They hylobatids, or gibbons, diversified by 9 million years ago and today, there are around a dozen or so species. The largest of them – the siamang – is pictured above. These “lesser apes” have taken the primates’ fondness for trees to a whole new level. Their wrist is made up of a ball-and-socket joint, much like our shoulders or hips. That means a swinging gibbon can rotate its entire body around its wrist, giving them a unique style of movement called brachiation (video). They can zoom through treetops with a top speed of 35 miles per hour.

While the gibbons’ movements are all style and grace, their chromosomes are a chaotic mess. They’ve rearranged around 10-20 times faster than most other mammals and, as with lorises, it’s not clear why. That’s a mystery for a future study to solve.

Image by Suneko