Science reveals whether the chicken or the egg came first; know more

A recent discovery is about to offer a revealing answer to the long-standing controversy over which came first: the chicken or the egg.

According to a groundbreaking study, the ancient ancestors of reptiles, birds and mammals may have adopted a surprising approach to breeding, giving birth to live young instead of lay eggs.

The discovery is the result of an analysis involving 51 fossil species and 29 living species. For the researchers, they were species that lay eggs, scientifically known as oviparous, and the species that generate live young, viviparous. The research can be seen in the magazine Nature Ecology & Evolution.

According to the study, the discovery of oviparity in a supposedly extinct group of viviparous species is justified under the primitive reproductive mode called Extended Embryo Retention (EER, in the acronym in English).

They suggested that EER was the initial reproduction method, in which mothers retained fetuses for a period, possibly while seeking more favorable conditions for survival.

But who came first?

This new perspective challenges previous understandings of the evolution of reproduction in the ancestors of reptiles, of birds and mammals, providing an intriguing insight into the ancestral reproductive patterns of this lineage.

For science, the primitive tetrapods that developed fins, similar to those of fish, could be considered amphibians due to their habits.

The researchers suggested, among other things, that these creatures should live near rivers so that they could guarantee food and thus also be able to reproduce.

According to Professor Michael Benton of the Bristol School of Earth Sciences, the appearance of amniotes around 320 million years ago gave these ancestors the ability to detach themselves from the water, all due to the development of impermeable skin and other mechanisms to manage to survive away from water.

However, the crucial element was the emergence of the egg amniotic, which acted as a protected environment, allowing the developing reptiles to avoid dehydration in hot climates. The new adaptation provided the amniotes with the opportunity to leave the water and conquer life on land.

This perspective challenges the conventional view, as recent studies have revealed the presence of flexible reproductive strategies in several lizards and snakes.

Species demonstrate the ability to alternate between oviparity, laying eggs, and viviparity, giving birth to live young.

Fossil discoveries provided additional evidence revealing that many of these ancient species were capable of viviparous reproduction – which gave birth to live children -, indicating a gradual transition between the two reproductive methods.

So, for science, these perspectives still remain a mystery, but we are certainly getting closer to a final answer.

For now, as the study indicates, the chicken may have come first, as the first fossils indicate viviparous rather than oviparous reproduction.

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