Does This Mean We Stopped Being Animal and Started Being Human Due to ‘Copy Paste’ Errors?

A Surprise Finding About Ancestral Genes In Animals Could Make You Rethink The Roles And Functions That Genes Play

Over 700 million years ago, a pivotal moment in evolutionary history unfolded with the emergence of a rudimentary creature boasting a front, a back, and a defined top-to-bottom orientation.

Though modest by today’s standards, this early organism marked a transformative milestone by establishing the fundamental body plan that would serve as the blueprint for myriad complex animals, including humans.

Residing in the ancient seas of Earth, this inconspicuous creature was the last common ancestor of bilaterians—a vast assemblage encompassing vertebrates (such as fish, amphibians, reptiles, birds, and mammals) and invertebrates (comprising insects, arthropods, mollusks, worms, echinoderms, and more).

A recent study led by researchers at the Centre for Genomic Regulation (CRG) in Barcelona has shed light on the genetic legacy of this ancient progenitor.

By analyzing 20 diverse bilaterian species, ranging from humans to sharks, mayflies, centipedes, and octopuses, the team uncovered over 7,000 groups of genes that trace back to this evolutionary forebear.

The study, published in the journal Nature Ecology and Evolution, highlights the role of gene duplication events that occurred hundreds of millions of years ago.

Surprisingly, the study revealed that approximately half of these ancient genes have been repurposed by animals, specifically for specialized roles within certain body parts, notably in the brain and reproductive tissues. This discovery is unexpected because typically, ancient and conserved genes are responsible for fundamental and essential functions needed throughout the body.

Upon closer examination, researchers identified a sequence of fortuitous ‘copy-paste’ errors during the evolution of bilaterians. For instance, a pivotal moment occurred early in vertebrate history when a cluster of tissue-specific genes emerged alongside two significant whole genome duplication events.

This allowed animals to retain one copy for essential functions while utilizing the duplicated copy as material for evolutionary innovation. Such evolutionary events, occurring at various scales, were a consistent phenomenon throughout the bilaterian evolutionary lineage.

“Our genes are like a vast library of recipes that can be cooked up differently to create or change tissues and organs,” explains author Federica Mantica.

“Imagine you end up with two copies of a recipe for paella by accident. You can keep and enjoy the original recipe while Evolution tweaks the extra copy so that it makes risotto instead.

“Now imagine the entire recipe book is copied – twice – and the possibilities it opens for evolution. The legacy of these events, which took place hundreds of millions of years ago, lives on in most complex animals today.”

The study’s authors discovered several new, tissue-specific capabilities enabled by these ancient genes’ specialization. For instance, the genes TESMIN and tomb, which descended from the same ancestor, each went on to fulfil a distinct function in the testis of both insects and vertebrates. The fact that mutations in these genes may impair sperm production and so influence fertility in fruit flies and mice emphasizes the significance of these genes.

Ancestral gene specialization also provided some of the building blocks for the emergence of sophisticated neural systems. For instance, scientists discovered genes that are crucial for the myelin sheaths that surround nerve cells in vertebrates, which are necessary for the quick transmission of nerve signals.

They also discovered FGF17 in humans, which is believed to be crucial for preserving cognitive abilities into old age.

Insects’ ability to fly is partly due to the specialization of certain genes in their muscles and epidermis to produce cuticles. Other genes in octopuses’ skin developed specializations for light perception, which helps them blend in with their surroundings, change color, and interact with one another.

Through examining the evolution of species at the tissue level, the research shows that variations in the use of genes in various body regions have significantly contributed to the emergence of novel and distinctive characteristics in animals.

In other words, when genes begin to work in certain tissues, they might cause the creation of new physical features or talents, so contributing to animal evolution.

This new work “makes us rethink the roles and functions that genes play,” adds co-author ICREA Research Professor Manuel Irimia.

“It shows us that genes that are crucial for survival and have been preserved through millions of years can also very easily acquire new functions in evolution. It reflects evolution’s balancing act between preserving vital roles and exploring new paths.”

Source:10.1038/s41559-024-02398-5

Image Credit: Gettyimages

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