4000 years ago, Britain and Central Europe supplied copper and tin to Denmark, which has no metal sources of its own. Finished metal objects were imported and recast to fit local needs.
     2000-1700 BCE marks the earliest Nordic Bronze Age, when the availability of tin and copper in Scandinavia increased dramatically. The geographic origins of the metals in Scandinavian mixed-metal artifacts reveal a dependency on British and continental European trading sources during the beginnings of the Nordic Bronze Age.
     Isotope and trace  - element analyses on 210 Bronze Age artifact samples collected in Denmark and representing almost half of all known existing Danish metal objects from this period reveal imports of both raw metals and crafted objects into Scandinavia by two major maritime routes: one across the Baltic Sea from what is now eastern Germany and Bohemia, and another from the British Isles. Isotopic signatures and high tin contents with relatively pure copper in many of the British-style axes contrasts with an unexpected predominance of Slovakian copper.
     The analyses reveal metal recycling was common: smiths repeatedly hacked up imported and local metal objects to recast them for new local products. Metal mixing in this early period is distinct from the alloying of copper with tin to create high-quality bronze, though researchers also found evidence of rather pure copper from the eastern Alps beginning to be used this early. This characteristic copper would become crucial to Scandinavian smiths during the later Bronze Age.
     The results provide new evidence distinguishing the earliest Bronze Age period in Scandinavia from both the previous Neolithic period, and the later "breakthrough" period of the Nordic Bronze Age characterized by highly-sophisticated bronzework.  

Edited from EurekAlert! (24 July 2019)