If There’s No Adam, Why Did Jesus Have to Die

This week’s question is an oldie but goodie: “If we take away the idea of having an actual historical Adam and an actual fall, hence taking away the idea of original sin, then what is the purpose of Jesus coming and dying on the cross?”
And what do you know? I wrote a whole book on that! The Evolution of Adam: peteenns.com/shop/the-evolution-of-adam/