Chicken or the Egg, which one came first?

According to the hypothesis I first published in 2018, egg laying in species is due to consuming the big chunks of food and gestation is due to chewing the food into small pieces. Present day mammals chew the food into small pieces before consuming it. Whereas, birds and reptiles consume big chunks of food. Ancestor to birds and reptiles was still a mammal. They started shortening their gestation period when they started consuming big chunks of food instead of chewing it into small pieces. Slowly, they evolved into egg laying when the gestation period became one day. Based on the hypothesis presented in the following article, my answer to the question is that the ancestor to chicken existed first before it evolved into egg laying. Therefor the final answer to the question is chicken. I hope this settles the long running discussion about this question.
Article: Adaptation of gestation or egg-laying in species depends on the amount of internal heat generated in digesting the food
peerj.com/preprints/27460/