The egg came before the chicken.

The egg was laid by a red jungle fowl

DNA evidence suggests that it was red jungle fowl interbred by humans with grey jungle fowl in south east Asia about 8000 years ago

But red junglefowl is the maternal ancestor

(Making this Plurk because I don’t want to derail the DR Plurk further)

Dinosaurs also laid eggs

Indeed

And some of those dinosaurs were the theropod ancestors of chickens

eggs predate chickens by a considerable margin