Blood Sacrifices Existed Since Adam, Before the Law was Given - Quick & Clear Bible Study

There are some prophecies that have more Long before the law was given to Israel, blood sacrifices were being offered to God. Is there any significance for this happening?

Verses used in this study:
Genesis 3:7,21
Genesis 4:3,4
Genesis 8:20
Genesis 12:7,8
Exodus 20:22-26
Hebrews 10:10-18
John 6:47