Case closed on Ireland's washed-up 'chimpanzee arm'

After a month of investigation, the story behind a mysterious severed limb that washed up in Ireland is beginning to take shape.

Beachgoers who stumbled across the renegade remains initially thought them to be human, but the bones were later identified as a "chimpanzee arm", according to local reports. Chimps don't exactly make a habit of frequenting Irish shores, so that unusual verdict left locals all the more puzzled. Closer examination, however, has now revealed the bones' true origins.

Image: Clare FM/Facebook

Irish National Police (Gardaí at Ennistymon) were called in to retrieve the washed-up find after its discovery on Farrihy beach in County Clare. When the local coast guard failed to identify their origins, the bones were transferred to University Hospital Limerick for a post-mortem examination.

There, staff determined the bones were not human, but possibly belonged to some other primate. With the partial carcass no longer of interest to local law enforcement, the remains were handed off to County Clare's animal-control officer, Frankie Coote, for disposal.

"I became very curious and wanted to find out for myself what it could be," Coote told the The Clare Herald. "When I was on the radio [Clare FM] ... I just put it out there to see if anyone knew what it was. When you look at it, it does look like two arm bones, knuckles and fingers. It's as long as my own arm."

We reached out to comparative anatomist Dr Joy Reidenberg to see if she, or her colleagues, could help us to put a "face" to the appendage – and their suggestions point to an animal far better suited to the rocky Irish coastline. "I'd vote for a grey seal hind flipper," she told us.

The biggest clue here is the shape and thickness of the bones: a grey seal's tibia is typically three to four times thicker than the fibula that sits alongside it.

Other experts seem to agree. Speaking with The Clare Herald, Dr Simon Berrow, Chief Science Officer with the Irish Whale and Dolphin Group, reached a similar conclusion.

And in an interview with Clare FM, Seal Rescue Ireland operations manager Melanie Croce was even more specific: she noted that based on the size of the limb, the bones likely belonged to an adult male grey seal. "It's very long and sturdy," she explained.

It might seem odd that a seal – an animal that does not walk on legs (or at all, for that matter) – would possess such lengthy leg bones. To understand why this is the case, we need to look to the ancestor of all modern pinnipeds. That land-dwelling mammal, which resembled present-day river otters, needed strong walking legs. Millions of years of evolution, however, have led to some anatomical streamlining in its descendants.

The "building blocks" are still there, but we don't see a modern seal's "legs" because they're hidden by its bulky body. (You can see this for yourself in this CT-scanned harbour-seal skeleton from the Woods Hole Oceanographic Institution). The long toes, on the other hand, extend outwards and form the internal structure of the flipper.

With the mystery solved, Coote now has some creative ideas for putting the find to use. "I wanted to keep it as a back scratcher but my wife wouldn't allow me," he said.