ISTA | The Snail or the Egg?

Live-bearing has allowed Littorina snails to occupy and adapt to a diverse range of habitats. This has led to the evolution of many ‘ecotypes’ that vary in size, shape, and behavior.
© Fredrik Pleijel
When did eggs evolve? Eggs, in the context of reproduction, have been around for a very long time in the evolutionary history of life. The evolution of eggs is a complex process that occurred over millions of years, and different types of eggs have evolved in different lineages of organisms.An example of the scientific ignorance that underpins creationism is in the boringly repetitive "Gotcha!" question from creationist fools, "Which came first; the chicken of the egg?", as though they believe chickens had ancestors that never laid eggs and the chicken species started with a single individual, which either hatched from an egg or was given birth to.
The earliest evidence of eggs comes from fossils of small, shelled eggs that date back to the Early Cambrian period, around 540 million years ago. These eggs are believed to belong to a group of extinct marine animals. However, it's important to note that these early eggs were likely quite different from the eggs we are familiar with today.
The evolution of eggs in the context of vertebrates, such as birds, reptiles, and mammals, is a more recent development. Amniotic eggs, which have a protective shell and membranes that allow them to be laid on land rather than in water, evolved in the lineage leading to reptiles. This adaptation was crucial for the colonization of terrestrial environments.
Birds, a group of reptiles, are known for their hard-shelled eggs, and their evolutionary history is marked by the development of various features related to flight and parental care. Mammals, on the other hand, have live births or lay eggs with soft shells (monotremes like the platypus and echidna).
In summary, the evolution of eggs is a complex process that spans millions of years and involves various lineages of organisms, with different types of eggs evolving at different times in the history of life.
Of course, creationists believe chickens were created out of dirt by magic without any ancestors, so in their childlike, magical view of things their question makes some sort of sense.
In reality of course, ancestors of chickens laid eggs and egg-laying originated hundreds of millions of years ago at about the time multicellular organisms evolved.
All placental mammals have had live births ever since this evolved in Mammalia about 140 million years ago, but live birth has evolved independently in other classes multiple times. It is frequently found in the Reptilia, for example, and at least one insect, the tsetse fly.
A marine snail, Littorina saxatilis, is known to have transitioned from egg-laying to live young-bearing in the last 10,000 years - a mere blink in the evolutionary time scale. An international team of researchers, led by Dr. Sean Stankowski of the Austrian Institute of Science & Technology (ISTA) have now worked out the 50 genetic changes involved in this , which probably began about 100,000 years ago. Their research is explained in an ISTA news release: