False scientific claim rebuttal thread.

[creature386]

Well, Veronica does not completely deny fossils, she in fact believes that there are a few genuine fossils which have simply been misidentified:

However, it is most probable that the few bones that have been found belonged to other animals.

[Infinity Blade]

I didn't mean to refer specifically to her, just anyone who may believe that all fossils are fake.

[Infinity Blade]

More people who think giant pterosaurs couldn't fly. We meet again, I guess.

comments.deviantart.com/4/7738834/4689200464

1. How to you get the bones stable and lightweight enough to carry the weight of the wing, endure the stress flying puts on it, while at the same time being light enough to still enable flight?

By having exceptionally wide bone diameters and at the same time thin bone cortices (i.e. thin bone walls to reduce weight).

The only significant difference between the wings of giant and smaller azhdarchids concerns bone robustness, especially that of their joints. We would predict expanded wing bone diameters in large fliers as they enhance resistance to bending, and as giant animals they are going to experience proportionally greater bending stresses. If they flew, giant pterosaurs should have very large wing bones indeed, and - as is evident from the adjacent images - this is exactly what we find. Witton and Habib (2010) noted that the humeral shafts of giant azhdarchids are comparable in diameter to those of giant mammals, like hippos, despite the pterosaurs being a fraction of their weight (Witton 2008; Henderson 2010). Giant azhdarchid wing bones perform exceptionally well in bending strength tests, being able to resist multiple bodyweights before failing (Witton and Habib 2010), and their expanded diameters maintaining relative failure levels comparable to those of small or mid-sized pterosaurs, despite their size (Witton et al., in prep).

But for all their expansion, giant azhdarchid wings retain exceptionally thin bone walls. Even in Hatzegopteryx, the most robust of the group, they’re only 4-7 mm thick. This is a high value for a pterosaur, but still (in relation to bone diameter) at the low end of the cortical thickness spectrum. Other giant species have cortices of just 2 mm or so, values only just slightly larger than those of mid-sized pterosaurs. Expanded but bone-lite wings are another feature of flying creatures, being common to most flying birds and all large pterosaurs, and offering their owners a lightweight but bending-resistant flight skeleton. However, what optimises these skeletons for flight compromises resistance to buckling forces, which is why most non-volant animals tend to have much thicker cortices. The correlation between thin bone walls and flight is not watertight (Hutchinson 2001) but it's a feature we would predict for any seriously large flying animal, and is thus consistent with volant habits in giant pterosaur species.

To summarize, the giant azhdarchids had wing bones that were comparable in diameter to those of freaking hippos, despite being between 2/15ths and 1/6 of the body mass thereof. If you have long bones comparable in diameter to those of a megamammal 6-7.5 times heavier than you, that is bafflingly insane. At the same time, the cortical bone walling of these bones is also thin, reducing the weight of these bones for flight, and is a feature consistent with a large flying animal.

2. Where do the muscles necessary for flying attach to?

The shoulder. The deltopectoral crest. Where you'd basically expect them to attach to in a flying animal. This is hardly a rebuttal if at all one.

Secondly, the avian skeleton has two large girdles for limb muscles: an enlarged shoulder and chest region for flight muscles, and an enhanced pelvic region to anchor those powerful hindlimb launch muscles. Pterosaurs, in contrast, have only one large limb girdle - their shoulders, making this the de facto likely candidate for powering their launch cycles. Using volumetric modelling, Paul (2002) predicted that a giant azhdarchid would have space for 50 kg of muscle in their pectoral region, a value appropriate for initiating flight in 200-250 kg animals (Marden 1994). This strategy is a far more economical use of muscle mass because the same muscles that power flight can also initiate launch, thus allowing quad launchers to have smaller torsos - and thus lower masses - than bipedal launchers. For all their power, the moment birds have launched their legs are effectively useless - they're just dead weight to be hauled around until it's time to land.

We can make a number of predictions concerning muscle extent for giant taxa, the most important being related to the presence of a huge deltopectoral crest on their humeri. This broad flange of bone, situated at the proximal end of the humerus, anchored many muscles running from the shoulder to the wing and powered flapping motions in flight (Bennett 2003), so is a clear correlate for powered flight in giant species. The seemingly-small deltopectoral crest on the Hatzegopteryx humerus is sometimes raised as evidence of reduced flight ability: it’s actually just badly preserved with lots of bone missing on all margins (Buffetaut et al. 2002).

3. If there were giant flying pterosaurs, why don't we have giant flying birds or bats, since Convergent Evolution is a thing?

Rorqual whales are the biggest animals that ever lived, why don't we have fish that big? If there were sauropods as massive as whales, why don't we have elephants that big? Why are there penguins both smaller and bigger than the great auk ever was? Why are there canids both smaller and bigger than the thylacine ever was? Since convergent evolution is a thing?

Convergent evolution doesn't figure into this at all. It doesn't equate to convergences in body mass, just in body plan. Just because taxon A that does X achieves a certain size doesn't mean taxon B that also does X will too. Biomechanical constraints in different clades and/or even a lack of a need to get so large given ecological pressures exerted on the taxon can prevent birds and bats from getting anywhere near as large as azhdarchids.

Now, the reason why birds don't get this big is because pterosaurs have the advantage of quad-launching. Bats are restricted to even smaller sizes because their respiratory system is still like a typical mammal's (link->).

4. Why do we find the remains of giant pterosaurs only in some areas of the world- areas which were islands by the time the critters lived?

...What's your point here? That they were too large to sustain themselves on these islands?

Well, first of all, only one of the three super large azhdarchids I'm aware of actually lived on an island, that being Hatzegopteryx. And even then that island had enough resources to sustain sauropods weighing at least a tonne (i.e. Magyarosaurus). You don't think such an ecosystem could sustain an apex predator weighing 250 kg at most?

The other two, Quetzalcoatlus and Arambourgiania, didn't seem to have lived on islands. I don't know about Jordan, where the latter genus was also found, but it was also found in the United States (namely Tennessee) while Quetzalcoatlus was found in Texas, and these weren't islands even at the time.

What's funny is that the quotes I have come from Mark Witton's article on giant pterosaur flight, which this person was presented to. I'm not sure they read it thoroughly, seeing as how some of the answers to their questions could easily be found there.

[creature386]

In a perfect demonstration of why you can give wrong reasons for a correct opinion, I have seen people cite the bumblebee argument against the idea that pterosaurs were flightless.

The argument basically goes that the laws of aerodynamics predict that bumblebees shouldn't be able to fly, yet they can which disproves all of science.
I think the argument belongs in this thread.

1. The logic is wrong on so many levels. Science existed well before modern aerodynamics was formulated.
2. You can not disprove a well-established theory through a single gotcha argument. The laws of aerodynamics obviously work, otherwise, we couldn't build airplanes. In order to disprove them, we would need to find multiple inconsistencies which point to an alternative theory. This alternative theory should explain what aerodynamics explain today. Otherwise, the inconsistency is merely an unsolved mystery.
3. No scientist ever claimed bumblebees can't fly. Whoever makes that claim should give an example, it seems to be an urban legend. The closest origin that can be found are calculations which assume non-flapping wings.[1]
4. One might wonder how a bumblebee with so tiny wings could fly. As John Maynard Smith explains, air works differently at the scales of an insect than at the scales of an airplane. Due to viscosity, an insect can move much more air volume per wing area than a larger animal could.[2]

[1] en.wikipedia.org/wiki/Bumblebee#Flight
[2] www.vega.org.uk/video/programme/84 He explains it at around minute 21.

[Infinity Blade]

^To add to that, a 2005 study also concluded that insects flap their wings back and forth, not up and down. The angle to the wing ends up creating small vortices in the air (effectively, miniature hurricanes). The "eyes" of these vortices have lower pressure than the surrounding air, keeping air eddies above the bee's wings and helping it fly.[1] And while it's true that the bumblebee doesn't have an aerodynamically efficient bauplan, it seems to make up for this with sheer force.[2]

[1] www.livescience.com/33075-how-bees-fly.html
[2] www.sciencedaily.com/releases/2009/05/090507194511.htm

[dinosauria101]

I am not an expert on these downsizings nor these bears, so I can't give a big long refutation, just thought I would drop this off based on what I DO know:
'Short faced bears were large, impressive ursids'
Nope. The North American bear was downsized to 400-500 kg, and the South American one was downsized to 590 kg. Plus, they're ursine cheetahs of a sort, due to their gracile limbs and very poor adaptations to hunt prey.

NOTE: As I said, I am no expert here, so if I missed anything, do point it out

[theropod]

^Not really.

This is probably the best and most recent full-body restoration and size estimate for Arctodus simus, with a large specimen coming out at 700-800kg:
www.deviantart.com/blazze92/art/Arctodus-simus-The-short-faced-bear-388555635

Arctotherium seems to have attained similar or slightly larger sizes as well. This is a typical adult male, with the largest specimen estimated to be slightly taller than the Arctodus above, so isometric scaling would suggest a mass approaching 900kg.
www.deviantart.com/blazze92/art/Arctotherium-angustidens-440223159

Well below some of the more optimistic estimates far exceeding 1t, but nothing to laugh at and still a lot larger than most extant bears.

There’s nothing cheetah-like about them, their bodies are built like a tank, or an extant bear for that matter. The limbs are long, but still very much bearlike in morphology and not at all particularly cursorial.

So yeah, extinct Tremarctines were some of the largest and most impressive bears to ever exist, probably only rivaled by very large cave and polar bears

[dinosauria101]

^That's odd, as per Carnivora's threads I swear they were downsized. Are those the max sizes?
As per the cheetah part, I learned, also on Carnivora, that short-faced bear limbs were poorly adapted to restrain large prey and poorer at grappling than other bears due to longer limbs.

Then again, something must have gotten mixed up along the way.

[theropod]

Max size is relative in fossil organisms, but those are the sizes of the largest individuals known afaik.

Science 101: Don’t believe everything you read on Carnivora. I tend to trust blaze’s work a lot more, unless the source you talk about specifically refutes it.

[dinosauria101]

Ah, okay. It makes more sense now that you mention it; the downsizing I mentioned is the average, but the sizes you mentioned are the maximum

[theropod]

^But a 500kg average weight is far larger than any extant bear, so how exactly would that make the claim that 'Short faced bears were large, impressive ursids' false? It’s totally correct, they were large, impressive ursids, there is literally not a shred of doubt about that.

It’s not as if Arctodus were known only from some scrappy little bone that turned out to be incorrectly extrapolated to giant size (that may well be true for some other claims of giant bears though). Some maximum size estimates may be excessive (more so for Arctotherium, but that’s because it was considered to be the size of a small elephant…), but there are complete skeletons that demonstrate clearly that this was a large and impressive animal.

This was cast from a real skeleton:


So I really don’t get how one would conclude that 'Short faced bears were large, impressive ursids' is a "False scientific claim". At best the precise values of some size estimates for some specimens are debatable, but the status of this taxon as one of the largest bears (and terrestrial carnivorans!) of all time has never been in doubt.

[Infinity Blade]

R.E. Arctodus' forelimbs, grappling, and method of hunting: there is a 2012 study into the forelimbs of Arctodus which suggests that it represented a bear in an early stage of cursorial evolution.

Of course, the key word is early. So that doesn't mean it suddenly went full-blown cheetah. The cursorial adaptations analyzed in the study do make it sound like Arctodus would have been less adept at manipulating prey, but I can't tell exactly how much worse it would actually be.

dc.etsu.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=2670&context=etd;Cursorial

[theropod]

Yeah but this is compared to extant bears, which are ludicrously un-cursorial. In some ways (plantigrady…), Arctodus is still less cursorial than extant pantherines, good grapplers themselves. There’s certainly no comparison to a cheetah, altough it was longer- and more gracile-legged and probably a more efficient runner than extant bears, which basically take a complete brute force approach when they need to run fast (albeit surprisingly successfully).

[Infinity Blade]

Yeah but this is compared to extant bears, which are ludicrously un-cursorial. In some ways (plantigrady…), Arctodus is still less cursorial than extant pantherines, good grapplers themselves.

I agree.

[Infinity Blade]

According to an episode of Adam Ruins Everything:

“Weird. You are more aggressive than me, but also wronger. First of all, chimps aren’t our closest genetic relatives. Bonobos are. And bonobos live in a matriarchal society.”

Source: Natalie Angier. “In the Bonobo World, Female Camaraderie Prevails.” The New York Times, 10 Sep 2016.

Okay, first of all, their source for this says far more about the matriarchal society of bonobos than it does about their genetic relationship to humans. It addresses this only once, and guess what it says?

"The new results add depth and complexity to our emerging understanding of Pan paniscus, the enigmatic, lithe great ape with the dark licorice eyes, who lives only in the Democratic Republic of Congo and is seriously endangered. The bonobo is a sister species to the more widespread common chimpanzee, Pan troglodytes, and the two share equal footing as our nearest primate kin."

That's right. It clearly states that bonobos and the common chimpanzee are equally related to us, not that one of them is even closer to us than the other. How Adam can claim that bonobos are genetically closer to us than chimpanzees are is completely beyond me.

Secondly, of course, anyone who actually knows how phylogeny works will raise eyebrows at this, even without looking at the original source's claim. The more recent a common ancestor two taxa/clades share with each other, and consequently the closer they are to each other on the evolutionary tree, the more closely related they are to each other. So the genus Pan is more closely related to Homo than Pongo is because Homo and Pan share a more recent common ancestor than Homo does with Pongo. Pongo is a member of the Ponginae, whilst Homo and Pan are members of the Homininae. But here's the problem with Adam's claim: bonobos and chimps are two different species of the the same genus (Pan). We don't share a more recent common ancestor with bonobos than we do with chimps; the human-bonobo LCA and the human-chimpanzee LCA are one in the same.



Now, it may or may not be true that one is even more genetically identical to us than the other is, although, judging from the scientific literature, bonobos and chimps are just about equally genetically identical to us as (with similarity at ~98.7%; see ensuing discussion for more details). However, if you're trying to make extrapolations of what human social structure is or "should"* be like based off of how related certain species are to each other (i.e. patriarchal as per chimpanzees or matriarchal as per bonobos), this is frankly irrelevant. What really matters is cladistic equidistance, and in that case, chimps and bonobos are equally related to us.

And if you were trying to make a phylogenetic argument in favor of patriarchy vs matriarchy in humans, you would need more data than just the human-chimp-bonobo node to make any extrapolations. Bonobos are just about the only great apes that live in matriarchies. Occam's Razor comes in and tells us that they evolved matriarchal societal structures after their split from chimpanzees.

*Quotation marks around 'should' because, of course, arguing that human societal structures are or should be patriarchal or matriarchal (as per chimps and bonobos, respectively) because one of our closest relatives lives like that is ridiculous. I don't think Adam Ruins Everything was actually arguing that, but it was arguing against doing so, which I'll give the episode that.