The best evidence for this is that their returns have become more similar. In the mid-90s the correlation between monthly returns on MSCI's emerging markets index (in sterling) and the FTSE mining sector was often under 0.4, implying that the two assets would occasionally move in opposite directions. In the last five years, however, the correlation has been almost 0.8, meaning the two usually move together.
And for large moves, the two almost always rise and fall together. Since January 2008 there have been 14 calendar months when mining shares fell more than 5 per cent. In 13 of these 14 months emerging markets also fell, by an average over all 14 months of 6.2 per cent. And during this time there have been nine months in which emerging markets fell f5 per cent or more. Miners fell every time, by an average of 11.4 per cent.