The Origins of the Middle Finger

We can see the middle finger as a rude gesture as early as 419 BCE that's when erist offenies wrote his play the clouds. You couldn't flip it until about 1968 okay and i'm assuming that's that's to do with the actual hand gesture right because you physically flip your hand over and then the finger comes up correct? The gesture itself is way way i was going to get to this later if we wanted to but i said what the heck we'll do it now  in other cultures it means your older brother because it's taller than the adjacent thingOkay so in Shakespearean times you wouldn't give somebody your middle finger you'd bite your thumb instead of giving them