Existence is eternal. No beginning. No end.
When I first thought about this question I realized that it is a matter of what we call a “chicken-egg” -
- Chicken-egg = egg laid by a chicken — chicken came first
- Chicken-egg = egg that bares a chicken — egg came first.
The question is - what caused the chicken to become a chicken instead of whatever it had been - and did that happen within the egg?