A.Humans and chimpanzees.
•Chimpanzees are able to express a wide range of emotions – such as busting out in laughter or smiling – this trait was once thought to be a feature exclusive to humans.
•The smile can be linked to the activation of the brain’s limbic system – where the orbicularis oculi muscle involuntarily contracts and raises the cheeks, forming wrinkles around the eyes.
•This implies that the smile is a true and genuine smile. •Interestingly, this type of reflex has a name – the Duchenne smile.
• Moreover, research has shown that chimpanzees share 98.6% of our DNA – This means that humans and chimpanzees shared a common ancestor eons ago.
• It is important to also note that chimpanzees are the closest living relatives to humans.