How do we know that all humanity sinned in Adam?

In Romans 5:19, the Apostle Paul clarifies that 'by one man's disobedience many were made sinners.' This verse illustrates the concept of federal headship, where Adam acted as the representative for all humanity. When he sinned, his guilt and the resulting spiritual death were imputed to all of us. This theological understanding emphasizes that, because of Adam's fall, every person born thereafter is born into this state of sin and spiritual death, needing redemption through Jesus Christ.