The gene switches that set humans apart from monkeys

Parts of our DNA’s regulatory code may have been responsible for our humanity in the first place.

Researchers have pinpointed areas of the human genome that may be accountable for our unique human abilities. The DNA regions, known as HAQERs (Human Ancestor Quickly Evolved Regions), regulate the expression of protein-coding genes and play a role in the formation of our brain, digestive system, and immune system. They arose soon after the split between human and chimpanzee ancestry. Despite their usefulness, HAQERS can spread illness.

While chimpanzees and gorillas are primates like us, there are important ways in which we humans stand apart from them. Even though there are few variations between human and great ape protein-coding genes, progress has been slow in elucidating the genetic basis of our “essentially human” traits. However, there is mounting evidence that the most significant alterations occurred in regions of our genome that do not code for proteins and were previously thought to be meaningless “junk DNA.”

Quick shifts

An American research group led by Riley Mangan of Duke University has started looking for evidence of human evolution in these non-coding regions of the genome. Up until recently, it was thought that the most promising DNA sequences were those that were relatively stable for a long period of time yet underwent significant alteration in our ancestors. It was thought that a shift in selection was responsible for the rapid pace of molecular evolution.

On the other hand, Mangan and his team have searched previously volatile parts of the genome. Unlike in other animals, humans’ brain sizes, limb lengths, and face proportions varied throughout time. The scientists used high-throughput sequencing and genome comparisons to hunt for DNA segments in these genomic locations that altered very fast after the chimpanzee and human lineages separated around 7.5 million years ago.

Inherent HAQER in our DNA

Indeed, the team was able to single out almost 1,500 such passages. The acronym HAQER, which stands for “Human Ancestor Quickly Evolved Regions,” was given to these places. According to the findings, these regions of DNA have undergone some of the most rapid changes throughout the human genome. However, when exactly did this dramatic evolutionary leap occur on the timeline of early, or prehistoric, human development? Or did it occur before the divergence from chimpanzees?

After human ancestry diverged from that of the chimpanzee, we subsequently developed the HAQER regions.

This was confirmed by comparing the 13 most relevant sequences from Mangan’s HAQERs sections to those of Neanderthals, Denisova people, chimpanzees, and the reconstructed genome of the presumed common ancestor of humans and chimps.

This means that the HAQERs originated after our ancestors diverged from those of the chimpanzee but before those of the Denisova people and Neanderthals. This means that these sequences were present in other early human and prehuman animals.

Regulating the nervous system and digestive system

So, why do we need the HAQER sequences? The researchers refer to these snippets of DNA as “regulatory DNA” because of their “switch-like” function. Specifically activating genes seems to be a result of this process. There are certain cell types where this occurs, as well as specific stages of development when this occurs. And sometimes it takes a shift in circumstances, as Mangan’s coworker Craig Lowe describes. There were certain gene switches in the human operating system that the HAQERs introduced.

Research has shown that these gene switches play an important role in shaping the human nervous system, digestive system, and immune system. The gene switches empower us to fine-tune our responses to shifting environmental conditions.

Typical human illnesses may be triggered by HAQERs

What caused HAQERs to emerge? Rapid appearance of genomic areas often has one of two causes: either they are the result of local mutations or they are so beneficial to a species that they become established via natural selection. The scientists discovered support for both hypotheses in the newly described DNA sequences, indicating that the most diverse sections of the human genome were sculpted by a combination of these two processes.

The researchers speculate that HAQERs, in making us humans, not only provided us with favorable qualities like huge brains, but also formed the foundation for common human disorders. Conditions including schizophrenia, bipolar disorder, and unipolar depression may fall within this category.

Mangan and his coworkers found that, although all people have very identical HAQER sequences, there are still some differences, and that these variations have a tendency to correspond with certain diseases. More study may be needed to determine the nature of the connection.

By Bertie Atkinson

Bertie Atkinson is a history writer at Malevus. He writes about diverse subjects in history, from ancient civilizations to world wars. In his free time, he enjoys reading, watching Netflix, and playing chess.