Electrons quite easily move from one place to another. One example was the fear that a moon landing would cause a rush of electrons into or out of the space craft due to potential difference between the moon and the craft. Every time you touch something at a different potential to yourself you either gain or lose some electrons. Are electrons extremely long lived as the creation of electron - positron pairs and the mutual cancellation of electron - positron pairs seem to be quite a rare occurrence. Could you, for instance, say that some of the electrons in your body may have existed in a pile of dinosaur dung?

Yep. The matter/antimatter imbalance appears to have existed for some time, which means that electrons have been around for a while, too.

 

You're also breathing some air breathed in by a T - rex, as well as drinking some of his/her urine whenever you chug a beverage.