The scientists at the Yerkes National Primate Research Center, located at Emory University, said their unprecedented finding has the potential to move the scientific community closer to understanding why age-related neurodegenerative diseases, such as Alzheimer's disease, are uniquely human and seem to never fully manifest in other species, including humans' closest evolutionary relative, the chimpanzee.

Doctoral student Rebecca Rosen and Research Professor Lary Walker, in collaboration with colleagues at UCLA, made the discovery during a routine postmortem study of an aged, female chimpanzee that died of natural causes. The researchers also discovered deposits of beta-amyloid protein in plaques and blood vessels in the chimp's brain tissue.

"We've seen these plaques in aged chimpanzees before but this is the first time researchers have found both hallmark features of Alzheimer's disease -- plaques and neurofibrillary tangles -- in a non-human primate," said Walker. Brain plaques and tangles associated with the disease are prime suspects in damaging and killing nerve cells that cause memory loss and dementia.

The research appears in the online issue of the Journal of Comparative Neurology.