When looking at daggers from the early copper age to the iron age, I noticed that some of them have midribs and others don't. Was there a reason for them to have them or were they mainly of astetical nature?
Early daggers from each age are weaker because of the new material is being explored. The properties of the new material at that time weren't fully known. So what do you do if you are working with a material you aren't sure of if it will be strong enough? You add structural elements that will make the object, the midribs on the daggers in this case, stronger. Later on when the properties were fully known of the material, the structural elements are in some cases left out and in others kept as a decorative element.