Some of the earliest human fossils ever discovered could be at least 36,000 years older than previously thought, according to new analysis.
The fossils — known as Omo I and discovered in Ethiopia in the late 1960s — are now believed to be about 233,000 years old, based on a new examination of ash layers from ancient volcanic eruptions, according to the study in the journal Nature.
The Omo I fossils discovered in the lower Omo valley of south-west Ethiopia close to the borders of modern-day Kenya and South Sudan were previously considered about 197,000 years old.
The reassessment of the age of Omo I aligns it more closely with current thinking about the emergence of modern man.
The history of fossils has long been a source of controversy, with disagreements over dating leading to conflicting views of the human story and how Homo sapiens — humans — spread around the world.
Homo sapiens are believed to have emerged around 300,000 years ago in southern and eastern Africa. Homo sapiens differed from previous species, with different skull structures to house large brains.
Researchers from seven countries including the UK, Ethiopia and the US examined the fossils at Omo and Herto, 700 kilometres to the north-west, to reassess their dates as they are considered to have the most distinct characteristics of Homo sapiens among ancient finds.
Early Homo sapiens that date back more than 130,000 years have only been found at eight sites in Africa.
The Omo fossils were at one time believed to be the oldest ever discovered but subsequent finds have been dated to even earlier times.
Fossils at Jebel Irhoud, Morocco, are the oldest ever found at about 300,000 years old. The discovery pointed to Homo sapiens being widespread across Africa at that time as most research points to the species emerging from further south.
Experts believe Africa was where a diverse group of human ancestors gathered and mingled to create Homo sapiens, from where they spread across the globe.
A jawbone discovered in Israel has been dated to 194,000 years ago and some experts believe early humans arrived in Europe about 210,000 years ago.
“Shifting the age of the oldest known Homo sapien fossils in eastern Africa to before around 200,000 years ago is consistent with independent evidence for greater antiquity of the modern human lineage,” said the study.