According to the video in the middle of that story, they were found in a silt layer which would have been buried 15k years ago [0] [0]: https://youtu.be/HyfSsg

According to the video in the middle of that story, they were found in a silt layer which would have been buried 15k years ago [0] [0]: https://youtu.be/HyfSsgCrjb0?t=1m21s https://youtu.be/HyfSsgCrjb0?t=1m21s