In a groundbreaking study published by researchers from the University of Cambridge, evidence suggests that the egg came before the chicken. According to the study, eggs evolved more than a billion years ago, whereas chickens have been around for only 10,000 years. This finding supports the idea that all sexually reproducing species make eggs, which includes 99.99 percent of all eukaryotic life—meaning organisms that have cells with a nucleus, so all animals and plants, and everything but the simplest life forms.
The study provides an explanation for this evolutionary timeline, noting that the first eukaryotic cells likely emerged around 1.5 billion years ago, and these early single-celled organisms would have already been reproducing sexually and producing eggs. In contrast, chickens and other avian species evolved much more recently, emerging from theropod dinosaurs around 10,000 years ago.
This research challenges the traditional “which came first” debate, firmly establishing that the egg predates the chicken by an enormous margin. The implications of this discovery extend beyond just the chicken and egg conundrum, as it sheds light on the fundamental origins and evolution of sexual reproduction in complex lifeforms.