Gen 30:3-5
3 Rachel said, "Here's my maid Bilhah. Sleep with her. Let her substitute for me so I can have a child through her and build a family." 4 So she gave him her maid Bilhah for a wife and Jacob slept with her. 5 Bilhah became pregnant and gave Jacob a son.

Just like with Abraham, humans decided to do things only based on what they could see and do, we should learn from this.