Modern and Archaic Humans: New Method Reveals Genetic Differences

For years, scientists have learned genetic differences between modern humans and extinct hominins that explain their biological and physical differences.

The advancement of sequencing technologies and the analysis of the genomes of both modern and archaic humans have driven the discovery of many breakthroughs in human understanding of its evolutionary history, according to Nature.

These include the discovery of the interbreeding between Homo sapiens and extinct hominins, like Neanderthals and Denisovans; the development of an increasingly detailed description of how modern humans disperse throughout the world from Africa; and the adaptations humans had to make to adapt to their environments.

Now a study from Stanford University dives deeper into the genetic differences between modern and archaic humans by studying 14,000 genetic differences at a new level of detail, finding that gene activation and not just genetic code underlie the evolution of the brain and vocal tract.

Comparing Genomes of Modern and Ancient Humans

The genomes of Neanderthals and Denisovans helped in the discovery of genetic differences in sequences between modern and ancient humans.

However, most of these genetic differences are noncoding. So, scientists do not have all the layers and marks that are usually found in samples from modern humans that will help in interpreting the RNA or cell structure, the news release from Stanford University reported.

David Gokhman, a postdoctoral fellow in biology at Stanford University said that all they can do is stare at it and hope someday they will be able to understand it because they only have the naked DNA sequence.

But because of this, they and a team of scientists from the University of California, San Francisco (UCSF) were motivated to create a new method to harvest more information from these genomes to reveal the physical consequences of the genetic differences between ancient and modern humans.

They published their study, entitled "The cis-regulatory effects of modern human-specific variants," in eLife focusing on sequences related to gene expression or the process of gene activation that determines when, how, and where instructions of DNA are followed.

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Massively Parallel Reporter Assay

With so many variants to analyze, the researcher used an ew method known as "massively parallel reporter assay" to tell which of the sequences affect gene regulation.

According to the news release, this technique was first developed by Ahituv, but the version of these scientists involves packaging the DNA sequence variant into a reporter gene inside a virus that is put inside a cell.

Scientists hypothesize that if this variant affects gene expression, the reporter gene will produce a barcoded molecule that will help them identify what specific DNA sequence it came from. This method is a shortened version of how each variant works in a cell in real life and reports the results.

The researchers found that out of the 14,042 genetic variants unique to modern humans, they found that 407 of them specifically contribute to differences in gene expression, specifically in the vocal tract and cerebellum.