Human evolution didn’t stop at split from chimpanzees, 155 tiny new genes identified: Study

Some of the new genes linked with growth defects, diseases, say scientists

By Rohini Krishnamurthy
Published: Wednesday 21 December 2022
Human evolution didn’t stop at split from chimpanzees, 155 tiny new genes identified: Study
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Humans have evolved to gain 155 tiny new genes, but their role in health and diseases is currently unclear, according to a new study.

Some of the new genes have evolved from scratch, building on ‘junk’ or non-coding DNA sequences, the study published in the journal Cell Reports stated. Non-coding sequences do not code for amino acids, the building blocks of protein.

Mutations can allow new genes to be born from a piece of DNA that was not previously a gene, lead author Aoife McLysaght from the Trinity College Dublin, told Down To Earth.

Alternatively, new genes can evolve from existing genes when they get accidentally duplicated. Over the years, they gather mutations to form a new gene, according to a report in the journal Nature.

A previous 2017 study published in PLOS Biology journal suggested that humans are losing harmful genetic mutations that reduce people’s lifespan. 

Researchers from Greece and Ireland studied the human ‘reference’ genome. It is not a DNA sequence of a single person but an accepted representation of the human genome sequence.

They compared this with the genomes of 99 vertebrate species and tracked the relationship of these genes across evolution.

As many as 155 microgenes stood out as unique, showed the study. Microgenes are simply very small genes, McLysaght explained.

These genes are generally under-studied because of the challenges in analysing them in the genome, she added.

The authors of the paper explained that they have yet to decode the role of the 155 new genes but noted that these seem to carry out essential functions.

For example, 44 of the 155 new genes are associated with growth defects, according to McLysaght. These defects showed up in cells grown in the lab, the expert shared. “This demonstrates that these are functional and not ‘junk’.”

There are other clues as well. Three of the 155 new genes have links with diseases such as muscular dystrophy, retinitis pigmentosa and Alazami syndrome. 

The researchers, however, were not entirely sure of the genes’ impacts on human health. “The only thing we know about them is where in the body they are expressed,” McLysaght noted.

One new gene is expressed or forms a functional protein in the human heart. This suggests that they may play a role in the heart, according to the researchers.

This gene emerged in humans and chimpanzees right after the split from gorillas, they highlighted.

“It will be very interesting in future studies to understand what these microgenes might do and whether they might be directly involved in any kind of disease,” Nikolaos Vakirlis, a scientist with the Biomedical Sciences Research Center “Alexander Fleming” (A non-profit research organisation) and study’s author, said in a statement.

McLysaght said she would study what factors trigger the emergence of new genes from scratch.

It is possible that periods of environmental change are conducive to the evolution of new genes because they might be important for adaptation, she added.

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