Evolutionary legacies
Download
1 / 33

evolutionary legacies - PowerPoint PPT Presentation


  • 248 Views
  • Updated 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.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
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 l.jpg

Evolutionary Legacies

February 9, 2005


Is natural selection still working l.jpg
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 l.jpg
Is Natural Selection Still Working?

  • Infectious Disease

  • Chronic Diseases

    • Hypertension

    • Obesity/Heart Disease/Diabetes

    • Arthritis


Evolutionary legacy l.jpg

Evolutionary Legacy

Evolution of Human Sexuality


Some intriguing questions l.jpg
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?


Sources l.jpg
Sources

  • “Male Nipples and Clitoral Ripples” Stephen J. Gould

  • “The Evolution of Human Sexuality” Jared Diamond


But why l.jpg
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 l.jpg
Male Nipples

  • Early theories: hermaphroditic pre-human ancestor


Male nipples9 l.jpg
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 l.jpg
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 l.jpg
Other Confounding Factors

  • Concealed estrus

  • Concealed ovulation

  • Linked to:

    • Social food gathering

    • Male role in child rearing


Why is human sexuality so bizarre l.jpg
Why is human sexuality so bizarre?

  • Social group (like wolves or lions)

  • Pair bonding

  • Enormous Penises

  • Enormous Breasts

  • How is any of this adaptive?


Testes l.jpg

More sex = Bigger Testes

Larger Testes = Greater Chance of Pregnancy

Cost/Benefit

Testes


Penis l.jpg

Adaptive to human sex?

No.

Organ of Display

Why?

For Whom?

Penis



Breasts l.jpg

Human female breasts are large and permanent

Enlargement occurs before first pregnancy

Breasts


Concealed estrus sex l.jpg
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 l.jpg
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 l.jpg
Why is human sexuality so bizarre?

  • Human sexuality is adaptive for reasons other than conception


Theory 1 l.jpg
Theory 1

  • Concealed ovulation/copulation reduces competition and enhances cooperation among male hunters


Theory 2 l.jpg
Theory 2

  • Concealed ovulation/copulation enhance bond between man and woman by making woman continuously receptive


Theory 3 l.jpg
Theory 3

  • Male chimps are more likely to share food with females in estrus.

  • Concealed estrus may ensure steady food supply


Theory 4 l.jpg
Theory 4

  • Concealed estrus exploits male paranoia over paternity, enhances pair bond


Human paradox l.jpg
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 l.jpg
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 l.jpg
So, why do we have such large penises/breasts?

  • Arbitrary sexual display symbols


Example 1 saltshakers curse l.jpg
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 l.jpg
Example 1: Saltshakers Curse

  • High blood pressure caused by

    • Genetics

    • Environment (intake of salt, fat, alcohol, high stress)


Slide30 l.jpg
Salt

  • 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 l.jpg
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 l.jpg
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 l.jpg
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.


ad