Re: the General News item at http://www.themodernantiquarian.com/post/78067/news/british_isles.html -

"Mummies, possibly of ‘Celtic’ origin and some 3,000 years old, have been unearthed in the Tarim Basin of western China for nearly 100 years. ‘Cherchen Man’ is just one of these but one of the most interesting. Cherchen Man is tall, red haired and wears a red tunic and tartan leggings. His mummified body, along with others, are now kept in Urumqi City Museum in Xinjiang province. Perhaps even more interesting are the burial sites where Cherchen Man and his people are found – these bear signs of a Celtic influence and include standing stones similar to British dolmens as well as icons reminiscent of sheela-na-gigs."

The mention of 'signs' of a Celtic influence, as well as standing stones similar to British dolmens and icons reminiscent of sheela-na-gigs is interesting (though I can't find any pics of them on the internet) and if true would seem to push back the sheela-na-gig tradition to at least 1,000bce.