What Science Once Believed About Sex — And Why It Was Wrong

 

For most of human history, sex was surrounded by mystery — not because people were shy, but because the science simply didn’t exist yet. Long before genetics, microscopes, or hormones were understood, early scientists built theories from what they could observe with the naked eye. Many of those theories were wrong, but each one pushed science toward the truth.This is the story of three major myths about sex that shaped — and mis‑shaped — science for centuries.

Myth #1 — Only humans and animals “choose” mates

For centuries, scientists believed plants were passive, decorative life forms. The idea that they had anything resembling reproduction was considered absurd.

That changed in the 1600s when German botanist Rudolf Jakob Camerarius discovered that plants had male and female organs, and pollen acted like a reproductive cell. His work proved that plants “mate,” just not in a way humans can see.

This discovery transformed biology and eventually led to modern agriculture, crop genetics, and the understanding of plant reproduction.

Myth #2 — Sex is the default way life reproduces

In the 1800s, biologists assumed all complex organisms reproduced sexually. Then August Weismann studied tiny freshwater creatures and found something shocking: some species could reproduce without mating at all.

This process — parthenogenesis — is now known to occur in certain lizards, sharks, and birds. It shattered the idea that sex was universal and revealed that evolution uses multiple strategies depending on environmental pressure.

Myth #3 — Sperm and eggs carry equal “instructions”

Before genetics, many scientists believed the sperm contained a tiny, fully formed human — a “homunculus” — and the egg was just a container. Others believed the opposite: that the egg contained everything and the sperm simply “activated” it.

Both theories were wrong.It wasn’t until the 20th century that researchers discovered sperm and egg each contribute half of the genetic material, and that traits are shaped by DNA inheritance, not miniature humans curled up inside cells.

This breakthrough laid the foundation for modern genetics, IVF, and reproductive medicine.