A time signature of 4/4 meter does not mean that each measure has only four quarter notes. It means each measure has only four beats. These beats may contain half notes, quarter notes, eighth notes, rests, whatever the composer wants, but all note and rest values must combine to equal no more or less than the top number (or numerator) of the time signature
Latin Music, when first brought into the United States was a fusion of jazz and african music. Most of the time it had spanish lyrics and instruments but an african beat.