Final answer:
Oxytocin is the hormone thought to promote bonding in reproductive partners, contributing to various social and reproductive behaviors.
Step-by-step explanation:
The hormone that is thought to promote bonding in reproductive partners is oxytocin. Oxytocin is often referred to as the "love hormone" and is associated with social bonding, sexual reproduction, childbirth, and the period after childbirth. It plays a significant role in behaviors such as maternal bonding, pair bonding, and during intimacy between partners.