Who Came First: The Egg or the Hen? Swiss Scientists Provide an Answer

The question of "Who came first, the egg or the hen?" has puzzled minds for centuries. Now, scientists at the University of Geneva (UNIGE) in Switzerland believe they’ve cracked this age-old mystery. According to their recent research, it’s the egg that holds the historical crown. Their findings offer fascinating insights into the evolution of multicellular life and the genetic mechanisms that long predated modern animals—including the humble hen.

A billion-year-old answer

The key to solving this riddle lies not in birds but in a tiny, ancient organism called Chromosphaera perkinsii. This single-celled life form was discovered in marine sediments near Hawaii in 2017 and has been present on Earth for over a billion years—long before the first animals appeared. The research, led by Omaya Dudin, an assistant professor of biochemistry at the Faculty of Science, investigated Chromosphaera perkinsii's ability to form multicellular structures that resemble early animal embryos.

Their studies suggest that the genetic instructions essential for embryonic development—the complex cellular processes that transform a fertilised egg into a living organism—were present even before animals emerged. This implies that the "genetic toolkit" necessary to form eggs existed well in advance of animals like chickens. In other words, evolution had already devised the means to "create eggs" long before there were any creatures that could lay them.

How Chromosphaera perkinsii sheds light on evolutionary history

The importance of Chromosphaera perkinsii lies in its remarkable ability to create structures that resemble early embryos despite being a single-celled organism. This capability indicates that the early foundations for multicellular life, including the genetic programs for forming eggs, were already present in these ancient life forms. This discovery adds weight to the theory that eggs were an evolutionary milestone, predating the existence of animals like chickens.

Embryonic development, fundamental to animals today, is guided by genes that instruct cells on how to grow, divide, and specialise. The study reveals that this cellular "language" was not a new invention for animals but rather a process that evolved gradually over billions of years, beginning with early organisms like Chromosphaera perkinsii.

The broader implications of this discovery

This research not only gives insight into the egg-versus-chicken debate but also helps explain some of the basic mechanisms behind life on Earth. It shows that some of the essential genetic elements required to build complex life were already present in the ancient genetic code well before animals began to emerge. These genetic instructions served as the groundwork for later evolutionary developments, allowing life to evolve from simple single-celled organisms into the wide variety of multicellular forms we see today.

From an evolutionary perspective, this finding is significant because it underscores how certain traits—like the formation of an egg—are rooted deeply in the history of life on Earth. The emergence of the egg was a fundamental evolutionary step, occurring before any animals or birds, thus supporting the idea that the egg indeed came before the chicken.

Published findings and future prospects

The research, published in the journal Nature, opens doors to further exploration of how genetic programs evolved and were repurposed over millions of years, ultimately leading to complex animal life. With this new understanding, scientists can now look further back into evolutionary history, examining how similar genetic programs might have shaped other critical developments in life’s timeline.

This discovery by Swiss scientists provides a compelling answer to an ancient question with profound implications for our understanding of evolution and the origins of life. For now, it seems the mystery is solved: the egg, in a fundamental sense, came first. Nature had the genetic ingredients ready to make eggs long before there were any chickens around to lay them.