VARI, Greece — Humans are continuing to evolve — seven million years after splitting off from other mammals.
An international team of scientists has identified 155 “microgenes” that spontaneously arose from tiny sections of DNA since the split from our chimpanzee ancestors. Some date back to the ancient origin of mammals, with a few linked to diseases.
The team created an ancestral tree comparing Homo sapiens to other vertebrate species. It showed the genes arose from scratch rather than from duplication events that already existed in the genome.
“This project started back in 2017 because I was interested in novel gene evolution and figuring out how these genes originate,” says first author Nikolaos Vakirlis, a scientist at the Alexander Fleming Biomedical Sciences Research Center, in a media release.
“It was put on ice for a few years, until another study got published that had some very interesting data, allowing us to get started on this work.”
An analysis found 44 of the genes are associated with growth defects in cell cultures, demonstrating their importance in maintaining a healthy, living system. They are specific to humans, making direct testing difficult. Dr. Vakirlis and the team linked them to illnesses by examining patterns found within the DNA.
The study, published in Cell Reports, opens the door to explore the genes’ effects on the body in more detail.
“It was quite exciting to be working in something so new,” adds senior author Aoife McLysaght, a scientist at Trinity College Dublin. “When you start getting into these small sizes of DNA, they’re really on the edge of what is interpretable from a genome sequence, and they’re in that zone where it’s hard to know if it is biologically meaningful.”
New genes tied to several diseases
Two had DNA markers pointing to connections with the wasting disorder muscular dystrophy and retinitis pigmentosa — which leads to vision loss. Another contained chemicals which have been linked to increased risk of dwarfism, or Alazami syndrome.
Apart from disease, the researchers also found a new gene that is associated with human heart tissue. This gene emerged in humans and chimps right after the split from gorillas and shows just how fast a gene can evolve to become essential for the body.
“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,” says Vakirlis.
The findings shed light on previous global studies of our DNA which have suggested natural selection has recently made changes and continues to do so. Certain traits created by genetic mutations help an organism survive or reproduce. Such mutations are more likely to be passed on, so they increase in frequency.
“These genes are convenient to ignore because they’re so difficult to study, but I think it’ll be increasingly recognized that they need to be looked at and considered,” McLysaght concludes. “If we’re right in what we think we have here, there’s a lot more functionally relevant stuff hidden in the human genome.”
South West News Service writer Mark Waghorn contributed to this report.