Nominal sentence is a grammatical feature of some languages that a grammatical correct sentence can have no explicit verb. The implicit verb at least in Arabic is simple present form of 'to be', e.g. in Arabic, "I am happy" becomes "ʾanā saʿīd" (أنا سعيد), literally "I happy".
My question is from evolutionary linguistic point of view, where they come from or what their existence imply. First I was assuming that they were originally verb having sentences and over the time languages having those kind of structures have evolved to make "to be" the default verb for sentences don't have verb (guess that can be the case for English that apparently just recently is making such sentences for shortening news titles?) but then thought what if nonverbal sentences were what language was about initially, and verb and verb having sentences is actually a recent (say 5-10k years?) development and nominal sentences, at least on older languages listed on the Wikipedia page, just indicates that legacy.