The powerful and formidable aurochs finally died out in 1627 due to over-hunting, providing the first recorded case of extinction in the process. Once the largest mammal on the European continent, this massively horned cattle species almost equaled the size of an elephant. But in a bizarre twist, the death of the aurochs didn't quite stick.
During the rise of the Nazi party in the early 20th century, the idea that domesticated animals could be bred back to their wild origins gained traction. The Nazis embraced this theory of de-extinction, using breeding techniques to recreate animals from Germany's ancestral landscape and provide a return to their "pure" origins. The aurochs breeding experiment, one of many programs run by the Nazi Party, paralleled the rise of new technology which promoted German advancement.
The de-extinction experiment continues today, using the research of German brothers Lutz and Heinz Heck. And as scientists attempt to bring back woolly mammoths and other long-gone species, the Nazi program lives on - with mixed results.
Intent on creating a pure race of Germans, Adolf Hitler's ideas didn't stop at human beings. Hitler believed the Nazi Party could re-create the ancient German landscape, complete with long-extinct animals.
Strong and aggressive, Hitler saw the aurochs as the embodiment of his country's power. For him, the resurrection of the aurochs also symbolized Germany's return to its "pure," ancestral roots.
The Heck brothers used a concept called "back breeding" to create their aurochs. Back breeding works opposite to most breeding programs; instead of selecting traits that make an animal more suitable for domestication, back breeding singles out domestic traits and seeks to remove them.
Since domestic cattle - the ancestors of aurochs - were bred for docility, the Heck brothers attempted to undo that quality. The pair used Spanish fighting bulls and Hungarian steppe cattle (among other breeds) for aggression, toughness, and sheer size.
In the end, the resulting cattle appeared similar to aurochs, with huge bodies and long, intimidating horns.
Around the time the Heck brothers began their careers as zoo directors and experimental breeders, scientists in Europe started seeing new genetic possibilities. Mixing lions and tigers together, the liger and tigon arose.
But while many scientists sought to create new breeds of animals, the Heck brothers took the unique route of looking back in time to revive long-lost species.
Though Lutz and Heinz Heck shared similar lives at first, the 1930s saw the two brothers take very different paths. Lutz joined the Nazi Party, making friends with high-ranking members and gaining the favor of Adolf Hitler thanks to his breeding projects.
Heinz, meanwhile, became one of the first people sent to the Dachau concentration camp. A suspected communist already, Heinz also married a Jewish woman. Though eventually released, he reportedly never bought into the Nazi Party's ideas of ethnic and ecological purity the way his brother did.