They represent areas of equal pressure<em /><em /> because they are isobars.
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Answer:
Iron and Bronze Age.
Explanation:
According to the widely accepted Kurgan hypothesis or Steppe theory, the Indo-European language and culture spread in several stages from the Proto-Indo-European Urheimat in the Eurasian Pontic steppes into Western Europe, Central and South Asia, through folk migrations and so-called elite recruitment. The 1st millennium BC was the period of time between from the year 1000 BC to 1 BC.
