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Anthro 1026F/G Lecture Notes: Human Adaptation, Race/Ethnicity, and Sex/Gender

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Western University
Anthropology 1026F/G
Alexis Dolphin

Human Adaptation, Race/Ethnicity, and Sex/Gender Human Biological Adaptation: Plasticity: capacity to change physiologically in response to environmental stress - Can be: physical environment (temp, exposure to sun, etc.) cultural environment (available food, etc.) - Flexibility to adapt  humans have some capacity to adapt Homeostasis: a condition of balance in a biological system  dynamic steady state Levels of Adaptation: 1) Genetic: Allele frequencies in a population Irreversible  population wide 2) Ontogenetic: Changes that one experiences while they’re growing Individuals (rather than population wide) Differential growth / development Irreversible  eg. volume of lungs, shape of organs (physical response to environment – once you stop growing these changes are permanent) 3) Physiologic: Individuals Reversible Acclimation: short term change (eg. tan) Acclimatization: longer term change during lifetime (eg. athlete competing at higher altitudes may go to the place early to adjust to the air pressure etc.  will go back to the way things were when they leave again) Adaptations to Climate: a) Bergmann’s Rule: For mammals of the same shape Generally – smaller animals lose more body heat b) Allen’s Rule: For mammals of the same size More linear shape = lose more heat c) Limb Proportion and Climate: Cold climate: mammals have short limbs and stocky bodies Hot climate (close to equator): mammals have long, slender limbs and linear bodies Adaptations to Heat: a) Sweating: Lose heat by evaporative cooling Can lose too much!  dehydration b) Vasodilatation: Capillaries at skin’s surface widen to allow increased blood flow  lose heat Adaptations to Cold: a) Shivering: Generates body heat BUT: requires energy b) Vasoconstriction: Restriction of capillaries / blood flow at skin’s surface Keeps core protected More efficient than shivering / heating up BUT: danger of frostbite Long-term: Inuit people cycle through vasodilatation and vasoconstriction  retain heat in core, then warm whole body again to avoid frostbite Adaptations to High Altitudes: a) Hypoxia: Oxygen starving (>2400m – oxygen in air is getting thin and body feels heavy) Physiological adaptation: more red blood cells Ontogenetic adaptation: higher lung capacity Developing children will grow larger lungs (will permanently stay with them) – eg. in Machu Picchu – barrel shaped ribs (altitude changes lungs which changes shape of ribs) Adaptation to Malnutrition: (Bad for children, and especially bad for fetus) - Nutritional Status: • Dietary intake + work/activity + growth + repair (eg. ill – need more intake) + storage • Undernutirion: poor quantity and quality • Impaired growth and development (for kids) – especially in stature (won’t grow as tall as quickly) • *note: malnutrition can also be overeating Variation in Human Biology: - Relative homogenous species - Polytypic Species: local variations in the expression of one or more traits (traits are not always linked) - Phenotypic Variation: 1000s of genes, 1000s of phenotypic outcomes • Interests in skin, eyes, hair (phenotypic traits that are easy to see): certain phenotypes are more common in some populations • These traits follow Clinical Variation - Clinal Variation: • Cline: gradual change in the frequency of genotypes and phenotypes from one geographic region to another • Eg. blood types, skin colour Skin Colour: Adaptation to Solar Radiation (example of when species have adapted to their environment): - Melanin: absorbs UV radiation - Everyone has the same number of melanocytes (melanocytes produce melanin) - UV rays trigger melanocytes to produce melanin (absorbs UV rays) - Environment with little UV protection – may have a problem with cancer (may not reproduce and pass on genes) - Natural selection for more melanin where there is more sun  selective advantage for darker skin in places with high UV radiation - Eg) At equator: not as many clouds as Scandinavia  hominins originated in Africa – people spent long time here (therefore there are high amounts of people with darker skin) • BUT: people of the New World are not as dark  question: why doesn’t everyone have dark skin if everyone originated from Africa?? • Solar Radiation and Vitamin D  Northern Regions = less UV radiation  UV stimulates vitamin D production • Vitamin D deficiency = results in rickets  Therefore when people move out of Africa (these people have darker skin)  downside to dark skin because it blocked all the sun in places with less UV radiation and these people didn’t get enough vitamin D  makes bones soft (especially in children – result: femur and tibia bow in children – weight affects lower limbs and pelvis can be misshaped  doesn’t improve  therefore, will always have this)  Natural selection for less melanin where there is less risk of UV damage **Essentially: people in Africa have more melanin and therefore have darker skin. BUT: humans are thought to have all originated in Africa and then moved to different parts of the world – so, why doesn’t everyone have dark skin?  in colder places, there is less UV radiation – SO: people with a lot of melanin don’t get as much vitamin D in these places (because high amounts of melanin in colder places will block out all UV rays (which also blocks out vitamin D, since UV is a source of vitamin D). SO: people with lighter skin had a better chance of survival (and therefore were selected for in terms of natural selection) in colder places Interpretations of Human Variation: - Egyptians classified humans according to skin colour: • Red = Egyptians • Yellow = people to the East • White = people to the North • Black = Africans from the South Biological Determinism: - Associates physical characters with behaviour and capabilities - Argues that some groups are naturally
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