Muscular evolution in humans
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Muscular evolution in humans is an overview of the
Introduction
As is the standard for all evolutionary adaptations, the human muscle system evolved in its efforts to increase survivability. Since muscles and the accompanying ligaments and tendons are present all throughout the body aiding in many functions, it is apparent that our behavior and decisions are based upon what we are and how we can operate. It is believed that our ancestor’s original habitat was not on the ground but in the trees and we developed new habits that eventually allowed us to thrive on the ground, such as changes in diet, gathering of food, energy expenditure, social interactions, and predators. Life in the canopy meant a food supply similar to that of herbivores: leaves, fruits, berries; mostly low-protein foods that did not require a large amount of energy to find. However, if any could be found, meat was also consumed. At this time our ancestors had not yet switched to full-time bipedalism and so searching for food on the ground did not make sense because there was too much energy and risk involved. This habitat also lacked the predators found on the ground that our chimp-like ancestors would have been poor defenders against. As they became bipedal, they began to live in groups that used weapons to fend off predators and hunt down prey. Running became a key aspect to the survival of the species.[4] Even with all this, it is the development of the brain that has guided the development of the muscle functions and structures in humans.
Skull, neck, and head
It is suspected that H. sapiens ancestors’ did not initially forage on the forest floor; instead they migrated from the trees for various reasons. In that environment, they survived on a diet high in plant matter with some
Upper body/back
Humans became taller as the years passed after becoming bipedal which lengthened
Lower body/below waist
The conversion to full-time bipedalism in our distant ancestors is the main argument for the adaptations our muscle structure and function have made. By having to center the force of gravity on two feet, the human
Strength changes
Compared to our closest living relatives, chimpanzees and bonobos, Homo sapiens' skeletal muscle is on average about 1.35 to 1.5 times weaker when normalized for size. As little biomechanical difference was found between individual muscle fibers from the different species, this strength difference is likely the result of different muscle fiber type composition. Humans' limb muscles tend to be more biased toward fatigue-resistant, slow twitch Type I muscle fibers.[12] While there is no proof that modern humans have become physically weaker than past generations of humans, inferences from such things as bone robusticity and long bone cortical thickness can be made as a representation of physical strength. Taking such factors into account, there has been a rapid decrease in overall robusticity in those populations that take to sedentism.[13] For instance, bone shaft thickness since the 17th and 18th centuries have decreased in the United States, indicating a less physically stressful life.[14] This is not, however, the case for current hunter gatherer and foraging populations, such as the Andaman Islanders, who retain overall robusticity.[15] In general, though, hunter gatherers tend to be robust in the legs and farmers tend to be robust in the arms, representing different physical load (i.e., walking many miles a day versus grinding wheat).
References
- ^ "How Many Amino Acids Does the Body Require? | Healthy Eating | SF Gate". Healthyeating.sfgate.com. 4 November 2012. Retrieved 2018-06-07.
- ^ Larry L Mai; Marcus Young Owl; M Patricia Kersting (2005), The Cambridge Dictionary of Human Biology and Evolution, Cambridge & New York: Cambridge University Press, p. 45
- PMID 28652350.
- ^ Foley, Lee, R.A., P.C. (1991). "Ecology and energetics of encephalization in hominid evolution." Philosophical Transactions of the Royal Society of London, Series B, vol. 334, pp. 223-232.
- ^ Sicher H (1944) "Masticatory apparatus in the giant panda and the bears." In: Field Museum of Natural History (Zoological Series), Chicago.
- ^ Saladin, Kenneth S. (2003). 3rd. ed. Anatomy & Physiology: The Unity of Form and Function. McGraw-Hill. pp. 286–287
- ^ Vogel, Steven (2001). Prime Mover: “A Natural History of Muscle”
- ^ Sieg, Adams, Kay, Sandra (2009). "Illustrated Essentials of Musculoskeletal Anatomy"
- ^ "Evolution Library:Walking Tall." Evolution Library. Web. 20 Jun 2011.
- ^ Saladin, Kenneth S. "Chapter 8." Anatomy & Physiology: the Unity of Form and Function. 5th ed. Dubuque: McGraw-Hill, 2010. 281. Print.
- ^ Aiello, Dean, Leslie, Christopher (1990). An Introduction to Human Evolutionary Anatomy. Oxford: Elsevier Academic Press.
- PMID 28652350.
- ^ Timothy M. Ryan and Colin N. Shaw, Gracility of the modern Homo sapiens skeleton is the result of decreased biomechanical loading, Proceedings of the National Academy of Sciences, 10.1073/pnas.1418646112, 112, 2, (372-377), (2014).
- ^ Timothy M. Ryan and Colin N. Shaw, Gracility of the modern Homo sapiens skeleton is the result of decreased biomechanical loading, Proceedings of the National Academy of Sciences, 10.1073/pnas.1418646112, 112, 2, (372-377), (2014).
- ^ A Stock, J. (2006). Hunter-gatherer postcranial robusticity relative to patterns of mobility, climatic adaptation, and selection for tissue economy. American Journal of Physical Anthropology, 131(2), pp.194-204.