evolutionary legacies
Skip this Video
Download Presentation
Evolutionary Legacies

Loading in 2 Seconds...

play fullscreen
1 / 33

evolutionary legacies - PowerPoint PPT Presentation

  • Uploaded on

Evolutionary Legacies. February 9, 2005. Is Natural Selection Still Working?. YES! How we have come to be the way we are How we are still being affected. Is Natural Selection Still Working?. Infectious Disease Chronic Diseases Hypertension Obesity/Heart Disease/Diabetes Arthritis.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'evolutionary legacies' - Samuel

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
evolutionary legacies

Evolutionary Legacies

February 9, 2005

is natural selection still working
Is Natural Selection Still Working?
  • YES!
  • How we have come to be the way we are
  • How we are still being affected.
is natural selection still working3
Is Natural Selection Still Working?
  • Infectious Disease
  • Chronic Diseases
    • Hypertension
    • Obesity/Heart Disease/Diabetes
    • Arthritis
evolutionary legacy

Evolutionary Legacy

Evolution of Human Sexuality

some intriguing questions
Some Intriguing Questions:
  • Why do males have nipples?
  • Of the 5 ape species, which has the largest penis?
  • Of the 5 ape species, which has the largest breasts?
  • Why do humans have sex in private when all other social animals do it in public?
  • “Male Nipples and Clitoral Ripples” Stephen J. Gould
  • “The Evolution of Human Sexuality” Jared Diamond
but why
But Why?!?!?!
  • Is a feature adaptive (functional), maladaptive, or neither?
  • Example: Humans have big butts
    • Explanation: those are important muscles that hold us upright—FUNCTIONAL
male nipples
Male Nipples
  • Early theories: hermaphroditic pre-human ancestor
male nipples9
Male Nipples
  • Developmental explanation:
    • Embryos are generalized before sexual differentiation
    • Males have nipples because they are functional in females
    • Evolutionary side effect, neither adaptive nor maladaptive
clitoral ripples
Clitoral Ripples
  • Freud: female sexual stimulation begins in clitoris and moves to vagina
  • WRONG!
  • Clitoris and Penis develop from the same embryonic tissue
other confounding factors
Other Confounding Factors
  • Concealed estrus
  • Concealed ovulation
  • Linked to:
    • Social food gathering
    • Male role in child rearing
why is human sexuality so bizarre
Why is human sexuality so bizarre?
  • Social group (like wolves or lions)
  • Pair bonding
  • Enormous Penises
  • Enormous Breasts
  • How is any of this adaptive?
More sex = Bigger Testes

Larger Testes = Greater Chance of Pregnancy


Adaptive to human sex?


Organ of Display


For Whom?

Human female breasts are large and permanent

Enlargement occurs before first pregnancy

concealed estrus sex
Concealed Estrus, Sex
  • Female primate genitals swell and color (red, pink, blue) to indicate estrus
  • Humans:
    • Concealed ovulation
    • Constant sexual receptivity
    • Brief period of fertility during menstrual cycle
why is human sexuality so bizarre18
Why is human sexuality so bizarre?
  • Ape sex: dangerous luxury
    • Burns valuable calories
    • Takes time that could be used gathering food
  • Human sex for conception:
    • Waste of time
    • Waste of energy
    • Maladaptive
why is human sexuality so bizarre19
Why is human sexuality so bizarre?
  • Human sexuality is adaptive for reasons other than conception
theory 1
Theory 1
  • Concealed ovulation/copulation reduces competition and enhances cooperation among male hunters
theory 2
Theory 2
  • Concealed ovulation/copulation enhance bond between man and woman by making woman continuously receptive
theory 3
Theory 3
  • Male chimps are more likely to share food with females in estrus.
  • Concealed estrus may ensure steady food supply
theory 4
Theory 4
  • Concealed estrus exploits male paranoia over paternity, enhances pair bond
human paradox
Human Paradox
  • Men and women desire their children to survive and must cooperate in child rearing
  • Must also cooperate with other pairs in economic activity
  • Sexual relations
  • Economic relations
human paradox25
Human Paradox
  • Concealed ovulation/copulation reinforce the distinction between sexual partners and economic partners
  • Sex as social cement rather than simple procreation
so why do we have such large penises breasts
So, why do we have such large penises/breasts?
  • Arbitrary sexual display symbols
example 1 saltshakers curse
Example 1: Saltshakers Curse
  • African-Americans:
    • Higher blood pressure
    • Twice the risk of hypertension
    • Ten times more likely to die
    • By age 50, half of black men are hypertensive
    • Can cause heart disease, kidney failure or stroke
example 1 saltshakers curse29
Example 1: Saltshakers Curse
  • High blood pressure caused by
    • Genetics
    • Environment (intake of salt, fat, alcohol, high stress)
  • Needed in body
  • Excreted in urine
  • White and Black Americans consume about the same amount of salt
  • Black Americans consume less potassium and calcium
    • Experience more stress
    • Are less likely to have medical care
example 1 saltshakers curse31
Example 1: Saltshakers Curse
  • Black Americans retain salt longer than do White Americans
  • Hyptertension is more likely to be “salt sensitive” in Black Americans
  • Labeled as a “defect”
selecting agent slave trade
Selecting Agent: Slave Trade
  • 70% of captured Black Africans died between capture and sale
  • In between: long marches, heavy burdens, Middle Passage
    • Sweat
    • Vomit
    • Diarrhea (Cholera)
selecting agent slave trade33
Selecting Agent: Slave Trade
  • Slave trade selected for “superefficient” kidneys that retain salt
  • Salt retention was adaptive until modern medicine
  • Saltshaker’s “Curse”: proliferation of salt in our diet makes salt retention maladaptive.