Cultural transmission—when social behavior shapes a population's genetic makeup—is almost exclusively a human phenomenon. Ancient Europeans, for example, kept consuming milk and milk-based products long after childhood, and eventually that choice left a mark in their genes, bestowing them with lactose tolerance, ABC Science explains. But now new research has found an example of cultural transmission in dolphins, too. In certain locations in Australia, dolphins that use tools have a sequence of heritable genes that dolphins that do not use tools lack.

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In Australia's Shark Bay, some bottlenose dolphins hold sponges at the tip of their mouths when foraging—probably to protect their beaks from getting scraped up, ABC Science reports. In other parts of the bay, where the water is shallower, however, the dolphins usually don't use sponges.

A team of researchers observed dolphins in the bay and took a few genetic samples to see if these behaviors made a difference in the animals' genetics. Sure enough, dolphins from the shallow waters were almost all haplotype H, while those in Shark Bay's deeper waters were haplotype E or F. Teasing out those initial results, the researchers found that only dolphins that inherited haplotype E actually use the sponges.

"This striking geographic distribution of a genetic sequence cannot be explained by chance," the lead researcher said in a statement. "This is one of the first studies to show this effect – which is called cultural hitchhiking – in animals other than people."