Which came first, the egg or the chicken? A group of scientists have put forward a new theory to resolve this age-old question.
Before adulthood brought us concerns like taxes, electricity bills, and life plans, our biggest worries included what to have for dinner, our next playdate, or the classic conundrum of whether the chicken or the egg came first.
Researchers from the UK’s University of Bristol’s School of Earth Sciences aimed to settle this debate once and for all.
There are different camps in this debate. Some believe that eggs came first, laid by dinosaur ancestors of modern chickens. Others think a chicken appeared first and then laid an egg.
In their study, published in Nature Ecology & Evolution, scientists examined 51 fossil species and 29 living species. They categorized these species into two groups: oviparous (egg-laying) and viviparous (giving birth to live young).
Their findings revealed that the early reptilian ancestors of chickens were viviparous, meaning they gave birth to live young rather than laying eggs.
Both the Bristol and Nanjing University teams noted that the evolution of animals laying hard-shelled eggs was a significant innovation, but this research offers new insights.
The research suggests that extended embryo retention (where the mother keeps the young inside before birth) provided better protection for these ancient animals. Essentially, live birth was safer than laying eggs.
Professor Michael Benton from the University of Bristol elaborated: “Before the amniotes, the first tetrapods to evolve limbs from fishy fins were broadly amphibious in habits.”
“They had to live in or near water to feed and breed, as in modern amphibians such as frogs and salamanders.”
“When the amniotes came on the scene 320 million years ago, they were able to break away from the water by evolving waterproof skin and other ways to control water loss. But the amniotic egg was the key.”
He added: “Our work, and that of many others in recent years, has consigned the classic ‘reptile egg’ model of the textbooks to the wastebasket.”
Project leader Professor Baoyu Jiang stated: “This standard view has been challenged. Biologists had noticed many lizards and snakes display flexible reproductive strategy across oviparity and viviparity.”
“Sometimes, closely related species show both behaviors, and it turns out that live-bearing lizards can flip back to laying eggs much more easily than had been assumed.”
So, the debate might finally be cracked—or at least chipped—with this new theory suggesting the chicken may have come first.
What do you think?