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The Chimpanzee Brain
Accepting evolution we know that Homo sapiens are distant relatives of chimpanzees, sharing a common ancestor ape between four to six million years ago. Depending on who you ask and what is being measured we share a figure of 95%+ of our DNA with chimps (some put the figure as high as 98.5%). One of the most significant organs we have inherited is the ape brain and by looking at the chimpanzee brain we can hopefully learn some useful information. However, the human brain operates in significantly different ways and this is what has allowed our rich, diverse culture to develop.
Before discussing the main topic in more detail let me recap on a central thesis that I am exploring in this blog.
The human brain is split between two hemispheres. In our normal waking life both of these hemispheres are engaged but most of us (though not all) are left brain hemisphere dominant (making us, for the most part, rational thinkers capable of reading, writing and speaking). Our right brain hemisphere is engaged when we deal with emotional issues and becomes dominant when we sleep…but also when we meditate (hence my interest in relating this information to the practice of karate and other fighting arts).
Dr Julian Jaynes was the first to put forward the idea that our current left brain hemisphere dominance is perhaps NOT our natural state and that we were all originally right brain hemisphere dominant. We have therefore experienced a shift in hemispherical dominance and Dr Jaynes traces this to at least as early as ancient Greece. Another significant influence on me has been Tony Wright, author of Left in the Dark. Mr Wright traces the origins of this shift in hemispherical dominance back over some 200,000 years, arguing that the change was initiated because of climatic and environmental change in Africa which forced out ancestors to shift from a fruit-based diet (including plants and nuts) to a meat-based diet as lush forestry began to disappear and Africa, once a haven for human life, began to become more and more inhospitable. What Mr Wright would argue therefore is that Dr Jaynes is recording the final stages of the shift to left brain hemisphere dominance (significantly as reading and writing became more and more widespread, both of which are heavily dependent on the utility of the left hemisphere). Another important point to note in passing here is that this process is dynamic and is continuing today (and can be reversed through the practice of meditation, whether static or dynamic, among other methods, again hinting at my interest in relating this process to martial arts).
The human brain then is a product of evolution as is, I will suggest below, its lateralization. Let us briefly consider the story of evolution.
Scientists estimate that humans and chimpanzees split from a common ancestor some four to six million years ago. At this time we were much more apelike that humanlike until Lucy, of the Australopithecus species emerged a little more than three million years ago. The theory behind the appearance of Lucy in Africa is that as deforestation occurred the space between trees widened and prevented our ancestors from swinging from branch to branch in pursuit of food. This forced them to the ground where, walking on all fours, they were easy targets for predators. In response to this our ancestors began to walk upright from tree to tree so as to be able to extend their range of vision and detect potential enemies at a greater distance thereby increasing their chances of survival. From this point on we came to resemble how we look and move today. Homo habilis and Home erectus emerged next around 2.5 million years ago and the two lived side by side. Stone tools began to be used and this period marks the beginning of the Lower Paleolithic. By approximately 1.8 million years ago Homo erectus was looking remarkably like modern humans though with nowhere near the same brain size. Various other sub-types also came and went, but one of the most potentially significant is Homo antecessor which may be a common ancestor of both humans and Neanderthals. Current archaeological evidence indicates Homo sapiens emerged some 200,000 years ago; African Eve, the mother to all mothers currently living today, lived around 150,000 years ago while African Adam, the father to all fathers alive today was around 60,000 to 140,000 years ago.
So, back to the chimpanzee brain.
The human brain (by human I refer to Homo sapiens man) is currently around three times larger than that of a chimpanzee. Both brains however are split between two hemispheres, the right and the left. In the left hemispheres of both brains the area thought to control language is larger than the corresponding area in the opposite hemisphere. Although researchers do not believe chimpanzees possess some kind of language, it is thought that they employ a method of communication that we are currently unable to decipher. Researchers at the Yerkes National Primate Research Center found that chimps predominantly use their right hands when communicating with one another as compared to showing no preference when doing things like wiping their noses. As is popularly known, the left hemisphere controls the right side of the body, including the hand and we as humans shake hands with our right hands (lefties have no real choice other than to comply, though the action is for them unnatural). The fact then that chimps use their right hand for expression reinforces the thesis that the left brain hemisphere is concerned with communication. This suggests that the urge to use the right hand / left hemisphere for communication is a precursor to the development of language, which for most humans also utilizes the left hemisphere (and most humans are right handed).
The chimpanzee brain is sufficiently advanced to allow them to demonstrate a basic ability to use tools and solve problems in certain situations and they are even capable of abstract thought to a limited extent. Chimps have also demonstrated a meager ability to consider a solution to a problem.
That said, apart from seeming to prefer the right hand for methods of communication, most chimps do not have any preference and are found, in non-communicative activities, to be equally right or left handed, or ambidextrous. This indicates, again in non-communicative activities, that the chimpanzee brain does not have the kind of overtly specialized lateralization that the human brain has. For example, a paper in Proceedings of the National Academy of Sciences of the United States of America (vol. 104 no. 43) examined brain activity in humans and chimps while wakeful but resting and found that while both chimps and humans displayed high levels of activity within default mode areas there were differences, including (in chimps) a comparatively lower level of activity in the left-sided cortical areas involved in language and conceptual processing in humans. The researchers conclude that "[These] results raise the possibility that the resting state of chimpanzees involves emotionally laden episodic memory retrieval and some level of mental self-projection, albeit in the absence of language and conceptual processing." Is this more akin to how the human brain once functioned?
The research on right-handedness for communication among chimps does however challenge the notion that we as humans are predominantly right-handed because of tool use. This is an important point that I will return to in the future. Note for now that Dr Jaynes detected shifts from right to left brain hemisphere dominance when reading and writing (communicative activities) were becoming more and more widespread and we moved away from the pictographs used by the Egyptians (art is better appreciated by the right hemisphere). This suggests that language and communication are responsible for, at the very least, reinforcing brain lateralization with an emphasis on the left hemisphere. Of further note is the importance placed on silence while meditating and the idea that eternal spiritual truths cannot be communicated verbally. He who knows does not speak…
Although there are similarities then between a human brain and that of a chimpanzee, one of the most significant differences is the degree of lateralization both employ. We as humans use brains that are far, far more lateralized than that of a chimp (this is also true when compared to other animals and, we can presume, when compared to our common ape ancestor). This raises several points to ponder.
When and why did the human brain become so heavily lateralized?
Should we take it for granted that it is “normal” for a human to be left brain hemisphere dominant, or should we consider the possibility that this brain dominance is actually the result of a discernible process that, one might even argue, has skewed our consciousness?
If we so desire, what methods are available to us to allow us to experience right brain dominance and what would this feel like?
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