new lecture 8: reproductive ecology - harvard...

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Lecture 8: Reproductive EcologyLecture 8: Reproductive Ecology

•• NutritionNutrition

•• Exercise/WorkloadExercise/Workload

•• Energy BalanceEnergy Balance

•• Age DifferencesAge Differences

•• Hormonal Levels and Hormonal Levels and

ConceptionConception

•• Population DifferencesPopulation Differences

•• Set pointsSet points

Behavioral Biology of Women — 2007

Are these women Are these women

dysfunctional?dysfunctional?

What is What is

Reproductive Reproductive

Ecology?Ecology?

Female Ovarian FunctionFemale Ovarian Function

•• Female ovarian function is an adaptive Female ovarian function is an adaptive

response to the probability of successful response to the probability of successful

reproductive outcome.reproductive outcome.

Female Ovarian FunctionFemale Ovarian Function

•• Variation in female ovarian function is an Variation in female ovarian function is an

adaptive response to the probability of adaptive response to the probability of

successful reproductive outcome.successful reproductive outcome.

•• Designed by natural selection to enhance Designed by natural selection to enhance

reproductive success by avoiding reproductive success by avoiding

reproduction when there is a diminished reproduction when there is a diminished

probability of success.probability of success.

The Continuum of Ovarian FunctionThe Continuum of Ovarian Function

Ovarian

Function

Ecological

Behavioral

Constitutional

“Stress”

Fully Competent Cycles

Follicular Phase Suppression

Luteal Phase Suppression

Ovulatory Failure

Oligomenorrhea

Amenorrhea

+

Ellison, 1990

—

—

+

22

A Few Terms...A Few Terms...

•• Fecundity:Fecundity: The capacity to bear offspring.The capacity to bear offspring.

•• Fecundability:Fecundability: The monthly probability of The monthly probability of

conception. conception.

•• Fertility:Fertility: Successful reproductionSuccessful reproduction

How do we measure hormones?How do we measure hormones?

P

R

O

G

E

S

T

E

R

O

N

E

RadioimmunoassayRadioimmunoassay

Enzyme Enzyme

ImmunoassayImmunoassay

Rosalyn Yalow

Yalow & Berson 1959Nutrition

Boston

Lese

Effects of Moderate Weight Loss

(Lager & Ellison, 1990)

Lower Luteal

Progesterone with

weight loss

33

Weight Loss & ProgesteroneWeight Loss & Progesterone

•• Women losing weight Women losing weight

had lower had lower

progesterone levels progesterone levels

than controlsthan controls




had lower had lower


than controlsthan controls

•• Small levels of weight Small levels of weight

loss can lead to luteal loss can lead to luteal

suppressionsuppression




had lower progesterone had lower progesterone

levels than controlslevels than controls

•• Small levels of weight Small levels of weight

loss (1.9 loss (1.9 kg/mthkg/mth) can ) can

lead to luteal lead to luteal

suppressionsuppression

•• Significant effect in Significant effect in

postpost--weight loss cycleweight loss cycle


(Ellison, et al., 1989)

Lese HorticulturalistsLese Horticulturalists

•• Lower levels of progesterone than Lower levels of progesterone than

Boston controls Boston controls —— correlated with correlated with

lower nutritional statuslower nutritional status


44


•• Lower levels of progesterone than Lower levels of progesterone than

Boston controls Boston controls —— correlated with correlated with

lower nutritional statuslower nutritional status

•• Progesterone levels in Lese Progesterone levels in Lese

ovulatory cycles higher than ovulatory cycles higher than

““averageaverage”” Lese cycles, but Lese cycles, but

lower than Boston controlslower than Boston controls


Workload/ExerciseWorkload/Exercise

!Kung

San

PolandBoston

(Ellison & Lager, 1986)

Lower Luteal

Progesterone with

Running

(Ellison & Lager, 1986)

Lower Progesterone

with Running

Boston RunnersBoston Runners

•• Recreational runners Recreational runners


levels than nonlevels than non--runnersrunners

55

What about Women with Heavy Workloads?

Workload in !Kung San Workload in !Kung San

•• Lactation alone cannot Lactation alone cannot

account for long birth account for long birth

spacingspacing

Workload in !Kung San Workload in !Kung San

•• Lactation alone cannot Lactation alone cannot

account for long birth account for long birth

spacingspacing

•• Heavy workloads of Heavy workloads of

!Kung San women in !Kung San women in

addition to lactation and addition to lactation and

nutritional factors nutritional factors

contribute to long intercontribute to long inter--

birth intervalsbirth intervals

Does heavy work alone suppress ovarian function?

66

Jasienska & Ellison

Workload without Workload without

Nutritional StressNutritional Stress

•• WomenWomen’’s energy s energy

balance and weight balance and weight

didndidn’’t changet change

•• Lower progesterone Lower progesterone

levels of women with levels of women with

high workloadshigh workloads

Jasienska & Ellison

Energy Balance

Nepal

Orangutans in

Borneo

Boston

Energy BalanceEnergy Balance

The net difference between The net difference between

energy intake and energy energy intake and energy

expenditureexpenditure

Effect of Seasonal Differences in Energy Balance among the

Tamang of NepalNepalese Women Nepalese Women -- Seasonal StressSeasonal Stress

•• Decreased progesterone Decreased progesterone

levels during monsoon levels during monsoon

for women who lost for women who lost

weight (.5 kg decrease)weight (.5 kg decrease)

(Panter-Brick, et al., 1993)

77


Women who LOST weight


Women who GAINED weight

Nepalese Women Nepalese Women -- Seasonal StressSeasonal Stress

•• Decreased progesterone Decreased progesterone

levels during monsoon levels during monsoon

for women who lost for women who lost

weight (.5 kg decrease)weight (.5 kg decrease)

•• Women who gained Women who gained

weight showed no weight showed no

decreasedecrease

•• Thus, changes in energy Thus, changes in energy

balance were most balance were most

importantimportant(Panter-Brick, et al., 1993)

Exercise with Weight Loss vs. Exercise with Weight Loss vs.

Weight MaintenanceWeight Maintenance

•• Women ran 4Women ran 4--10 10

miles/daymiles/day

•• 3 1/2 hours of 3 1/2 hours of

sports/daysports/day

•• Nutritional intake Nutritional intake

regulated so one group regulated so one group

would lose weight and would lose weight and

the other group would the other group would

maintain maintain

Exercise with Weight Loss and Exercise with Weight Loss and


(Bullen, et al. 1985)

0

10

20

30

40

50

60

70

80

Delayed Menses Loss of LH surge

Weight Maintenance Group Weight Loss Group

Exercise with Weight Loss Exercise with Weight Loss

and Weight Maintenanceand Weight Maintenance

•• Lower Lower

hormonal hormonal

functioning functioning

in women in in women in

negative negative

energy energy

balance.balance.


0

10

20

30

40

50

60

70

80

90

Irregular

Cycles

Delayed

Menses

Loss of LH

surge

Weight Maintenance Weight Loss

88

Does thisDoes this Phenomenon apply to Apes?Phenomenon apply to Apes?

•• Mast fruiting Mast fruiting

= great = great

fluctuations fluctuations

in fruit in fruit

availabilityavailability

Mean Energy Balance Mean Energy Balance

(Kcal(Kcal’’s)s)

Mean Energy Balance (Kcal)

-5000

-2500

2500

5000

7500

10000

0

Nov 94

Dec 94

Jan 95

Feb 95

Mar 95

Apr 95

May 95

Jun 95

Jul 95

Aug 95

Sep

95

Oct 95

Nov 95

Males

Females

Fat StorageFat Storage

99

Estrone Conjugates during Estrone Conjugates during

High and Low Fruit High and Low Fruit

AvailabilityAvailability

Pg Estrone Conjugate/M

g Creatinine

0

5000

10000

15000

20000

25000

30000

High Fruit Availability Low Fruit Availability

n=25 n=14

What can we What can we

learn from apes?learn from apes?

•• Ovarian function is also Ovarian function is also

affected by changing affected by changing

nutritional status and nutritional status and

energetic statusenergetic status

What can we What can we

learn from apes?learn from apes?

•• Ovarian function is also Ovarian function is also

affected by changing affected by changing

nutritional status and nutritional status and

energetic statusenergetic status

•• This was probably an This was probably an

important mechanism important mechanism

during human evolutionduring human evolution

Energy FluxEnergy Flux

The fluctuation between calories The fluctuation between calories

taken in and calories expended.taken in and calories expended.

Age EffectsAge Effects

1010


•• 1818--23 year old 23 year old

controls had lower controls had lower

progesterone progesterone

levels than 25levels than 25--35 35

year old controlsyear old controls


•• 1818--23 year old controls 23 year old controls


levels than 25levels than 25--35 year 35 year

old controlsold controls

•• Older runners had Older runners had


equal to younger nonequal to younger non--

runnersrunners

Is the same age pattern shown crossIs the same age pattern shown cross--culturally? culturally?


1111


•• Age pattern of greatest # of Age pattern of greatest # of

ovulatory ovulatory cycles between 25cycles between 25--

35 yrs. same in Boston and 35 yrs. same in Boston and

LeseLese



•• Age pattern of greatest # of Age pattern of greatest # of

ovulatory ovulatory cycles between 25cycles between 25--35 35

yrs. same in Boston and Leseyrs. same in Boston and Lese

•• Percent of cycles Percent of cycles ovulatory ovulatory

lower in all age groups in lower in all age groups in

Lese women compared to Lese women compared to

BostonBoston


How doHow do Differences in Hormonal LevelsDifferences in Hormonal Levels Develop? Develop?

Apter & Vihko study of Finnish Girls

Years until 50% Cycles are Years until 50% Cycles are

OvulatoryOvulatory

(Apter & Vihko, 1983, 1990)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

<12 Years 12.0-12.9 Years 13.0> Years

Age at Menarche

Progesterone/Estradiol LevelsProgesterone/Estradiol Levels

(Apter & Vihko, 1983, 1990)

051015202530354045

<12 Years 12.0-12.9

Years

13.0> Years

Cycles with Adequate Luteal Progesterone

Estradiol Levels (100 nmol/liter)

Age at

Menarche

Do absolute hormonal levels Do absolute hormonal levels

make a difference? make a difference?

•• Higher levels of estradiol and progesterone Higher levels of estradiol and progesterone

are associated with an increased probability are associated with an increased probability

of conceptionof conception

YES!YES!

1212

Lipson & Ellison

Higher

Progesterone

in Conception

Cycles

Are HigherAre Higher Hormonal Levels Hormonal Levels ““BetterBetter””? ?

NO!

YES!

Are there crossAre there cross--cultural cultural

differences in hormonal levels? differences in hormonal levels?

Differences in Differences in

Lifetime Exposure Lifetime Exposure

to Ovarian to Ovarian

HormonesHormones

Age at Menarche

Age at First pregnancy

Number of Pregnancies

Time spent Lactating

Number of Menstrual Cycles

17 yrs

18 yrs

6

10 yrs

10-20

12 yrs

26 yrs

2

3 mth

300

1313

Implications of crossImplications of cross--cultural cultural

differencesdifferences

•• Exercise and nutrition affect the probability of Exercise and nutrition affect the probability of

conceptionconception





•• Women in industrialized societies have higher Women in industrialized societies have higher

levels of ovarian hormones levels of ovarian hormones ---- may be may be

responsible for increased risk of reproductive responsible for increased risk of reproductive

cancerscancers





•• Women in industrialized societies have higher Women in industrialized societies have higher

levels of ovarian hormones levels of ovarian hormones ---- may be may be

responsible for increased risk of reproductive responsible for increased risk of reproductive

cancerscancers

•• Hormonal levels from women in industrialized Hormonal levels from women in industrialized

countries may not provide an accurate countries may not provide an accurate ““normnorm””

for women in other countries.for women in other countries.

Do differences in hormonal Do differences in hormonal

levels cause differences in levels cause differences in

conception rates crossconception rates cross--

culturally?culturally?

Between PopulationsBetween Populations

•• Higher hormonal levels Higher hormonal levels maymay be associated be associated

with increased probability of conceptionwith increased probability of conception

•• Women may have different setWomen may have different set--pointspoints

and/or

1414

Hormonal SetHormonal Set--PointsPoints

•• Hormonal characteristics at menarche are carried Hormonal characteristics at menarche are carried

later in lifelater in life

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

<12 Years 12.0-12.9 Years 13.0> Years


•• Hormonal characteristics at menarche are Hormonal characteristics at menarche are

carried later in lifecarried later in life

•• The conditions of development affect the The conditions of development affect the

hormonal trajectoryhormonal trajectory


•• Hormonal characteristics at menarche are Hormonal characteristics at menarche are

carried later in lifecarried later in life

•• The conditions of development affect the The conditions of development affect the

hormonal trajectoryhormonal trajectory

•• The absolute level of hormones needed to The absolute level of hormones needed to

ovulate may differ between populationsovulate may differ between populations

Energy Balance HypothesisEnergy Balance Hypothesis

•• Menstrual taboos almost always involve a Menstrual taboos almost always involve a

decrease in womendecrease in women’’s workloads workload

Adaptive/Evolutionary Hypotheses

Knott

Sample of Behavioral Changes during MenstruationSample of Behavioral Changes during Menstruation

????Less strenuous Less strenuous

laborslabors

NoneNoneRungusRungus

NoNoCannotCannot cook cook

for familyfor familyCanCan’’t draw t draw

water or prepare water or prepare

foodfood

CanCan’’t enter t enter

family family

compoundcompound

DogonDogon

NoNoCannot Cannot

cook, cook,

prepare prepare

food,food,

Cannot gather Cannot gather

water or water or

firewoodfirewood

Cannot touch Cannot touch

weapons or weapons or

huntinghunting geargear

YurokYurok

NoNoCannot bake Cannot bake

breadbread

Cannot fastCannot fastCannot perform Cannot perform

religious ritualsreligious ritualsTurkeyTurkey

??Cannot cook Cannot cook

for menfor men

Cannot work in Cannot work in

field, chopfield, chop woodwood

Cannot touch Cannot touch

another another

womanwoman’’s fires fire

BengBeng

Intercourse?Intercourse?CookingCookingEnergyEnergyTaboosTaboos

Menstrual TaboosMenstrual Taboos

Rungus Rungus of Borneoof Borneo

•• No No ‘‘taboostaboos’’

•• But But …… performs less performs less

strenuous tasks.strenuous tasks.

1515

Menstrual TaboosMenstrual Taboos

Beng Beng of Ivory Coastof Ivory CoastEarly European Menstrual HutEarly European Menstrual Hut

Menstrual Taboos in NepalMenstrual Taboos in Nepal

What happens physiologically What happens physiologically

when you decrease your energy when you decrease your energy

expenditure?expenditure?


•• Menstrual taboos almost always involve a Menstrual taboos almost always involve a

decrease in womendecrease in women’’s workloads workload


Knott

•• Decrease in activity levels and workload have a Decrease in activity levels and workload have a

positive effect on the probability of conception!positive effect on the probability of conception!

Exercise with Weight Loss and Exercise with Weight Loss and


•• Lower hormonal functioning in women in negative energy balance.Lower hormonal functioning in women in negative energy balance.


0

10

20

30

40

50

60

70

80

90

Irregular

Cycles

Delayed

Menses

Loss of LH

surge

Weight Maintenance Weight Loss

1616

What happens if cycling women What happens if cycling women

spend one week a month resting spend one week a month resting

versus working?versus working?

Increased Probability of Increased Probability of Conception inConception in Next Cycle!Next Cycle!


•• Menstrual taboos almost always (or always) Menstrual taboos almost always (or always)

involve a decrease in womeninvolve a decrease in women’’s workloads workload


Knott

•• Decrease in activity levels and Decrease in activity levels and

workload have a positive effect on the workload have a positive effect on the

probability of conceptionprobability of conception

•• Thus, these practices may ultimately Thus, these practices may ultimately

increase the probability of conception increase the probability of conception

by decreasing energy expenditure and by decreasing energy expenditure and

thus may serve an thus may serve an adapative adapative functionfunction

Menstrual Menstrual

TaboosTaboos

Explanations of Menstrual TaboosExplanations of Menstrual Taboos

•• AntiAnti--Cuckoldry HypothesisCuckoldry Hypothesis

•• Energy Balance HypothesisEnergy Balance Hypothesis

•• Menotoxins Menotoxins -- bacterial contaminants bacterial contaminants

•• Hunting Hunting -- menstrual odor interferencemenstrual odor interference

Functional Hypotheses

•• Castration AnxietyCastration Anxiety

•• Male DominanceMale Dominance

•• Dilemma of WifeDilemma of Wife’’s Fecunditys Fecundity

•• Social ControlSocial Control

•• Inducement to huntInducement to hunt

Cultural/Psychological Hypotheses


Next Time...Next Time...

•• Male Reproductive Male Reproductive

BiologyBiology

•• Male Puberty Male Puberty

RitualsRituals

•• Testosterone and Testosterone and

BehaviorBehavior

•• Male Reproductive Male Reproductive

EcologyEcology

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