Glad they cracked this one

Now, a new theory as to which came first has been suggested by researchers at the University of Bristol’s School of Earth Sciences.

Many argue that the egg came first, laid by a dinosaur ancestor of the chicken while others say that a chicken came from nowhere to lay the first egg.

In a study published in Nature Ecology & Evolution, a team of scientists decided to take 51 fossil species and 29 living species and split them into two categories.

The categories were oviparous (laying hard or soft shelled eggs) and viviparous (giving birth to live young).

The study found that early reptilian ancestors of chickens were viviparous, giving birth to live animals.

Both the team in Bristol and at Nanjing University in China noted that while the laying of hard-shelled eggs has been one of the greatest innovations, it was far safer to give birth to live chickens back then than laying an egg.

Professor Michael Benton, from the University of Bristol, said: “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.

“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 said: “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 behaviours, and it turns out that live-bearing lizards can flip back to laying eggs much more easily than had been assumed.”

So, according to this research, it was the chicken that came first.