I know that when hubs were used there was the possibility of collisions whenever two devices would transmit data at the same time. However on that time I believe that communication was done in Half-Duplex mode rather than Full Duplex like today.
Hypothetical Question: Suppose that Full-Duplex communication would have become really popular before the invention of Ethernet Switches. Would Switches have been so necessary in that case. Would it have been possible that switches would have been delayed because they would not be needed AS MUCH as they were because the communication between Network Interface Cards would have been already Full-Duplex and collision would have been already rarer?