New study shows that super hearing in dolphins developed at least 26 million years ago

The earliest ancestors of the toothed whale group, which includes dolphins, killer whales and porpoises, are thought to have had the ability of echolocation based on microcomputed tomography (microCT) images of the fossilized cochlea of Oligocene xenorophidae. The researchers who made this discovery, led by Travis Park at Monash University in Melbourne, Australia believe O. xenorophidae had robust hearing in high-frequency sounds.

Based on head shape, it was suspected that these creatures were capable of echolocation but the research team now has proof of this in the form of findings from scans of the fossilized inner ear of this species. The cochlea’s characteristics indicate that the xenorophid was capable of detecting the echo of high-frequency sounds produced in its nasal passages. The specimen came from a rock formation at Onslow Beach, Camp Lejeune Marine Base, North Carolina, USA. According to Travis Park, he “was blown away by just how similar this incredibly old toothed whale was to a modern echolocating dolphin.” The question of when this ability evolved was open until now. Finding echolocation characteristics in this specimen puts development of the ability at 26 million years ago at least.

This group of mammals has reached such a high level of evolutionary development in part because of their special ability to interpret minute details through hearing. The unique ability to produce high-frequency sounds and listen to echoes to evaluate their surroundings has contributed to their ability to navigate and find food effectively, reports an article in Cosmos magazine.

Source: Cosmos magazine; Park T, et al. Ultrasonic hearing and echolocation in the earliest toothed whales. Biology Letters. 2016 Apr;12(4).