Many landforms, such as mountains or rivers were uncrossable to early civilizations, so they stayed where they were, away from other groups
In order for early civilizations to develope they needed a good source of water. With water they could irrigate their crops and improve travel. If they did not have a solid source of water to develop farming early civilizations like the Egyptians(Nile River), Mesopotamians (Tigrus and Euphrates Rivers), or Indus river civilizations would not have survived.
the geography of Greece made more independent communities (city states) which helped foster participation in political affairs which gave them their own laws and military power.
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Obviously not or we would not be referring to them as "early" civilisations.
Greece was not centered around a river valley.
Greece's physical geography had several effects on its early civilization. It is very rugged and mountainous which made it difficult to travel overland. People in different areas formed societies which developed in different ways leading to several independent city-states. As a consequence of the difficulty of travel, Greeks developed into very competent sailors and traders who traveled around the Mediterranean Sea.
Because of its geography
Isolation from other early civilizations
Physical geography and fear of the unknown.
Mesopotamia was in an area that was harsh and unpredictable. There was floods
they were separate from all other cultures and developed a equine one themselves
Small and Independent.
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Separate city-states developed
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The Achaeans.