Let us take the instance of humans and chimpanzees. Although it was traditionally believed that only humans could smile or burst into laughter, chimpanzees are capable of a wide variety of emotional expression. The orbicularis oculi muscle spontaneously contracts and lifts the cheekbones when the limbic system of the brain is activated, causing wrinkles to appear around the eyes. This suggests that the smile is real and sincere. The Duchenne smile is a moniker for this peculiar reaction. Furthermore, studies have revealed that chimpanzees and humans share 98.6% of our DNA, indicating that long ago, both species had a common ancestor. Noting that chimpanzees are the closest living species to humans.