event "unique and worthy of detailed study in its own right".

Patterns and Processes in Vertebrate Evolution combines clear exposition of details - and what appears to be an encyclopedic knowledge of vertebrate history - with a willingness to tackle big questions. Sometimes Carroll seems to take both sides of debates, but that is a reflection of respect for complexity, not of unengaged fence-sitting. The result is a useful overview for students or outsiders; it also seems to have established itself as a minor classic within the field.

You might want to purchase Patterns and Processes in Vertebrate Evolution from bn.com or read some of Danny's other evolution book reviews. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.

Comments

definitions of species

[Alien54]

There has been a lack of clarity and precision in the definition of individual species. For example, in certain bears, and other wide ranging creatures, you get variations that lead some scientists to classify two different animals as different species, when in fact they could crossbreed with viable young.

As an example closer to home take a look at common dogs. I can bet that some biologist in the far future (say 100 million years from now) is going to find all of these dog fossils, especially in pet cemetaries, etc. and conclude that these were all different species of animal. A chihauhau vs a Saint Bernard? the same species? come on now.... ;-)

This loose grey zone is probably part of the problem. and I can see them trying desperately trying to find the intermediate forms in the fossil record. They will have just "mysteriously appeared"

Re:definitions of species

[LMCBoy]

The entire concept of a "species" is the problem; the "loose grey zone" is the reality.

We classify organisms into species in order to make some sense of what we observe, but we should always keep in mind that the classification is artificially imposed, and somewhat arbitrary. The fossil record of any group of related organisms shows discrete snapshots of a continuous variation through time and geography (punctuated equilibrium does not refute this, it just says that the rate of evolution is not constant).

The species model describes evolutionary change as "creatures evolving from species A to species B to species C", with the implicit understanding that these are just arbitrary markers along the continuous evolutionary path, not coincidentally placed where there are well-preserved examples in the (incomplete) fossil record.

Unfortunately, this implicit understanding doesn't really get through to popular understanding of evolution; hence the many heated debates about speciation and how to tell when it occurs, when in fact speciation is not a real phenomenon at all, but a classification tool.

Re:definitions of species

[!splut]

The delineation of species boundaries necessarily takes into consideration more than the ability to interbreed and produce viable offspring. Indeed, the taxonomic definition of the "species" classification is very plastic, and differs with the groups of organisms considered.

The advent of the use of genetic markers for classification provides some greater degree of accuracy and standardization in the process, but it does not eliminate the inherant flexibility in the definition. (From a bioinformatic standpoint, there is a whole other set of problems with trying to accurately portray evolutionary distances from genetic variation.)

Consider a group of animals with a continuous distribution over a very large area. All the members of this population are capable of interbreeding, and the uninterrupted distribution allows for genetic drift throughout the entire population. Individuals from different geographic regions will have subtly different physical characteristics, but the whole population is still considered a single species. This is a fairly classic situation. (The benefit of a large gene pool likely outweights the benifit of these subspecies differentiating into wholly different species, if you want to look at it that way.)

Then, consider a group of animals with a discontinuous distributuion over a large range. Individual populations may be able to interbreed with one another, but there is no natural genetic exchange among these separate populations. Subtle differences between the groups may, in this case, warrent classification as separate species, because they represent different gene pools drifting in different directions.

The complexity of the issue compounds when one looks outside the animal kingdom. For instance, essentially the entire family or orchids, with some 1000 genera and 20,000 species, exhibits a high degree of genetic plasticity, with species readily hybridizing across genera. And again, the definition of "species" must be reevaluated when one considers the bacterial world.

Anyway, the point of all this is to show that the grey zone is there for a reason. The alternative is to explicity redefine taxonomic criteria for every different group of organisms, which defeats the entire purpose of a single classification system.

Re:Define order, Define disorder

[Fiver-rah]

perhaps someone should attempt to define order or disorder, without being circular in their definitions.

Someone did. His name was Boltzmann. The more ordered a system is, the fewer microstates available to it. What does that mean? Well, a macroscopic example is this: imagine you have a bunch of books you're putting on a shelf. There's only one way to put the books alphabetically (assuming you have no duplicate copies). But there's a really large number of ways to put them on if you put them every which way. So let's compare the order of two systems. Our first system is our books on the shelf, restricted to alphabetical ordering. The second is our books on the shelf. The first system has only one way it can be arranged; the second (assuming we have more than one book) has more. So the first system is more ordered.

This is a little simplistic, but it gets the point across.

Trust me, entropy really is a well-defined concept. Or don't trust me; read for yourself.

Re:All things considered

[scotch]

Please. You make it sound like creationism and evolution are on equal scientific footing. This is simply not true. There is a mountain of evidence that supports evolution. For creationism, there is hardly even any definitive statement of what the "theory of creationism" is. Most evidence creationists cite is actually supposed evidence against evolution, not support for creationism. Just check the web - there are dozens of bad arguments out there - once they are introduced, they never die, arm chair "creation scientists" keep repeating them. My favorites are the onces involving the moon recession rates and the amount of dust on the moon - real gems.

Calling evolution a religion is either dishonest or an exercise in destroying the meaning of "religion" and making the word so vague that you can call anything a religion. Take your pick.

Why Fundamentalist "Christians" Care

[Tyrone Slothrop]

They don't care about evolution but what it implies, which is, according to them, a weakening in the requirement to believe in god.

Without god, there are no moral absolutes, goes the argument. And without moral absolutes, why, what's to prevent all sorts of immorality?

Therefore, attempts to debate the theory of evolution with "christian" fundamentalists, or their fellow travelers, is pointless, because you are challenging their entire world view, not objectively evaluating competing scientific theories.

FWIW, almost all thinking non-fundamentalist Christians, as do most educated people regardless of religious belief/nonbelief, realize evolution is a scientific reality.

And we, the vast majority, further realize that evolution doesn't imply anything about morality, or the existence of god, one way or the other.

And therefore there is no reason to waste time in high school science classes teaching theories like creationism that are neither theologically nor scientifically interesting.

Re:Why Fundamentalist "Christians" Care

[SN74S181]

It's quite possible to believe that God created the universe that evolution is one part of.

In fact, 'creationists' would build a stronger basis for their faith if they'd just acknowledge this truth. Clinging to their literal interpretation of scripture is vain, even blasphemous.

Re:Why Fundamentalist "Christians" Care

[Tyrone Slothrop]

"What bothers me most as a Christian is that the theory of evolution is presented as fact"

Nonsense.

What bothers you most as a christian is that you believe that somehow evolution implies something about the truth of your beliefs. Otherwise, it's such an esoteric and complicated theory you wouldn't waste your time coming up with examples.

For example, it is rare indeed to see a statement such as "what bothers me as a christian about the infectious theory of disease is..." or "what bothers me as a christian about the theory of musical harmony.."

Just like disease theories and musical theories, evolution implies nothing about either your religion or about how to behave and discussing the theories is totally irrelevant.

Therefore, attempts to argue the truth of evolution with someone arguing "as a christian" is pointless. Again, it has nothing whatsoever to do with christianity as most people understand the religion.

However, what IS germane is to point out, over and over again, is that the argument for creationism is really about the effort to force a particular, and IMO very ugly, moral agenda into public schools. An agenda which, again, squares not at all with the moral agenda of most practicing religious people.

Theory != Some vague possibility

[FreeUser]

I know it's nitpicky but evolution is a scientific "possibility". It is still regarded as a theory after all.

All things short of a methematical 'proof' in science is theory, including gravitation and even cause-and-effect itself. The word 'theory' in science has an entirely different connotation to what it has in common parlence, and in particular to the way you use it here.

In the American vernacular, "theory" often means "imperfect fact" - part of a hierarchy of confidence running downhill from fact to theory to hypothesis to guess.

Well evolution is a theory. It is also a fact. And facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world's data. Theories are structures of ideas that explain and interpret facts. Facts don't go away when scientists debate rival theories to explain them. Einstein's theory of gravitation replaced Newton's in this century, but apples didn't suspend themselves in midair, pending the outcome. And humans evolved from ape-like ancestors whether they did so by Darwin's proposed mechanism or by some other yet to be discovered.

In science "fact" can only mean "confirmed to such a degree that it would be perverse to withhold provisional consent." I suppose that apples might start to rise tomorrow, but the possibility does not merit equal time in physics classrooms.

Evolutionists have been very clear about this distinction of fact and theory from the very beginning, if only because we have always acknowledged how far we are from completely understanding the mechanisms (theory) by which evolution (fact) occurred.

-- Stephen J. Gould, "Evolution as Fact and Theory"; Discover, May 1981

What you are equating evolution with is a hypothesis, not a theory, and the two are very different. Or, put another way,

A few words need to be said about the "theory of evolution," which most people take to mean the proposition that organisms have evolved from common ancestors. In everyday speech, "theory" often means a hypothesis or even a mere speculation. But in science, "theory" means "a statement of what are held to be the general laws, principles, or causes of something known or observed", as the Oxford English Dictionary defines it.
[-- Douglas J. Futuyma]

The theory is not did evolution happen. We already know evolution did and does happen, there is a mountain of factual data underscoring that point. What is theoretical and debated (by scientists) is what the mechanism is by which primates became human and dinasaurs became birds. The fact that it happened is denied only by those with a religious agenda, whose fragile beliefs are challenged by the factual data collected by thousands of researches all over the face of the planet.

And I know this non-fundamental Christian believes God could have used evolution to create us.

And I know this Athiest believes aliens could have seeded the Earth with proto-human life, but until I see some sensible evidence indicating that such might be the case, I'm not going to pay the notion much heed.

Re:read Not By Chance!

[tgibbs]

He proves rigorously that Neo-Carwinian evolution could not have happened -- or rather is about as unlikely as tossing 10,000,000 coins at random and having them all come up heads (yes, that is "possible", I guess).

Let's say I toss 10,000,000 coins, and make a careful record of the sequence of heads and tails. Now, I calculate the probability of that exact sequence, and discover that it is exactly as low as the probability of having them all come up heads. Have I proved that the coins are weighted? Or influenced by God? No, because every sequence of coins has exactly the same very low probability, but nevertheless one of them has to come up. This is the falacy of calcuating probabilities backwards. Every attempt I've seen to calculate the probability of evolution falls into that same basic error.

Remember, also, that natural selection is not a random process, even though it has random elements. For example, it is possible to use an evolutionary simulation to solve an equation, even when there is only one possible solution--and it is far more efficient than trying to guess the answer randomly.

Raising a good question: introductory texts?

[hyacinthus]

I hate to intrude into the creationism vs. evolution debates which seem to be dominating this discussion, but I actually have a _different_ question. We all know that high school and perhaps introductory college texts on general biology have often become seriously watered down and error-ridden. Stephen Jay Gould wrote one amusing essay on how a particular error (something to do with _Eohippus_, which isn't named _Eohippus_ anymore I guess, but I like the old name) has propagated itself, unchecked, from text to text.

Frankly I don't trust many high school or freshman level textbooks in _any_ subject. So I'd like to know: can anyone recommend a scholarly, well-referenced textbook, aimed about about the twelfth-grade level, in biology, in particular one which does a good job of covering evolution? Any particular authors and titles stand out? Any good resources to reviews and critiques of popular science textbooks?

The popular works have their place, but they're all deficient in some way. Gould is too scattershot--he's an essayist, really--and Dawkins is too polemical (frankly I think Dawkins has become an unmitigated jackass in recent years, and I'm not a creationist.)

hyacinthus.

Re:read Not By Chance!

[tgibbs]

Whether we're talking about 10,000,000 heads coming up or some other combination is beside the point. The point is that the odds are vanishingly small of any pre-specified combination coming up (where the result for each coin is specified independently). The odds in this case are very easy to compute: 1/2 raised to the 10,000,000 power.

Precisely. And the key lies in the meaning of "prespecified." The outcome of evolution is not "prespecified" because we already know the outcome, just as I already knew the outcome of my series of coin tosses. Both are "post-specified" after the fact. And that makes that sort of probabilistic calculation invalid.

And of course natural selection is not a random process, but natural selection cannot work until reproduction is established, hence it cannot help produce the first living cell.

So what? Natural selection is not even hypothesized as being the origin of the first replicating organism, so that is a straw man. The origin of life is a completely different question from the evolution of living organisms. And since nobody has any real knowledge of what the first replicating organism was like, there is no meaningful way of calculating its probability.