It was common to think that lungs and body parts are key innovations specific to the vertebrate transition from water to land.
However, the genome basis of air-breathing and limb movement was supposedly already well defined in our fish ancestors approximately 50 million years earlier.
According to recent research that mapped primitive fish organized by the University of Copenhagen, among others.
The new study contradicted the understanding of a critical milestone in the human evolutionary process.
To start from the beginning, most scientists agree that humans and other vertebrates evolved from fish. The convention was that some fish shimmied towards the land nearly 370 million years ago and became some form of primitive, lizard-like animals called tetrapods.
The explanation sounds like this – The fish ancestors of humans left their water biome by converting their fins to limbs and switching from breathing underwater to air-breathing.
It turned out that limbs and lungs aren’t particularities that appeared as late as many scientists thought.
Our common fish ancestor that existed some 50 million years before the tetrapod stage already had the genetic codes for limb-like forms and air-breathing required for landing.
The codes are still observable in humans and some species of primitive fishes.
That affirmation is backed up by recent genomic analysis from the researchers of the University of Copenhagen and their associates.
The new study shows that the evolution of the ancestral genetic codes possibly contributed to the vertebrate water-to-land transition, which alters the traditional convention of the sequence and timeline of the enormous evolutionary step.
The study was posted in the scientific journal Cell.
Guojie Zhang, professor of the Villum Centre for Biodiversity Genomics of the University of Copenhagen’s Department of Biology and principal author of the study, said:
“The water-to-land transition is a major milestone in our evolutionary history. The key to understanding how this transition happened is to reveal when and how the lungs and limbs evolved. We are now able to demonstrate that the genetic basis underlying these biological functions occurred much earlier before the first animals came ashore.”
A group of ancient living fishes may keep the secret explaining how the tetrapod got to grow its limbs and start breathing air.
The fish group includes the bichir that is present in shallow freshwater biomes in Africa.
The species is unique to most other extant bony fishes by packing particularities that our early fish ancestors possibly had more than 420 million years ago.
Thanks to genomic sequencing, the researchers discovered that the genes required to develop limbs and lungs were present in those primitive specimens.
Pectoral fins with locomotor functions like limbs, the bichir can similarly move on land as the tetrapod.
For some years, the scientists discovered that the species’ pectoral fins are very similar to the fins that the early fish ancestors presented.
The new genome analysis proves that the joint between the metapterygium bone with the radial bones of the pectoral fin in the bichir is homologous to the human synovial joints that connect the upper arm to the forearm bones.
The DNA sequence responsible for the control of the formation of synovial joints was already present in the common bonefish ancestors. It’s still observable in the primitive fish and some terrestrial vertebrates.