General Questions on Evolution & Evolutionary Theory

Factual Questions
1

Folks,

I’m writing an essay on the potential of evolutionary (neo-Darwinian) evolutionary thought in cultural studies, and need some brief pointers on whether some of the parallels I’m drawing are reasonable. I’m not trying to “disprove” evolution: I’m fully convinced of the explanatory validity of evolution.

But I’d like to get more up to speed on the real things that evolutionary theory cannot do yet. Therefore, these questions; I’ve appended my sources (as so far consulted) in brackets. I may come up with other questions…

  1. Would it be correct to say that evolutionary biology cannot *predict *the course of future evolution? [This is general conclusion from all readings.]

  2. Would it be correct to say that evolutionary biology cannot (in most cases?) determine the *reasons *for particular evolutionary developments in the past? That is to say, while we know what species developed from which, the reasons these developments are usually obscure? [This I conclude from Dawkins’s Darwin’s Dangerous Idea, 304ff.]

  3. To sum these two points up, would it be adequate to speak of evolutionary biology as a form of natural history, which retroactively can trace and interpret developments rather than explain them, except on the most basic level? Is the aspiration of evolutionary biology to be able to predict evolutionary moves at some point?

  4. Is it correct to say that there is still an ongoing dispute in evolutionary biology whether the gene, the individuum, kin, or species are the target of selection?
    [This I draw from readings in Dawkins, Dennett, Gould, and Wilson.]

  5. Would it be correct to say that there is still debate on the merits of punctuated equilibrium? [This I think I draw from an online debate I cannot find anymore?]

  6. Is it correct to say that while we are able to identify the chromosomal structure of some genes, we are still do not fully understand their interaction? As a corollary, is it correct that there is some dispute about the (common, high school-level) belief that genes are essentially stretches of base sequences in our DNA, and may be more complicated than this? [I don’t remember where I read that suggestion.]

  7. What is the standing of sociobiology in the biological sciences? It’s pretty much derided in much of the humanities, but I’d like to have a different view.

I’d be happy to be pointed to one or two books that give me an overview of the current state of debate in evolutionary biology, but it would need to be genuine debate, not one book saying this, the other saying that, since I’ve plenty of those; it’s the weighing of the relative importance of each stance that’s the problem I have.

Oh: and since I’ve got a really bad track record of going back to say, thank you!, let’s make sure I’ve said it at least once: thanks in advance for your replies!

2

1 and 2. Yea.

  1. Yes except for the last part, no.

  2. Not really sure about that one.

  3. On whether or not it happens? No. On its relative importance in the overall scheme of things? Not sure.

  4. Yes. Genes are often influence by other genes and can even be turned on or off by reactions to things in the environment. See epigenettics.

  5. Evolutionary psychology is often criticized for putting forth untestable hypothesis (or hypotheses that are so hard to test as to be virtually untestable).

3

Has anyone (who knew what they were talking about) ever really thought that selection happens at the level of the species? I doubt it. Otherwise, as I understand it, there is a good deal of dispute over whether all selection can be reduced to selection at the gene level (quite apart from the problems, that you note, about pinning down exactly what a gene is) or whether there are emergent properties of whole organisms, groups of kin, or even of unrelated groups of interacting individuals, upon which selection can act. Furthermore, even if it were resolved whether there are such emergent properties at any of these levels, there would still be the question of how significant the selective pressures acting at that level might be, compared to the other levels.

Do people still talk about “sociobiology”? As John Mace implies, the niche it once occupied in the intellectual landscape has now been taken over by something called “evolutionary psychology,” which remains controversial (as sociobiology was). I do not knew what biologists, specifically, think about evolutionary psychology (I expect opinions are divided, as they are elsewhere). A lot of people (including me) think that a lot of rubbish has been promulgated under the banner of Evolutionary Psychology", but that does not mean that its foundational principles are necessarily unsound.

4

Good question! Has anyone? I think some of the things Gould has said about punctuated equilibrium might be understood to suggest it; but I’d also be happy to not go further “up” the ladder than kin.

Yes, good point; so it might be any of the above, all of the above, and different values of the above, in play in each “selection event” (whatever that might be).

There’s also evolutionary anthropology, which, as far as I could make out, makes many of the same points of sociobiology without sounding like it’s been made up by Nazis. I also wonder, but that’s just an aside, how much of the promulgated rubbish is the sociobiologists’/evolutionary psychologists’, and how much their opponents’, making up things they think follow from the argument of sociobiology that really don’t…

**njtt **and John Mace, thanks for your replies!

5

I’d like to answer this completely, but I fear it would take pages, and far more time than I have freely available these days. I will say in general I want to go in and reword nearly everything you’ve written to make it more precise. There’s a small but significant thread of not-quite-using-words-rightness that hinders simple responses.

I will tackle this, as it’s probably the simplest:

“Chromosomal structure” in the context of genes isn’t a meaningful phrase. If you compare it to a landscape, “chromosomal structure” is like where mountains, plains, and forests are, and “genes” is more on the level of streets and houses.

If you consider a gene to be a stretch of DNA that encodes a biologically functional molecule, either protein or RNA, which is how most biologists would define it, then we fully understand the gene itself. We can point to a stretch of DNA from here to here and say “that is the gene that encodes molecule X” with complete certainty. With the advent of genomics, doing this for any gene in any sequenced genome is now trivial and commonplace.

Now, when you say “we do not fully understand their interaction”, what do you mean by “they”? The stretch of DNA or the gene products (ie protein or RNA)? If you mean the gene products, then no, we don’t understand those interactions fully. Those interactions essentially make up all of biology, so understanding all of them would mean having a full and complete understanding of everything that happens in biology. If you mean the DNA itself, well, genes don’t really interact at the DNA level. They are controlled - turned on and off and levels of expression modified - in hundreds and thousands of different ways, and we are still working those all out. New methods of genetic regulation are discovered constantly. Epigenetics as a field is essentially just figuring out a whole language of regulation we didn’t know about before. But we understand a lot of it. It’s not like it’s a complete mystery. So I’m not sure what you’re getting at here.

As for your last question, again, the answer is sort of. A gene is a stretch of DNA. Period. But obviously a stretch of DNA can’t do anything in the cell by itself. Just as a program on a CD can’t do anything but look shiny without a computer, the information in the DNA can’t do anything without the hardware required to access it. There are whole hosts and families of proteins and RNAs that bind to the DNA, control how, when, and where it’s used, and turn the information into useful parts of the cell. None of these things can be considered “part” of the gene, but they are all absolutely essential if the gene is to function properly, or at all.

Hopefully this gives you some idea not only as to the answers to that question, but why it’s going to be tricky to get full answers to all of your other ones as well.

6

I don’t think evolutionary biologists are trying to predict evolutionary moves, but there have been recent studies by virologists regarding the sort of mutations that bird flu would need to make it able to spread from mammal to mammal (currently it spreads only from bird to mammal). I can imagine folks from several disciplines wanting to know how likely it is for any number of animal viruses to become transmittable to humans, and what the form the mutated virus would be likely to take.

Not quite the same thing as evolutionary biologists trying to predict, but close.

I’ve been meaning to read Carl Zimmer’s books on evolution. There are three and the last is a textbook, newly released, written with evolutionary biologist Douglas Emlen. I imagine that it would give an overview of the state of the current debates within the discipline. As a textbook, Evolution: Making Sense of Life isn’t cheap, though.

Amazon has a look inside for **Evolution: The Triumph of an Idea ** The Table of Contents doesn’t have a listing that looks like a review of current debates. Does anyone know if The Tangled Bank: An Introduction to Evolution has such a section?

7

I was conversing with a paleontologist friend recently about a high-profile case of academic fraud involving a evolutionary psychologist. The impression I got was that he was particularly annoyed with this case because the field involved is already having a hard time establishing legitimacy. Not an illegitimate area of study, but one that’s been rife with half-baked, untestable theories.

Obviously, that’s just one view, but he’s definitely somebody who tends to know the way the winds are blowing within the sciences, attitude-wise.

8

I would say that it’s not so much that evolutionary biology cannot predict the course of future evolution so much as it doesn’t try to. Evolutionary biology is a historical science; much as is the case when studying human history, evolutionary biology strives to explain how organisms in the present came to be. It can, perhaps, in limited cases, further be used to predict the future course of populations, but that couldn’t really be stated to be a goal of the field in any meaningful sense.

Firstly, Dennet wrote Darwin’s Dangerous Idea, not Dawkins.
Secondly, that section of the book is basically Dennet arguing against Gould’s idea that events such as the Cambrian Explosion may have been due to a fair amount of luck as much as anything else, not an argument against being able to tousle out evolutionary pathways or mechanisms. Basically, Gould was a believer in chance happenings being major players in shaping the history of life, Dennet disagrees (for the record, I agree with Gould on this point).

Much of what we do know about specific evolutionary pathways comes from evidence found within a combination of the fossil record and developmental biology. Much of what we know about evolutionary mechanisms comes from Darwin’s theories, further built upon by subsequent researchers, and supported by experimentation (both thought and actual, much as with other sciences).

When dealing with extinct organisms, then, it may well be the case that some questions are doomed to remain unanswered, simply because we don’t have anything biological to work with (e.g., no cells, DNA, genes, etc.). But I wouldn’t say it’s “most” such questions.

I believe it would not be adequate to state such. Evolutionary biology is able to explain much about the nature and history of populations, both extant and extinct, even at this stage.

Not really. There may be debate around the fringes, but the basic question is largely settled: genes are the replicators, individuals are the primary locus of selection. Higher levels, up to and including species, may or may not be loci for selection (possible in theory, but difficult to determine in fact).

Any debate there is is probably due to a misunderstanding of what punctuated equilibrium is. It is not a proposed evolutionary mechanism, novel or otherwise. It is an explanation for the appearance of the fossil record - seemingly static populations which arise suddenly and disappear equally suddenly - that goes beyond Darwin’s supposition that the fossil record was merely woefully complete. In essence, it’s an argument against pure gradualism, and for speciation and extinction being rapid events, geologically-speaking. There is little debate that this is, indeed, the case, currently.

9

Don’t forget that evolution also happens in repsonse to changes in environment - including new competitors and predators and food sources. As a result, the whole is generally unpredictable, except in the superficial. i.e. global warming and less pack ice likely means less polar bears able to feed well and survive; but what this means for their prey in the long run, or the bears themselves - unknowable. Similarly, giant asteroids that kill any animal of significant size or make thier environment unsurvivable - again, not terribly predictable (and significantly punctuational).

IANAB, but as I understand it. The sequences of base pairs in DNA are not nice long pretty strings of spiral structure - the string twists and knots like an overwound elastic band; the resulting surface forms the catalyst points to allow the formation of complex organic molecules that drive the cellular processes, from hemoglobin or insulin to steroids and hormones. Additionally, most complex organic molecules in those processes are combinations of several such constructed components at different sites which then combine at other sites. (I’m sure someone will correct my impression here). Thus, it may be possible to analyze the final shape of a gene, and predict what it will produce chemically, but the order of complexity is such that we are not able to predict what will or will not happen in most cases.

10

Indeed; it’s not a matter of flawed methodology that prevents any kind of predictive power for evolutionary biology, but the inherent chaos (in the mathematical sense) of biological systems and their interactions (and their interactions with geological, meteorological, astronomical, etc. phenomena). Or, to put it another way, there are way too many variables to be able to make any long-term predictions regarding a population - and evolution is really all about long-term processes.

11

No, that really is not right.

I think you are confusing DNA with enzymes (which are proteins, consisting of strings of amino acids, and which do have complex and irregular 3D structures). Most of the catalytic functions within a cell are carried out by enzymes (though some also involve molecules such as RNA of various sorts, and various co-enzymes which are neither protein nor nucleic acid).

Although it is a bit of an oversimplification, for most purposes it is indeed valid and useful to regard the sequences of base pairs in DNA as ‘nice long pretty strings of spiral structure’. These linear strings of DNA bases encode the information for making the proteins, but they do not share the irregular 3D structure of the proteins they describe, any more than my description of a tangled mass of string must itself be tangled. The information is encoded in the linear order of the base pairs within the string, much as the meaning of a written sentence is encoded in the linear order of the letters on the page.

12

Just in case Darwin’s Finch’s answers weren’t clear enough,

I don’t think you’re quite correct. There’s absolutely no problem with the theory; it’s just that in most cases we don’t know enough particular details about the world to make predictions. Predicting genetic changes in, say, the gray squirrel population in upper Manhattan, is really hard, both because it’s a really complex environment and because we don’t know enough about the genetics of the current population. But in simpler cases, evolutionary theory can and has made successful predictions. Antibiotic resistance is maybe the easiest and best example, but there are others.
I think Mr Finch’s answers for the rest are clear enough. Maybe I’ll say that the “Punctuated Equillibrium” debate is probably one of those ‘debates’ where at this point it goes without saying that things are somewhere in the middle: there are certainly periods in many organism’s history of more rapid evolutionary change, but not as overwhelming and dramatic as the most extreme statements of punctuated equilibrium would have it.

13

IAAG and offer a bit of clarification

**bolding **mine

True. At the high school level, genes are basically stretches of DNA. There are many regulatory elements that strongly effect the expression of a gene (whether a gene is turned “on” or “off” and under what circumstances).

The sequence of base pairs is indeed a “long pretty string” but the physical shape the DNA molecule takes when wound up has no real bearing on the shape of the final protein product.

But… that long string in not always an unbroken string. Many genes have non-coding introns which break up the coding sections, the exons, which do get translated into RNA. RNA then, subject to further splicing, may be translated into a structural protein.

Our understanding of the splicing process is developing. But we cannot 100% read a DNA sequence and, from that alone, understand what the 3d structural protein product would look like and *fully[/I ]elucidate its function. We might see certain sequences and deduce that a certain portion of a gene is coding for a trans-membrane element or an ATP binding site, but protein folding is a rather complicated process and fully predicting a protein function based solely upon the gene coding that protein’s formation is currently a bit beyond our ability.

It may be a battle of semantics, but* in vivo* enzymes have been identified which are made up of proteins and even some which are solely RNA.

And, at least in vitro, DNA enzymes have been demonstrated. It is indeed possible that DNA has direct enzymatic activity in vivo.

14

My mistake about Dawkins/Dennett (they’re all the same to me! no, not really). In any case, I would disagree that Dennett’s main point here is arguing against a claim by Gould that “a fair amount of luck” was involved. Rather, he is seeking to elucidate what precisely it might be that Gould actually claims, since he seems to be claiming (to Dennett, at any rate) that Gould suggests that the extinction of the Burgess shale fauna was random–and then reverses that suggestion. This is Dennett’s central problem with Gould throughout, not necessarily the points Gould makes but rather them impossibility of really pinning him down much of the time. I don’t think you’ll find Dennett arguing against the role of chance in the history of life (p-312: “a little bit of chance, a little bit of ever”). That’s an aside, I suppose…

In plain term, then, what would you say?

Well, it was a new evolutionary mechanism for Gould and Eldredge, was it not? But I’ll note that that debate is off the table.

Again, just so it doesn’t poison my questions, I don’t think for a minute that there is a problem (as in, things don’t work) with evolutionary theory, I’m just trying to dig out some places where evolutionary biology does not do what some people think it does–and to see if some analogies between the research processes and results of the humanities and evolutionary biology might be found. So your point here is very valuable: small scale versus large scale explanation and prediction, something that might not easily translate.

Yes, that’s what I took from Dennett; it seemed persuasive enough, too. Thanks!

Question 6 was the simplest?? That’s a surprise! At any rate, yes, I supposed that the actual answers might be a bit complicated–but for my purposes, I would translate your answer into a “yes, saying this gene does that is usually a simplification”. I don’t expect I’ll ever really grasp how this all works, since I lack training, and the analogies I draw will be somewhat superficial at best–but they are supposed to be, or at least I accept that they will be, so that’s not a problem.

15

If you are looking for a very serious and succinct critique of EP, you might want to check out my article here:

A slightly revised version was recently accepted for publication in the journal Theory and Psychology. It summarizes the main theoretical problems of EP: namely that their assumptions are inconsistent with what we know about neurobiology, that the mind may indeed turn out to be ‘partially modularized’ for reasons that are not genetic, and that as a result of some fallacious assumptions, they end up treating culture, learning, and the modern-day environment in ways that are highly problematic.

I posted a follow-up discussion based on some reactions here:

http://modernpsychologist.ca/evolutionary-psychology-theoretical-faith/

16

I don’t see it as a claim on Gould’s part, but rather a suggestion (he does lead off with ‘perhaps’, after all). But then, Dennett’s counterargument is just as hedge-worthy (“Some really ingenious reverse engineer might someday be able to tell an awfully convincing story about why the winners won and the losers lost.” - emphasis mine). So really, it’s just a minor pissing contest between two scientists with a difference of opinion, and really doesn’t say anything, in itself, about what evolutionary biology can or cannot do. Essentially, that whole section read (to me) as Dennett arguing for a type of evolutionary determinism - if you replay the history of life, it will turn out fundamentally the same. He was also an outspoken critic of punctuated equilibrium.

I would say that, much like human history, there are things lost to time that we will never be able to objectively determine.

Not really a new mechanism, but a new claim regarding pacing, perhaps. A complete fossil record (that is, were it possible to recover all organisms that had ever been fossilized) would look substantially the same: dominated by static populations which appear and disappear suddenly. And not because there is a new mechanism beyond natural selection at work, but because speciation and extinction events are geologically rapid (note that Punc Eq tends to favor allopatric speciation as the primary mode of speciation over Darwin’s preferred model of sympatric speciation).

17

I agree with that in general, with the exception of the last, I think: Dennett is an outspoken critic of some of the stronger claims about punctuated equilibrium, while he is entirely fine with the idea that some evolutionary developments may occur within geologically short time spans.

Ah, yes, that seems an apt point.

Right, but this seems pretty much like what Dennett is saying, at least to me–and it’s what Gould seems to be saying some of the time, while not at others. At any rate, this is getting away from my questions–but interesting, thanks!

Modern_psychologist, thanks for the link and the article. I read it with interest. My university library doesn’t apparently subscribe to Theory and Psychology, so it was useful to have it open access. As an aside, there’s a rather lengthy review of some recent publications in evolutionary psychology in the latest New Yorker; rather critical, on the whole.