Modern Human Variation 3

Question 1

developmental plasticity

Answer 1

• genome-environment interactions

Question 2

skin

Answer 2

• a type of epithelium; protective layer of cells
• largest organ in integumentary system; skin, hair, fingernails
• three layers, hyodermis, dermis, epidermis

Question 3

functions of skin

Answer 3

• protection of tissues
• thermal regulation
• excretion
• sensation
• storage
• vitamin D synthesis
• protection from UV

Question 4

melanin

Answer 4

• produced by melanocytes; epidermis
• pigment granules concentrated in melanosomes

Question 5

human skin tone phenotype

Answer 5

• melanin production; can vary depending on environmental factors
• dispersion from basal cells

Question 6

human skin tone genotype

Answer 6

• polygenic; >60 genes
• MC1R gene; highly polymorphic, evolutionary context

Question 7

gloger’s rule

Answer 7

• greater pigmentation = lower latitudes
• clinal distribution

Question 8

Disadvantages of UV rays

Answer 8

• sunburn
• skin barrier
• cancer
• chemical and vitamin breakdown

Question 9

what does melanin act as

Answer 9

a protective barrier

Question 10

natural selection and skin tone

Answer 10

• UV rays are necessary for human survival; vitamin D production is stimulated by UV
• another lesser-factor is folate, which is aquired from diet

Question 11

vitamin D

Answer 11

• causes skeletal growth, calcium transportation, kidney function
• required exposure
• if insufficient, can cause rickets or osteomalacia

Question 12

adaptation to UV environment

Answer 12

• darker skin serves as a protective function from the sun; important when there is intense UV radiation
• lighter skin allows for higher vitamin D production, important when there is less UV radiation

Question 13

vitamin D and Folate

Answer 13

• both important in reproductive outcomes
• folate and pregnancy; neural development, DNA synthesis and repair, sperm
• vitamin D and pregnancy; sex hormones, semen, gonads
• need balance between sufficient vitamin D and protection of folate

Question 14

evolution of human skin tone

Answer 14

• dark skin pigmentation evolved in humans; lighter skin tone + pelts, when there was a loss of pelts there was a need for increased melanin production
• light skin mutation found in neanderthals; M1CR, found at higher altitudes
• migration to higher altitudes with less sunlight decreased melanin production

Question 15

evolution of human skin tone and africa

Answer 15

• genotype-phenotype
• almost all skin types are known to exist in africa
• SLC24A5 dipigmentation gene also evident in africa; polygenic
• some light skin tone variants in europe have origins in africa

Question 16

‘cheddar man’

Answer 16

• prehistoric remains in UK
• aDNA genetic sequencing
• estimation of skin and eye colour

Question 17

vitamin D and skin tone

Answer 17

• seasonal variation of vitamin D in toronto
• circulating vitamin D in lower east and south asian groups
• implications for health in cold, heavily clothes environment

Question 18

racial categories linneaus

Answer 18

• europaeus albus: ‘governed by laws’
• americanus rubescens: ‘governed by opinion’
• asiaticus fiscus: ‘governed by opinion’
• africanus niger: ‘governed by caprice

Question 19

racial categories cuvier

Answer 19

• caucasoid
• mongoloid
• negroid

Question 20

factors of racial categories

Answer 20

• geographical
• cultural affiliation, religion, language

Question 21

problems of racial categories

Answer 21

• socially constructed, highly variable
• variation exists in response to different selective pressures
• conventionally based on place of origin
• there is more genetic variation seeen WITHIN groups vs BETWEEN groups
• there is actually greater variability within africa, with decreasing variability with distance from africa

Question 22

racial categories/visual appearance

Answer 22

• skin tones
• hair/eye colour
• body shape and proportions
• facial/cranial characteristics

Question 23

problems in visual appearance of racial categories

Answer 23

• what about non-visual variants?
• polygenic traits; continuous not discrete variation, different genes experiencing different selection pressures

Question 24

out of africa model

Answer 24

Homo sapiens developed first in Africa and then spread around the world between 100 and 200,000 years ago, superseding all other hominid species

Question 25

“race is not biology but it matters”

Answer 25

• racial categories are socially constructed but have real consequences
• has health and social implications; social media, justification of practices towards certain groups

ex. health disparities among black women
- risk of pregnancy related death 3-4x higher
- black infants 2x likely to die
- trends remain among healthy, wealthy and educated black women

• black americans are undertreated for pain
• racial groups experience different health events differently