Geology and the First Europeans
In my first post, I mentioned the connective power of Earth Science — its ability to combine surprisingly varied strands of enquiry. Well quite obligingly, this month brought another prime example. A longstanding gap in human history has just been filled — using limestone.
Twelve years ago, pieces of a fossilised skull were unearthed in a Turkish quarry, near Kocabaş, 300 miles south of Istanbul. They were soon identified as the remains of a Homo erectus — a prehistoric ancestor of modern humans. The Kocabaş Hominid— as it became known — was the only such specimen ever found in Turkey, and for archaeologists, its discovery was long overdue.
A persistent mystery in early human history is the question of how Europe was first colonised. Archaeological finds in Spain suggest that this move started around 1.4m years ago (Homo sapiens — the baby of the hominid world — only emerged around 200,000 years ago). The ancestors of these first Europeans had, of course, come from Africa — walked from Africa no less. But the path they had taken between the continents was unclear.
Turkey's location at the gates of Europe had always made it a likely migration route, via the Middle East. But the Turkish fossil record was frustratingly sparse, making this theory impossible to verify. The discovery of the Kocabaş Hominid in 2002 clearly had the potential to change that — but to understand its significance to the human story, the fossil had to be dated.
Dating an ancestor
The breakthrough was announced in the March 2014 edition of Earth and Planetary Science Letters. In an attempt to determine the age of the Kocabaş Hominid, a diverse team of researchers — led by Anne-Elisabeth Lebatard, of Aix-Marseille University — turned their attention to the rock in which it had been preserved (it was travertine, since you ask — a type of limestone deposited by freshwater springs).
Previous attempts to date the rock had been inconclusive; one estimate said it was a million years old; another half that. To pin down the true age, Lebard and colleagues used a rigorous new approach, combining geochemical (radiometric) and geomagnetic dating techniques.
Their analysis was long and laborious, and if you're in the mood to wade through it follow the reference at the bottom. But it boiled down to an age: the rocks, and therefore also the skull inside them, were revealed to be between 1.1 and 1.3 million years old.
The Road to Europe?
Those four numbers could change human history. They show that Homo erectus was living in Turkey at very nearly the same time that Europe was first being colonised — perhaps as little as 100,000 years (a geological eye-blink) before humans first reached Spain.
The geological analysis had revealed that the first Turks had been close chronologically, as well as geographically, to the first Europeans: the strongest evidence yet that the latter had originally reached Europe through Turkey.
The limestone which had preserved the ancient skull had also been the key to placing it in history: an image, frozen in rock, of an otherwise lost step in the history of humanity.
Dating the Homo erectus bearing travertine from Kocabaş (Denizli, Turkey) at at least 1.1Ma. A.E. Lebatard et al. (2014) Earth and Planetary Science Letters 390