...By Alan Peterson for TDPel Media.
The scientific community has successfully identified the first animal to appear on Earth, shedding light on the origins of animal life.
This groundbreaking discovery reveals that a peculiar jellyfish-like creature called a ctenophore, commonly found in modern aquariums, holds the distinction of being the earliest lineage to branch off from the animal tree.
Reconstructing Ancient Ancestors:
For over a century, biologists have been intrigued by the nature of the earliest animals that emerged in the ancient oceans more than half a billion years ago.
Due to the lack of direct fossil records for these soft-bodied animals, understanding their characteristics has been a challenge.
However, through comparisons across living animals and the analysis of DNA strands called chromosomes, scientists have gained valuable insights into our common ancestors.
Ctenophores: First Branch of the Animal Tree:
The international research team discovered that ctenophores, also known as comb jellies, were the first lineage to separate from the animal tree.
These unique creatures can be found across the world’s oceans, ranging from polar regions to the equator and from the ocean surface to the deep sea.
Sponges were the next group to emerge, followed by the evolution of all other animals, including the lineage leading to humans.
The emergence of simple single-celled life forms dates back approximately four billion years.
New Approach to Investigating Origins:
Lead author Dr Darrin Schultz from Vienna University highlighted the development of a novel approach that provides deep insights into the origins of animal life.
By examining the chromosomes of various animals, including ctenophores, sponges, and non-animal organisms, the team uncovered significant evidence regarding the evolutionary timeline and relationships between different species.
Evolutionary Milestones:
While most familiar animals, such as worms, flies, mollusks, sea stars, and vertebrates, including humans, possess common features like a centralized brain, a digestive tract, muscles, and other shared traits, they had already evolved by the time of the “Cambrian Explosion” around 500 million years ago.
On the other hand, jellyfish, sea anemones, sponges, and ctenophores have simpler body plans, lacking a well-defined brain, nervous system, or muscles.
However, they still exhibit key characteristics of animal life and develop multicellular bodies from fertilized eggs.
Ctenophores and Sponges: Different Evolutionary Paths:
Traditionally, sponges were considered the earliest surviving branch of the animal tree due to their primitive features.
They lack a nervous system, muscles, and other advanced characteristics found in more evolved animals.
However, the recent findings challenge this view.
Ctenophores, despite their superficial resemblance to jellyfish, are genetically distinct and represent a separate lineage.
Comparisons of chromosomes revealed significant differences between ctenophores and other animals, indicating that ctenophores branched off earlier in the evolutionary timeline.
Unveiling Ancient Chromosome Evolution:
To understand the genetic relationships between various organisms, the research team sequenced the genomes of comb jellies, sponges, and other single-celled organisms.
Through a comparative analysis, they discovered that ctenophores and non-animal organisms shared specific gene-chromosome combinations, while sponges and other animals exhibited different rearrangements in their chromosomes.
This evidence further supported the notion that ctenophores branched off before significant genetic rearrangements occurred.
Conclusion:
The identification of the first animal on Earth, the ctenophore, marks a significant milestone in our understanding of the origins and evolution of animal life.
By utilizing innovative approaches and analyzing genetic information encoded in chromosomes, scientists have gained valuable insights into the ancient ancestors that paved the way for the remarkable diversity of life we observe today.
These findings serve as a foundation for future research and a deeper understanding of the complex evolutionary history of animals.
