Why would you include in your sample the bones that prompted you to ask the question? You need to exclude the 3 mammoth bones from the Rotterdam museum. At best your sample size is 1 anomalous vertebra in 6, rather than 3 in 9. Although it's hard to even know what to make of your 'sample' when you include some vertebrae 6 and some vertebrae 7. Aren't there mammoth bones in museums all over northern Europe? I don't think this study was ready for publication, even in a little online journal.