Evidence of the earliest humans, living more than 1 million years ago in western Europe, has been revealed in the journal Nature today.
Part of a human lower jawbone, including several teeth, were found along with stone tools and animal bones at the Atapuerca site, Sima del Elefante, in northern Spain.
Eudald Carbonell, of the Universitat Rovira i Virgili in Tarragona in Spain, and his team, dated the human fossil remains to between 1.1 and 1.2 million years old, making them the oldest in western Europe so far.
Finding out when the first humans began living in Europe has been tricky in the past. Scientists have debated this for many years and there has been much controversy.
Early Homo erectus fossils are known from Dmanisi in Georgia and are dated to about 1.7 million years ago. 'The oldest European fossils, from the Gran Dolina site at Atapuerca in Spain, and from Ceprano in Italy, are only about half that age,' says Professor Chris Stringer, human origins expert at the Natural History Museum.
'There are sites in Spain, France and Italy which appear to have stone tools dated as far back as 1.5 million years, but these have no associated human fossils, and some workers have expressed doubts about the reliability of the dating.'
This new find is significant because the human remains were found together with tools and animal bones and they show signs of human activity such as hammering and cut marks. This means the evidence for human occupation is stronger.
The team used a combination of 3 different techniques to date the fossils. One was called palaeomagnetism, which analyses past changes in the Earth's magnetic field. Biostratigraphy (using non-human fossils) enabled an estimate of the age relative to other sites. And cosmogenic nuclides, a relatively new method, was used to measure the radioactive decay of quartz isotopes in sediments.
'Together, these provide firmer evidence of antiquity than some of the potentially older archaeological sites,' Stringer adds.
Scientists analysed the fossil jawbone and compared it with other known specimens.
'The jaw bone is small, perhaps from a female,' says Stringer, 'and on the outside surface it mainly shows features found in earlier fossils of Homo erectus and even Homo habilis. But on the internal surface, it is quite lightly built - an advanced feature found in later humans.'
Evidence suggests that modern humans or Homo sapiens evolved in Africa around 200,000 years ago and migrated out about 50-70,000 years ago. As well as remaining in Africa, they spread throughout the world to become the human species we know today.
However, there were much earlier migrations out of Africa of more ancient human relatives, such as Homo erectus.
Stringer adds 'However the specimen is classified, when combined with the emerging archaeological evidence, it suggests that southern Europe began to be colonised from western Asia not long after humans had emerged from Africa - something which many of us would have doubted even 5 years ago.'
The authors of the study think the new jaw fragment may have belonged to Homo antecessor, or Pioneer Man, (originally named in 1997 for the Atapuerca Gran Dolina fossils). 'However, the equivalent jaw area is not preserved in those specimens,' Stringer adds, 'so some doubt must attach to this classification.'
'Equally, until more material has been discovered (and hopefully more finds of this age will now follow from Atapuerca and elsewhere), I am cautious about inferring that this new find indicates that Homo antecessor originated in western Europe out a founding population like those known from Dmanisi,' Stringer concludes.