Omo Kibish is a rock formation and archaeological site on the Omo River in Ethiopia. Sites in the area have produced some of the earliest examples of hominin remains and stone tools. Early evidence of fire use is also found at Omo.
One of the most intriguing discoveries at Omo Kibish is the collection of modern Homo sapiens fossils, including two almost complete crania. The finds were made by a team led by Richard Leakey, and based on modern classification, they are the oldest known modern human remains.
The original dating techniques applied to the fossils suggested they were older than 125ka (thousand years) old. However, recent reanalysis has been conducted on some volcanic ash (known as ‘tuff’) at the site, and has shed new light on the fossils.
By studying the chemical composition of the ash, namely the different proportions of potassium and argon, scientists have established a rough date of around 195ka ago, making them the earliest known Homo sapiens
This puts the date for the development of modern humans somewhere around 200ka ago, but this is debatable. Firstly, H. sapiens fossils are very rare in Africa until much more recently, and so we are basing this date on very little concrete fossil evidence. Secondly, the anatomical features of Omo Kibish aren’t entirely ‘modern’.
The fossils are relatively large for a start, larger than those of today’s human population, and Omo II has other rather ‘archaic’ features. This should be compared to the fossils of Jebel Irhoud, from Morocco. They are dated to around 170ka ago (so younger than Omo I and II), yet are not classed as ‘modern H. sapiens’.
In fact, all over Africa, hominin fossils from 600ka onwards seem to show a mosaic of modern and archaic traits, with only an overall trend to what we recognise as modern. This reminds us that evolution is not a process with an end-goal: lots of small, mobile populations adapted and developed differently to different environments, and arriving at Homo sapiens was a consequence, not an aim.
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