Around 24,500 years ago, the body of a 4-year-old child was wrapped in an ochre-dyed shroud and lowered into a burial pit in the Lapedo Valley of central Portugal. Unlike any whippersnapper alive today, however, this extraordinary child exhibited a unique blend of modern human and Neanderthal features, disproving everything we thought we knew about the history of our species.

Known as the Lapedo Child, the youngster’s complete skeleton was discovered in 1998. Until then, anthropologists had assumed that modern humans evolved in East Africa before spreading across Eurasia and replacing the more archaic hominids that lived there – including Neanderthals.

This narrative supposed that we and our ancient relatives were completely separate species that could not interbreed, and that our expansion resulted in the extinction of our more primitive cousins. The Lapedo Child ripped up this script, prompting the discoverers to propose that modern humans did mate with Neanderthals, and that the genetic code of this extinct species persisted within the hybrid lineage that flowed from the loins of our cross-pollinating ancestors.

Thought to have been a male, the child himself possessed the chin and inner ear of an anatomically modern human, along with the stocky frame and limbs of a Neanderthal. Such a finding initially sent shockwaves through the anthropological world, sparking fierce debate as to what this all meant for human history.

In their original study on the skeleton, the authors note that the child lived several thousand years after Neanderthals had supposedly disappeared, suggesting that these ancestral traits must have been deeply ingrained within the human genome and that the young boy was therefore “the descendant of extensively admixed populations.” In other words, interbreeding between humans and Neanderthals didn’t just happen once or twice, but occurred on a population level, resulting in significant hybridization.

This, in turn, implies that Neanderthals didn’t simply die out when modern humans came along, but repeatedly hooked up with their new neighbours to the extent that they partially merged with them.

At the time of the discovery, this idea was seen as pretty radical and somewhat shocking, prompting some scholars to refute the original findings. One analysis, for instance, concluded that the Lapedo Child was not a hybrid after all but, was just an oddly-shaped modern human sprog.

However, the admixture theory was finally proven in 2010 when researchers sequenced the Neanderthal genome. In doing so, they revealed that all modern non-African populations contain between 1 and 4 percent Neanderthal DNA, thus confirming that our ancient ancestors did interbreed with these extinct hominids.

Thankfully, our phenotypes have straightened out somewhat over the millennia and we no longer possess the Neanderthal physique. However, like the Lapedo Child, those of us who hail from outside of Africa are all modern human-Neanderthal hybrids.