Since the Bible clearly tells us how God created man, in Genesis, and Paul tells us we are the children of God by adoption, and John tells us in John 1 that when we believe in Jesus Christ, we have the "right to BECOME the children of God"....we can safely assume this "offspring" in Acts 17 is to be taken figuratively.
Anyone who is adopted--always has a previous F(f)ather. Who was the previous F(f)ather of our spirits--before we are adopted?
Ephesians 4:4-6----King James Version
4 There is one body, and one Spirit, even as ye are called in one hope of your calling;
5 One Lord, one faith, one baptism,
6 One God and Father of all, who is above all, and through all, and in you all.