5 case

The reconstruction of Proto-Indo-European grammar identifies
eight inflected cases:  vocative, nominative, accusative, dative,
genitive, ablative, locative, and instrumental, I believe.
If those are the same eight cases used in some grammars,
then PIE is the likely explanation.

Of course, there are more than 8 functions, IE languages use
a mixture of cases and prepositions to mark such relationships.
Finnish, for example, only appears to have a huge number of
case endings because it happens to use postpositions instead
of prepositions.  There are speculations that PIE cases
might have evolved from some kind of agglutinated
postpositional particles.

Vincent Broman,  code 572 bayside,                                  =   o     
Naval Command Control and Ocean Surveillance Center, RDT&E Div.   =  _ /- _   
San Diego, CA  92152-5000,  USA                                  =  (_)> (_)  
Internet Email: broman@nosc.mil    Fax: +1 619 553 1635   Phone: +1 619 553 1641