Nobody knows who she was, just that she was different: A teenage girl from over 50,000 years ago of such odd uniqueness she appeared to be a ‘hybrid’ ancestor to modern humans that scientists hadn’t seen before.

Only recently, researchers have uncovered evidence she wasn’t alone. In a 2019 study analyzing the tangled mess of humanity’s prehistory, scientists used artificial intelligence (AI) to identify an unknown human ancestor species that modern humans encountered – and shared dalliances with – on the long trek out of Africa millennia ago.

“About 80,000 years ago, the so-called Out of Africa occurred, when part of the human population, which already consisted of modern humans, abandoned the African continent and migrated to other continents, giving rise to all the current populations,” explained evolutionary biologist Jaume Bertranpetit from the Universitat Pompeu Fabra in Spain.

As modern humans forged this path into the landmass of Eurasia, they forged some other things too – breeding with ancient and extinct hominids from other species.