The evolution of Homo sapiens has been one of the most compelling mysteries this planet has ever witnessed (Saniotis 5), but equally fascinating has been the emergence of a wondrously large and complex brain associated with this species (Vallender 168).
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With its singular importance and astonishing complexity, comprehending the forces that came into play to create an enabling environment for the emergence and evolution of the human brain has become an issue of protracted interest for academics (Gonzalez-Voyer 2267). In line with this paradigm, this paper purposes of evaluating why Homo sapiens might have developed such large and complex brains and if environmental factors have a significant role to play in this evolution.
Scientists have demonstrated that the expanded absolute brain mass characteristic of Homo sapiens and other high-order primates is geometrically related to their cognitive ability and cognitive performance (Montgomery et al 1) and that human brains developed in mass and complexity to allow for greater cognitive and/or linguistic abilities (Vallender 171).
Researchers have also been able to show that primates with a large brain size demonstrate increased cognitive flexibility. Still, other studies have demonstrated that the frontal lobe, the structure of the brain that controls cognitive functions such as decision-making, advanced thinking, empathy, planning, language, and the regulation of emotions, is larger and more complex in Homo sapiens than in other primates (White 23, 34).
The evidence above, therefore, demonstrates that one of the reasons that Homo sapiens might have developed such large and complex brains was to enhance their cognitive abilities and flexibility.
To bring the issue of the environment into context, it can be argued that cognition is an adaptive process (Montgomery et al 1) as individuals develop cognitive abilities to adapt to shifting situations in the environment. Consequently, the environment plays a significant factor in the evolution of human brains, particularly in relation to the development of cognitive abilities.
The social brain hypothesis proposes that primates, including Homo sapiens, evolved large and complex brains to effectively manage their unusually complex social systems (Dunbar 562). Humans are traditionally social animals and, as such, it can be argued that their brains evolved to enable them to handle complex relations and the demands for sociality (Dunbar 565).
Consequently, the symbolic social communication and the complex social systems characteristic of Homo sapiens might have played a big role in the development of large and complex brains. Complex social systems occur within the environment and, therefore, it can be argued that environmental factors play a significant role in the development of human brains.
Scientists have also employed the ecological hypothesis, which emphasizes the relationship between diet and size and structural complexity of the brain, to demonstrate why Homo sapiens might have developed such large brains (Sherwood et al 429). Although there are a few versions of this hypothesis, the version that best fits human description stresses the need for the development of mental maps and presupposes that the size of the brain forces the size of the mental map.
Consequently, Homo sapiens need large and complex brains not only to meet their greater memory requirements of large-scale maps but also to enable them to control the bigger territory where they ‘scavenge’ for food and engage in other daily activities (Sherwood et al 436). Again, this hypothesis places the environment as central to the evolution of the human brains because territorial issues are environmental in nature and the quest for humans to conquer bigger territory bears environmental underpinnings.
Lastly, the epiphenomenal hypothesis, based on the supposition that evolution of the brain is not a consequence of external-related influences but rather simply a consequence of normal biological growth (Zelazniewicz 243), can be used to explain why Homo sapiens developed such large and complex brains.
In humans, this biological growth can be explained in terms of nerve growth, secreted growth factors and their receptors, and single gene mutations or deletions (Jaaro & Fainzilber 192). In some quarters this theory has been criticized as being too mechanistic since it only argues along the paradigm of brain size and body size evolution, without considering environmental influences.
Dunbar, R.I.M. “The Social Brain Hypothesis and its Implications for Social Evolution.” Annals of Human Biology 36.5 (2009): 562-572.
Gonzalez-Voyer, Alejandro, Winberg, Svante, & Kolm, Niclas. “Distinct Evolutionary Patterns of Brain and Body Size during Adaptive Radiation.” Evolution 63.9 (2009): 2266-2274.
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Jaaro, Hanna & Fainziber, Mike. “Building Complex Brains – Missing Pieces in an Evolutionary Puzzle.” Brain, Behavior & Evolution 68.3 (2006): 191-195.
Montgomery, Stephen H., Capellini, Isabella, Barton, Robert A & Mundy, Nicholas I. “Reconstructing the Ups and Downs of Primate Brain Evolution: Implications for Adaptive Hypothesis and Homo Floresciensis.” BMC Biology 8.1 (2010): 1-19.
Saniotis, Arthur. “Future Brains: An Exploration of Human Evolution in the 21st Century and Beyond.” World Future Review 1.3 (2009): 5-11.
Sherwood, Chet C., Subiaul, Francys & Zawadzki, Tadeusz W. “A Natural History of the Human Mind: Tracing Evolutionary Changes in Brain and Cognition.” Journal of Anatomy 212.4 (2008): 426-454.
Vallender, Eric J. “Exploring the Origins of the Human Brain through Molecular Evolution.” Brain, Behavior & Evolution 72.2 (2008): 168-177.
White, Daniel D. Evolution of the Brain: Neuroanatomy, Development and Paleontology. Web.
Zelazniewicz, Agnieszka. Evolution of Human Intelligence – Hypothesis for the Causes. 2007. Web.