Dementia and psychiatric disorders may be the price of being human, scientists believe, after comparing the genetic differences between chimpanzees and humans.
Researchers at Stanford University found human brains produce far greater levels of a protein which controls the activity of neurons and has been linked, in humans, to diseases such as Alzheimer’s, dementia and schizophrenia.
Chimpanzees are our genetically closest living relative, sharing about 98.6 per cent of our DNA. So studying the differences can help scientists understand what allowed humans to evolve into more complex beings.
Scientists have suggested that the brain changes that allowed humans to advance to form sophisticated societies and cultures also put us more at risk of mental disorders.
“Evolution of the primate brain may have involved adding sophisticated neuromodulatory features to neural circuits, which under certain conditions can be perturbed and increase susceptibility to neuropsychiatric disease,” said Sergiu Pasca, associate professor of psychiatry and behavioural sciences, Stanford School of Medicine.
Measuring differences in how genes operate in humans and chimps is tricky because their brains develop at very different rates.
To get round the issue, scientists fused human and chimp stem cells together and coaxed them into assembling into a small brain-like structure called an organoid.
As the 3D clusters of brain cells develop and mature in a dish, their genetic activity mimics what happens in early neurodevelopment in each species.
Because the human and chimpanzee DNA are bound together in the same cellular environment any differences in the genetic activity can be attributed to actual differences between the two species.