University of California, Santa Cruz, researchers have found more than 480 “ultraconserved” regions of “junk” DNA that are completely identical across the man, mouse and rat species, implying that they are essential to the descendants of these organisms. The regions largely match up with chicken, dog and fish sequences too.

The most likely scenario is that they control the activity of indispensable genes. The sequences may help slice and splice RNA into different forms and control embryo growth.