A new species of human

The old man of the mountain

The fossil record reveals both a hitherto unsuspected mountain-dwelling hominid and, in this article, how the dinosaurs began

Mar 25th 2010 | From The Economist print edition

MYTH and fantasy populate the world with “othermen”—the elves, goblins, dwarfs and giants that live in the wild wood, in the cave or on the high mountain peak. Not animal, but not quite human either, they feed fear and imagination in equal quantity. Nor are such creatures merely the province of the past and the poetaster. The story of the yeti—the abominable snowman that haunts the Himalaya—has provoked serious investigation by explorers hoping to find not-quite-human humans. Sadly, there is nothing there. But not so long ago there might have been. For a bunch of explorers of a different sort, using DNA sequences instead of hiking boots, have discovered a real otherman from the mountains of Asia.

Svante Paabo, of the Max Planck Institute in Leipzig, was the inspiration for Michael Crichton’s novel “Jurassic Park”. His group extracts and sequences genetic material from fossils, and has produced DNA analyses of both mammoths and Neanderthal man. Their latest object of study is a finger bone found in a cave in the Altai Mountains of southern Siberia (pictured above). The team Dr Paabo assembled to look at this bone, led by Johannes Krause, assumed it was either from an early modern human or a Neanderthal, both of whom once lived in the area. What they found shocked them. It was neither.

The new, as yet unnamed species—the first to be defined solely by its DNA—is unveiled in this week’s Nature. Anatomically, it consists of the distal manual phalanx of the fifth digit or, in layman’s parlance, the tip of the little finger. Even by the standards of palaeontology, one of whose early practitioners, Georges Cuvier, claimed to be able to extrapolate an entire animal from a single bone, declaring a species from evidence this slight would be ambitious. It was not the bone itself, though, but what was in it, that allowed Dr Krause and Dr Paabo to be so confident.

Fingering the truth

From 30 precious milligrams drilled out of the sample they extracted mitochondrial DNA. The mitochondria, a cell’s power packs, are the much-modified descendants of bacteria that took up residence in the ancestors of modern animal and plant cells a billion years ago. As a relic of that ancestry they still have a few genes of their own and, because each cell has thousands of mitochondria, those genes are easier to find in old samples than are genes from the nucleus, of which there is only one per cell.

Using the latest DNA-sequencing technology, Dr Krause and his colleagues worked out the order of the genetic “letters” of over 1m fragments of DNA from their sample. By looking for overlaps between these fragments and fitting the resulting contiguous sequences to reference sequences from humans and Neanderthals the team were able to come up with a DNA sequence for most of the mitochondrion, and it was nothing like one that would have been expected from either a modern human or a Neanderthal.

The rate at which random changes over the generations occur in mitochondrial DNA is fairly well known and, using that knowledge, Dr Krause estimates that the newly discovered species last shared an ancestor with modern humans about 1m years ago. That is extraordinary. It means that its ancestors must have emerged from Africa (where that million-year-old common ancestor would have lived) independently of the migrations which gave rise to Neanderthals and humans.

The common ancestor is, however, too recent for the new species to be a remnant of the first human excursion from Africa, the one that led to Java man and Peking man, now known as Homo erectus. It is, in other words, a fourth example of anthropological tourism from Africa to the rest of the world, on what is now looking like a well-worn route. Yet it is the lone example. That shows how fragmentary and ill-understood human history is.

The finger bone was found in strata dated to between 48,000 and 30,000 years ago (the bone itself has not yet been dated). That means the creature was contemporary with both Neanderthals and modern humans in the area. There was, then, a real ecosystem of othermen in southern Siberia. In 2003 the scientific and popular press were both filled with the discovery of a similar arrangement on the Indonesian island of Flores. A hitherto unsuspected species of dwarf human turned up in caves there, contemporary with modern humans. It was quickly dubbed the “hobbit”. Do not be surprised if, whatever proper name it is eventually assigned, the new, mountain-dwelling, central-Asian species actually becomes known as the yeti.