Why are humans the animals with the weirdest sex lives?

Mark wiens


Outlier sex, monogamy, menopause, menopause... These seemingly perverse behaviors may be the reason why humans have risen to the top of the food chain and dominate the planet.

In Sexual Interest Revealed, Jared Diamond uses his research into the history of human sexuality to explain how it evolved into the way it is today, and to help us understand our unique sexuality.

You're no stranger to Diamond, the author of such books as "Breakdown" and "The World Before Yesterday". How does the world's most famous scholar talk about sex?

1. Humans have the weirdest sex lives of any animal, Diamond says

If your dog could talk and you asked her what she thought about human sex life, her answer would surprise you: "You humans are weird, having sex whenever you want, even when you know you can't get pregnant. And even weirder, why can't you mate openly in front of your own kind, like us dogs, and have babies behind closed doors!"

It's true that we humans behave differently from other animals, and by the standards of the 30 million other animals in the world, it's an anomaly. Even if we narrow it down from 30 million to 4,300 mammal species, human sexual behavior is still pretty unusual.

For example, whether lions, wolves, or chimpanzees, they mate in front of each other. In addition, they do not pair up or care for their offspring with their partners. In contrast, in many mammals, adult males and females tend to act alone, gathering together only to mate, and the male's semen is their only contribution to offspring and temporary mates. Otherwise, the male has no value for them.

So would our closest ape relatives always be the same? Not really. The main difference between humans and chimps, besides upright posture and brain size, is sexual behavior. For example, they don't have regular mates, and the males don't care for the young.

We all know that walking upright and having a big brain helped us evolve and become the planet's dominant species. So what's the use of our weird behavior? What about the evolutionary perspective?

2. Monogamy in human society is designed to protect the next generation

While every parent's situation is different, most dads are involved in parenting. Do you take that for granted? If you look at human conception, the problem is really complicated.

For one thing, both parents have different inputs when it comes to forming a fertilized egg. Although both eggs and sperm contain half the chromosomes needed for offspring, the body uses more resources to make an egg than sperm does. In addition, an egg contains nutrients that an embryo needs to develop, whereas a sperm needs only a tail to swim and enough energy to survive for a few days. We're talking statistics. Human eggs mature a million times the size of sperm.

So women are much more invested in creating a new baby than men. As a result, women are inherently more involved in raising children than men.

Not only that, but evolutionarily speaking, if a male chooses to live with a mate and offspring, he's actually sacrificing a lot of opportunities to get out. From conception to birth, and after birth, the female must devote herself to the care of her baby. The mother has no choice but to escape the physiological effects of pregnancy and the needs of her baby, but the male has no choice but to take advantage of different females and impregnate them. Now, if a human male gives up the chance to mate with another female in order to take care of one offspring, the chance of passing on his genes is greatly reduced!

By this logic, males should not be left to raise their offspring. But then again, all animals have one goal in common: to pass on their genes. In order to achieve this goal, it is also a good way for both parents to raise their children together.

This is the origin of our human society. Men and women paired up to live together, which was more conducive to the survival of women and their children, and thus the monogamy we are familiar with was born.

Passing on the family line promotes monogamy in humans. In addition, the timing and frequency of human sex also promote monogamy.

Most animals mate only at certain times (at conception). In baboons, for example, when females mate, their genitals swell, they become red, and their bodies emit a distinctive odor, all of which signal to the males. Human women, however, are not restricted by pregnancy and can have sex whenever they want.

Why? For the simple reason that human men cannot rely on animal instincts to determine whether a woman is in pregnancy. Therefore, in order to improve the chances of conception, we have to make as many babies as possible in order to target women during this hidden ovulation period.

But that's not a good idea. Why? Because sexual activity takes too much effort, time, and even risks death and injury.

First, sperm production is expensive for males. In an experiment with worms, scientists found that when worms with a genetic mutation produced less sperm, they lived longer. To put it bluntly, men use their lives to produce sperm.

Second, sex would have taken up valuable time that could have been spent searching for food for primitive humans.

Finally, it is easy to relax guard when enjoying sex, which is also the best time for natural enemies or romantic rivals to launch surprise attacks. Therefore, although human's sexual behavior is not as restricted as that of animals, in order to better survive, human beings dare not do as they please.

On the other hand, this seemingly inefficient human behavior has its benefits. For example, women may have evolved hidden ovulation in order to have regular partners, allowing men to stay with their partners and children.

Understandably, it's easier for both parents to raise a child than it is for one person to do it alone. Raising a child is hard work for a single mother even today, let alone in hunter-gatherer prehistoric times.

So, over time, humans became more and more monogamous.

3. Non-evolution of male lactation: Men can breastfeed their babies

Seeing here, I don't know if you will think that the division of labor between men and women should be like this, men find women to eat and give birth to children. It's not. Seahorses, for example, are responsible for raising young, not females, but males.

As we've said, human sexuality and the human body have evolved incredible features, and one of them is breastfeeding.

For many mammals, they can lactate without being pregnant. In fact, constant mechanical stimulation of the nipple can produce milk.

In addition, it has been found that even if a woman adopts a child rather than giving birth herself, she can produce milk if she uses a breast pump every few hours in the month leading up to the adoption. In traditional societies, if a pregnant woman is not well enough to nurse, her mother, the child's maternal grandmother, will do the task for her.

What's even more surprising is that, biologically speaking, men can breastfeed! Under the influence of various hormones, mammalian sex characteristics do not become apparent until puberty. Injections of estrogen and progesterone, two hormones normally released when a woman is pregnant, stimulate breast growth and milk production, not just in women, but also in men.

All of these findings suggest that there was an evolutionary process in which male breastfeeding could have become the norm, but it didn't. Why?

In fact, only 10 percent of mammal species require paternal care, mainly lions, wolves, gibbons, marmoset monkeys, and us humans. Some female friends might think, if the male can also nurse, for the survival of the offspring of these species, isn't there an extra layer of protection?

Not necessarily. Nursing is not the most desirable contribution of a male animal. Take lions, for example, when their cubs are threatened by coyotes or other lions, the most useful place for a male lion is to stand up and scare off the enemy, you can't let a better male lion nursing, still in confinement out of the fight, right? For the same reason that our ancestors did, men should go out and patrol their territory, not sit at home and feed their children.

4. Menopause adds years to a woman's life

In addition to lactation, there is another amazing creation of nature, menopause, which stops women from producing eggs and making them infertile.

Compared to other animals, the menopause in humans is pretty bizarre. Why? Because most animals remain fertile throughout their lives, including human males. Human women, on the other hand, begin to lose fertility dramatically around the age of 40, and within 10 years they almost completely lose it.

If natural selection is meant to screen out a species' genes and improve their chances of survival, why would there be genes that keep females from producing offspring? Isn't that a contradiction?

In fact, menopause also has its reason for existence. If there is any difference between us and apes, the main one is menopause. Even apes cared for in zoos rarely live past the age of 60. And humans may be outliving them thanks to menopause, which helps keep us healthy.

What's going on here? Our bodies and organs, just like our cars, need maintenance and repair, and car maintenance costs money, and body maintenance also requires resources, so when we get older, we use the energy we use to produce children to repair our bodies, thus extending the lifespan of our bodies.

In effect, the relationship between fertility and health is an indicator of longevity and varies from species to species. For example, female mice can give birth to five pups every two months from the time they are a few months old, whether they recover or not. Do you know why mice are so rampant?

A mouse gives birth to five babies every other month, so if two of those five mice are female, they give birth to five babies every two months, just think of the goose bumps, that's an exponential increase in reproduction! However, the creator is a little fair, mice born more, life is very short.

Even lab mice with relatively good living conditions live only about two years, the study found. By contrast, living to 100 is not a far-fetched dream. Because for species like mice, reproduction is really more important than good health, because they can die so easily, and they have to hurry to reproduce before they die.

Therefore, human women have menopause, is completely the creator's love, effectively regulate fertility loss and life period. In addition, menopause can reduce health risks for women and their potential offspring. Because maternal mortality rates and rates of fetal malformations increase as women age, simply put, the older a woman is, the higher her risk of having children, and the higher the rate of malformed fetuses.

In addition, if women have fewer children, they have more time and energy to raise children and even grandchildren, which increases the survival rate of offspring.

Menopause played a very important role in human society, especially prehistoric society, because of its ability to extend human life span. For example, in 3300 BC, before the creation of writing in Mesopotamia, old people were encyclopedias of valuable information and life experiences. With the help of menopause, these people live long enough to pass on knowledge from generation to generation.

In short, sex isn't just about procreation or entertainment. It actually involves a variety of behaviors, some of which are determined by genes and others that may come from strange, seemingly anti-evolutionary choices. By studying human sexuality, we can gain a deeper understanding of human evolution and social development.

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