Chicken or egg - what came first? Science may finally have the answer

The revelation comes from the study of a single-celled organism called Chromosphaera perkinsii, an Ichthyosporean microbe that has existed for over a billion years.

In Short

• It resembles the early stages of animal embryonic development
• This could also be a case of convergent evolution
• At times similar traits evolve independently in different organisms

In a new discovery, scientists have found evidence that could answer the age-old puzzle of what came first - chicken or egg?

The new results suggest that the ability to form embryo-like structures may have predated the emergence of animals themselves.

This revelation comes from the study of a single-celled organism called Chromosphaera perkinsii, an Ichthyosporean microbe that has existed for over a billion years.

A team led by biochemist Marine Olivetta from the University of Geneva observed that C. perkinsii reproduces in a manner strikingly similar to animal embryonic development.

As biochemist Omaya Dudin of the Swiss Federal Institute of Technology explains, "Although C. perkinsii is a unicellular species, this behavior shows that multicellular coordination and differentiation processes are already present in the species, well before the first animals appeared on Earth."

The researchers discovered that C. perkinsii undergoes a process called palintomy, which closely resembles the early stages of animal embryonic development.

Following this division, the organism forms a cluster of cells reminiscent of a blastula, a hollow ball of cells characteristic of early animal embryos. Remarkably, at least two distinct cell types were identified within this colony.

This finding is particularly significant because Ichthyosporeans diverged from the animal lineage over a billion years ago.

The similarities between C. perkinsii's reproductive process and animal embryonic development suggest that the genetic programming for embryo formation may have existed long before the evolution of complex multicellular organisms.

However, scientists caution that this could also be a case of convergent evolution, where similar traits evolve independently in different organisms. The unique development observed in C. perkinsii has not been seen in other Ichthyosporeans, making it difficult to determine whether this is an ancestral trait or a result of parallel evolution.

Regardless of its origins, this discovery opens new avenues for understanding the evolutionary mechanisms that led to the emergence of animal multicellularity.

As the researchers note, further studies on C. perkinsii could provide crucial insights into the genetic toolkit available to early life forms and the evolutionary path that ultimately led to the diverse animal kingdom we see today.

This groundbreaking research, published in Nature, not only sheds light on the origins of animal life but also demonstrates the remarkable complexity and versatility of even the simplest life forms on our planet.