Scientists Uncover The Ancient Love Triangle That Made You

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In 2008, the discovery of a pinky bone added a new, mysterious character into the history of humanity. A decade later, the same cave has yielded another revolutionizing find: a hybrid between two of our closest, most recent ancestors.

This means that humans, Neanderthals and the recently-discovered Denisovans all interbred with each other in a 10,000-year-long orgy, creating the face of humanity we know today.

A reconstruction of the Neanderthal “Old Man.” (From the Neanderthal Museum, Mettmann, Germany)

The Denisova cave in the Altai Mountains of Siberia straddles the border between Russia and Kazakhstan. Ten years ago, a Russian scientist found a fragment of a pinky bone which, after extensive genetic analysis, turned out to belong to a species we had never before found. They named it the “Denisovan.”

The European “Flat-head”

Since the early 1800s, Europeans had been finding fragments of what looked like deformed, ancient human skulls. In 1856, the first complete such skull was found by miners in the Neander Valley. Bewildered by the find, Prussian schoolteacher Johann Fuhlrott left his job and rode across the country to deliver the bones to professor Hermann Schaalffhausen. Together, they determined the find was no human “flat-head” as the papers had reported– it was a new species entirely. They named it the “Neanderthal.”

For centuries, the Neanderthal was disparaged and painted as an ape-like brute with little relation to man. Guided by Church doctrine and racism, European scientists refused to admit they had anything in common with such a “primitive being.”

A 20th century depiction of the “savage” Neanderthal. (By Kupka, Illustrated London News (ILN), Feb 27th, 1909)

Then, in 2001, the human genome, the entire three-billion-letter code that forms you and me, was first sequenced. Pieces of Neanderthal DNA were similarly sequenced a decade later. They revealed a startling discovery: Europeans, Asians, and Native Americans all carry 1-3% of Neanderthal DNA.

The finding forced us to re-examine our hubris and acknowledge Neanderthals as our closest cousins. In fact, traits such as light skin and hair or a more specific immune system were likely inherited from Neanderthals and preserved for generations because they helped the ancestors of today’s Europeans survive the cold.

The case seemed closed. Neanderthals were our brothers, and when we invaded Europe some 30,000 years ago, we interbred, outcompeted, and maybe even murdered them. It was the Biblical story of Cain and Abel come true.

A Third Biblical Brother?

Yet as scientists sequenced the genomes of different people from around the world, they found genes in Melanesians and Tibetans that were neither Neanderthal nor human. The mystery cracked open when the 41,000- year-old pinky from the Denisova cave yielded a microscopic fragment of DNA.

Humans and Neanderthals were not alone. A third member had claimed their place in our tight-knit family. Although no Denisovan fossils have been found outside this tiny cave, somehow, they left their genetic legacy on people thousands of miles to the south. For instance, the genes that allow Tibetans to cope with high altitude living likely came from these mysterious cousins of ours. In fact, as much as 5% of Melanesian DNA is Denisovan in origin. How did the genes get so far? And why did Denisovans leave no traces of their existence outside of one lonely cave?

Buddhist Nuns in Tirdam, Tibet, China

The Pinky and the Toe

Now, according to a recent publication in Nature Communications, we may have a clue. A fragment of a toe bone, found four years after the original pinky bone (what’s with Denisovans and digits?), has been revealed to belong to a first-generation hybrid between a Denisovan father and a Neanderthal mother. The mother was actually a Western Neanderthal from Europe, who somehow found her way into the Denisovan cave in Siberia thousands of miles to the east.

Despite having such disparate parents, this hybrid girl survived into her teenage years, proving to scientists that Neanderthal-Denisovan hybrids were viable and maybe even common.

Since the first ancient DNA sequencing, it has been painfully obvious that humans had interbred with, and perhaps even raped, Neanderthals during the conquest of Europe. Now we know that we weren’t the only ones. Numerous different “proto-human” lineages, some still waiting to be discovered, may have interbred with us, and with one another, in hundreds of interactions over thousands of years.

Although Denisovan fossils have been confined to their small cave, Neanderthals had a long and wide range, even making their way to Asia (Asians actually have more Neanderthal DNA than Europeans). The recent finding suggests that in this ancient, millenia-long orgy, some Neanderthal hybrids may have carried Denisovan genes across the continent, where they eventually made their way into the Southeast Asian gene pool, and have stayed there ever since.

Another vector for Denisovan genes may have been a fourth possible suitor, Homo Erectus, with whom human migrants into Asia could have likewise interbred. The details of the archaic love triangle (or quadrangle or pentagon!) remain a mystery.

Sharing Genes and Futures

There’s still much to learn about our sexual travails from the Pleistocene. But what we do know is that our past is far less straightforward, and far more diverse, than we ever thought.

The fact that our “simple-minded” ancestors had no qualms about starting families with foreign, bizarre-looking species forces us to question how we treat fellow members of our own species. The Denisovans may have been few in number, but they have left their mark on billions of descendants, thousands of years later. The genes we share with one another today will determine the face of humanity tomorrow.

A pinky or toe, and an ancient case of love or lust, is all it takes to rewrite human history.

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