“Elders” existed before the giving of the law at Sinai, and if they are not simply heads of Families then they are the products of social/cultural impotence, political bondage, and the slave mentality acquired in Egypt.
1. Exodus 3:16
2. Exodus 12:21; 2 Chronicles 19:8
3. Exodus 5:6,14; Numbers 11:16
Patriarchs as "Elders"
In the New Testament, the "elder" is usually considered an exclusively "ecclesiastical" office. In the Old Testament it is usually considered a "civil" office. In both testaments they are either a temporary, pedagogical appointed office, or they are the natural patriarchal heads. (Of course there is no such thing as "natural"; a Godly patriarch is a gift of God's grace.) The goal is the unification of "civil" and "ecclesiastical" functions in the family, if they are legitimate functions at all.