DNA comparisons reveal a previously overlooked part of DNA that distinguishes Humans from chimpanzees and that had been omitted in previous studies.

In evolutionary terms, the chimp is our closest living relative, and evidence indicates that our relationship stems from the same ancestor. Our evolutionary pathways diverged approximately five to six million years ago, resulting in the modern chimp and Homo Sapiens, humankind in the twenty-first century.

In a new study, stem cell researchers at Lund University explored what it is about our DNA that distinguishes human and chimp brains — and have found some interesting answers.

In this study, instead of studying or using living humans and chimpanzees, they developed stem cells in a lab.

They used stem cells to grow brain cells from humans and chimps and compared the two cell types. The researchers then discovered that humans and chimps use a portion of their DNA differently, which appears to play a significant role in our brain development.

“The part of our DNA identified as different was unexpected. It was a so-called structural variant of DNA that were previously called “junk DNA,” a long repetitive DNA string which has long been deemed to have no function. Previously, researchers have looked for answers in the part of the DNA where the protein-producing genes are — which only makes up about two per cent of our entire DNA — and examined the proteins themselves to find examples of differences,” explained the study authors.

Thus, the new findings reveal that the differences appear to be located outside of protein-coding genes in what has been dubbed “junk DNA,” which was previously assumed to have no purpose and makes up the majority of our DNA.

“This suggests that the basis for the human brain’s evolution are genetic mechanisms that are probably a lot more complex than previously thought, as it was supposed that the answer was in those two per cent of the genetic DNA. Our results indicate that what has been significant for the brain’s development is instead perhaps hidden in the overlooked 98 per cent, which appears to be important. This is a surprising finding.”

Source: DOI: 10.1016/j.stem.2021.09.008

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