PEOPLING

The Omo Fossils Grow Older

~233,000 years ago or more

Palaeolithic · Middle Stone Age · MIS 7

Two partial skeletons found in 1967 near the Omo River, in southern Ethiopia, are the oldest fossils that almost everyone accepts as fully Homo sapiens. Their age has been argued over for half a century: argon dating of volcanic layers first placed them near 196,000 years, and a 2022 study matched the ash just above the bones to a dated eruption of Shala volcano, pushing their minimum age to about 233,000 years.

Why it matters

Every date in this deep past leans on a volcano. The Omo people cannot be dated directly; what can be dated is the ash that buried their world, and identifying which eruption produced that ash moved our species' oldest accepted fossils by nearly forty thousand years. It is a reminder that the timeline of human origins is still being redrawn, layer by layer.

Dating & uncertaintyDisputed

Two readings of the same rocks. Argon dating of the Kibish tuffs first placed the Omo I skeleton near 196,000 years, a result later defended by tephra correlations across Ethiopia. In 2022, a geochemical match between the ash bed overlying the fossils and a dated eruption of Shala volcano moved the minimum age to 233,000 +/- 22,000 years. The fossils are older than that ash; how much older is unknown.

Sources

1. McDougall et al. (2005), Nature · Stratigraphic placement and age of modern humans from Kibish, Ethiopiadoi:10.1038/nature03258
2. Vidal et al. (2022), Nature · Age of the oldest known Homo sapiens from eastern Africadoi:10.1038/s41586-021-04275-8
3. Brown et al. (2012), Journal of Human Evolution · Correlation of the KHS Tuff of the Kibish Formation to volcanic ash layers at other sites, and the age of early Homo sapiens (Omo I and Omo II)doi:10.1016/j.jhevol.2012.05.014

Our species’ history as one day

06:14:5117 h 45 min before midnight

if the 315,000 years of Homo sapiens were compressed into a single day