What Was the First Form of Sex? The Surprising History

Ever wonder how sex started? Not the "birds and bees" talk your parents gave you. We mean how did sexual reproduction begin on Earth?

The answer involves weird ancient fish, tiny cells getting together, and a story going back over a billion years.

This guide explains the history of sex from the very beginning using simple, easy words.

What You'll Learn

This guide explains:

1. When sex first started (way earlier than you think)
2. How living things made babies before sex existed
3. The first animals to actually have sex
4. Why sex evolved
5. How human sex is different
6. Strange sex facts from history

Bottom line: Sex is super old, really weird, and more interesting than school taught you.

Before Sex Existed: Just Copying Yourself

Life Without Partners (3.5-2 Billion Years Ago)

Here's the crazy part: For billions of years, sex didn't exist at all.

How did life make babies?

Living things just copied themselves. No dating. No mating. No partners needed at all.

The process was simple:

• Living thing grows big enough
• Splits in half
• Now there are two identical copies
• Do it again

What this looked like:

• Bacteria divided into exact copies
• Every living thing could make babies alone
• No mixing genes from two parents
• Babies were identical to parent
• Very boring

Daily life for early life:

1. Eat food
2. Don't get eaten
3. Sometimes split in two
4. That's everything

Some smart bacteria learned to swap DNA with neighbors (like trading cards). But their babies were still made alone—no real sex involved.

Learn about how life evolved on Earth.

The Big Change: 1-2 Billion Years Ago

When Living Things Started Mixing Genes

What happened: Around 1-2 billion years ago, a tiny cell invented something new—sex cells.

What changed:

How Sex Works (Simple Version)

The basic idea:

Normal cells:

• Have complete instructions for making a living thing
• Have two copies of every gene
• Can't make babies alone

Sex cells:

1. Only have HALF the instructions
2. Need to join with another sex cell
3. Together they make complete instructions

Why this matters: Instead of copying the same genes over and over, living things could now mix genes from two parents. Like shuffling cards instead of just restacking the same deck.

The First Sexual Living Thing

Name: Bangiomorpha pubescens
Age: Over 1 billion years old
Famous for: Oldest living thing we know had sex

How scientists know it had sex:

The old fossils show three different cell types:

• Copy cells - for cloning itself
• Male cells - for having sex
• Female cells - for having sex

This tiny thing like algae could do both. Feeling lazy? Copy yourself. Want variety? Find a partner. Pretty smart.

When Sex Started: Simple Timeline

The First Real Sex: 385 Million Years Ago

Meet Microbrachius dicki (Yes, That's Really Its Name)

Fast forward to 385 million years ago. For over a billion years after sex evolved, living things were still just bumping into each other or releasing eggs and sperm into water.

Then came a fish with a funny name.

Basic facts:

• Name: Microbrachius dicki
• Size: 8 centimeters (3 inches) long
• Type: Fish with armor
• Special thing: First known intercourse
• Named by: Robert Dick (scientist from the 1800s)

How These Fish Had Sex

What males had:

• Bony L-shaped sex organ called a "clasper"
• Used to put sperm directly into female
• Not very romantic

What females had:

• Small bones
• Locked male organs in place during mating
• Nature's first lock-and-key system

The weird part: Where these organs were located meant these fish had to swim side-by-side to mate.

One scientist said: "These fish looked more like they were square dancing than mating."

So the first animals to have real sex were doing an awkward side-by-side swim-dance. Not exactly sexy.

Learn about how reproduction works today.

Why Did Sex Start?

The Big Question

If copying yourself works fine, why bother with complicated sex?

Problems with sex:

• Takes more energy
• Need to find a mate
• Only give half your genes to babies
• Complicated
• Might not find partner

Sounds like a bad idea, right? So why did it happen?

Good Reasons for Sex

Reason #1: Different Babies

Problem with copying:

• Every baby is identical
• Disease that kills one kills all
• Can't adapt to changes
• Evolution super slow

Good thing about sex:

• Every baby is different
• Some survive diseases
• Variety helps species live
• Evolution happens faster

Reason #2: Fighting Germs and Parasites

The running race:

Imagine running as fast as you can just to stay in the same place. That's what living things do with germs.

How it works:

• Germs learn to attack you
• You need to learn to fight back
• Germs learn new attacks
• You learn new defenses
• Never stops

Why sex helps: Making different babies every time gives better chance some will survive the germs.

Reason #3: Fixing Broken Genes

The backup plan:

When two sets of genes combine:

• If one has a broken gene
• The other might have a working copy
• Works like a backup copy
• Helps keep genes healthy

Bottom line: Sex is hard work but helps species survive better over time.

Human Sex Is Different

What Makes Human Sex Special

Timeline: Humans showed up about 200,000 years ago. Sex was already super old by then. But human sex is different from animal sex.

5 Ways Human Sex Is Different

1. We Can Have Sex Anytime

Most animals:

• Only have sex during "heat" time
• Females only want sex when making babies is possible
• Sex = making babies only

Humans:

• Can have sex any day of year
• Don't need to be making babies
• Sex for fun and feeling close

2. We Can Do It Face-to-Face

What changed: Standing up on two legs changed everything.

Most animals: Only mate from behind

Humans:

• Can mate face-to-face
• Can look in eyes during sex
• Feels more personal
• Makes emotional connection

3. Big Brains, More Pleasure

Human brains focus on:

• Feeling good during sex
• Connecting with partner
• Strong feelings
• Making relationships

Result: Sex became about more than just making babies.

4. Hidden Fertility

Most animals:

• Females show when they can get pregnant
• Males know exactly when to mate

Humans:

• Women don't show obvious signs
• Men can't tell when women can get pregnant
• Maybe helps couples stay together

5. Babies Need Years of Care

Why this matters:

Human babies can't take care of themselves for years, not weeks. This needed:

• Long-term partnerships
• Both parents helping
• Sex to keep couples together
• Complex family groups

Explore sexual wellness information.

Sex Through Human History

How Ideas About Sex Changed

Ancient Times (Before Year 500)

General ideas:

• More open about sex than later times
• Different in different places
• Celebrated fertility
• Prostitution accepted in many places
• Men had more freedom than women

Examples:

• Greeks and Romans pretty open
• Some religions had temple prostitutes
• Some cultures accepted homosexuality
• Women still had fewer rights

Middle Ages (Year 500-1500)

What changed:

Official rules:

• Christianity said sex should wait for marriage
• Sex before marriage was sin
• Must be married for sex

What really happened:

• People still had sex before marriage (especially poor people)
• Prostitution everywhere
• Rich people married for money, not love
• Big gap between rules and reality

1700s-1800s (Victorian Times)

The Big Contradiction:

For rich women:

• Knew nothing about sex
• Wedding night scary
• Lots of layers of clothes
• Separate bedrooms from husband

For poor people:

• Less privacy
• More practical
• More kids
• Less worried about being "proper"

Modern Times (1900s-Now)

Big changes:

1920s-1950s:

• Victorian rules slowly relaxing
• Birth control becoming available
• Women getting more freedom

1960s-1970s:

• Sexual revolution
• Birth control pill common
• Women's rights movement
• Gay rights starting

1980s-Now:

• HIV/AIDS changes things
• Internet gives information
• LGBTQ+ rights expand
• More open talking about sex

Crazy Sex Facts From History

Things That'll Blow Your Mind

1. Old Birth Control Was Insane

Methods people really used:

1. Ancient Egypt: Crocodile poop as birth control
2. Middle Ages: Drinking special water from blacksmiths
3. Victorian times: Cleaning inside with Lysol or bleach (super dangerous!)
4. Ancient Rome: Special plant (worked so well they used it all up)
5. 1800s America: Mercury pills (poisonous!)

2. Rich Couples Had Separate Bedrooms

1700s-1800s wealthy couples:

1. Husband had his bedroom
2. Wife had her bedroom
3. Visited each other for sex
4. Not because they didn't love each other
5. Just considered proper

3. Victorian Wedding Nights Were Scary

The problem:

Many Victorian brides knew absolutely nothing about sex.

What happened:

1. Mothers told them nothing
2. At most said "lie still and think of England"
3. First time was terrifying
4. Some couples never figured it out
5. Husbands often clueless too

4. Prostitution Was Huge

1800s London numbers:

• About 80,000 prostitutes in city
• Average man visited prostitute twice a week
• Seen as "necessary evil"
• While "good" women stayed pure
• Caused big health problems

5. Old Birth Control Methods Still Used

Ancient methods:

Pulling out:

• Used for thousands of years
• Mentioned in old religious texts
• Doesn't work great but widely used

Tracking fertility:

• Ancient people understood women's cycles
• Catholic Church approved this method
• Better than nothing

Plant remedies:

• Plants to prevent or end pregnancy
• Some actually worked
• Many were dangerous or useless

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Common Wrong Ideas About Sex History

The Truth About Old Beliefs

Wrong Idea #1: "Ancient people were more shy about sex than us"

The truth: Many ancient cultures were way more open about sex than Victorian people or even some modern societies. Greeks and Romans were pretty relaxed. The shyness was mostly a Victorian thing that we wrongly think applied to everyone in the past.

Wrong Idea #2: "Everyone only had one partner in the past"

The truth:

While marriage was common, reality included:

• Lots of affairs
• Prostitution everywhere
• Common sex before marriage
• Mistresses accepted
• Rules existed but people broke them

Wrong Idea #3: "Sex was only for making babies"

The truth:

If sex was only for babies:

1. Why did birth control exist?
2. Why was prostitution so common?
3. Why have sex when pregnancy impossible?
4. Why is there so much old pornography?

People always had sex for fun and feeling close.

Wrong Idea #4: "Gay and lesbian people are modern"

The truth:

Same-sex relationships existed throughout history:

• Ancient Greeks accepted it
• Native Americans had "two-spirit" people
• Chinese and Japanese history records it
• Evidence from every culture ever

What changed was being open and legal, not existing.

Wrong Idea #5: "People never talked about sex in old times"

The truth:

They talked about it all the time—just not in public.

Evidence:

• Private letters discuss sex openly
• Doctor books detailed sex
• Pornographic art in every time period
• Dirty songs and jokes popular
• Advice books gave detailed instructions

Frequently Asked Questions

When did sex first start?

Sex started around 1-2 billion years ago when tiny cells developed sex cells that could join with a partner's cells. But actual intercourse didn't happen until about 385 million years ago with ancient fish.

Why did sex evolve?

Sex creates variety by mixing genes from two parents. This helps species adapt to changes and fight diseases. While it takes more energy than copying yourself, it helps species survive better over time.

What was the first animal to have intercourse?

Microbrachius dicki, a small armored fish that lived 385 million years ago. Males had bony organs to put sperm directly into females. It's the oldest known evidence of actual intercourse.

Did Victorian people really have sex with all those clothes on?

Women's underwear in the 1800s was open between the legs, so sex was possible without taking all clothes off. Plus, most married couples had sex in bed at night wearing nightclothes, not their day clothes.

Is human sex different from animals?

Humans are different because we can have sex anytime (not just during fertile times), we can do it face-to-face, and our sex is tied to feelings and bonding. But many animals also have sex for fun and social reasons, not just making babies.

Conclusion

Sex evolved from simple cells joining over a billion years ago into what humans do today. The journey went from tiny organisms mixing genes to awkward fish doing a weird swim-dance to humans who turned sex into something involving pleasure, feelings, and bonding. 

Understanding this history shows that sex has always been varied, important, and always changing—and humans have been finding creative ways to enjoy it our whole existence.

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