Physicists and engineers decide how to analyze evolution

| 146 Comments

A big story in the press today. Scientists – mechanical engineers and physicists, one working for Boeing with his office only a few miles from my home – show that the evolution of airplanes works the same way as the evolution of organisms:

The evolution of airplanes

A. Bejan, J. D. Charles and S. Lorente

J. Appl. Phys. 116, 044901 (2014);

http://dx.doi.org/10.1063/1.4886855

(fortunately this paper can be downloaded for free).

They make allometric plots of features of new airplane models, log-log plots over many orders of magnitude. The airplanes show allometry: did you know that a 20-foot-long airplane won’t have 100-foot-long wings? That you need more fuel to carry a bigger load?

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.

At least we may rejoice that the authors are not overly shy. They make dramatic statements on the implications for biology:

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.

and

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

Thanks, now I finally know what evolution is. And that biologists should go home and leave its study to the physicists and engineers.

[Note: I will pa-troll the comments as aggressively as I can and send trolling and troll-chasing to the Bathroom Wall.]

146 Comments

Hang on folks – I couldn’t get previewing of my post to work so I have posted it, and then I can see the error messages. Wait for it …

OK, it is sort-of-formatted now, so please comment. I am not sure why I cannot stack the lines of the citation without putting blank lines in between them, but let that pass.

Am I being too negative about the relevance of engineering? Hypersensitive?

By the way, aerodynamic engineering has been applied to analyzing bird evolution at least since the work of John Maynard Smith (an aircraft engineer turned evolutionary biologist) in 1953 (Birds as aeroplanes in New Biology).

Well this is expected. If following the anti-evolution war over the past decade or so has taught me anything, it’s that engineers are always the supreme experts on evolutionary biology!!

:)

Oh no, they used the “D” word. I can confidently predict that creationists will be citing this paper for the next hundred years as proof of design in nature and the ability to detect design in nature. IT doesn’t matter if it makes any sense or not. It doesn’t matter if the paper proves the exact opposite. Little things like that aren’t going to stop them.

Yeah, seems pretty silly from your description. Of course evolution and engineering will often converge on things like wing-to-body ratio; both methods reward body shapes that use the minimum resources to accomplish some task. That doesn’t mean engineering and evolution are the same method.

But I’d bet that even my generalization above is wrong, once we get more granular than the general ‘rule of thumb’ level. I bet any in-depth look at birds would show that similarly-sized birds would have very differently sized wings when they use them in different ecologies. A glider is not going to have the same ratio as a more acrobatic flyer, wing lenght may sometimes be affected by sexual selection, and the proportionaly really goes in the crapper when you start comparing flyers to birds like ostriches and penguins.

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.

Its not a motive organ so maybe this is an unfair counterexample, but I can think of one organ [cough BRAIN cough] in which there are some obvious cases where the proportionality fails - in both the ‘too big’ and ‘too small’ directions.

Wow! So…selection pressure is selection pressure? Whodathunk?

So, what is the unit of heredity for an airplane?

Ugh. I just looked at the figures. Please tell me that this is a joke like the Sokal hoax.

I’m surprised to know that the jet engine evolved from the internal combustion engine and propellers.

It’s not like airplane evolution includes revolutionary changes as well as evolutionary changes, while biologic evolution doesn’t, is it?

Glen Davidson

This isn’t as bad as the usual intrusion of physicists into biology, in which they tell us that we’re doing it all wrong, and then proceed to reinvent some result of R. A. Fisher’s from 1930.

Ooh, Fig. 1 gives a nice impression of diffusion away from an absorbing barrier.

John Harshman said:

This isn’t as bad as the usual intrusion of physicists into biology, in which they tell us that we’re doing it all wrong, and then proceed to reinvent some result of R. A. Fisher’s from 1930.

This is the Journal of APPLIED Physics. Translation: Engineers.

Don’t blame theoretical or particle physicists for this turkey.

Which reminds me: which airplane has the same design as the turkey?

I suppose that it should be noted as well that no way could any animal manage to evolve to the size of even a small plane and be able to sustain powered flight, rather than being merely held up by updrafts. Invention and engineering came up with engines that are far more powerful than are muscles, which utilize materials that are practically barred from biologic evolution.

We did what the Designer could not do. Unless, of course, we’re going to fall for the dreary, “we don’t know what the Designer wants,” which is utterly wrong anyway, since clearly said “Designer” wanted to work within the limitations of biologic evolution, rather than within the less limited options of intelligence and design. Cause the Designer is analogous with humans, except that it works very differently from us, and for different (inscrutable–aside from revelation) purposes.

It took humans to make large and fast flying machines. The Infinite Designer couldn’t, chose not to in its Infinite Wisdom.

Glen Davidson

Maybe a biologist should submit a paper to the same journal teaching engineers about the circulation of airplanes’ bodily fluids.

Has anyone tried to compare phylogenies of engineered objects to biological systems? Engineered items might make for a better control in Figure 1.2.1 here: http://pandasthumb.org/archives/201[…]-3.html#more since it wouldn’t be a completely random distribution.

chriscaprette said:

So, what is the unit of heredity for an airplane?

Ugh. I just looked at the figures. Please tell me that this is a joke like the Sokal hoax.

I’ve ‘always’ been under the impression that the gas turbine was invented by Ægidius Elling.

Which reminds me: which airplane has the same design as the turkey?

That reminds me of this:

As God is my witness, I thought turkeys could fly.

So I think I follow this. If you extend the concept of evolution to include anything that changes over time, then anything that changes over time is a form of evolution. And therefore, if you loosen the definition of “understand what’s going on” sufficiently, it follows that physicists understand everything that’s going on. QED. Physics FTW!

But I think one of the crucial points of Darwinian evolution is the fact that there is nobody intentionally selecting the traits to be inherited in “new models”, which is a marked contrast from aerospace engineering. Even domestication is a wholly different process from evolution. It seems silly to me to claim that the modern dairy cow “evolved” in its present form, though it had the same constraints of inheritance as other living things. (You could speak of a symbiotic relationship between humans and domesticates, but this is not a useful way of understanding how domestication itself works, though it may put it in a large context.)

I don’t see how there is any value in extending evolution even further to engineered machines.

Actually, there is something I was thinking about recently (I’m sure I’m not the first) that if anyone got really serious about studying “design” and its properties, there would be one mark of design that distinguishes it, namely the violation of common descent.

Lateral gene transfers are hypothetically possible but very uncommon. Lateral technology transfers occur all the time. You can’t make a silk purse out of a cow’s ear, but you can make a leather purse following a similar fabric pattern. The zipper is used as a fastener in many unrelated places. It is fabricated of different materials, but is recognizably a zipper, very often to the point of non-functional similarities, such as having a little hole in the pull.

Whenever something with similar function (e.g. fish fins and mammalian flippers) is seen in unrelated living organisms, by contrast, the differences are always more significant than between different kinds of zippers. A designer doesn’t have this constraint, indicating that common descent is an important distinguishing characteristic of living things that is better explained by evolution than by design.

One thing that is not an indicator of “designed” technology is any rational basis for a design. Serendipitous discoveries are recorded throughout technological history. It seems to me that to a first approximation, the main advantage a human “designer” has over natural selection is the ability to transfer designs freely rather than any magical ability to originate them.

Hmmm… How do they account for the proportions of the U-2 and the Super Guppy?

I looked at that paper the other day and did a double take. Who were the reviewers anyway? Could this be a joke?

If engineers are really following the laws of physics in their designs, they would be evolving more compact machines with increasing energy densities and efficiencies. They would be following naturally occurring aerodynamic trends in order to make these machines slip through the air with less energy loss per unit of distance.

They would be designing some machines optimized for distance, others for speed, others for carrying capacity, and still others for hybrid uses.

No matter what craft they build, energy considerations, cost, efficiency, and durability would be factors going into the design. But the designs also have to conform to human constraints; and that may cause some deviations from optimal design of a particular feature. So we would find statistical correlations rather than one-to-one correlations in the evolution of the design of specific features. Sometimes these optimal features are found by trial and error (e.g., put different shapes into wind tunnels and pick the “best” one).

Well, DUH, guess what? You might get something that looked a little like it was sculpted by natural selection. In fact, engineers have often discovered already optimized designs they can copy from nature. We don’t try to build machines that violate the laws of physics – well, not unless one is a crackpot.

And nature isn’t a crackpot designer either; it doesn’t violate any laws of physics, and it finds approximate optimal features by trial and error. It may often miss the optimal shapes and structure if something works “well enough.” Evolution moves on before “optimization” can occur. Organisms can occupy niches in their environment, just as engineered products can find niche markets.

Living organisms don’t violate the laws of physics either. Larger animals like elephants are constrained to have shapes and frames that can withstand gravitational forces. Spiders can’t be scaled up to the size of elephants. Whales can grow big and develop the shapes they have because buoyancy takes away gravitational constraints.

Why these engineers and “physicists” didn’t think of comparing their “insights” with artificial selection rather than natural selection escapes me. Actually, why they wrote the paper at all escapes me. The paper seems a bit sophomoric to me.

The functional shapes of powered flying objects are constrained by physics, and two different processes of development and diversification of these flying objects over time will result in similar shapes for similar functions as flight “designs” mature.

That’s about all there is to it. The IDiot mistake (or fraud, whether intuitive or deliberate) is to pretend that development of functional possibilities simply must be due to design, either by Meyer’s bogus “standard” that design is all that produces substantial function today, or just by pretending that function necessarily indicates design.

But yes, biologic evolutionary development of function and design improvements of function will tend to produce convergence, due to physical constraints.

Kinda obvious.

Glen Davidson

Golkarian said:

Has anyone tried to compare phylogenies of engineered objects to biological systems? Engineered items might make for a better control in Figure 1.2.1 here: http://pandasthumb.org/archives/201[…]-3.html#more since it wouldn’t be a completely random distribution.

Engineered objects don’t really have phylogenies, since there is so much borrowing of innovations from one firm to another. They also don’t evolve by a biased random search, either, so the simple stochastic models we use in molecular evolution are usually not appropriate. There is tinkering but also deliberate design.

callahanpb said:

So I think I follow this. If you extend the concept of evolution to include anything that changes over time, then anything that changes over time is a form of evolution. And therefore, if you loosen the definition of “understand what’s going on” sufficiently, it follows that physicists understand everything that’s going on. QED. Physics FTW!

But I think one of the crucial points of Darwinian evolution is the fact that there is nobody intentionally selecting the traits to be inherited in “new models”, which is a marked contrast from aerospace engineering. Even domestication is a wholly different process from evolution. It seems silly to me to claim that the modern dairy cow “evolved” in its present form, though it had the same constraints of inheritance as other living things.

I would qualify that a bit. The goals of artificial selection are human artifacts, but the response to that selection is affected by mutation, and genetic drift in much the same way as with natural selection. My postdoctoral advisor, the late and much-lamented Alan Robertson did brilliant work using the equations of theoretical population genetics to predict things like the expected selection response with different strengths of selection, where stronger selection meant breeding from fewer offspring so that there was more genetic drift. He was able to come up with an optimal strength of selection for greatest expected response (in short, breed from the top half of your herd).

In August I am invited to give a talk to the World Congress of Genetics Applied to Livestock Production, in nearby Vancouver, B.C. They wouldn’t be asking to hear about phylogenies, and I wouldn’t be agreeing to show up, if there was no connection between the quantitative genetics of natural populations and the genetics used in animal breeding.

W. H. Heydt said:

Hmmm… How do they account for the proportions of the U-2 and the Super Guppy?

It’s easy. You do a log-log plot, so being one unit off the fitted line means you are 10x bigger or smaller. But it looks like a close fit when you’re on that log scale.

Here is an engineering optimization problem.

You want to store lots of sand on your property for future use. You want it to occupy the maximum volume for the minimum amount of area taken up on your property. You don’t want to invest in containers because that costs money for material and labor. What do you do?

Well, a pile of sand will occupy the largest volume within that smallest area if it is stacked in a conical shape at the angle of repose of a sand pile, which is the arctangent of the coefficient of static friction between sand particles.

So, just dump it in a pile wherever you want it, and let nature do the rest.

Mike Elzinga said:

Here is an engineering optimization problem.

You want to store lots of sand on your property for future use. You want it to occupy the maximum volume for the minimum amount of area taken up on your property. You don’t want to invest in containers because that costs money for material and labor. What do you do?

Well, a pile of sand will occupy the largest volume within that smallest area if it is stacked in a conical shape at the angle of repose of a sand pile, which is the arctangent of the coefficient of static friction between sand particles.

So, just dump it in a pile wherever you want it, and let nature do the rest.

For similar reasons, you should have spherical cows in your barn.

Glen Davidson

https://me.yahoo.com/a/JxVN0eQFqtmg[…]X_Zhn8#57cad said:

Mike Elzinga said:

Here is an engineering optimization problem.

You want to store lots of sand on your property for future use. You want it to occupy the maximum volume for the minimum amount of area taken up on your property. You don’t want to invest in containers because that costs money for material and labor. What do you do?

Well, a pile of sand will occupy the largest volume within that smallest area if it is stacked in a conical shape at the angle of repose of a sand pile, which is the arctangent of the coefficient of static friction between sand particles.

So, just dump it in a pile wherever you want it, and let nature do the rest.

For similar reasons, you should have spherical cows in your barn.

Glen Davidson

If they were to be milk producers, that would be udderly impossible.

This post has also been commented on in a post by P.Z. Myers at Pharyngula.

I wanted to get it up here quickly once I saw that the airplane paper was getting a lot of media attention. It was only a matter of time before someone argued that it was a brilliant validation of evolution, and I wanted to point out the problems early on.

The paper argued that their results flowed from something mysterious called Constructal Theory, though they never clarify what that is. They do give references to earlier papers of theirs on this.

I’ll remember this event when biologists venture outside their discipline.

As a mechanical engineer I must say that that is one of the dumbest papers I’ve read, and I’ve read some pretty dumb papers! My god who reviewed this??? I review technical papers all the time and I would have laughed this one off. I can certainly see the whack job ID people running with this one.

https://me.yahoo.com/a/JxVN0eQFqtmg[…]X_Zhn8#57cad said:

For similar reasons, you should have spherical cows in your barn.

Glen Davidson

But they stack better if they’re cube-shaped.

Joe Felsenstein said:

Guess what? The Discovery Institute’s Evolution News and Views has discovered the Bejan et al. paper. Their line is pretty much as we predicted.

I keep having this sense of déjà vu about Bejan’s “Constructal Law.” I know I looked at a couple of his papers or presentations some time ago and concluded they were “strange;” to put it mildly.

I don’t recall the context of the discussion, but I thought that UD had already sneered at one of these papers over a year ago and was making the arguments for design in biology based on design as seen in engineering. I saved in my pseudoscience folder on 9/15/2012 a paper by Bejan entitled “Constructal theory of generation of configuration in nature and engineering” from the JOURNAL OF APPLIED PHYSICS 100, 041301 (2006).

Was that discussion here on Panda’s Thumb? I haven’t been able to find it. I’ve been away a lot.

prongs said:

Dave Luckett said:

… I wonder if the Air Force actually does that kind of research?

No doubt they do. The Navy has (or had) a group researching cold fusion, abandoned by almost everyone as pathological science, just to make certain there wasn’t something genuine there (potentially useful for submarine propulsion, no doubt). NSA has advanced mathematics, in secret, beyond the current state of open knowledge. There are rumors of the US Military investigating prayer and mental telepathy, just to be certain nothing’s been overlooked.

Prudent research all, so long as it doesn’t get sidetracked (as some think the naval cold fusion research was).

http://en.wikipedia.org/wiki/Stargate_Project

Whether this was prudent research is a subjective evaluation.

Massive increase in psychic powers were one of the big three predictions of classic twentieth century science fiction. That, along with development of incredibly human-like androids who would have a tendency to develop human motivations, and faster-than-light travel with humans colonizing much of the universe. All by now.

Small powerful computers, exploding knowledge of molecular genetics, human contribution to climate change…that stuff, they somehow didn’t “foresee”.

The airplanes show allometry: did you know that a 20-foot-long airplane won’t have 100-foot-long wings? That you need more fuel to carry a bigger load?

Are prototypes, such as NASA’s Helios with its 247 ft wingspan, allowed in these examples of allometry?

Then there are also the ”flying wing” aircraft.

Mike Elzinga said:

The airplanes show allometry: did you know that a 20-foot-long airplane won’t have 100-foot-long wings? That you need more fuel to carry a bigger load?

Are prototypes, such as NASA’s Helios with its 247 ft wingspan, allowed in these examples of allometry?

Where would it be on their allometric plot? (They plotted only produced commercial aircraft, I think).

Also, as for flying wing designs, I think they were mentioned earlier, upthread, as obvious violations of their plot.

Mike Elzinga said:

I keep having this sense of déjà vu about Bejan’s “Constructal Law.” I know I looked at a couple of his papers or presentations some time ago and concluded they were “strange;” to put it mildly.

I don’t recall the context of the discussion, but I thought that UD had already sneered at one of these papers over a year ago and was making the arguments for design in biology based on design as seen in engineering. I saved in my pseudoscience folder on 9/15/2012 a paper by Bejan entitled “Constructal theory of generation of configuration in nature and engineering” from the JOURNAL OF APPLIED PHYSICS 100, 041301 (2006).

Was that discussion here on Panda’s Thumb? I haven’t been able to find it. I’ve been away a lot.

Your déjà vu is sound. I could not find any earlier discussion on the Thumb, but did find a post on the Constructal Law at The Skeptical Zone on September 5, 2012. Gregory subsequently mentioned it in a comment at Uncommon Descent on March 5, 2013 but it got no traction there.

You might want to read the remarks of one of the TSZ commenters in that thread, a guy named Mike Elzinga.

By the way, let me qualify my scorn for the Constructal Law. It can’t possibly be a fundamental law of physics, that is a strange idea. But it might be a useful law for time changes in flows in networks. I don’t know whether it is of use there, but can’t rule that out.

Joe Felsenstein said:

Your déjà vu is sound.

Ah, that’s where it was; I wasn’t imagining things. I’ve been pretty busy with a number of ongoing projects, so those discussions seem to have faded from my memory. Thanks.

I haven’t been to that Skeptical Zone site much after Elizabeth left and turned it over to those guys who were excommunicated from UD. It started getting pretty weird over there; too much like UD.

I am telling from long time ago: Biologists needs to wake up and responding to a war against Physicians and Mathematicians, invading the field of Physicists for discovering the basic of life’s properties, as I tried building the Matrix/DNA Theory. They are occupying everything due arrogance from technological success, now they invaded natural evolution. Biologists are the culprit because they had taken this illusioned success as a indicative how nature works, and the Physics/Math interpretations of the whole Universe as the unique and the right world view. When designing airplanes models they are mimicking some methods and processes applied by Nature, but then, like did the Bible’s authors, they are thinking that they are great and the center of human intelligence, and they believe that there is a ( a non confessable) God, so they are projecting themselves as the personality of God. The jump for such believer invading natural evolution, taking the drive of this field from Biologists, because Biologists are not such elected by God, has no great divine intelligence as they have…have been the normal course of religious dictatorship dominance.

If airplanes and birds were designed by the same methods and processes , should not have a way for making an airplane flying from New York to Paris, because they would always taking the direction North/South Poles, following the Earth’s magnetic field.

Physicists and Mathematicians built a wrong world view because their Cosmos have no the principles forces that evolved into life’s properties. Their cosmological evolution has nothing to do with the Cosmos’ final product - biological evolution. There is a method for Biologists to fix this big error. Making the reverse way of evolution: you have the son, now, calculates the parents based on what you know about the son. Here we will find a better interpretation of the real truth. I tried it under rough and very limited conditions but the results already are surprising. As this papers reveals, these engineers forgot that airplanes have no DNA.

Nobody needs a “war” between physicists and biologists. Physicists have valuable mathematical methods and physical insights, and these are welcome in evolutionary biology. It is just that sometimes engineers and physicists get arrogant and fail to inquire what evolutionary biologists have actually done. They then reinvent the wheel or make elementary mistakes.

I am not sure what your “Matrix/DNA Theory” is, I have not previously heard of it. As for “calculat[ing] the parents based on what you know about the son”, this sounds like the main research program of work on phylogenies: reconstructing the relationships and the forces of change, as well as inferring the features of the ancestors, from data on multiple present-day species. We’re doing all that already.

Maybe we should blame the physicists. This paper is all about that planes always got heavier (see fig. 1). Here is an ordered list of the 10 heaviest birds (http://en.wikipedia.org/wiki/List_o[…]argest_birds): Ostrich, Southern cassowary, Northern cassowary, Emu, Emperor penguin, Greater rhea, Dwarf cassowary, Lesser rhea, King penguin and Great bustard. The last one in this list is a little bit odd, so we ignore it. My take on this paper is that Boeing is going to change its business and moving away from planes - taking the design(!!!) principles of heavy birds - to flightless planes! These new generation planes can be of course much heavier than the planes Boeing produces now. So it is mainly marketing paper. Isn’t it much fancier to travel on a flightless plane instead of a train or bus and a flightless, aquatic plane instead of a ship?

klaus.schliep said:

Isn’t it much fancier to travel on a flightless plane instead of a train or bus and a flightless, aquatic plane instead of a ship?

:-)

Flightless airplanes; “interesting” concept.

Maybe there is a lesson to be learned here. ;-)

Back in the 1990s, Kodak management decided to reject “filmless imaging” and shot all its researchers. Then it did a long, slow spiral into bankruptcy.

Mike Elzinga said:

Flightless airplanes; “interesting” concept.

Ladies & genetlmen, I give you the Bennie Monorail.

stevaroni said:

Mike Elzinga said:

Flightless airplanes; “interesting” concept.

Ladies & genetlmen, I give you the Bennie Monorail.

Apparently potential investors saw it as a “dodo on a zip line.”

E = mc squared.

The rest is implementation detail.

klaus.schliep said:

Maybe we should blame the physicists. This paper is all about that planes always got heavier (see fig. 1). Here is an ordered list of the 10 heaviest birds (http://en.wikipedia.org/wiki/List_o[…]argest_birds): Ostrich, Southern cassowary, Northern cassowary, Emu, Emperor penguin, Greater rhea, Dwarf cassowary, Lesser rhea, King penguin and Great bustard. The last one in this list is a little bit odd, so we ignore it. My take on this paper is that Boeing is going to change its business and moving away from planes - taking the design(!!!) principles of heavy birds - to flightless planes! These new generation planes can be of course much heavier than the planes Boeing produces now. So it is mainly marketing paper. Isn’t it much fancier to travel on a flightless plane instead of a train or bus and a flightless, aquatic plane instead of a ship?

By the way, this list of heavy birds illustrates the problem of ignoring phylogeny. The whole list comes from three groups. One is the Great Bustard, one is the ratites, and one is the penguins. All the ratites, large and small, are flightless, and so are all penguins. So you can’t conclude that flightlessness is enabled by heaviness (in fact probably heaviness is made easier to evolve if the bird is flightless).

Joe Felsenstein said: By the way, this list of heavy birds illustrates the problem of ignoring phylogeny. The whole list comes from three groups. One is the Great Bustard, one is the ratites, and one is the penguins. All the ratites, large and small, are flightless, and so are all penguins. So you can’t conclude that flightlessness is enabled by heaviness (in fact probably heaviness is made easier to evolve if the bird is flightless).

Technically (phylogenetically) speaking, the ratites are two groups, not one. So yay, there are four data points.

John Harshman said:

Joe Felsenstein said: By the way, this list of heavy birds illustrates the problem of ignoring phylogeny. The whole list comes from three groups. One is the Great Bustard, one is the ratites, and one is the penguins. All the ratites, large and small, are flightless, and so are all penguins. So you can’t conclude that flightlessness is enabled by heaviness (in fact probably heaviness is made easier to evolve if the bird is flightless).

Technically (phylogenetically) speaking, the ratites are two groups, not one. So yay, there are four data points.

And penguins (the best birds) fly in the water. Three data points.

Oops. Actually, and according to the most recent results incorporating moas and elephant birds, the extant ratites are at least three groups. And flying in the water is close enough to flying. So 5 data points!

John Harshman said:

Oops. Actually, and according to the most recent results incorporating moas and elephant birds, the extant ratites are at least three groups. And flying in the water is close enough to flying. So 5 data points!

Five data points, two of which “fly”. So both a noisier inference than we might have thought if we just tabulated species, and a less clear pattern.

Ah, but how many independent contrasts can you get from the tree of airplanes? You do have a tree of airplanes, don’t you?

John Harshman said:

Ah, but how many independent contrasts can you get from the tree of airplanes? You do have a tree of airplanes, don’t you?

If we have a lineage of the form p1 –> p2 –> p3 –> p4 –> … and if we (very naïvely) assume a covarying Brownian motion model, just as we often do in evolutionary biology, and if each of the planes p1, p2, … are observed without measurement error, then the differences between successive planes in the lineages, scaled by the square roots of the times between those planes, are the contrasts.

I leave it to you, as an exercise, to do the resulting plots.

My wife is always telling me I need more exercise, but I’m not sure that’s what she means.

John Harshman said:

Ah, but how many independent contrasts can you get from the tree of airplanes? You do have a tree of airplanes, don’t you?

How often did flightlessness arise in airplanes?

TomS said:

John Harshman said:

Ah, but how many independent contrasts can you get from the tree of airplanes? You do have a tree of airplanes, don’t you?

How often did flightlessness arise in airplanes?

Pretty much after every crash.

Glen Davidson

Does a ground effect vehicle like the Lun Ekranoplan count as a flightless airplane?

Just Bob said:

Does a ground effect vehicle like the Lun Ekranoplan count as a flightless airplane?

Amazing ekranoplan photos here and here.

That is all.

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