If you indeed mean Adam and Eve, illimey, then you need to look into Sumerian mythology for their origins as well. The Goddess Namu commanded her
son, Enki, and the Goddess Ninhursag to knead the "heart" of clay and give it form, whereupon humans were created. The two immediately had a fight
over the results. Upon resolving their differences, they had children who healed the wounds Enki received during the battle, and the one who healed
Enki's rib was named Ninti. One of Ninki's names/titles is "lady of the rib". The Sumerian mythos contains all the core concepts of Genesis (and
that of other early books of the Old Testament), clearly reworked at a later time to suit a monotheistic perspective.
As to marriage as a means of breeding strong and healthy individuals, one has only to look to the existant (and accounts of those since dispersed)
primal tribal groups. Rites of passage and feats of physical prowess to win a potential mate are in every body of mythology, and even remain in the
fairy tales. I'm not sure how you can miss this.
Arranged marriage is, indeed, a way to ensure the continuity of a culture, social class, and/or wealth. However, there is also the danger of
inbreeding, and the genetic hazards are evident in both the royalty of ancient Egypt and that of Europe. (See
Hemophilia in the European Royal Families for an illustration of the latter.) In modern
times, other societies have also shown the dangers of arranged marriage within a closed system. The Amish are one example, and India has had its
share of problems as well.
Love as a basis for marriage has historically been the perogative of the lower and working classes, though in some cultures all follow the arranged
model. When done by the upper classes, overlooking the convention has led to a great deal of contention and worse, as in the case of Caesar &
Cleopatra and King Edward & Wallis Simpson. In both cases cited, the cause of the problem may be simple xenophobia, but traditionally closed
arranged-marriage systems are not accepting of "outsiders", thereby limiting the gene pool and leading back to the dangers of inbreeding.
Love certainly does have a physiological component, and there is a body of research that would seem to suggest there are many biochemical and
olfactory cues influencing what attracts us to an ideal partner. Some are less a matter of physical compatibility than one would think, as I recently
saw an article that women subconsciously respond to men whose perspiration smells similar to that of their own fathers. To me, this would indicate
attraction to a person who may prove to be a better parent in the caregiving sense, rather than merely the physical.