Why We Have Sex

This helps explain why sex persists as a dominant mechanism for producing offspring.

A fossil called Bangiomorpha pubescens is a multicellular organism that sexually reproduced, the oldest reported occurrence in the fossil record.

The evidence that these fossils sexually reproduced is in the finding that the spores or reproductive cells they generated came in two forms – male and female. Today we know that red algae lack sperm that actively swim. They rely on water currents to transport their reproductive cells, which is likely how they have been doing it for the last 1.2 billion years.

Two members of the same species combine their DNA to produce a new genome.

Some of their offspring will carry a beneficial mix of good genes from both parents, meaning they will respond better to environmental stresses that would leave asexual species in grave danger.

It is a "learning" process – an organism "learns" new information, especially in a changing environment, and the organism passes those lessons on (in its DNA) to the next generation to help them survive.

Darwin suggested that natural selection was not the only evolutionary pressure at work in sex. There was something else going on as well, something Darwin called sexual selection. This is a preference by one sex for certain characteristics in individuals of the other sex.

A study published in 2015 found that it is vital for males to compete for reproduction and females to choose between those competing males.