If you could un-invent something, what would it be?

I think, as a collective species, we have invented quite a lot of things, and if we see our evolution, then most of these things have been helping in growth as humankind. Of course, each invention has its own pros and cons, but to just look at these invention, they have elevated us. And yes, that includes our mobile phones and all sort of devices that distract us. They have made our life smoother, even though while travelling in Underground, I am sometimes amazed by the number of people staring at their phones (I know they are watching something on it).

However, that one invention, I am sure even the inventor is somewhere in the Universe is wondering why, is plastic. I will not go into the details of it, I am sure one point of time it did help, but we are not in a position to ever say that again..