Charles Darwin first explained the principles of sexual selection in his controversial book The Descent of Man (1871). Ever since then, people have wanted to tinker with human evolution via artificial sexual selection. Dictators, mad doctors, and crazed social scientists have proposed — and even carried out — human breeding experiments aimed at improving the species. For some definition of "improving." Here are five of the most bizarre and tragic experiments with human evolution from the last century.

The Eugenics Movement
The most famous example of eugenics in action is Adolf Hitler's forced breeding program, in which SS officers systematically impregnated women deemed to be appropriately Aryan. The children, bred in a program called Lebensborn, were supposed to be the beginning of a new master race. Hitler's evolutionary intervention also involved genocides of "undesirables," because while you're building a new race, why not get rid of the supposedly undesirable ones too? The Eugenics movement didn't start with Hitler, though. It had a long, rich history that began in the nineteenth century and was very popular in the United States. Early twentieth-century country fairs in the U.S. often featured eugenics contests at country fairs, with awards going to the most "genetically sound" white families. Below, you can see a group of girls from a 4H club who won in a genetic fitness contest circa 1925. Nicolae Ceausescu's Decree No. 770
In the late 1960s, Romanian dictator Ceausescu decided that the population of his country needed to grow much larger to provide strapping workers for industrial labor. First he tried to reward women who had several babies, but that program didn't work quickly enough. So in 1966, he outlawed abortion. Women were forbidden from using contraception, and underwent fertility checks at work. In 1967, the birth rate in the country doubled. The children born that year were called Decreteii, or children of the decree. Many suffered or died young because they were unwanted or had been born under adverse circumstances.

Chinese 1 Child Per Couple Policy
To cut back on its population, the Chinese government in the early 1980s mandated that each couple may have only one child or suffer penalties. There have been widespread reports of couples choosing to abort or abandon girl children. In some areas of the country, this breeding program has turned homo sapiens into a species whose male population exceeds its female population by 163.5 to 100. Apparently the UN recommends a "normal" ratio is no more than 107 to 100. Clonaid
Clonaid is a company that purports to be engaging in human cloning, specifically to change the human species. They were embroiled in scandal when it was revealed that many Clonaid "scientists" were members of the Raelian cult (or religion, depending on how you feel about it) that believed humans were descended from cloned aliens. Scientists from Clonaid claim to have cloned a human, though they offer no concrete proof. So far, they have had zero impact on human evolution, but get points for trying to achieve evolutionary intervention via publicity.

Fertility Treatments and IVF
Two years ago, 3 million babies had been born world-wide thanks to IVF and other fertility treatments. In a scenario of pure, wild Darwinian sexual selection, none of those babies would have been born. Those 3 million plus babies represent a dramatic shift in human evolution that we are only beginning to understand.

Send an email to Annalee Newitz, the author of this post, at annalee@io9.com.