You’ve heard endlessly about humans as the 98% or 99% chimpanzee (and rightly discounted it if you have any capacity to analyze an argument). One group of students decided to look at the human genes that are different:
A team of student researchers from John Jay College of Criminal Justice has discovered human microRNA genes not shared with any other primate species and which may have played an important role in the unique evolution of the human species. The students, under the direction of John Jay Professors Dr. Hunter R. Johnson and Dr. Nathan H. Lents, found at least three families of microRNA genes on chromosome 21…
Although the team found that the long arm of human chromosome 21 aligns well with that of other extant ape species, the short arm aligned poorly, suggesting that this region of the human genome has recently and substantially diverged from that of other primates.
According to their analysis of prehistoric human genomes, these changes predate the divergence of Neanderthals and modern humans. The genes also show little to no sequence-based variation within the modern human population. The team therefore theorized that the microRNA (miRNA) genes found in that region [miR3648 and miR6724] likely evolved in the time since the chimpanzee and human lineages split, sometime in the last seven million years, and are specific to humans.
The City University of New York, “Student researchers discover genes unique to humans in search for source of our evolutionary distinctiveness” at ScienceDaily (March 8, 2022)
The authors attribute the differences to de novo genes (genes that just suddenly appear):
“Understanding the genetic basis for human uniqueness is an important undertaking because, despite sharing nearly 99% of our DNA sequences with the chimpanzee, we’re remarkably different organisms,” said student researcher José Galván. “Small post-transcriptional regulatory elements like miRNAs and siRNAs [small interfering RNA] are under-appreciated and often misunderstood in the effort to understand our genetic differences.”
Thanks to their small size and structural simplicity, miRNA genes have fewer barriers to de novo creation than other gene types. MicroRNA genes can be extremely prolific in their regulation of other genes, meaning that modest changes to DNA sequence can result in wide-ranging impacts to the human genome. The creation of miR3648 and miR6724 serve as excellent examples of this process. This study revealed a new possible mechanism for the creation of new miRNA genes through duplications of rRNA genes, which calls for further research on how general this phenomenon may be.
The City University of New York, “Student researchers discover genes unique to humans in search for source of our evolutionary distinctiveness” at ScienceDaily (March 8, 2022)
The paper is closed access.
Note: One of the faculty advisors is Nathan Lents, known to many readers as the author of a book, Human Errors: A Panorama of Our Glitches, from Pointless Bones to Broken Genes, claiming that humans are poorly designed. Perhaps we will soon hear that these unique, de novo genes were poorly designed.