Despite sharing 99% of genetic code with chimpanzees, human cells are still younger than theirs. Many people live up to their 70s and 80s, with some even reaching 100 years old or older. However, chimpanzees rarely reach the age of 50.
Although the advancement in medicine over the last 200 years have made human lives longer, researchers from Duke University believe that there could be a more ancient explanation for why humans are long-lived primates. Their study suggests that the secret of human longevity may be found in the clock-like epigenetic changes that tick slower for humans.
Chemical changes in the DNA of human cells
The researchers think that part of the secret of human longevity lies in the changes in the DNA within the human cells, which slowed down the rate of human aging around seven to eight million years ago when ancient humans went their separate ways from other primates, such as the chimpanzees.
They have found over the past decade that chemical marks on the human genome change as the person ages. These chemical marks are modifications that affect the gene activity without altering the DNA sequence.
Their study was published on September 21 in the journal Philosophical Transactions of the Royal Society B. Led by researchers at Duke University and George Washington University.
Lead author Elaine Guevara, an assistant research professor of evolutionary anthropology at Duke University, said that their study marks the first time that such age-related changes have been made to examine chimpanzees.
Their study showed that specific regions along the human DNA gain or lose chemical tags known as the methyl groups in a way that marks time, similar to a metronome. Due to its consistency, it could be used as an "aging clock" to determine the age of a person within less than four years.
The researchers examined around 850,000 of these sites in blood from 83 chimpanzees that are one to 59 years old.
Aging ticked faster in chimpanzees
The researchers found that aging leaves a mark on the genome of chimpanzees, just as how it does in humans. Over 65,000 of the DNA sites examined by the scientists revealed that there are changes in a clock-like way across the lifespan of both humans and chimpanzees. Some of them gaining methylation, and some are losing it.
According to Guevara, a lot of the genomes of chimpanzees show an age-related problem. The pattern was so consistent that researchers were able to use DNA methylation levels to determine the age of chimpanzees to within 2.5 years. That is more accurate than the existing methods for estimating the age of wild animals by the amount of wear on their molars.
Compared to humans, the results of their analysis on the changes in the genome of the chimpanzees they found that the epigenetic clock of chimpanzees ticks faster than those in humans.
Guevara says that it is still unknown whether these changes track aging or if it contributes to it. But they hope that their research could lead to clues to the gene regulatory mechanisms that explain the physical and cognitive decline that usually comes with aging, and that their study would hopefully lead to new ways of fighting aging-related illnesses.
READ MORE: Are Scientists Close to Discovering a Way to Delay Aging?
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