From CNN:
It’s a question that has baffled scientists, academics and pub bores through the ages: What came first, the chicken or the egg?
Now a team made up of a geneticist, philosopher and chicken farmer claim to have found an answer. It was the egg.
Put simply, the reason is down to the fact that genetic material does not change during an animal’s life.
Therefore the first bird that evolved into what we would call a chicken, probably in prehistoric times, must have first existed as an embryo inside an egg.
Professor John Brookfield, a specialist in evolutionary genetics at the University of Nottingham, told the UK Press Association the pecking order was clear.
More here.