Around 300 million years ago, something magnificent happened: evolution hatched the egg.

Specifically, the shelled egg. Most eggs then, and many still today, were gelatinous and could only survive in water. Like those of frogs or fish.

But the shelled egg that could contain water and nutrients and be viable on land allowed some species to move out of the water and populate the land.

Early shelled eggs were leathery, pliable and soft, like those still found in turtle and crocodile species. These rarely survive in the fossil record.

Later, eggs developed hard shells that preserve somewhat better—though not well, since their calcium compounds dissolve in acidic soils.

Still, enough were preserved for us to know that the first hard-shelled eggs came around 200 million years ago, at first for dinosaurs, then for birds, and more recently on breakfast tables.

That’s because with all their benefits, eggs had a weakness: they’re a nutrient package just waiting for a hungry predator. Some nutritionists call them the perfect food.

So most mammals developed the capacity for live birth to protect offspring longer. Even some reptiles are developing this capacity today.

If all this egg talk has you pondering the old question, Which came first, the chicken or the egg? ... the paleontologist would answer that the chicken-type egg preceded the very first chicken-like bird by 130 million years.