What explanation can you give for this difference?

The symbols found on the map below indicate where fossils have been found in the same layer of sediment. each unique symbol represents fossil locations of a particular species.

What service name do you like? 1.schoolbrella 2.schoolplicity 3.studentaxle 4.studiley 5.edulliance 6.savantsnap 7.peaklemon 8.swiftgrasp 9.educaco 10.vistarise 11.iqpursuit 12.studentpivot 13.edgyadvice 14.studenterra

To what is the growth of civilization most clearly traced