A Critical Review of “Ravens, New Caledonian crows and jackdaws parallel great apes in motor self-regulation despite smaller brains"

June 11, 2016

Abstract

A new study¹ of ravens, crows, and jackdaws may cause scientists to rethink the widespread belief that larger brain size is a necessary indicator of greater rational capabilities. Previous studies involving mammals seemed show a correlation between larger brain size and greater “motor self-regulation”. However, in this new study by Kabadayi et al, corvids perform very well compared with the great apes in trials testing their self-regulatory abilities. This could have large implications for the human evolutionary paradigm. If further test results continue down this path, no longer would it necessary to hold that ancient hominids’ expanding brain size necessarily caused more complex behaviors. Further research could give us insight into why, for example, the neanderthals, despite their larger brain sizes, were unable to compete with modern humans.

Background Information

Evolution

In the past, there is generally a consistent pattern of brain-size growth among hominids pre-dating humanity. The australopithecines are a genus believed to have evolved between an ape like ancestor – the common ancestor of the chimpanzee and human – and humans. After the australopithecines appeared, the homo genus arrived which eventually lead to homo sapiens sapiens, also known as modern man.² During this process, the average brain size expanded from about 400cm^3 to 1350cm^3.³ Although this path is not always clear⁴, there is a definite expansion in brain size leading up to modern humans, which have apparently outsized heads and brains.⁵ This seems to have led to other changes in human anatomy, such as wider hips among females for birthing babies with large brains.

It is commonly believed among evolutionists that the larger brain size was a necessity for the sudden explosion of art and culture among humans. According to the latest research, humanity came on the scene and suddenly so did art, culture, religion, and other indicators of our humanness.⁶ This is somewhat dampened by the knowledge that neanderthals had brains as large or larger than ours, and, by all indication, did not have a human-like capacity for culture.⁷ However, despite the knowledge that brain size is not sufficient for a human-like culture, it is commonly believed to be a necessary condition.

Current Study

Kabadayi et al. expanded upon the study by MacLean et al. in order to more fully study birds, specifically Corvus corvid birds like ravens, crows, jackdaws etc., ability for motor self-regulation.⁸ The ability for motor self-regulation is a similar skill to the scientific definition of self-control but somewhat less demanding. Essentially, the animal has a tempting avenue before it, but must understand to not take that action and to take another instead.⁹ Self-control is important for understanding cognitive capabilities.¹⁰ The authors write, “Without well-developed regulation, self-control will not come about easily. Studying [motor self-regulation] comparatively across closely and distantly related taxa has its merits. It helps establish whether there is a link between levels of motor self-regulation and levels of self-control, and other cognitive skills.”¹¹ So, motor-self regulation is a good, if preliminary, indicator of self-control capabilities and therefore of higher brain function and problem solving abilities.

The previous work by MacLean et al. studied a variety of animals’ ability for motor self-regulation. Kabadayi et al. comment on the study, “MacLean and co-workers compared motor self-regulatory tasks for 36 species, mostly primates.”¹² This study determined that the great apes have by far the best ability for motor self-regulation and further, that “absolute brain size was the best predictor of success.”¹³ However Kabadayi et al. believe that birds, specifically corvids, were underrepresented, and they decided to expand the study with a variety of birds to compare data.

Summary

Method

The birds in the study were made familiar with an “opaque cylinder” containing a reward in their aviary, and were familiarized with the basic mechanics of the test. Then, a transparent cylinder replaced the previous opaque cylinder, and the birds were tested. The birds should have learned to go through one of the openings, as with opaque cylinder, and should not attempt to reach directly for the reward through the transparent cylinder.¹⁴ The researchers used this approach to make sure the animals did not have an acclimation period in which they learned the test. The test was for their motor self-regulation, and not their learning abilities, so this step was necessary to weed out false negatives.

Kabadayi et al. decided to modify the previous study slightly. They removed a separate task because they decided it was not implemented correctly.¹⁵ Secondly, they took precautions to acclimate the birds they studied to the pieces of the task at hand, since they noted that in the MacLean and co-workers study, birds seemed to improve over the set of trials.¹⁶

Results

The results of the study were compared with the earlier study focusing on primates. The highest scoring primate was the Chimpanzee, with 100 points. In the current study, ravens also scored a 100 on the tests. On the combined rank chart, orangutans were third, at 99.1, and jackdaws fourth at 97.0. The New Caledonian crow also placed in the top 10, at number 9, with a score of 92.0. ¹⁷

These results show that corvid birds are in some cases as successful as primates at motor self-regulation tasks which, as mentioned earlier, are an important indication of higher mental functions. This is incredible because the two highest scorers on the test, chimpanzees and ravens, have vastly different brain sizes. The chimpanzee has an endocranial volume of 368.4 cm^3, while ravens have an endocranial volume of 14.5 cm^3. Jackdaws, the fourth ranked species, only have an endocranial volume of 5.2 cm^3. ¹⁸ According to Kabadayi et al., “Clearly, absolute brain size is no overall predictor of motor self-regulation across a wider range of animal taxa. However, as among primates, absolute brain size does appear to be a significant predictor across bird species, but on the other hand relative brain size is as well a significant predictor within birds.”¹⁹ Therefore, the size of the brain does not seem to have a direct correlation to motor self-regulation. The ravens performed just as well as the Chimpanzee, which is an animal considered highly intelligent.

When drawing conclusions, the authors are careful to state that they cannot make “far-reaching conclusions about evolution and brain size.”²⁰ They desire further information from the previous study (MacLean et al.) about how the animals proceeded in their task, and if their failures were “clean failures” (by the animal clearly doing the task incorrectly), or if the failures were by the animal exploring but touching the failure area nonetheless.²¹ Still, the authors conclude, “What is without doubt is that great apes and Corvus corvids (the birds from the current study) have pronounced motor self-regulatory behaviour in relation to the cylinder task, despite very different absolute different brain sizes.”²² Despite their caveats, the authors conclude that absolute brain size does not seem to have a large effect on motor self-regulation, which could very well be indicative of a similarity of higher brain function despite the difference in brain size between great apes and corvid birds.

Implications

General Implications

This study certainly has not settled any questions surrounding evolution generally, nor human evolution particularly. It simply raises additional questions, especially on the evolutionary side of the creation-evolution debate. It brings into sharp relief just how little we seem to know about the brain and how it functions. More studies will need to be done before concrete implications can be drawn, but the lack of a connection between absolute brain size and higher intelligence raises many questions.

Evolutionary Paradigms

The implication for evolutionary paradigms is stark. If the strong survive via natural selection, and humans survived, our large brains must have some role. But if larger brain sizes are not required for higher brain function, what purpose do larger brains have? Furthermore, why didn’t neanderthals – who had comparable brain sizes to humans – make whatever transition humans did into modern culture? They had the same opportunity, yet homo sapiens made the transition and homo neanderthalensis did not.

So, based on the study by Kabadayi et al., we can certainly question evolution’s motives (to anthropomorphize a blind set of processes) in generating larger brain sizes. Evolution should be moving closer to organisms that have survival advantages, and the most obvious end of larger brains is organisms like ourselves who can think creatively. But the downsides of large brains are well-known. It requires more food to power it, it requires anatomical changes to the females because children are born with large heads, and other such changes. Yet we still don’t know why human culture emerged, nor what makes us so different from the animal, outside of our brain size. But if Kabadayi et al. are right, brain size might not be such the advantage it first appeared to be. It certainly leaves more questions than answers.

Creationist Paradigms

The study by Kabadayi et al. has implications on creationist paradigms as well. Creationist paradigms are rarely naturalistic and tend to believe in a soul: a non-material entity which is united with our brains in some way to produce the distinctively human-like quality among humans.²³ Creationists are faced with a similar problem as evolutionists: why are human brains so large? Did God have a purpose in the human form, or could we have been the size and shape of ravens yet been just as intelligent and had a similar culture? Creationists explain why other large brained creatures have not evolved into a culture-rich form as humans have, claiming that humans were specially given their ability for culture by God. Yet, few dualists deny a relationship between the physical brain and immaterial soul.

Future Considerations

Kabadayi et al. note a few important caveats to their conclusions. They note, first, that it’s possible that as absolute brain size increases, the number of neurons in the brain does not increase in exactly the same way. However, at the time of this study, there is not enough data to say for certain that great apes and corvids have a similar number of neurons in the brain.²⁴ Second, there is a lack of data across bird species to say for certain whether absolute or relative brain sizes have an effect on these skills.²⁵ If the neuron count is somehow near equal between great apes and corvid birds, this still raises additional questions. Why is there a pattern of brain growth among hominids leading to humans, and why are humans’ brains so large if it isn’t needed for higher intellect? Is the difference between human and animal that of a totally different nature? And how does it relate to the brain? These questions and studies could lead to further understanding on how human brains are different than animals and whether this change is possible and likely under evolutionary conditions. Kabadayi et al. brings new questions to the already great questions surrounding our knowledge of the brain and evolution.