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They don’t understand allometry!

I think the engineers are just trying to wind me up, again. Joe Felsenstein tackles a paper published in an applied physics journal that redefines evolution and tries to claim that changes in aircraft design are a good model for evolution. It’s a terrible premise, but also, the execution is awful.

But permit me a curmudgeonly point: This paper would have been rejected in any evolutionary biology journal. Most of its central citations to biological allometry are to 1980s papers on allometry that failed to take the the phylogeny of the organisms into account. The points plotted in those old papers are thus not independently sampled, a requirement of the statistics used. (More precisely, their error residuals are correlated). Furthermore, cultural artifacts such as airplanes do not necessarily have a phylogeny, as they can borrow features from each other in massive “horizontal meme transfer”. In either case, phylogeny or genealogical network, statistical analysis requires us to understand whether the points plotted are independent.

The paper has impressive graphs that seem to show trends. But looking more closely we notice that neither axis is actually time. If I interpreted the graphs as trends, I would conclude that birds are getting bigger and bigger, and that nobody is introducing new models of small airplanes.

And they really do redefine evolution.

Evolution means a flow organization (design) that changes over time.

I’m going to redefine bridge construction as gluing together lots of matchsticks. Hire me, everyone, to help fix your infrastructure problems! I can probably underbid everyone!

But it’s just kind of amazing that they’ve defined evolution without any mention of populations or shifting allele frequencies or any of the processes (which don’t include design) that lead to changes in genotype, or even a recognition of how these processes derive from a core unity and lead to diversity. Design done did it.

My big gripe is that they got this paper published that is all about allometry with scarcely any understanding of the concept. Here’s the abstract of The evolution of airplanes.

The prevailing view is that we cannot witness biological evolution because it occurred on a time scale immensely greater than our lifetime. Here, we show that we can witness evolution in our lifetime by watching the evolution of the flying human-and-machine species: the airplane. We document this evolution, and we also predict it based on a physics principle: the constructal law. We show that the airplanes must obey theoretical allometric rules that unite them with the birds and other animals. For example, the larger airplanes are faster, more efficient as vehicles, and have greater range. The engine mass is proportional to the body size: this scaling is analogous to animal design, where the mass of the motive organs (muscle, heart, lung) is proportional to the body size. Large or small, airplanes exhibit a proportionality between wing span and fuselage length, and between fuel load and body size. The animal-design counterparts of these features are evident. The view that emerges is that the evolution phenomenon is broader than biological evolution. The evolution of technology, river basins, and animal design is one phenomenon, and it belongs in physics.

Isn’t it cute how they claim biology as a small subset of physics? Blech.

But they only address a very narrow part of allometry. There is a functional constraint on form: you won’t survive if you have a human-sized body and a mouse-sized heart; if you scale the diameter of your legs linearly with your height, you won’t be able to walk; for a given metabolic rate and mass, you need a certain amount of respiratory surface area. That’s interesting stuff to a physiologist, but it’s also purely defined by necessity.

A developmental biologist might be more interested in how the relative sizes of different body parts change over time. Again, relative growth rates of different parts of your body are not linearly related; imagine being six feet tall with the same proportions as a baby. There are regulatory constraints on development that impose different rates in different areas.

But these guys are talking about evolution and allometry…and they treat it as a simple function of physics, where you need an engine of size X to propel a plane of size Y. Then how come every animal of the same size don’t look identical? Why doesn’t every passenger plane that carries a certain number of customers look the same (well, they do kind of blur together for me, but I’m sure any aerospace aficionado can tell me about all the differences between Boeing and Airbus. But many of these differences in animals are a result of inherited patterns, and phylogeny is essential to understand them.

For example, here’s a plot of brain mass relative to body mass (yeah, ugh, “lower” and “higher” vertebrates; let’s call them anamniotes and amniotes instead).

eq

Notice that there are two lines drawn. Both show an upward trend, with a slope that’s proportional to the 2/3 power of the body size (that N2/3 shows up a lot in allometric growth plots). But given a fish (an anamniote, or “lower” vertebrate) and a mammal (an amniote, or “higher”) of exactly the same body mass, the mammal will have a relatively and absolutely much larger brain.

Explain that, engineer, with nothing but algebra and no concern about phylogenetic relationships. It takes more to understand evolution than physics alone, and you have to take into account history, environment, inherited properties, selection, and chance as important parameters.

Oh, well, I’ve learned that physics must be really simple. I can design a plane from the ground up if I simply postulate a spherical 747. Ha ha, all those fools getting engineering degrees when they could just bring in a clever biologist to solve all their trivial little problems.

Comments

  1. says

    By the way, there are other problems with that abstract. I leave it as an exercise for the reader to determine what they are.

  2. jamessweet says

    Well hold on now, their definition of “evolution” is not necessarily all that bad — see the non-biology-related definitions here: http://www.merriam-webster.com/dictionary/evolution

    The problem is the overloading of the word. “Evolution” in the sense of “My feelings towards radical feminism have undergone an evolution over the past decade” is not the same as “evolution” in the sense of “Evolution is entirely sufficient to explain the diversity of life on earth.” Substituting either results in nonsense: In the former case, it is certainly not true that my feelings towards radical feminism have been changed as a result of descent with modification or anything of the sort. And in the latter case, to simply say that “things change over time” is not nearly sufficient to explain life’s diversity. They are just totally different words.

    They didn’t redefine evolution, as you say. They just used a perfectly valid definition in a totally absurd context.

  3. says

    I didn’t see a date on the article (apart from the year), is ist possible that it was published in early April, really really early April?

  4. kieran says

    When a Mammy plane and a Daddy plane love each other very much, they hug in a special way and that’s why aircraft hangers have doors.

  5. Kele Cable says

    That graph includes alligators as “lower vertebrates” so apparently “higher vertebrates” independently evolved twice!

  6. dhall says

    I might be wrong, but haven’t there been lots and lots of relatively small planes that were very fast and capable of long range flights? Otherwise, how did the fighter escorts keep up with the bombers in WWII (once belly and wing fuel tanks were added to the fighters). Modern military fighters and bombers are also fast–faster than commercial jets and yet much smaller–and in some cases capable of relatively long flights. Large planes are probably more fuel efficient, but to make a blanket statement like: “the larger airplanes are faster, more efficient as vehicles, and have greater range,” is simply incorrect in many cases.

  7. Rob Grigjanis says

    Isn’t it cute how they claim biology as a small subset of physics?

    Yeah, this sort of thing is really annoying. I like this answer;

    The fact is that every science comes with its own set of fundamental laws. These laws are strictly reducible to ‘lower-level’ laws in a philosophical sense, but the lower-level laws don’t directly lead to the higher-level fundamental ones. Thus, an understanding of the lower-level laws, no matter how thorough, does not automatically imply an understanding of the higher-level ones.

  8. okeydoke says

    You sure that guy isn’t a troll? The name Felsenstein could be translated as Rockstone. It’s just weird.

  9. monad says

    @6 Kele Cable:
    It looks like they did. I imagine PZ is assuming an overly phylogenetic take in calling them amniotes and anamniotes, and they probably meant endotherms and poikilotherms, or fluffies and scalies.

  10. twas brillig (stevem) says

    tl;dr.
    I am certain that the “evolution” of airplane design has frequently been used as an analogy for biological evolution. It seems this author has taken the analogy concept too far; to places the analogy was not intended. In short: It is an Analogy, not a valid Model of Evolution. How do papers like this get through “peer-review”?

  11. otrame says

    Isn’t it cute how they claim biology as a small subset of physics?

    Well, as Pratchett says, geology is just physics slowed down with some trees on it, so, yeah. It is. Just like sociology, psychology, history, and geography are subsets of anthropology. It’s trivially true but we have these subsets for a reason. Nobody can study it all in depth.

  12. says

    Again, relative growth rates of different parts of your body are not linearly related; imagine being six feet tall with the same proportions as a baby.

    Try as I might, I cannot imagine what that would look like.

  13. Nick Gotts says

    Just like sociology, psychology, history, and geography are subsets of anthropology. – otrame@13

    WTF? Anthropology has its own methods and problems, which are entirely distinct from those of history, geography and psychology, and largely distinct from those of sociology. I doubt you’d find anyone from any of the other disciplines, or more than a very few anthropologists, who would agree with your claim.

  14. ehmm says

    I always thought language was a much better (though not perfect) analogue than comparisons to obviously man made artifacts. Mainly, that languages are obviously complex but not designed, they can be effected by environmental influences and they change over time as new generations of language speakers replace older ones.

  15. says

    This paper is totally wrong from an aeronautical engineering point of view too. Fuselages are not round to minimize drag but to lower manufacturing costs and solve the structural engineering problem of differential pressure. If this were not the case fuselages would be like German sailplanes or the old Lockheed Constellation. He completely ignores the fact that Boeing and others are working on flying body designs.

    The reason why planes are limited and Concorde didn’t work too well is because of a simple physical constraint – the speed of sound in air. Air cannot “communicate” the path of the airplane and therefore there is a huge increase in drag. Concorde failed because it used old military engines with afterburners and could not meet the noise, fuel consumption and reliability goals.

    It appeasr he is trying to make a name for himself.

  16. originalantigenicsin says

    This doesn’t seem to be a joke (unfortunately): The lead author of this paper is a “Professor of Mechanical Engineering” at ( Duke University ) and has obviously come up with a law that “explains” development in a multitude of fields, physics, biology, technology and society (again, not a joke). My favourite paper title from a quick skimming of his publication.is The Evolution Of Speed In Athletics: Why The Fastest Runners Are Black And Swimmers White.

  17. says

    Dunning-Kruger strikes again? What is it with my fellow engineers* that they fall into this trap all the time?!

    *Granted, I’m a much different type of engineer than this person seems to be.

  18. cactusren says

    okeydoke @9:

    You sure that guy isn’t a troll? The name Felsenstein could be translated as Rockstone. It’s just weird.

    Felsenstein is the one who wrote a take-down of the article in question, and he is certainly not a troll, despite the odd name. He is well known in the field of phylogenetic systematics, and proposed the “phylogenetic independent contrasts” statistical test in 1985. Something these engineers should have considered using if they wanted any kind of meaningful result.

  19. Lynn says

    I’ve heard so many engineers/physicists claim biology as a subset of their One True Science that it no longer surprises me. I simply bathe in the mockery they get when they’re horribly, stupidly wrong.

  20. monad says

    otrame @13:

    Just like sociology, psychology, history, and geography are subsets of anthropology.

    The things they study may be subsets, but a field of science is defined just as much by what methods can be applied to study them.

    Physics involves looking at universal laws, and chemistry involves looking at atoms subject to universal laws. So from some perspective it would be a type of physics. But in practice, the things you need to do to investigate atoms are so completely different, it is only sensible to describe chemistry as a separate field of study.

    This applies even further to biology. Both physics and chemistry apply to it, but those don’t even really have a place for taxonomy or phylogenetics, and without them those applications have no context.

  21. robro says

    I know practically nothing about biological evolution (mostly learned here), but isn’t this 100% BS?

    The prevailing view is that we cannot witness biological evolution because it occurred on a time scale immensely greater than our lifetime.

    I’ve read PZ and others in biology say that biological evolution can go pretty quick in microorganisms. We can even detect genetic changes in larger organisms, such as humans. So, evolution occurs continuously and the results can be detected now quite easily.

    As I understand it, these are typical answers to the fundamentalist claim that you can’t witness evolution, so there’s no “poof”. In fact, the statement sounds suspiciously like anti-evolution rhetoric…note specifically the use of the word “witness,” a concept deeply embedded in Christianity. And, of course, “design” because where there is design there must be a designer.

  22. Kevin Kehres says

    “Human-and-plane species”? Someone doesn’t understand what a species is…

  23. Amphiox says

    Well, if you made your spherical 747 out of rubber, and filled the interior with helium gas….

  24. Peter B says

    So biology is a small subset of physics?

    Let’s think:
    Chemistry is a small subset of physics.
    Biology is a small subset of chemistry.

    Therefore:
    Biologists need to know much of chemistry and physics.
    Chemists need to much of physics. (P Chem anyone?)
    Physicists should just stick to physics.

  25. palmettobug says

    As a practicing scientist, I really don’t understand why engineering profs feel the need to try to publish in science journals (or engineering journals, for that matter). Shouldn’t they be busy translating science into products, starting companies, and doing consulting for companies? Why on earth are they trying to play scientist and suck up NSF grants and pollute journals with dreck? They often mistakenly think that their technical prowess with equations or complex machinery gives them an ability to do science. With a few exceptions, whenever I see engineers in the author list of a paper, I see one or more of the following:

    -a complete ignorance of the fact that everything in the paper was done years ago by real scientists, but engineers typically don’t read journals so the authors didn’t know
    -a complete failure to engage with the relevant literature or even textbook knowledge
    -lack of adequate controls
    -lack of coherent hypothesis
    -bad writing
    -lack of proper discussion of the results, alternative explanations, uncertainty
    -lots of hype, press-releases, postings on science news-aggregator sites
    -persistence of crank/crackpot ideas

    They really just don’t teach scientific method, scientific controls, advanced science, and the structure of scientific theory in engineering school. There are occasional profs in engineering depts who have a science Ph.D. and understand how to do science, but most don’t.

  26. Lofty says

    kieran

    When a Mammy plane and a Daddy plane love each other very much, they hug in a special way and that’s why aircraft hangers have doors.

    Well the existence of Piper Cubs confirms that theory.

  27. maddogdelta says

    Wait… you mean someone took a very lame analogy which could be used to explain to 3rd graders what “adaptation” means, and turned it into a published paper?

    Wow….that puts the Journal of Applied Physics down on a level with the Journal of Creation Research.

    Christ, there are real scientists who have real papers being rejected by that rag and they publish this piece of crap?

  28. Al Dente says

    Avram Davidson wrote a short story “Or All the Sea With Oysters” about how paperclips evolve into coat hangers and coat hangers evolve into bicycles. It won the Hugo Award for Best Short Story in 1958.

    “I mean, of all the machines in the world, only bikes come male and female.

  29. moarscienceplz says

    I’ve read PZ and others in biology say that biological evolution can go pretty quick in microorganisms. We can even detect genetic changes in larger organisms, such as humans. So, evolution occurs continuously and the results can be detected now quite easily.

    Yes, but the creotards would just say that you started with microorganisms and ended with microorganisms, so no macroevolution was demonstrated. I saw a comment from a guy one time that Darwin’s observations of finch beaks proved nothing because, “they are all still finches”.

  30. Pierce R. Butler says

    … we cannot witness biological evolution because it occurred on a time scale immensely greater than our lifetime.

    [We all share the same lifetime? Grammatical failure pops up in almost every My Great Theory™ (there oughta be a Somebody's Law, or at least a bingo square).]

    It appears that none of the authors of this breakthrough has heard of Punk Eek; likewise its editors and peerless reviewers.

    Facepalm Trauma Units will have a busy night tonight.

  31. kmk05 says

    @28 palmettobug:

    engineers typically don’t read journals

    That’s awfully arbitrary, and so are your generalisations.

    I can only speak for the engineering departments I work in (materials, civil engineering, and earth science and engineering), but most academics I’ve met do ‘understand how to do science’. (I’m not claiming knowledge about mechanical engineering, though!)

    Most scientists are engineers by trade, because we are assigned to the faculty of Engineering. You assume the science is already there, for us to ‘translate it into products’, but that simply isn’t the case. Research into solidification, photovoltaics, fuel cells or sand piles isn’t any more or less deserving of funding that other fields.

  32. lpetrich says

    As to why it’s a male gorilla, it’s because all the rest are female. That’s because the female sex is usually less shaped by sexual selection than the male sex in many animal species, and thus more closely reflects selection to the environment than the male sex, at least in the opinion of some biologists.

    Females are the ecological sex: sex-specific body mass ecogeography in wild sifaka populations (Propithecus spp.)

    Previous work in primates has shown that body size often covaries with ecological parameters related to resource or energy availability in the environment. This relationship may differ for males and females as access to resources has greater importance for reproductive success in females. We test the hypotheses that (1) female body mass may be more tightly constrained than male body mass by ecological variables, and (2) female body mass may respond more strongly than male body mass to changes in ecological variables (i.e., population-specific female mass may vary more across an ecological gradient than male mass). Specifically, we investigate the relationship between climatic variables and sex-specific body mass in Propithecus, a genus in which species-specific body mass has already been demonstrated to covary significantly with climatic variables. Data from 733 wild sifakas are used to identify sex-specific body mass for 27 populations representing all nine described sifaka species, and climatic data for each population are derived from the WorldClim database. We use phylogenetic generalized least squares models to demonstrate that body mass in both sexes is significantly correlated with annual rainfall and number of dry months. Furthermore, coefficients of determination are always higher for female models, and coefficients for each climatic variable are higher for females in all significant models. These results support the two hypotheses tested, indicating that ecological forces can have a greater impact on female mass than on male mass in primates.

  33. palmettobug says

    @35 kmk05
    #NotAllEngineers!
    I hope it was clear in my comment that these were general impressions, and I was not claiming that these were universal truths. I am in the U.S. and I’m guessing (from the timestamp and the non-typical-for-US use of “Faculty”) that you are not. The science/engineering divide varies by country. It appears that in your country scientist faculty typically work in engineering departments, whereas here they do not.

    I think you and I also disagree about what is science. While tweaking the composition of photovoltaics to improve efficiency might count as “research”, I wouldn’t classify it as Science, unless it is driven by a nontrivial hypothesis and leads to a better fundamental understanding of the underlying processes.

    To me it seems pretty self-evident that if the research isn’t science (i.e., furthering our understanding), and if it isn’t tightly coupled to actual production (i.e., if it is “purely academic engineering”, just mucking around with process variables, no industrial partnerships, with little or no chance of commercialization), then it is pretty much worthless.

  34. kmk05 says

    @37 palmettobug:

    It seems as if there actually is quite a large divide between the US and the UK then (I work as a postdoc at a UK university).

    If you get funding from an exclusively industrial source (e.g. Rolls Royce), then you may be beholden to it (and you have to research what they tell you).

    OTOH, it would be quite unlikely to get any sort of public funding that isn’t about ‘furthering our understanding’ (i.e. the equivalent of NSF funding). You may get an enormous chunk of public funding which will yield money for multiple sub-projects/PhD projects, and at that point there may be one of these projects that becomes ‘academic engineering’.

    But let’s be real: there can be quite a few PhD/research projects which are about mucking about with variables. Sometimes the fact that the research isn’t groundbreakingly novel or significantly contributing to the existing field is down to a researcher who isn’t up to the task, or to a bad supervisor who didn’t direct the project properly. But I’m fairly certain this isn’t only in engineering and happens in all other scientific fields.

    I’d like to add that, in the UK, public funding for engineering, physics and mathematics comes from the Engineering and Physical Sciences Research Council, while funding for more biological/medical things is usually from two or more funding bodies (the Biotechnology and Biological Sciences Research Council and the Medical Research Council, to name the first two. So engineering doesn’t compete directly with biology for funding.

  35. palmettobug says

    kmk05
    I agree that much research is fruitless and in the end doesn’t accomplish much, but that doesn’t mean that research that is neither scientific nor highly translational is useful. Much of academic engineering research in the U.S., IMO (as a science prof, grant and article reviewer, etc) is useless stamp-collecting, with no clear path to commercialization and no real science.

  36. David Marjanović says

    How come *male* gorilla?

    Because males are easily 50 % larger than females.

    That graph includes alligators as “lower vertebrates” so apparently “higher vertebrates” independently evolved twice!

    Yep. “Higher vertebrates” are meant to be birds and mammals and nothing else. Complete lack of evolutionary perspective!

    You sure that guy isn’t a troll? The name Felsenstein could be translated as Rockstone. It’s just weird.

    Joe Felsenstein isn’t an author of the failure of peer review, he’s the author of the reply. He’s also extremely well known in the field of phylogenetics, and… occasionally comments right here on Pharyngula; stay for longer, and you’ll encounter him.

    The weirdness of his name makes sense in context: compare Edelstein, Goldstein, Silberberg, Eisenstein… it’s from the time when the German Jews were made to take surnames and to pay for the privilege.

    How do papers like this get through “peer-review”?

    Reviewers are chosen by editors. If the editors don’t understand that the manuscript needs to be sent to an evolutionary biologist for review…

    peerless reviewers

    *steal* :-)

  37. David Marjanović says

    (The one thing that’s worse than higher vertebrates is higher eukaryotes, which means all eukaryotes except yeast – a group of secondarily unicellular mushrooms.)

  38. Crip Dyke, Right Reverend Feminist FuckToy of Death & Her Handmaiden says

    I don’t know, Jenny6833a seems to have a definition of higher feminists that seems worse.