It's a tricky task to learn because the sponge messes with the dolphins' echolocation abilities. The team examined nearly 30,000 sites across the dolphins' genomes where DNA methylation – a common epigenetic modification – can occur. DNA methylation acts like a dimmer control rather than an on-off switch. Scientists have traditionally thought that epigenetic changes switch genes either "on" or "off", but research shows those changes can also 'dial down' gene expression in a graded way. But research in roundworms suggests that epigenetic changes can also be inherited, transferred from one generation to the next.