Why is Sex Fun? - Deepstash

Keep reading for FREE

THE BATTLE OF THE SEXES

  • Most male mammals have no involvement with either their offspring or their offspring’s mother after inseminating her; they are too busy seeking other females to inseminate.
  • We're exceptional animals in that our fathers and mothers often remain together after copulating and are both involved in rearing the resulting child.

145

3.44K reads

External Vs Internal Fertilization

  • If fertilization is external, neither mother nor father is automatically committed to anything further, and both are theoretically free to seek another partner with whom to produce more fertilized embryos.
  • Yes, their just-fertilized embryos may need some care, but mother and father are equally able to try to bluff the other into providing that care.
  • But if fertilization is internal, the female is now pregnant and committed to nourishing the fertilized embryos until birth or laying.
  • If she is a mammal, she is committed for even longer, through the period of lactation.

140

2.17K reads

Uncertainty In Male's Paternity

  • But males of mammals and other internally fertilized animals have no corresponding confidence in their paternity.
  • Yes, the male knows that his sperm went into a female’s body. Sometime later, out of that female’s body, comes a baby. How does the male know whether the female copulated with other males while he wasn’t looking?
  • In the face of this uncertainty, the evolutionary conclusion reached by most male mammals is to walk off the job immediately after copulation, seek more females to impregnate, and leave those females to rear their offspring.

143

1.83K reads

Sex Chromosome

  • Our sex is ultimately laid down by our genes, which in humans are bundled together in each body cell in twenty-three pairs of microscopic packages called chromosomes.
  • One member of each of our twenty-three pairs was acquired from our mother, and the other member from our father.
  • Men, who have a big chromosome (termed an X chromosome) paired with a small one (a Y chromosome).
  • Women instead have two paired X chromosomes.

141

1.63K reads

Bipotential Gonad

  • Many X chromosome genes specify traits unrelated to sex, such as the ability to distinguish red and green colors.
  • However, the Y chromosome contains genes specifying the development of testes.
  • In the fifth week after fertilization human embryos of either sex develop a “bipotential” gonad that can become either a testis or an ovary.
  • If a Y chromosome is present, that bet-hedging gonad begins to commit itself in the seventh week to becoming a testis, but if there’s no Y chromosome, the gonad waits until the thirteenth week to develop as an ovary.

142

1.38K reads

WHY DON’T MEN BREAST-FEED THEIR BABIES?

  • The evolutionary battle of the sexes has resulted in parental care being provided by the mother alone in about 90 percent of all mammal species.. Not only do males of those species have no need to lactate; they also don’t have to bring food, defend a family territory, defend or teach their offspring.
  • Only for those 10 percent of mammal species in which male parental care is necessary does the question of male lactation even deserve consideration.

138

1.36K reads

THE NON-EVOLUTION OF MALE LACTATION

Those minority species include lions, wolves, gibbons, marmosets— and humans. But even in those species requiring male parenting, lactation isn’t necessarily the most valuable form that the father’s contribution can take. What a big lion really must do is to drive off hyenas and other big lions bent on killing his cubs.

139

1.2K reads

Importance Of Breastfeeding

  • Human milk is more dilute in nutrients, sugary, and low in fat.
  • Breast-fed babies acquire stronger immune defenses and are less susceptible to numerous diseases, including diarrhea, ear infections, early-age-onset diabetes, influenza, necrotizing enterocolitis, and SIDS (Sudden Infant Death Syndrome).
  • The helpless condition of human infants makes lots of parental care necessary for many years.

139

1.17K reads

Why do most animals consider sex fun only when the female can be fertilized?

  • There’s a simple reason why most other animals are sensibly stingy about copulatory effort: sex is costly in energy, time, and risk of injury or death.
  • Natural selection favors those individuals whose behavior lets them pass their genes to the most babies.

138

1.28K reads

THE EVOLUTION OF RECREATIONAL SEX

  • For the cavewoman, the male’s departure would expose her eventual child to the likelihood of starvation or murder.
  • What can she do to keep that man? Her brilliant solution: remain sexually receptive even after ovulating! Keep him satisfied by copulating whenever he wants! In that way, he’ll hang around, have no need to look for new sex partners, and will even share his daily hunting bag of meat.
  • Recreational sex is thus supposed to function as the glue holding a human couple together while they cooperate in rearing their helpless baby.

152

1.26K reads

THE ANIMAL WITH THE WEIRDEST SEX LIFE

It arose at a time when our ancestors were still promiscuous or living in harems. At such times, concealed ovulation let the ancestral ape-woman distribute her sexual favors to many males, none of which could swear that he was the father of her child but each of which knew that he might be. As a result, none of those potentially murderous males wanted to harm the ape-woman’s baby, and some may actually have protected or helped feed it.

141

1.17K reads

WHAT ARE MEN GOOD FOR?

  • By the criterion of services offered to mates and children, males of most mammal species are good for nothing except injecting sperm.
  • The males of many territorial animal species, such as songbirds, lions, and chimpanzees, spend much time patrolling their territories.

138

1.2K reads

Advantages Of Show-off

  • The show-offs also gains some advantages apart from adultery, such as prestige in his tribe’s eyes. Others in the tribe want him as a neighbor because of his gifts of meat, and they may reward him with their daughters as mates. For the same reason, the tribe is likely to give favored treatment to the show-off’s children.
  • A woman is best off married to a provider, but a man is not best off being a provider.

139

1.04K reads

  • Parent’s interests may be better served by abandoning one offspring and devoting resources to other offspring, whereas the offspring’s interests may be best served by surviving at the expense of its parents.
  • Natural selection ensures that our body unconsciously maintains and repairs itself.

NATURAL SELECTION

140

960 reads

MAKING MORE BY MAKING LESS - FEMALE MENOPAUSE

  • Menopause - a woman’s egg supply gets depleted or impaired by around the time she is fifty years old. The challenge is to understand why we evolved that seemingly self-defeating detail of reproductive physiology.
  • That one cruel fact underlying human female menopause: the birth of each child immediately jeopardizes a mother’s previous children because of the mother’s risk of death in childbirth.

138

1K reads

THE EVOLUTION OF FEMALE MENOPAUSE

  • Even in affluent, twentieth-century Western societies, the risk of dying in childbirth is seven times higher for a mother over the age of forty than for a twenty-year-old mother.
  • But each new child puts the mother’s life at risk not only because of the immediate risk of death in childbirth but also because of the delayed risk of death related to exhaustion by lactation, carrying a young child.

138

888 reads

Risk Of Accidental Death

  • Animals whose lifestyles carry a high risk of accidental death are evolutionarily programmed to stint on repair and to age rapidly.
  • Turtles, protected in the wild by a shell, are programmed to age more slowly than other reptiles, while porcupines, protected by quills, age more slowly than mammals comparable in size.

141

875 reads

TRUTH IN ADVERTISING

  • We too rely on signals as arbitrary as a widowbird’s tail and a bowerbird’s crest. Our signals include faces, smells, hair color, men’s beards, and women’s breasts.
  • Human females signal reproductive maturity by expansion of the breasts. Later in life, we signal our waning fertility and attainment of wise elder status by the whitening of our hair.

138

834 reads

THE EVOLUTION OF BODY SIGNALS

  • Muscles are a truthful signal of male quality, like a deer’s antlers.
  • One might reason that beauty says nothing about good genes, parenting qualities, or food-gathering skills. However, the face is the part of the body most sensitive to the ravages of age, disease, and injury.
  • Especially in traditional societies, individuals with scarred or misshapen faces may thereby be advertising their proneness to disfiguring infections, inability to take care of themselves, or burden of parasitic worms.

139

846 reads

DISTRIBUTION OF WOMEN'S BODY FAT

  • Our remaining candidate for a truthful signal is women’s body fat.
  • Lactation and child care are a big energy drain on a mother, and lactation tends to fail in an undernourished mother.
  • Hence a woman’s body fat would be a truthful signal to a man that she was capable of rearing his child.
  • Women of all populations tend to accumulate fat in the breasts and hips, to a degree that varies geographically.
  • Men throughout the world tend to be interested in women’s breasts, hips, and buttocks.

142

879 reads

Deceptive Specific Signal

  • Scientists have suggested that large fatty breasts are not only an honest signal of good overall nutrition but also a deceptive specific signal of high milk-producing ability (deceptive because milk is actually secreted by breast glandular tissue rather than by breast fat).
  • Similarly, it has been suggested that fat deposition in the hips of women is also both an honest signal of good health and a deceptive specific signal suggesting a wide birth canal (deceptive because a truly wide birth canal would minimize the risk of birth traumas but mere fat hips would not).

140

815 reads

WHY MEN HAVE LARGE PENIS?

  • The length of the erect penis is only about 1 ¼ inches in gorillas and 1 ½ inches in orangutans but 5 inches in humans, even though males of the two apes have much bigger bodies than men.
  • The size of the penis that we evolved was unfortunately limited by the length of a woman’s vagina.
  • Hence a large penis’s cost should be regarded as a lost-opportunity cost: the energy squandered on one structure comes at the expense of energy potentially available for another structure.

140

965 reads

UNSOLVED EVOLUTIONARY QUESTION

  • Almost anyone would assert that the functions of the penis are to eject urine, inject sperm, and stimulate women physically during intercourse.
  • But the comparative approach teaches us that those functions are accomplished elsewhere in the animal world by a relatively much smaller structure than the one with which we encumber ourselves.
  • Thus, even the most familiar and seemingly most transparent piece of human sexual equipment surprises us with unsolved evolutionary questions.

136

839 reads

"Our greatest distinction as a species is our capacity, unique among animals, to make counter-evolutionary choices."

JARED DIAMOND

142

967 reads

CURATED BY

prince_rahul

"A good idea should be like a girl's skirt; long enough to cover the subject and short enough to create interest."

CURATOR'S NOTE

To us humans, the sex lives of animals seem weird. But it's our own sex lives that are truly bizarre. Stranger yet, we have sex at any time, even during periods of infertility, such as pregnancy or post-menopause. Why does the human female, virtually alone among mammals, go through menopause? Why does the human male stand out as one of the few mammals to stay with the female he impregnates, to help raise the children that he sired? Why is the human penis so unnecessarily large?

More like this

stash-superman-illustration

Explore the World’s

Best Ideas

200,000+ ideas on pretty much any topic. Created by the smartest people around & well-organized so you can explore at will.

An Idea for Everything

Explore the biggest library of insights. And we've infused it with powerful filtering tools so you can easily find what you need.

Knowledge Library

Powerful Saving & Organizational Tools

Save ideas for later reading, for personalized stashes, or for remembering it later.

# Personal Growth

Take Your Ideas

Anywhere

Organize your ideas & listen on the go. And with Pro, there are no limits.

Listen on the go

Just press play and we take care of the words.

Never worry about spotty connections

No Internet access? No problem. Within the mobile app, all your ideas are available, even when offline.

Get Organized with Stashes

Ideas for your next work project? Quotes that inspire you? Put them in the right place so you never lose them.

Join

2 Million Stashers

4.8

5,740 Reviews

App Store

4.7

72,690 Reviews

Google Play

Ashley Anthony

This app is LOADED with RELEVANT, HELPFUL, AND EDUCATIONAL material. It is creatively intellectual, yet minimal enough to not overstimulate and create a learning block. I am exceptionally impressed with this app!

Shankul Varada

Best app ever! You heard it right. This app has helped me get back on my quest to get things done while equipping myself with knowledge everyday.

Sean Green

Great interesting short snippets of informative articles. Highly recommended to anyone who loves information and lacks patience.

samz905

Don’t look further if you love learning new things. A refreshing concept that provides quick ideas for busy thought leaders.

Ghazala Begum

Even five minutes a day will improve your thinking. I've come across new ideas and learnt to improve existing ways to become more motivated, confident and happier.

Giovanna Scalzone

Brilliant. It feels fresh and encouraging. So many interesting pieces of information that are just enough to absorb and apply. So happy I found this.

Jamyson Haug

Great for quick bits of information and interesting ideas around whatever topics you are interested in. Visually, it looks great as well.

Laetitia Berton

I have only been using it for a few days now, but I have found answers to questions I had never consciously formulated, or to problems I face everyday at work or at home. I wish I had found this earlier, highly recommended!

Read & Learn

20x Faster

without
deepstash

with
deepstash

with

deepstash

Access to 200,000+ ideas

Access to the mobile app

Unlimited idea saving & library

Unlimited history

Unlimited listening to ideas

Downloading & offline access

Personalized recommendations

Supercharge your mind with one idea per day

Enter your email and spend 1 minute every day to learn something new.

Email

I agree to receive email updates