SCHEMA:
CREATE TABLE table_23537091_1 (early_chalcolithic VARCHAR, ubaid_period_in_mesopotamia VARCHAR)
User Question:
When the second intermediate period of egypt is the  ubaid period in mesopotamia how many early calcolithics are there?


SELECT COUNT(early_chalcolithic) FROM table_23537091_1 WHERE ubaid_period_in_mesopotamia = "Second Intermediate Period of Egypt"