Outgroups AG3-MA1 Chukchi Dusun Igorot Iran_Neolithic Karitiana Kosipe Kostenki14 Lebbo Levant_Neolithic Mbuti Satsurblia Ust_Ishim Villabruna Latvia_MN2 Eastern_HG 0.788±0.096 Western_HG 0.135±0.078 Nganasan 0.076±0.038 chisq 10.493 tail_prob 0.486685 Latvia_MN_merge Eastern_HG 0.735±0.090 Western_HG 0.190±0.072 Nganasan 0.075±0.035 chisq 11.189 tail_prob 0.427555I couldn't test Latvia_MN1 separately due to a lack of markers. However, using exactly the same setup on the older samples from Jones et al. 2017, the Nganasan-related signal fails to show for Latvia_HG and only registers at 0.5% for Ukraine_HG/N. But that 0.5% looks somewhat shaky considering the ten times higher standard error. The other coefficients make good sense.
Latvia_HG Eastern_HG 0.314±0.042 Western_HG 0.686±0.042 Nganasan 0 chisq 10.035 tail_prob 0.612908 Ukraine_HG/N Eastern_HG 0.676±0.153 Western_HG 0.319±0.129 Nganasan 0.005±0.053 chisq 11.114 tail_prob 0.433755So, you're probably asking, does Latvia_MN-related ancestry explain the elevated Nganasan-related ancestry in modern-day far Northeastern Europeans such as Finns? Perhaps some of it, but not all of it. Note the slight drop in the Nganasan-related ancestry for the Finns with the inclusion of Latvia_MN in the model.
Finnish Lengyel_LN 0.305±0.020 Western_HG 0.135±0.014 Yamnaya_Samara 0.457±0.025 Nganasan 0.104±0.008 chisq 12.401 tail_prob 0.25911 Finnish Latvia_MN 0.137±0.113 Lengyel_LN 0.316±0.070 Western_HG 0.119±0.051 Yamnaya_Samara 0.354±0.123 Nganasan 0.074±0.020 chisq 1.429 tail_prob 0.99764My verdict: the minor Nganasan-related signal in Latvia_MN, or at least Latvia_MN2, is probably real, and the extra Nganasan-related admixture in modern-day Finns possibly arrived in Northeastern Europe in several waves from the Middle Neolithic onwards, including with early speakers of Uralic languages during the Bronze or Iron Age.