Why is the doctrine of the virgin birth based on the fact that the fetus's blood comes from the father?
The virgin birth doctrine rests on the physiological fact that a fetus's blood comes only from the father, not the mother. Since Jesus had no human father, He did not receive human blood but divine, untainted, incorruptible blood, enabling Him to be sinless and making the virgin birth essential to salvation.
Les teaches that the basis of the virgin birth doctrine is the physiological fact that the mother's blood never enters the fetus; the fetus's whole blood system comes only from the Father. Had Mary's blood interchanged with Jesus while He was in the womb, His blood would not have been divine, untainted, and incorruptible. Because Jesus did not have a human father, He did not have human blood but divine blood. Les also says this is basic to salvation, and he cites cattle-breeding experiments showing that the mother's blood never enters the calf.