Is the answer to the 'chicken or egg' question now clear?
As an ancient philosophical question, a situation in which cause and effect are circular is called 'Which came first, the chicken or the egg?' Of course, this is just an analogy, but in the world of biology, there has been a long-standing debate about which actually came first. Meanwhile, a research team from the University of Geneva has published a paper arguing that 'it is highly likely that the egg came first.'
A multicellular developmental program in a close animal relative | Nature
The egg or the chicken? An ancient unicellular says egg! - Medias - UNIGE
https://www.unige.ch/medias/en/2024/loeuf-ou-la-poule-un-unicellulaire-ancestral-dit-loeuf
The 'chicken or the egg' question has been a difficult one that has plagued humanity for over 2,000 years, and in 2024, heated debate over the issue led to a murder. As far back as the 4th century BC, philosopher Aristotle argued that 'this problem is an infinite continuation.' In addition, around the 1st century, Greek philosopher Plutarch wrote about it in his book as a philosophical question, saying, 'It is a crucial question as to whether the world had a beginning.'
In the Christian world, it is believed that 'all living things were created by God,' so it was believed that the chicken came first. However, since Darwin proposed the theory of evolution, the scientific world often argues that 'the egg came first' because 'chickens had ancestors that were not chickens.'
A research team from the University of Geneva studied Chromosphaera perkinsii, a single-celled organism discovered in marine sediments around Hawaii in 2017. This organism branched off from the animal evolutionary lineage more than a billion years ago, and it is said that it may hold the answer to the mystery of how single-celled organisms transitioned to multicellular organisms.
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The team reports that once Chromosphaera perkinsii cells reach a maximum size, they stop growing and divide to form multicellular colonies similar to early animal embryonic development. These colonies persist for about a third of their life cycle and are characterized by the presence of at least two distinct cell types.
Below is a picture of Chromosphaera perkinsii forming a multicellular colony. The red part is the cell membrane, and the blue part is the nucleus containing DNA.
'Although Chromosphaera perkinsii is a single-celled organism, this characteristic shows that the process of multicellular coordination and differentiation was already present long before the first animals appeared on Earth,' said Associate Professor Ommaya Dudin of the University of Geneva, who led the research team.
Furthermore, analysis of gene activity revealed that these colonies had intriguing similarities to those observed in animal embryos. This suggests that the principles of embryonic development may have existed before the emergence of animals, or that Chromosphaera perkinsii may have independently evolved the mechanisms for multicellular development. 'The genetic program controlling complex multicellular development may have existed for more than a billion years,' the team argues.
'Our results suggest that nature had the genetic tools to make eggs long before it invented the chicken,' said Marine Olivetta, a researcher at the University of Geneva's Faculty of Science and lead author of the paper. 'We conclude that the answer to the question of which came first, the chicken or the egg, is most likely the egg.'
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