Herto Skulls: Homo sapiens idaltu from Ethiopia's Middle Awash

The Herto skulls are three fossil human crania found in 1997 near the village of Herto Bouri in the Middle Awash valley of Ethiopia. Dated to about 160,000 to 154,000 years ago and announced in 2003, they were named Homo sapiens idaltu and became some of the clearest early evidence that our species arose in Africa. Cut marks and polish on the bones also suggest that these people treated their dead in special ways.

Background: the Middle Awash

The Middle Awash is a stretch of the Awash River valley in the Afar Region of north-eastern Ethiopia. Its layered sediments, interbedded with datable volcanic ash, preserve a record of human evolution spanning more than five million years. Fossils of Ardipithecus, early Homo and later humans have all come from this region.

Since the 1980s the area has been explored by the Middle Awash research project, an international team co-directed by the American palaeoanthropologist Tim White, the Ethiopian palaeontologist Berhane Asfaw and the Ethiopian geologist Giday WoldeGabriel. In the late 1990s the team was surveying sediments of the Herto Member of the Bouri Formation, near the settlement of Herto Bouri.

The 1997 discoveries

In November 1997 team members spotted fragments of human skulls eroding from the surface. Careful collection and sieving produced three crania, catalogued with the prefix BOU-VP-16:

• BOU-VP-16/1, an adult, probably male, with a nearly complete braincase and much of the face. Its brain volume has been estimated at about 1,450 cubic centimetres, within the range of living people.
• BOU-VP-16/2, a second adult, more fragmentary.
• BOU-VP-16/5, a child aged about six or seven years, whose skull had shattered into more than 200 pieces and had to be painstakingly reassembled.

Fragments of other individuals were also found. Cleaning and reconstruction took several years, and the finds were published in June 2003, in two papers in the journal Nature.

Dating and the name idaltu

Argon-argon dating of volcanic layers above and below the fossil-bearing sediments gave an age of between about 160,000 and 154,000 years. At the time this made the Herto crania the oldest securely dated fossils of near-modern humans, though older Ethiopian finds from Omo Kibish were later dated to more than 230,000 years.

The adult skull looks broadly modern, with a high braincase and a flat face, but it is very large and robust, with a strong brow and a long, angular back of the skull. Because of this mixture the team named a new subspecies, Homo sapiens idaltu, from an Afar word meaning “elder” or “first born”. The name signalled that the Herto people were members of our species, but slightly more archaic than living humans.

Many researchers have not adopted the subspecies name, arguing that the differences fall within the natural variation of early Homo sapiens. The fossils themselves, however, are universally regarded as important.

Cut marks and treatment of the dead

The most striking feature of the Herto skulls is what happened to them after death. Both the adult and the child crania carry cut marks made by stone tools, showing that flesh and muscle were removed. The marks are not like those produced by butchering animals for food.

The child’s skull is also polished in places, as if it had been handled repeatedly over a long time. The researchers compared this to practices recorded in some recent societies, in which the skulls of relatives are cleaned, kept and handled as part of mourning or ancestor rituals. They cautioned that the exact meaning cannot be known, but the evidence points to deliberate treatment of the dead roughly 160,000 years ago.

Life at Herto

The same layers contain many stone tools and animal bones. The tools include late Acheulean handaxes alongside flakes and points of the kind typical of the Middle Stone Age, showing a period of technological transition. Hippopotamus and bovid (cattle-family) bones bear cut marks, indicating that the Herto people butchered large animals, probably beside a shallow freshwater lake that then occupied the area.

Timeline

• c. 160,000-154,000 years ago: The Herto people live beside a lake in the Middle Awash; their skulls are later buried in lake and river sediments.
• 1997, November: The Middle Awash team finds the skull fragments near Herto Bouri.
• 1997-2003: The crania, including the shattered child’s skull, are cleaned and reconstructed.
• 2003, June: Two papers in Nature describe the fossils and name Homo sapiens idaltu.
• 2005: New dates for Omo Kibish place those Ethiopian fossils earlier than Herto.

Why it matters

The Herto skulls arrived at a key moment, when geneticists had argued that all living people descend from an African population of roughly 200,000 years ago. Well-dated, nearly modern fossils from Ethiopia matched that prediction and helped establish the African origin of Homo sapiens as the mainstream view. Together with the older Omo Kibish fossils and finds such as the Florisbad skull, they show how our species took shape across Africa long before the spread of modern humans to other continents.