 Complete the following phrase:  Martin Richards estimated that only 11 of European mtDNA is due to immigration in this period, suggesting that farming was spread primarily due to being adopted by indigenous Mesolithic populations, rather than due to immigration from Near East. Gene flow from SE to NW Europe seems to have continued in the Neolithic, the percentage significantly declining towards the British Isles. Classical genetics also suggested that the largest admixture to the European PaleolithicMesolithic stock was due to the 