Human Variation Flashcards
The most morphologically cariable species of all living animals
Humans
The genetic basis of this variation is likely quite small
How much do humans and chmipanzees differ
They differ genetically by 1-2%
Skin Color
Most frequently explained traits
Most systems of classification of human variation were based upon it
1350 BC racial classifications (from the Egyptians)
Red: Egyptians
Yellow: People of the East (asians)
White: People of the North
Black: Africans from the South
16th Century
Intense explotation
The first scientific attempt to categorize the newly discovered variation among humans
Linneaus’
Himi europaeus, Homo afer, Homo asiaticus, Homo americanus
Johann Friedrich Blumenbach
Classified humans into 5 categories
Caucasoid, Mongoloid, Malay, Ethiopian, American
White, Yellow, Red, Black, and Brown
Blumenbach’s criticism of his work
Skin color was not a discrete category
overlapping expression between groups
Uniform traits
Traits that are uniformly expressed
“Either/or”
Nonadaptive Traits
Characteritics that are stable not influenced by the environment
Skin color is adaptive ->changes with sun exposure
Cephalic Index
Method of describing the shape of the head
How was the cephalic index derived?
Dividing the maximum head breadth by maximum length and multiplying by 100 to gvie ratio of head breadth to length
Doliochocephalic
Index less than 75
Northern europeans
Brachicephalic
Index over 80
Southern Europeans
Mesocephalic
Index between 75 and 80
Early attempts criteria for human variation classification
- Outward physical characteristics
- Geographical origin
Some anthropologists turned to ____
Blood type
Carlton Coon Human Classifications
- Austaloids
- Mongoloids
- Caucasoids
- Congoids
- Capoids
Why doesn’t describing people in a geographical area work for human calssification?
Migration
How do biological anthropologists think of human variation?
A result of evolutionary factors
- Genetic drift
- Gene flow
- Founder Effect
- Adaptation (via Natural Selection)
Skin Color
Long term adaptation and Natural selection in human populations
Gloger’s Rule
Populations of birds and mammals living in warmer climates have more melanin and therefore have darker skin/fur/feathers
Skin Color is influenced by 2 substances
- hemoglobin
- Carotene
- Pigment Melanin
Melanin
Granular substance produced by specialized cells in the epidermis called melanocytes
All humans have the same number of:
Melanocytes
What affects different skin color?
The amount of melanin and the size of the melanin granules
Melanin provides:
Protection form overexposure to sunlight radiation
What does exposure to sunlight trigger?
A protective mechanism in the form of temporarily increased melanin productions
Rickets
Insurfficient amounts of vitamin D during childhood
