Human Evolution and Diversity Flashcards
Australopithecus (SG)
-Smaller body & brain size
-“Southern apes”
-First bipeds (but not efficient)
-Very sexually dimorphic
-Vegetarian
Early Homo habilis (SG)
-East and south Africa
-Larger brain
-Started making stone tools
-Smaller jaws and teeth because they became opportunistic meat eaters
Middle Homo erectus (SG)
-“upright” efficiently!
-First to leave Africa
-Increased body and brain size
-Longer childhood period to allow for brain growth
-Stone tools
-True hunters- more meat reliant- more energy for brain growth
-Were around for 2 million years which is longer than any other homo
Later Homo sapiens (SG)
-Evolved outside of Africa
-Increased brain size
-Sothern & eastern Africa
-Advanced tools, hunting, diverse diet
-fire mastery
-Changes in: locomotion, behavior, social organization, culture
Gene Flow and Human Migration (SG)
-Erectus left Africa and adapted to different climates
-Erectus evolved into Neanderthals in Europe and Denisovans in Siberia
-Sapiens interbred with Neanderthals and Denisovans
Neanderthal SNPs
-1-4% of genome of Europeans and middle eastern peoples is Neanderthal
-Over 135,000 genes identified but only 1400 tested
-For each SNP an individual can carry 0, 1, or 2 variant copies but usually only carry a small subset of the genes
-Avg 23 and me customer carries 267
General Trends of Hominin Evolution (SG)
Increased: body size, brain size, bipedalism, socialization, meat reliance, tools/art/culture
Decreased dentition size
human variation
-Multiple migrations across the globe into varying habitats caused differing selective pressures and genetic drift
-Society and culture differences changing biology
human diversity (SG)
-Population specific differences important to understanding evolution of diseases and human adaptations
-Yet treatments should be based on individuals not groups/ethnicities/races
Genetic examples of cladal adaptations (SG)
- Tibetans- altitude- O2 delivery- EPAS1
- east Asians- temp- sweat glands- EDAR
- sub-Saharan Africans- malaria- sickle cell- beta globulin
- Inuit/Siberian- high fat diet- fatty acid oxidation- CPT1A
- middle east/Europe/Africa- milk consumption- lactase persistence- LCT
Habitual Bipedalism
- advantages
-Efficiently foraging in a cooling climate
oFood scarcity
oTraveling farther to get food
oEasier to forage on two feet b/c hands are free to grab
o Predator avoidance b/c can see farther
o Postural adaptation
-Bipedalism is energy efficient
o Fewer calories consumed to walk longer as compared to knuckle walkers
o Humans walk 4x more than chimps with same energy expenditure
o Not as efficient at running as chimps
o early hominins may have been slightly more efficient than chimps
-Bipedalism set the stage for tool making which has contributed to higher protein diet which in turn provided necessary energy for brain growth
-Each generation needed to improve reproductive and survival skills – traveling further to hunt/forage
Bipedalism Anatomy changes from chimp to sapiens (SG)
-Feet: facing forwards b/c thumb would get in way of walking
-Knees are close together to be more efficient with energy to move forwards
-Pelvis: more bowl shaped to hold organs
-Pelvic inlet: smaller because we need a narrow stance, so we don’t waddle which is more energy efficient to not waddle
-Shorter and less robust arms for carrying objects and tool making
-Shorter phalanges for precision grip
- spine: S shaped to support the weight of whole body
- legs: bipedal now to walk long distances and grab shit
Bipedalism and Knee adaptations
- quadrupeds
- bipedal
- Quadrupedal:
o Straight knees make it energetically expensive to stand for extended periods but more efficient for walking
o Chimps have to throw his weight over the supporting limb when walking on 2 feet - Bipedal:
o Pelvis is wide
o Knees are closer to the midline so feet are under our center of gravity which is energetically favorable because we don’t need to move our weight from one side to the other like chimps waddle
o Can keep balance standing on one foot
o Knees can lock to support body weight
Bipedalism and Back adaptations
- 4 limbs
- 2 limbs
- Body weight distributed on 4 limbs
o Have C-shaped spine
o convex thoracic region
o narrow and long pelvis on the back of the animal because doesn’t hold organs - body weight all on 2 limbs
o S shape spine because
1. 2 additional curvatures to develop spring like effects to deal with body weight
2. Larger lower vertebrae for support
o Broader and bowl-shaped pelvis for organs
o Increased pressure on lumbar vertebrae & intervertebral discs increases susceptibility to prolapsed/herniated discs, nerve damage, back pain (especially in pregnant women) (SG)
Bipedalism and foot adaptations
-Enlarges heel for support
-Loss of opposable hallux
-Shorter toes for locomotion
-Hallux in line with other toes to increase push off
-No longer used for grasping but optimize locomotion
-Arch to absorb shock and act
bipedalism and balance (SG)
-Center of gravity is right above feet and has a very small base area as opposed to chimps with a wide base
-Increased risk of falling when center of gravity is mover outside of our base especially in elderly
body size (SG)
- positives
- negatives
- Larger bodies offer greater protection and hunting
- Negatives are
o increased energy requirement but meat, cutting, fire made it easier to cook/eat food
o time to maturity lengthens so fewer offspring and more dependent
brain size and complexity (SG)
-one of defining features of Homo genus
-encephalization quotient: allometric relationship b/w brain capacity and body mass
-energetically expensive so put more energy into that instead of into muscle development like in chimps
why bigger brains ? (SG)
- Social Brain Hypothesis by Dunbar (more supported): the bigger the brains the bigger the social groups which creates an advantage for everyone in the group
- Tool making and higher reasoning: larger brain means better tools
brain power: large brain/body ratio (SG)
-Longevity
-High sociality = larger social groups = intragroup coordination
-Slow development
-Long parental investment
-Large frontal brain for: innovative behavior (tools), behavioral flexibility, communication abilities (language), spatial skills & memory
Sociality and Cognition (SG)
-Social brain hypothesis
-Individual fitness is advanced by maintaining stable social alliances
-As societal pressures increase you need to obtain more complexity of cognition
o Communication is key for the groups
o Led to sophisticated technology developed
o Building and maintaining bonds is essential
-Complex societies: more understanding of other, altruism, hierarchies
Evolution of Human Society and Disease risk (SG)
-Early homos lived in small groups on the move
-Increased cognition led to ability to control/develop
1. Agriculture
o Overreliance on certain foods
o Nutritional deficiencies
2. Animal husbandry
o Influenza (chickens), TB (cows), toxoplasmosis
3. Urbanization
o Sanitation and dispersal of infectious disorders
Disease risk for bipedalism
plantar fasciitis, increases susceptibility to prolapsed/herniated discs, nerve damage, back pain (especially in pregnant women), loss of balance
How has human diversity impacted disease? (SG)
Population specific differences are important to understanding evolution of diseases and human adaptations so we can treat individuals better. Diversity has impacted the way diseases have evolved in different populations and different defense mechanisms in response to those diseases. certain diseases affect one population because of where they evolved.
