Dolphin communications is 26 million years old
In a research published yesterday in Royal Society journal Biology Letters, scientists led by Travis Park, a doctoral student at Melbourne’s Monash University scanned the inner ear of a 26 million year old fossilised Oligocene xenorophidae, one of the oldest species of the toothed whale group.When he first saw CT images of the pre-historic giant’s cochlear, a spiral-shaped cavity within the inner ear, Park says he “was blown away by just how similar this incredibly old toothed whale was to a modern echolocating dolphin”, and suggests O. xenorophidae had similarly robust hearing, when it came to high-frequency sounds, as today’s toothed whales. “Toothed whales are the only marine mammals to have developed the ability to sense their watery world by hearing and analysing such high-frequency sounds,” said lead researcher Travis Park.”This, in turn, allowed them to spread around the globe and become the most diverse of all marine mammals, with at least 73 known species,” Mr Park said.Travis team’s discovery was based on the careful analysis of a fossil ear bone of one of the earliest known toothed whales, borrowed from the Smithsonian Institution’s National Museum of Natural History. Using cutting edge scanning technology in Melbourne, the scientists created high resolution pictures, in 3D, of the 26 million year old fossil.Dolphins belong to a family of toothed whales that also include orcas and pilot whales. And they all rely on echolocation, using reflected sounds to find objects and hunt together by surrounding and then trapping schools of unsuspecting fish.
“Our results were nothing short of extraordinary,” Mr Park enthused. “I was blown away by how similar this incredibly old toothed whale was to a modern echolocating dolphin.”It meant that even the most ancient ancestors of today’s toothed whales and dolphins had ears tuned for hearing high frequency sounds. “This indicated very strongly that they had the ability to echolocate like their living relatives,” he said.Based on the anatomy of their skulls, toothed whales had long been assumed capable of producing high-frequency noises. “But, for the first time, our research showed they could also hear such sounds a critical factor in being able to echolocate according to Mr Park.Past studies have shown the species’ ancient ancestors probably had the anatomy needed to produce high-frequency sounds, thanks to their head shape and hence, could likely echolocate like their modern cousins.”Until now we have lacked anatomical evidence from a fossilised inner ear to test for high-frequency hearing, and verify functional echolocation,” the paper reads.Because the fossil in question came from the earliest known divergent of the toothed whale group, the researchers say this evolutionary trait may have been present in all sub-species, but more research is needed to confirm this theory. “This provides extremely strong evidence that these creatures were doing so 26 million years ago. So, millions of years before humans walked the Earth, dolphins evolved their own complex sensory and communications system which have proved to be unique in the animal kingdom.” said Mr. Park.