ELI5 Milk and Eggs - why cows and chickens?

Why did we settle on chicken eggs as our standard eggs? Why not quail eggs, duck eggs or even ostrich eggs? What in evolution made chickens so productive? How did cow’s milk win over goats milk or bison milk? What is the concept of the butter line and why does it matter? ... we explain like I'm five Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: budford12, misanthropeX, greenstrong, acceptablemadness, alexl14, darkalman and cavemanjoe47 To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected]