- Inheritance in the heavens: 1 Peter 1:3-4, Hebrews 3:1, Philippians 3:14 
- 144,000 sealed out of every tribe of the sons of Israel. Revelation 7:4
- 144,000 who have been bought from the earth. Revelation 14:3
- Jesus said to his disciples they will judge the 12 tribes of Israel. Luke 22:28-30
- the one who shares in the first resurrection... they will be priests of God and of Christ, and they will reign with him for [the] thousand years." Rev 20:6
Summary: The Bible talks about two inheritances and two different resurrections - one on Earth and one in Heaven. The Bible talks about 144,000 sealed out of every tribe of the sons of Israel and also these 144,000 have been bought from the earth, and these ones will do judging and they will be priest of God and of Christ.
Sorry I could not answer your question any better.

I don't know but if the 144,000 we're bought from the earth, doesn't that explain that this number comes from the humans that lived on the earth?