Monkey X-ray (image) Princeton University Share Print E-Mail Caption Researchers have found that monkeys known as macaques possess the vocal anatomy but not the brain circuitry to produce human speech. The findings suggest that human speech stems mainly from the unique evolution and construction of our brains, and is not linked to vocalization-related anatomical differences between humans and primates. The researchers used X-ray videos (above) to capture and trace the movements of the different parts of a macaque's vocal anatomy -- such as the tongue, lips and larynx -- during a number of orofacial behaviors. Credit Image courtesy of Asif Ghazanfar, Princeton Neuroscience Institute Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.