Tuesday, 10 September 2013

Theropoda Sympatrico Pt.1



When the Dinosaur Renaissance gathered momentum during the Seventies, its biggest proponent and champion was one Robert T. Bakker – a palaeontologist who needs no introduction. Bakker was instrumental in displaying dinosaurs in a new light. Gone were the old depictions of cold blooded, slow moving, dim witted reptiles of the primeval swamps and in their place came this new dynamic clade of animals – animals that were fast, agile, rapidly evolving and, above all, warm blooded. Indeed, things would never be the same again and we all got swept away in this new glorification of the dinosaurian race.
Chief amongst Bakker’s evidence for proclaiming the existence of endothermian dinosaurs were the use of predator/prey ratios (PPR’s).  Simply put, in any specific ecosystem, the amount of carnivores that can be supported by any given population of herbivores can be measured as a ratio. Because cold blooded carnivores generate their body heat from the sun they can eat much less frequently and, as a result, larger numbers of carnivores can exist contemporarily. But because warm blooded carnivores need to generate their heat internally they must eat much more frequently so the amount of carnivores that can be supported in the ecosystem is much much lower.
Bakker argued at the time that by comparing, not only extant mammalian communities, but also Permian reptilian faunas with dinosaurian faunas, that because PPR’s in dinosaur communities were so low, and those in the Permian were so high, that dinosaurs must have been warm blooded. At the time this was seemingly ground breaking research and there were many believers but this was clearly wrong and we now know that there are many variables that rendered the hypothesis redundant.  Not only is it flawed to compare extant mammalian communities with extinct ones but sampling in the different formations is highly variable and problematic and thus it is difficult to formulate any ratio with any confidence.
Dinosaurs may very well have been warm blooded and there is a weight of evidence now that supports that they were, at the very least, more than ectothermic if not fully endothermic. However, there was a curious by product of the predator/prey hypothesis and that was that it was commonly accepted that you would generally expect to find, in any sampled dinosaurian fauna, only the one large predator in residence. This persisted for some years probably perpetuated by the fact that Tyrannosaurus rex, as one of the best known and well researched theropods, is, indeed, the only large carnivore in the Late Maastrichtian of North America.
It was strange too that the revelation that Daspletosaurus and Albertosaurus were contemporary large tyrannosaurs in both the Dinosaur Park and Two Medicine Formations was simply accepted as unusual. The most popular explanation was that this was evidence of niche partitioning with Albertosaurus primarily feeding on hadrosaurs while the more heavily built Daspletosaurus preyed upon ceratopsids (Russell 1970).
But eventually, as more and more formations became better sampled, it became apparent that, actually, sympatric large theropods are the norm with, perhaps, the most extreme example being the population of the Late Cretaceous Kem Kem Formation in Morocco which has produced Carcharodontosaurus, Deltadromeus, and Spinosaurus amongst others.
These co-habiting theropod populations bring their own unique problems to the table and continue to fascinate palaeontologist’s in trying to work out how these large carnivores managed to share out the various resources available. These issues are amplified when we look at the amazing populations of Laramidia which displays several much smaller pocket environments where it appears virtually impossible for there to be enough resources to go around for all dinosaurs – let alone the carnivores.
Dinosaurs are freaks then and this is precisely why you cannot simply compare extant faunal communities with dinosaurian faunas. It appears almost impossible in some cases for dinosaurs to be able to coexist at all – but they obviously did and what a magnificent race of creatures they are. So how can we explain how large theropods co-existed successfully in what would appear to be extraordinary circumstances? There are many things to consider but perhaps we should look at the nuts and bolts of the carnivorous dinosaur – what is a carnivorous dinosaur, what were their functions and, most importantly of all, how important were they to the ecosystem?
Theropod dinosaurs are spectacular – from the smallest raptorial forms right through to the largest tyrannosaurs. And it is safe to assume that, when compared to their herbivorous contemporaries, that they were relatively more “intelligent”. I have put the word intelligent in quotation marks because it is important to make the distinction between intelligence, as displayed by extant mammals, and that hypothesised for dinosaurs for it is unlikely that any dinosaur was capable of intelligent reasoning in comparison, for example, to a dolphin.
But it is obvious that they would have been smarter than their prey because their predatory nature demanded it and, I believe, it is safe to assume that this would also entail a degree of complexity. How complex, again, remains a matter of conjecture but it is a possibility (some of us believe likely) that there was a degree of social complexity within Theropoda whether they were solitary hunters or hunted in groups. This is highly suggestive that there would have been a significant variety in their behavioural patterns which would have included their hunting techniques, their courtship and mating rituals and even how they may have raised their young. We only have to look at birds to get, perhaps, a hint of what may have been a variety of different behaviours displayed by their dinosaurian ancestors.
Large theropods must truly have been a sight to behold. The largest of them would certainly have nothing to fear in their ecosystem aside, perhaps, from another of their species. Other dinosaurs may have been as equally impressive and many were indeed far larger than even the biggest theropod but for me they have no equal. And despite the fact that we know so much about them it is still the vast amount of information that we don’t know about them which is so fascinating. But the one thing we can be sure of, as with any ecosystem, theropods, and large theropods in particular were at the top of the food chain - the very peak of the trophic pyramid.
Carnivorous dinosaurs were essential components of their ecosystems and it is easy to think that all they did was eat prey animals – but this is far from the truth. Without the carnivores then chaos would soon ensue. Theropods evolved to eat their contemporaries -not withstanding therizinosaurs which we will come to a little later – and they were obviously very successful at it since they were dominant throughout the dinosaurs reign but we often forget, that throughout the Mesozoic, there were a multitude of different environments. Theropods evolved in tandem with deserts, forests, coastal plains, uplands, lowlands and everything else in between and every single ecosystem depended on them to function correctly.
Theropods were the major controllers of herbivorous dinosaur populations and it is safe to assume that the rules that govern the trophic pyramids of today would have applied to those of the past. I find it particularly interesting that we consider many aspects of dinosaur extinction, not only at the K-T boundary, but also the various phases of dinosaur extinction throughout the Mesozoic without often considering environmental disruption because a species, particularly a carnivore, became extinct. We all consider environmental change due to volcanoes, earthquakes, mountain building and even the occasional meteor strike, and no doubt these were considerable influences on the environment, but extinction due to the disappearance of species is well documented – even today.
In the next part of this mini-series we will look at the cause and effects of theropod extinction on an ecosystem and consider whether this too was a major driver in dinosaurian evolution and species turnover.
Reference
Russell, Dale A. (1970). "Tyrannosaurs from the Late Cretaceous of western Canada". National Museum of Natural Sciences Publications in Paleontology 1: 1–34.
 

20 comments:

Alessio said...

Great post, can't wait for the other entries!
But i wouldn't dismiss the possibility some mesozoic dinosaurs could have been as intelligent as modern animals; first of all we had to bear in mind that many behaviours we associate with mammals are more widespread that usually thought: forms of sociality akin to dolphins can be found in some species of sharks, for example... And then there's birds, which are dinosaurs from head to toe and in some case are smarter than many so called "intelligent mammals": the research on New Caledonian crows are illuminating for that matter ;)
All in all i'm pretty confident at least some dinos managed to achieve quite a complexity in their behaviors across their 160+ million of years history.

Daniel Permutt said...

Nice article.

Wouldn't sympatry suggest that two or more species sharing a direct common ancestor have occupied the same geographical location, while a reduced gene flow between populations has been the driving force separating them?

'Deltadromeus', 'Spinosaurus' and 'Carcharodontosaurus' did not evolve from a direct common ancestor. I'm not sure that this is sympatry at work. Whatever it is, it's fascinating.

Andrea Cau said...

'Intelligence' and 'behaviour' are different concepts: unfortunately, mixing them is the first rough error of many dinosaur aficionados, who usually jump along the two concepts as they were synonyms.
Mentioning the Caledonian crows as 'support' for Mesozoic theropod intelligence is absurd like, for example, mentioning modern apes as support for Repenomamus intelligence. Thus, we may confidentally believe that some Mesozoic mammals menaged to achieve quite an ape-like complexity in their behaviours across their history...

Andrea Cau said...

Daniel, you meant "sympatric speciation".
"Sympatry" means "living in the same area at the same time".
It must be noted that the stratigraphy of the Kem Kem theropods is not particularly detailed, so we cannot dismiss that what we call "Kem Kem fauna" is a series of distinct fossil association. Only one specimen of Deltadromeus is knows, and according to Sereno et al. 1996 was not found in the same level of the Carcharodontosaurus saharicus neotype.

Andrea Cau said...

Sorry for the typos.
I meant "fossil associations" and "known".

Alessio said...

Well, maybe i went a lil' over the edge, granted, but i don't think it's completely unreasonable to say that, if a modern dinosaur like those crows can display such feats, MAYBE some mesozoic dinosaurs could have been quite smart too; i don't know, despite the obvious advancement in dinosaur paleontology, it seems to me that the old "dinosaurs were dumb" trope still pops up quite frequently.

Andrea Cau said...

Alessio, you make all too simplicistic.
Intelligence and behaviour are part of the particular biology of an animal, and are the result of the animal particular evolution. You cannot simply translate what you see in just a couple of Holocene passeriforms into a completely distinct Mesozoic non-avian dinosaur just because they are somewhat related.
It's - at best - too naive to be considered an argument. Based on that argument, everything is possible, and thus, every speculative animal is a potential palaeontological object.
Palaeontology is the science of explaining the fossils found, not the art of arguing the possible existence of hypothetical animals based on naive analogies.

Mark Wildman said...

Hi guys and thanks for the comments. Alessio - I understand what you are trying to say but that is exactly the reason I was trying to be careful with my words. Instinctive behaviour can be misinterpreted as intelligence very easily. Many animals, even fish, can be perceived to exhibit simple intelligence - cunning anglers call it - but, more often than not, it is actually "learning" by association or recognition of danger.

This is problematical when attempting to perceive an extinct animals behavioural capabilities no matter what the inferences may be suggesting. It is also very hard to explain how theropods were "smarter" than their prey without mentioning the words intelligence,smarter or clever etc. Suffice to say, and as I said in the post, it appears reasonable to assume that hunting techniques and behaviour in predatory dinosaurs demanded greater brain power that that of their prey - however that may be peceived.

Andrea Cau said...

Mark, it is difficult for me to see a link between ecological roles (in particular predatory vs non predatory) and difference in "brain power". Most predatory styles are stereotyped, and do not need a "smarter" behaviour than those of the prey. Also, even prey would need a form of intelligence to avoid predation.
Note that the most relevant evolutions of intelligence among living terrestrial vertebrates are among frugivorous or omnivorous (not hypercarnivorous) species, and all are with complex parental care and altricial offsprings. None of these features are present together in theropods of the Mesozoic. I don't see why theropods needed to be "smarter" than predatory lizards and crocs of today (species that, we must remark, are smarter than usually though, but not "as smart" as most people would consider a "smart animal").

Alessio said...

Andrea, i didn't say mesozoic dinosaurs behaved JUST LIKE modern crows, that's a misunderstanding.
Maybe i'm making all too simplistic, granted, it's only that, considering what we really know of these animals so far (almost nothing, at least regarding their ecology, because, as you also said on "Theropoda" some time ago, we don't even have real bones to work with), i don't see why some reasonable speculation should be easily dismissed as "naive".

And about the "intelligence/behaviour" scenario... Are we really sure it's a true dichotomy and not a concept fueled by our anthropocentrism?

Mark Wildman said...

Hi Andrea - You may very well be correct and, at the same time, not all predators need to be "smart" and neither do their prey - base instinct is enough. The intelligence angle is actually somewhat irrelevant to the objective of these posts but it is interesting you mention omnivorous species because there are other interesting comparisons to be made within Theropoda as a whole.

Andrea Cau said...

Alessio, absence of evidence and speculative rethoric are not a special kind of evidence to support our feelings on extinct taxa: you cannot use such argument to fill the gaps in the fossil record. Just talk about what is known, not what may be but is absent in the record. As a palaeontologist, I'm interested on what fossils actualy say, not on the large empty space of things not preserved in fossils. This is the difference between science and science fiction.
Mark, in fact this is what I meant: we don't need "intelligence" (here meant as "not only instinct") to explain most of animal behaviours. I was replying to those that would love to speculate on things impossible to be determined from fossils. I agree with you: intelligence is irrelevant in these themes on theropod ecology, niche partitioning, morphology and evolution.

raptor_044 said...

@Mark Wildman

Hi, how are you? Sorry for not commenting in so long, but I've been bust with various things.

"Not only is it flawed to compare extant mammalian communities with extinct ones but sampling in the different formations is highly variable and problematic and thus it is difficult to formulate any ratio with any confidence."

To be fair, it's quite coincidental that the predator:prey ratios of both the basal synapsid & fossil mammal communities were what we expected for communities dominated by ectotherms/endotherms, respectively. Don't get me wrong though. I agree with you about it being problematic, especially given recent discoveries.

@Alessio

To be fair, Mark never said that Mesozoic dinos weren't "as intelligent as modern animals", just that they weren't intelligent "in comparison, for example, to a dolphin". Based on what I've read (See the quotes in my 2nd comment), 1) Archaeopteryx were probably as intelligent as domestic chickens (& thus, fell "about mid- range on the intelligence scale of birds": http://www.amazon.com/Raising-Chickens-Dummies-Kimberley-Willis/dp/0470465441/ref=sr_1_1?s=books&ie=UTF8&qid=1376016897&sr=1-1 ), & 2) non-bird maniraptorans were probably either as intelligent as or more intelligent than Archaeopteryx (I'm thinking the latter, given Bakker's emphasis on the difference btwn wild & domestic fowl, intelligence-wise).

@Everyone

I don't remember who (I read this blog post earlier today & then left to run some errands), but someone claimed that intelligence is irrelevant to theropod ecology/evolution. As indicated by the Walsh/Milner quote, birds show otherwise.

-Hadiaz

Quoting Walsh/Milner ( http://nms.academia.edu/StigWalsh/Papers/1199934/The_avian_brain_and_senses ): "A wealth of data is emerging that links telencephalon size in living birds to a variety of factors including new problem-solving feeding behaviors (Lefebvre et al., 1997; Nicolakakis & Lefebvre, 2000; Timmermans et al., 2000; Lefebvre et al., 2004; Iwaniuk & Hurd, 2005) and associated tool use (Lefebvre et al., 2002; Cnotca et al., 2008), and even the presence of consciousness (Eccles, 1992; Butler & Cotterill, 2006; Prior et al., 2008). Apart from some striking instances of sequential and meta-tool use that exceed the abilities of nonhuman primates (Hunt & Gray, 2007; Wimpenny et al., 2009), some species are thought to exhibit social learning (Tebbich et al., 2001) and complex social behaviors (Clayton et al., 2007; Emery et al., 2007) such as cooperative hunting (Yosef & Yosef, in press). Although undoubtedly enhanced in those modern groups (especially corvids and parrots) compared with early birds and their immediate ancestors, such improvements in cognition would presumably represent a competitive advantage over less encephalized coeval species. For instance, increased encephalization has been linked to species richness (Nicolakakis et al., 2003) and success during introduction to new environments (Marino, 2005; Sol et al., 2002, 2005). In this context, the metabolic cost of a large brain may well be offset by the improved success in exploiting available resources, possibly providing a further explanation for the retention of large brains by flightless birds."

raptor_044 said...

@Mark Wildman

In my 1st comment, I said "bust", but I meant "busy".

@Alessio

These are the aforementioned quotes.

-Hadiaz

Quoting Burish et al. (See “Abstract”: http://synapse.princeton.edu/burish_wang04_bbe.pdf ): “Vertebrate brains vary tremendously in size, but differ- ences in form are more subtle. To bring out functional contrasts that are independent of absolute size, we have normalized brain component sizes to whole brain vol- ume. The set of such volume fractions is the cerebrotype of a species. Using this approach in mammals we pre- viously identified specific associations between cerebro- type and behavioral specializations. Among primates, cerebrotypes are linked principally to enlargement of the cerebral cortex and are associated with increases in the complexity of social structure. Here we extend this analy- sis to include a second major vertebrate group, the birds. In birds the telencephalic volume fraction is strongly cor- related with social complexity. This correlation accounts for almost half of the observed variation in telencephalic size, more than any other behavioral specialization ex- amined, including the ability to learn song. A prominent exception to this pattern is owls, which are not social but still have very large forebrains. Interpolating the overall correlation for Archaeopteryx, an ancient bird, suggests that its social complexity was likely to have been on a par with modern domesticated chickens. Telencephalic vol- ume fraction outperforms residuals-based measures of brain size at separating birds by social structure. Telen- cephalic volume fraction may be an anatomical sub- strate for social complexity, and perhaps cognitive abili- ty, that can be generalized across a range of vertebrate brains, including dinosaurs.”

Quoting Walsh (See “Reptiles including nonavian dinosaurs and birds”: http://www.academia.edu/1061233/Directions_in_Palaeoneurology ): “It is now clear that while some theropod clades pos-sessed typically ‘reptile’-like brains (Giffin et al. 1988; Gif-fin 1989; Rogers 1999; Brochu 2000; Franzosa and Rowe 2005; Sanders and Smith 2005; Witmer and Ridgely 2009), at least some maniraptoran theropods had surpris-ingly bird-like brains (Kundra´t 2007; Balanoff et al. 2009; Norell et al. 2009). In these taxa, not only is the telen-cephalon significantly enlarged (sometimes to an extent greater than in Archaeopteryx), but flight-related regions such as the cerebellar flocculus, which are especially enlarged in birds, are also very well developed (Kundra´t 2007). This has fuelled the debate about whether these taxa, which often bear feathers, are in fact secondarily flightless birds rather than bird-like theropods (Witmer 2009; Kavanau 2010).”

Quoting Bakker ( http://blog.hmns.org/2012/06/bakker-blogs-the-kleptomania-continues-with-a-sid-vicious-julieraptor-dino-rustlers-part-ii/ ): “These mini-raptors were big-brained by dinosaur standards — as smart as a wild turkey (not the dumbed-down domestic version). Their eyes were huge — an adaptation for chasing nimble prey, like furry mammals and tree-climbing lizards. The extra-long arms and fingers gave the raptors three-dimensional abilities — they could scramble up trees quadrupedally, grabbing branches with claws on front and back paws. Long feathers on the arms and legs let the raptors glide from branch to branch like dino-flying squirrels.”

Andrea Cau said...

Again, having 'bird-like' brains does not mean being as 'smart' as a crow. Even pigeons have bird-like brains (they are birds), with encephalisation ratios larger than Archaeopteryx, but nobody considers them as particularly smart. Also, what does "intelligence" mean is problematic, given that these animals are extinct and we cannot test their intelligence in the same way we test it for crows or lizards. Thus, the mere presence of bird-like brains in many maniraptorans simply supports that they probably had a behavioural spectrucm comparable to large-bodied modern ground-dwelling fligtless birds (e.g., ratites), not that they were smart as the smartest flying passerines or psittacids.
You seem to follow a too simplicistic interpretation of "intelligence" or "behaviour" as something predictable from just the brain size. Intelligence is something you first have to define, then to observe... even when you define the first, the second is now completely lost in a fossil.

raptor_044 said...

@Mark Wildman

Sorry in advance for going off topic. Also, in my 2nd comment, I said "Quoting Walsh", but I meant "Quoting Walsh/Knoll".

I'm not sure if Cau was responding to me specifically in his last comment. If not, then he can ignore the rest of this comment. My bad for misinterpreting him.

@Andrea Cau

Assuming you were responding to me specifically in your last comment, I don't want to start a protracted argument, just clear some things up.

1stly, I never said that "having 'bird-like' brains" meant "being as 'smart' as a crow." To be brutally honest, this isn't the 1st time you've put words in my mouth (See my last 2 comments: http://blogevolved.blogspot.com/2013/03/good-semi-good-and-bad-dino-sources.html ) & I'd appreciate it if you'd stop doing that.

2ndly, assuming you read the papers I quoted above, you should've seen that 1) Archaeopteryx (Burish et al. 2004) &, by extension, non-bird maniraptorans (Walsh & Knoll 2011; "In these taxa, not only is the telen-cephalon significantly enlarged...sometimes to an extent greater than in Archaeopteryx") are estimated to have been cognitively similar to domestic chickens (which, while nowhere near corvids, are above & beyond ratites), & 2) these estimates are based on relative telencephalon size (as opposed to EQ alone).

3rdly, while it wasn't explicitly stated, my inclusion of the Walsh/Milner quote made it pretty clear that I was using the problem-solving ability/social complexity definition of cognition/intelligence. Furthermore, as shown by/pointed out in many a paper (E.g. Burish et al. 2004, Walsh & Milner 2011, & those cited therein), not only is there a significant correlation btwn problem-solving ability/social complexity & relative telencephalon size in living dinos, but it can be applied to extinct ones. Yes, we'll never know exactly how intelligent extinct dinos were compared to living ones, but we at least have a decent estimate of their cognitive capabilities (better than those based on EQ alone). In other words, I actually did "define the first" & the second isn't "completely lost" (thanks to guys like Walsh/Milner & WitmerLab reconstructing the brains of extinct dinos).

-Hadiaz

Andrea Cau said...

@Hadiaz: "this isn't the 1st time you've put words in my mouth".
Wow, there are people who takes notes of my comments online and report them many months later? I'm very honored by this :-)
Honestly, I realise now that you are the same person of that other comment (a comment that - I'm sorry - I've also quite forgotten in its details) in that other blog.
Hadiaz, please, do not consider these as personal attacks. We are just talking about fossils, and I'm talking about different interpretations of the fossil evidence. I've nothing against people who disagree with me.

About the topic, it seems to me we are saying the same thing in slightly different ways, since I hope we all agree that the intelligence is more than just brain size, nor the encephalisation ratios, nor rough telencephalic size/shape/development and so on. This is the meaning of my words: I disagree with ideas that "intelligence" is a feature that leaves fossil evidence in the body. If you provide evidence of some cultural feature, tools or artefacts, I may consider them as good evidence of intelligence. But the mere brain morphology is poorly relevant, since birds with comparable brains behave and shows intelligences very different.
"Cognitive capabilities" of a fossil skull are a mere nonsense if you cannot observe the living animal behaviours. A fossil skull (and the braincase inside it) are not sufficient to infer the intelligence of an extinct animal.
I agree that bird-like intelligence requires a bird-like brain, since that brain is the necessary physical pre-requisite, it's the hardware. But a pre-requisite is not sufficient evidence of presence of a particular kind of intelligence and cognition, since the intelligence is a combination of several biological factors, and not only brain morphology. Sociality, sensory system, metabolic level, even life-history matter as much as the mere brain features. Again, I aknowledge that people would love to discuss on "dinosaur intelligence", and you may provide all the brain features you think are necessary to the presence of intelligence: but - unfortunately - what is necessary is not sufficient, since these are hardware features, and intelligence is a software.

raptor_044 said...

@Andrea Cau

"Hadiaz, please, do not consider these as personal attacks. We are just talking about fossils, and I'm talking about different interpretations of the fossil evidence. I've nothing against people who disagree with me."

The main reason I remembered that comment (besides it being in my 1st Art Evolved blog post to receive comments) was b/c the words-in-mouth thing is 1 of my main pet peeves. In other words, I didn't mean anything personal by it. Also, thanks for confirming that you didn't mean anything personal about it.

As for the rest of this comment, when you put it that way, I guess we were saying more-or-less the same thing in different ways. You seem to be closer to pessimistic end of the spectrum of what we can learn about cognitive capabilities from brain reconstructions & I get why (in reference to how "birds with comparable brains behave and shows intelligences very different"). I think I'm closer to the optimistic end b/c of papers like those by Walsh/Milner & WitmerLab, which by combining dino brain reconstructions with whatever else we know about dino biology, seem to give decent ideas of how dinos behaved & showed intelligence (Lautenschlager et al. 2013 is the most recent example I can think of).

-Hadiaz

Andrea Cau said...

I don't consider myself as "optimistic" or "pessimistic": just try to avoid that my expectations biase (too much) my observation of the fossils.
I find the sentence "by combining dino brain reconstructions with whatever else we know about dino biology, seem to give decent ideas of how dinos behaved & showed intelligence" too vague.
For example, how do you interprete the differences among the brains of Carcharodontosaurus saharicus and Carcharodontosaurus iguidensis? They are very closely related theropods with comparable body plan, that lived at the same time in the same continent. Nevertheless, their brain endocasts are (quite unexpectably) notably different in both shape and cerebrum proportions. These differences are a fact. Does this fact mean something in term of behaviours and intelligence? It's plausible, but how could we test the possible alternative interpretations of such differences? In absence of the living animals in their natural environments, I feel it's just beyond science. Not because I'm "pessimistic", but because science recognises its limits.

raptor_044 said...

"For example, how do you interprete the differences among the brains of Carcharodontosaurus saharicus and Carcharodontosaurus iguidensis? They are very closely related theropods with comparable body plan, that lived at the same time in the same continent. Nevertheless, their brain endocasts are (quite unexpectably) notably different in both shape and cerebrum proportions. These differences are a fact. Does this fact mean something in term of behaviours and intelligence? It's plausible, but how could we test the possible alternative interpretations of such differences?"

That's why I said "decent" (as opposed to "good" or better). ;)

-Hadiaz

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