Serial verbs form a more marked means of expressing case relations than do prepositions. It is, therefore, relatively unlikely that a language which already had prepositions to mark case would develop serial verbs […]. On the other hand, it is relatively likely that a language which originally had only serial verbs as a case-marking device would subsequently develop prepositions […].
- Bickerton (1981), a pag.119

Serial verbs are usually interpreted as the result of African substratum influence on creoles, but creolists seldom if ever ask how those West African languages which have serial verbs […] happen to have come by them.
- Bickerton (1981), a pag.120