Jesus or the Messiah was the ultimate "repurchaser", so to speak. With his blood buying back mankind from sin. No amount of goat, sheep, pigeon, or ram's blood would equal a human. There ya go.
Besides, Jesus was not saddled with sin. Why? No human sperm. Remember, it's because of a man sin entered into the world, not because of a woman.
(Even though Adam's lady part Eve was complicit in the whole lying-thievery episode.)
Also, there's no just the act of Adam. It's everyone that came in history through his, well, boyz. His unborn progeny. Paul? rattled on about Abraham giving (when giving Melchezideck a tenth of everything he had) while the Levites gave too because they were considered to be inside Abraham at the time. That line of thinking pretty much covers everyone.