Why did Germany declare war on Russia on 1 August 1914?

Due to mobilization of the Russian side, as it was perceived as a threat by Germany

On August 1, Germany declared war on Russia, and on August 3, it declared war on France. On August 4, Britain and its empire entered the war as a result of Germany's violation of Belgian neutrality and British fears of German dominance in Europe. These actions reflect the European powers' fears, anxieties, and ambitions.

2. a land bridge connected asia and north america thousands of years ago.

4. crossing the land bridge would have been simple for the first migrants.

5. people might have crossed a land bridge while hunting animals.