According to scientists, it's the other 4 per cent, and the vast difference that makes us more vulnerable to certain diseases, including cancer and autism.
In a new research, Georgia Tech's Soojin Yi looked at brain samples of each species. She found that differences in certain DNA modifications, called methylation, might contribute to phenotypic changes.
The results also hint that DNA methylation plays an important role for some disease-related phenotypes in humans, including cancer and autism.
"Our study indicates that certain human diseases may have evolutionary epigenetic origins. Such findings, in the long term, may help to develop better therapeutic targets or means for some human diseases," said Yi, a faculty member in the School of Biology.
DNA methylation modifies gene expression but doesn't change a cell's genetic information. To understand how it differs between the two species, Yi and her research team generated genome-wide methylation maps of the prefrontal cortex of multiple humans and chimps.
"They are linked to autism, neural tube (brain and spinal cord) birth-related defects and alcohol and other chemical dependencies," said Yi.
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They found hundreds of genes that exhibit significantly lower levels of methylation in the human brain than in the chimpanzee brain. Most of them were promoters involved with protein binding and cellular metabolic processes.
The research has been published in American Journal of Human Genetics.