Denisovans on the Tibetan Plateau

Excavations at Baishiya Karst Cave on the Tibetan plateau are revealing details about the 

lives of Denisovans, a group of ancient humans about which little is known. Dongju Zhang’s group/Lanzhou University

Denisovans survived and thrived on the high-altitude Tibetan plateau for more than 100,000 years, according to a new study that deepens scientific understanding of the enigmatic ancient humans first identified in 2010.

Researchers analyzed thousands of animal bone fragments unearthed at Baishiya Karst Cave, 3,280 meters above sea level near the city of Xiahe in China’s Gansu province — one of only three places the extinct humans were known to have lived. Their work revealed that Denisovans could hunt, butcher and process a range of different large and small animals, including woolly rhinos, blue sheep, wild yaks, marmots and birds.

The team of archaeologists working at the cave also uncovered a rib bone fragment in a layer of sediment that dates back between 48,000 and 32,000 years, making it the youngest of the handful of known Denisovan fossils — a clue that the species was around more recently than scientists previously thought.          READ MORE...

The Roof of the World

If it wasn't for an extinct relative of modern humans known as the Denisovans, some researchers suspect our own species might never have made their home on the highest and largest plateau in the world.

The Tibetan Plateau, sometimes called the Himalayan Plateau, is nicknamed 'the roof of the world' because it sits, on average, 4,000 meters (13,000 feet) above sea level.

This vast sweep of elevated land, which covers most of Tibet, along with parts of China, India, Pakistan, and several other countries in the region, is usually considered one of the last places that Homo sapiens settled permanently. Studies suggest there have been periods of occupation by various ancestors taking place over the past 160,000 years, but gaps in the record are hard to interpret.

Have there always been people up on the roof of the world, or is each period a resettlement by a new community?

A geneticist and an archaeologist have now suggested another timeline that works just as well with the limited evidence we have on hand.

The researchers incorporated both archaeological and genetic evidence to develop two, contrasting models of occupation: one continuous and one divided up over time. Crucially, the two models can be tested, potentially telling us one day how far back modern populations stretch.

In the discontinuous model, humans visited on and off for tens of thousands of years, until finally staying put around 9,000 years ago.

Alternatively, current evidence could also support permanent colonization that began on the plateau between 30,000 and 40,000 years ago. If so, the long genetic lineage might have passed on some helpful tricks for living up where the air is thin.

According to recent DNA analyses, a single crossbreeding event between Denisovans and H. sapiens in East Asia, no sooner than 46,000 years ago, might have infused our species with the genes they needed to make their home in such a low oxygen environment.  READ MORE...

Unknown Ghost Ancestor

Desinova Cave, Russia

Nobody knows who she was, just that she was different: a teenage girl from over 50,000 years ago of such strange uniqueness she looked to be a 'hybrid' ancestor to modern humans that scientists had never seen before.

Only recently, researchers have uncovered evidence she wasn't alone. In a 2019 study analysing the complex 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.

Up until recently, these occasional sexual partners were thought to include Neanderthals and Denisovans, the latter of which were unknown until 2010.

But in this study, a third ex from long ago was isolated in Eurasian DNA, thanks to deep learning algorithms sifting through a complex mass of ancient and modern human genetic code.

Using a statistical technique called Bayesian inference, the researchers found evidence of what they call a "third introgression" – a 'ghost' archaic population that modern humans interbred with during the African exodus.

"This population is either related to the Neanderthal-Denisova clade or diverged early from the Denisova lineage," the researchers wrote in their paper, meaning that it's possible this third population in humanity's sexual history was possibly a mix themselves of Neanderthals and Denisovans.  READ MORE...