Steel was already in use in parts of Europe 2,900 years ago during the Bronze Age, new research revealed.
Until recently ,it was thought it hadn't been possible to produce suitable quality steel in the Early Iron Age (1200 BC to 550 BC), let alone the latter stages of the Bronze Age (3300 BC to 1200 BC).
But scientists discovered stone stelae - stone slabs with engravings of humans, animals and objects carved onto them - in Portugal could only have been carved using tools made from tempered steel.
The study team analyzed the stone carvings and even conducted experiments with chisels of various materials; out of which only the chisel made of tempered steel was capable of engraving the stone.
This led Dr. Ralph Araque Gonzalez, the lead author of the German study, to conclude that people living in the region during the final years of the Bronze Age were capable of tempering steel.
Up until this latest study, it was considered by most that steel had only become widespread in Europe under the Roman Empire, which began in 625 BC and lasted up until 476 AD.
However, scientists from the Faculty of Humanities at the University of Freiburg, in southwestern Germany, sought to debunk this theory.
Using several methods of analysis, the researchers studied stone stelae from the Iberian Peninsula dating back to 900 BC.
The team first analyzed the stones, found at the Rocha do Vigio archaeological site in southern Portugal, using geochemical analysis techniques - which determine proportions of metallic to non-metallic elements.
These tests asserted that the complex engravings could only have been carved using tempered steel.
They backed this up by studying the metallic microstructure of an iron chisel used during the same time period in the same region, and this chisel was shown to have the necessary carbon content to be proper steel.
Gonzalez's team then decided to run another, physical test by experimenting with different chisels made of various materials on the stone pillars used to make the stelae.
These experiments also found that only the chisel made from tempered steel was capable of engraving the stone and that those made of bronze or iron chisels could not sufficiently work the stone.
Gonzalez concluded that the tempering of steel must have been discovered by indigenous communities living in Iberia.
He said: "The chisel from Rocha do Vigio and the context where it was found show that iron metallurgy including the production and tempering of steel were probably indigenous developments of decentralized small communities in Iberia, and not due to the influence of later colonization processes.
"This also has consequences for the archaeological assessment of iron metallurgy and quartzite sculptures in other regions of the world."
The archaeological records of Iberia in the late Bronze Age are sparse across much of the region.
This is why such remaining stelae, carved with depictions of human figures, animals and various objects are of unique importance for the investigation into the history of the region.
Up until now, studies of the actual rocks from which these stelae were made in order to gain insights into the tools and materials used to make them have been rare.
But the Freiburg University team analysed the geological composition of the stelae in great detail, leading them to the discovery that many of the stelae were not made only from quartzite, as commonly presumed, but often also made from silicate quartz sandstone.
Gonzalez added: "Just like quartzite, this is an extremely hard rock that cannot be worked with bronze or stone tools, but only with tempered steel.
"The people of the Final Bronze Age in Iberia were capable of tempering steel. Otherwise, they would not have been able to work the pillars."
