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The Result of an Expanded Cerebellum Throughout Evolutionary Time

Throughout history the human brain has evolved in multiple ways, for example, at the beginning of our evolutionary history the human brain was similar to species such as Lucy Australopithecus afarensis as well as many other apes. However, in more recent evolutionary changes, the human brain has started to increase in size, especially in areas that are associated with language functions such as the cerebellum. The cerebellum is the section of the brain that controls multiple human functions. One of its major roles is to maintain motor control such as the monitoring and modifying of motor signals from the cortex. It helps maintain the balance and posture of the body and help coordinate the voluntary movements as well. More recent studies show that the cerebellum may also be playing an important role in the cognitive functions of the human brain, which leads into the hypothesis that the involvement of the cerebellum in the cognitive functions may be the force positively driving selection to increase its size. Therefore, being able to understand the role of the cerebellum and its functions allow us to understand not only the broad concept of the human brain, but also the advantages we may have in comparison to other species.

The cerebellum, along with its roles in other human brain and body functions, may be involved in humans’ cognitive functions as well. These hypotheses have been confronted through the recent studies that have found that the cerebellum may be involved more than what was previously thought in humans attention and language functions. The cerebellum may also play a role in more high-level cognitive functions such as planning, learning, memory, visual-spatial processing, and modulating emotional responses. However, the most important hypothesis was its association to language (speech production and perception, semantic and grammatical processing, and timing mechanisms) and intelligence (Schoenemann 2009). A study showed that a person who was suffering from cerebellar degeneration was not able to comprehend distinction in meanings due to the syntax’s inability to show discrepancies in the neocerebellum compared to someone whose cerebellum functioned normally (Lieberman 2002). Also, the cerebellum has been seen to have a role in timing motor activity due to the findings that intrinsic durations of English vowels were not affected when the voice-onset-time, time it takes from lip or tongue gestures to the periodic phonation generated by the larynx, sequence was tarnished (Lieberman 2002). Therefore, the role of the cerebellum in cognitive functions of the brain may be the cause of the expansion of the cerebellum size.

The cerebellum, in past years, has expanded in both apes and humans in contrast to the “Old World” monkeys. The cerebral hemispheres increased in size within early hominids while the cerebellum remained small, on the other hand, the Neanderthals and Cro-Magnon 1 possessed the largest cerebellum. However, in more recent studies, the size of the human cerebellum, compared to the rest of the brain, has been increasing in size while the cerebrum decreased in size (Schoenemann 2009). With both the development and implementation of motor tasks, visual-spatial skills and learning taking place in the cerebellum; the growth of the cerebellum is thought to have some form of correlation to greater human cognitive abilities (MacLeod 2003). The lateral hemispheres of the cerebellum are now 2.7 times greater in both humans and apes than they are in monkeys compared to evolutionary history (Schoenemann 2009). For example, these changes in the cerebellum size cannot be explained by greater muscle mass. This displays that some form of “tight developmental linkage” in relation to the rest of the brain, or selection in particular for the behavioral abilities, is taking place in the cerebellum. Due to the cerebellum's role in language processing, the increase in its size may play a role in its expansion (Schoenemann 2009). Therefore the need for humans to use a higher level of behavioral and cognitive functions in the current time period may be the reason for a positive selective force leading to the evolution and expansion of the cerebellum area.

The methods involved in the evolution of the cerebellum, which lead to the increase in its size, are still not completely understood, however, a number of studies have come up with a number hypothesis. Humans and apes are seen to be very similar to one another and the structures seen in the human brain are all found in the brain of apes as well (Vandervert 2007). They both are found to have similar brain structures in exception of the cerebellum size. Humans’ larger proportion of the cerebellum is what differentiates the two from one another. The human brain has evolved and diverged from the non-human apes based on the size of the cerebellum, allowing humans to develop cognitive functions. Looking at the patterns of size changes among brain structures over evolutionary time, show that specific lineages/species are distinguished. Also by comparing the size of the cerebellum at different time periods, the rate and timing of these neuroanatomical changes in evolutionary history can be hypothesized. These methods express that the differences in the size of the cerebellum and related cortical areas indicate taxonomic divergence in great apes and humans (Smaers 2014). Also, the relative sizes of the cerebellum compared to the fossils of hominids are no longer the same. The size of the actual cerebellum in comparison to the net brain size of recent humans showed that the cerebellum had expanded over evolutionary history. The brain size has increased almost three times in volume, which could have been a result of the computational base and memory size necessary to rapidly learn and store the meanings of new words (Lieberman 2002).

Weaver suggests that cerebellar and neocortical evolution occurred in three stages. The three states are “stage one: early encephalization involving expansion of the neocortexas Pliocene and Early to Middle Pleistocene humans developed an adaptive pattern of technologically assisted foraging” (Weaver 2005). Stage two stated that the neocortical expansion in humans is due to the emergence of cultural objects, which require an increase in the processing of pyrotechnology (Weaver 2005). Stage three stated that the increase in the cognitive efficiency resulted in the cerebellum to expand (Weaver 2005). In humans, the reciprocal neural connections can send signals to the to the sensorimotor areas along with areas of the frontal lobe. The areas in the frontal lobe, where the signals are sent, are able to receive signals not only from the thalamus cortex, but also from associated motor regions (Leiner 1986). Due to this overlap, the cerebellum can play a role in both language and cognitive functions, which indicates that the evolution of language and speech in humans may be causing the expansion to occur.

It has also been hypothesized that the cerebellums involvement in the cognitive function visual-spatial/speech and language could have caused selective pressures to the increased area of the cerebellum causing it to change in structure and evolve into the larger volume seen in the cerebellum now, differentiating it from other species. Vandervert et al. 2007 states that visual-spatial sketchpad and speech loop evolved together, and language was selected for, causing the increase in the cerebellum size. By selecting language, humans are allowed to share visual-spatial imagery and have a working memory, which allows us to have a conscious (Vandervert et al. 2007). Vandervert et al. states that a hunter-gather, who is out trying to collect food in order to take home in the woods, could get lost if they were not able to remember the spatial cues of sounds such as the waterfall or the description of the trees around him or her that can help him or her return home (Vandervert et al. 2007). Therefore, the selection of memory and conscious is hypothesized to have caused the selection of a larger cerebellum volume.

The overall cause for the evolution of the cerebellum, in which it is increasing in size, is still unknown. However many hypothesis are showing that the cognitive functions and the adaptive advantages humans have from the expansion of the cerebellum may be the reason behind evolutionary forces positively selecting for the expansion.

The combinations of the cerebellum motor and mental capabilities allow the cerebellum to confer on humans some adaptive advantages, which allows the human cerebellum to continue to enlarge. The advantage is that the cerebellum couples the motor function of articulating speech to the mental functions that select the language, which is spoken, providing humans with speech and language. It allows humans to move their lips and tongue to formulate the words and sounds that we need in order to communicate with one another. Gibson states that people who have mastered their native languages can make many precise, speech related, oral movements, and they can combine and recombine such movements to create large numbers of phonemes and a seemingly infinite number of unique vocal sequences (Gibson 2002). This allows us to not only use our mouth to communicate, but also expand our communication through our ability to coordinate our speech with our body movement.

It has also been suggested that the increase in the size of the cerebellum, due to the mental and motor activities, allow humans to think rapidly and move more rapidly than other species. The combination of the cerebellums ability to think and react quickly will be very advantageous in human survival. For example, when in a fight or flight situation, the ability to think and react quickly, will be favored. Such combination may have been a precondition for the emergence of fluent human speech and language, in which the motor activity of speech must be connected to the mental activity in order to communicate in a particular language (Leiner 2010). Overall the increase in the cerebellum size may be a result of the adaptive advantages resulting in the expansion to be selected for.

Overall the human brain is a very complex structure that is continuously evolving, especially the cerebellum. The cerebellum has been seen playing a role primarily in the maintenance of posture and the voluntary movement of the body. However, recent studies have shown that the cerebellum may be actually playing a major role in human cognitive functions such as speech and language. It has also shown that compared to evolutionary history, the cerebellum has expanded in size. The role of the cerebellum in the cognitive function is seen as the cause of this expansion of the cerebellum. However the research dealing with the cerebellum’s role in cognitive function and the cause of its expansion is still new and unknown.

By learning more about the expansion of the cerebellum and the causes associated with it, we are able to learn more about the divisions between different species and our ancestors. Also, we can learn what possible evolutionary forces, such as selection, may be acting on the cerebellum in order to cause it to increase in size. It can also provide us with information about the possible advantages humans have compared to other species due to the larger cerebellum and its connection to cognitive function such as the ability to speak and the ability to mentally interpret situation allowing us to formulate languages to communicate. Overall, the more information that we are able to obtain regarding the cerebellum, the more we will be able to learn about the human brain and its possible functions and advantages.

Citations Gibson, Kathleen R. "Evolution of Human Intelligence: the Roles of Brain Size and Mental Construction." Brain, Behavior and Evolution. 59 (2002): 10-20.

Leiner, H. C. (January 01, 2010). Solving the mystery of the human cerebellum. Neuropsychology Review, 20, 3, 229-35.

Leiner, HC, AL Leiner, and RS Dow. "Does the Cerebellum Contribute to Mental Skills?" Behavioral Neuroscience. 100.4 (1986): 443-54.

Lieberman, P. (December 01, 2002). On the nature and evolution of the neural bases of human language. American Journal of Physical Anthropology, 119, 36-62.

MacLeod, Carol E, Karl Zilles, Axel Schleicher, James K. Rilling, and Kathleen R. Gibson. "Expansion of the Neocerebellum in Hominoidea." Journal of Human Evolution. 44.4 (2003).

Schoenemann, P. T. (December 01, 2009). Evolution of Brain and Language. Language Learning, 59, 162-186.

Smaers, J. B., & Cerebellar Learning. (January 01, 2014). Modeling the Evolution of the Cerebellum. Progress in Brain Research, 210, 193-216.

Vandervert, Larry R, Paul H. Schimpf, and Hesheng Liu. "How Working Memory and the Cerebellum Collaborate to Produce Creativity and Innovation." Creativity Research Journal. 19.1 (2007): 1-18.

Weaver, A. H. (January 01, 2005). Reciprocal evolution of the cerebellum and neocortex in fossil humans. Proceedings of the National Academy of Sciences of the United States of America, 102, 10, 3576-80.

 WIKIPEDIA POST ON CERBELLUM PAGE HERE 

Link to edits: https://en.wikipedia.org/wiki/Cerebellum

The size of the human cerebellum, compared to the rest of the brain, has been increasing in size while the cerebrum decreased in size With both the development and implementation of motor tasks, visual-spatial skills and learning taking place in the cerebellum; the growth of the cerebellum is thought to have some form of correlation to greater human cognitive abilities. The lateral hemispheres of the cerebellum are now 2.7 times greater in both humans and apes than they are in monkeys compared to evolutionary history. For example, these changes in the cerebellum size cannot be explained by greater muscle mass. This displays that some form of “tight developmental linkage” in relation to the rest of the brain, or selection in particular for the behavioral abilities, is taking place in the cerebellum. Due to the cerebellum's role in language processing, the increase in its size may play a role in its expansion. Therefore the need for humans to use a higher level of behavioral and cognitive functions in the current time period may be the reason for a positive selective force leading to the evolution and expansion of the cerebellum area.

It has also been hypothesized that the cerebellums involvement in the cognitive function visual-spatial/speech and language could have caused selective pressures to the increased area of the cerebellum causing it to change in structure and evolve into the larger volume seen in the cerebellum now, differentiating it from other species. Vandervert et al. 2007 states that visual-spatial sketchpad and speech loop evolved together, and language was selected for, causing the increase in the cerebellum size. By selecting language, humans are allowed to share visual-spatial imagery and have a working memory, which allows us to have a conscious. Vandervert et al. states that a hunter-gather, who is out trying to collect food in order to take home in the woods, could get lost if they were not able to remember the spatial cues of sounds such as the waterfall or the description of the trees around him or her that can help him or her return home. Therefore, the selection of memory and conscious is hypothesized to have caused the selection of a larger cerebellum volume. The combinations of the cerebellum motor and mental capabilities allow the cerebellum to confer on humans some adaptive advantages, which allows the human cerebellum to continue to enlarge. The advantage is that the cerebellum couples the motor function of articulating speech to the mental functions that select the language, which is spoken, providing humans with speech and language. It allows humans to move their lips and tongue to formulate the words and sounds that we need in order to communicate with one another. Gibson states that people who have mastered their native languages can make many precise, speech related, oral movements, and they can combine and recombine such movements to create large numbers of phonemes and a seemingly infinite number of unique vocal sequences. This allows us to not only use our mouth to communicate, but also expand our communication through our ability to coordinate our speech with our body movement.

 ANNOTATED BIBLIOGRAPHY 

Leiner, H. C. (January 01, 2010). Solving the mystery of the human cerebellum. Neuropsychology Review, 20, 3, 229-35. http://osu.worldcat.org/title/solving-the-mystery-of-the-human-cerebellum/oclc/672648271&referer=brief_results. This article is about a research that was conducted to see why the Cerebellum grew so dramatically in the past million years. A group of scientist studied the contribution of the Cerebellum to the cerebral cortex. They studied the mental functions of the Cerebellum and its contribution to cognition. They said that the combination of motor and mental capabilities in the Cerebellum allows humans to have some adaptive advantages over other species. They said this is the reason why the human Cerebellum is growing so rapidly over time. The article states that these advantages is what allows humans to select the language they want to speak allowing helping humans produce a fluent human speech to be verified.

Lieberman, P. (December 01, 2002). On the nature and evolution of the neural bases of human language. American Journal of Physical Anthropology, 119, 36-62. http://osu.worldcat.org/title/on-the-nature-and-evolution-of-the-neural-bases-of-human-language/oclc/5152047025&referer=brief_results. This article discusses how the Cerebellum is usually associated with motor control and is active in motor learning. The study in this article is the study of Broca's aphasia, Parkinson's disease, hypoxia, focal brain damage, and a genetically transmitted brain anomaly (the putative “language gene,” family KE), and from relative studies of the brains and behavior of other species, displays that the basal ganglia sequence the distinct elements that composes a complete motor act, syntactic process, or thought process. It also discusses how Imaging studies of intact human subjects and electrophysiologic and tracer studies of the brains and behavior of other species backs these findings. The article will be helpful because it discusses how the knowing the evolution of on the brains of humans as well as other species gives us information about the evolution of the brains bases for human language which is controlled by the Cerebellum and how this whole processes started with our earliest hominid ancestors.

Schoenemann, P. T. (December 01, 2009). Evolution of Brain and Language. Language Learning, 59, 162-186. http://osu.worldcat.org/title/evolution-of-brain-and-language/oclc/5156527291&referer=brief_results.This article discusses the evolution of the brain and how that leads to the evolution of the human language. The article discusses how closely linked they both are. It discusses how language evolution is a different kind of adaption because it is apart of a more complex behavior than a physical feature. This article will be helpful because the article discusses the evolution of the brain such as the Cerebellum which leads to the evolution of language because the Cerebellum is what controls language.

Smaers, J. B., & Cerebellar Learning. (January 01, 2014). Modeling the Evolution of the Cerebellum. Progress in Brain Research, 210, 193-216. http://osu.worldcat.org/title/modeling-the-evolution-of-the-cerebellum/oclc/5598034402&referer=brief_results. This article talks about the evolution of the Cerebellum. It discusses how the knowledge and studies of the evolution of the Cerebellum can contribute to theories the functions of the Cerebellum. It shows the patterns of size changes of the brain structure over evolutionary time. It also shows how some species are different than others regarding the structure of the Cerebellum. This article will help me obtain information about how the Cerebellum and the evolution of the Cerebellum will affect the functions of it. It also will show me some of the changes over evolutionary history of the Cerebellum and the differences and similarities between humans and other species helping me understand more about the evolution of the human Cerebellum and its functions.

Weaver, A. H. (January 01, 2005). Reciprocal evolution of the cerebellum and neocortex in fossil humans. Proceedings of the National Academy of Sciences of the United States of America, 102, 10, 3576-80. http://osu.worldcat.org/title/reciprocal-evolution-of-the-cerebellum-and-neocortex-in-fossil-humans/oclc/111154167&referer=brief_results. This article discusses how the evolution of the human brain involves both neurological reorganization and an increase in the brain volume relative to body mass overall. It discusses how important the Cerebellum is because it connects to each of the 14-neocortical regions showing that it is very important regarding humans cognitive evolution. It discusses the trends seen in fossils and other historical finds regarding the Cerebellum. IN australopithecines and early members of the genus Homo, the cerebral hemispheres were a larger portion of the Cerebellum compared to other hominoids. It stated that the trend continues through the Middle and Late Pleistocene humans. Overall this article gives tells me about how the Cerebellum and cerebral hemisphere appear to have evolved tremendously and that the Cerebellar development in humans may have given humans a better ability to cope with increasingly complex culture and theoretical environment.