雄性美麗的廢物：生存無益

Sexual dimorphism

• a) Male, with mane b) Female

Sexual dimorphism

• The large, male California sea lion, is distinctive from the surrounding, smaller females.

Secondary sexual characteristics生殖表現有利

• This male kudu, a resident of Africa, sports spiraled horns which are part of its social display during the reproductive season.

Red winged blackbird

• This male red winged blackbird illustrates the colorful shoulder feathers, which are displayed during courtship and territorial defense.

Peacock • The peacock has a luxuriant tail and bright

body used to attract the attentions of the female, the peahen.

For what?

Sexual Selection 性擇• 性的二態性的形成由於動物物種內部的繁殖競爭引起的，競爭越激烈，二態性越明顯

配偶制不同與子代數之差異

雄性與交配對象的數量有關

Male-Male competition

雄性競爭內涵

- Female’s reproductive

potential

- Sperm Competition

雄性位階的確立是需名副其實

人類為例：具吸引的女人

→ 生殖潛能高

強暴：不正常的交配行為

一夫多妻的精子型態較長代表意味？

雄性暴力演化意義？

Why?

精神異常‧偶發事件

Hypothesis

(a) Density – dependence （ X ）

(b) Food （ X ）

(c) Quality for offspring （ X ）

(d) Fitness for male （ O ）

Question?

For female: why do not defend?

Female Reproductive Strategy

• Females produce large, energetically

expensive eggs

• Females often provide parental care

• Females increase reproductive success by

increasing the quality of their mates

Female Choice

• Good man or Good gene?

Choosy Females

• Female choice can dictate rules of male

competition and shape male behavior

• Selects for males that appeal to females

• Male sage grouse display in leks

• Male hangingflies offer nuptial gifts

有無好禮物的重要性

數字代表生殖成功對數Longer is better?

子代數也較多

Handicap Principle

“Look me! I am special!

I have good genes and I am strong!”

Sexy Sons Hypothesis

“Like mother like daughter.”

長尾巴偶然機會有較佳的存活他的子代也較強女兒學媽媽喜歡長尾巴兒子則為性感小生人見人愛

有選擇才知好僅一隻公的交配成功次數 9/41多隻公的交配成功次數 30/41

Male

female

Male Contests

• Females of some species cluster in groups

• Males of such species may fight one

another for access to harems

• Selects for large males that can defeat

other males in contests

高階的母猴喜歡生女兒；低階的則多生兒子WHY？ Fitness of Female

Why we need parental care?

Parental Care

• (a) The female parent defends and saves her three offspring, but she dies in the effort. Nevertheless, because half of her genotype is carried in the offspring (F1), a total of 1and1/2 of her genotype survives. (b) No parental defense and the female survives, but all offspring (F1) perish, leaving a total of only one (1) of her genotype surviving (the same applies to males).

有媽媽照顧的好處

Parenting Behavior

• Enhancing the survival of offspring can

increase parents’ reproductive success

• Parental behavior comes at a cost; drains

time and effort that could be spent

producing additional offspring

親子矛盾演化意義

小孩的天真可愛其演化的意義

Human Nature

Sociobiology 社會生物學http://www.ylib.com/author/wilson/books.htm