AWA415 - Why did the Romans completely abandon the spear in favour of the pilum?

Seth tracked Murray down via Facebook Messenger and asked: "Hi Murray, really appreciate your AWA podcast, great short bursts of knowledge. One question that bugs me about legionaries. Why did the Romans completely abandon the spear in favour of the pilum? Does it function effectively as a thrusting weapon as well as a thrown weapon? If you have a space for a two-for, do you have time to talk…