The "blood groove"is actually called a fuller and its intent is to give the blade strength while reducing the weight somewhat. No one knows exactly when it was developed, but it was a long,long time ago, like well before the Vikings were ravaging England and Northern Ireland and is quite a technological achievement.Its advantage is evident in the use of swords. There is some debate on whether or not it has value on a hunting knife. I have read arguements on both sides whether or not it actually aids in knife removal.