Shepoumaramth and its cultural evolution

It is traditionally believed that Maram, Mao, Poumai and Thangal have a common grandparent. The belief  is shared by all the four groups and has no rival oral tradition, and so it is plausible to hold it as true. The one word to denote these four groups is Shepoumaramth. Somehow along history it has come about that Mao and Poumai have much closer resemblance to each other than to Maram and Thangal, and vice versa. But the Maram, Mao, Poumai and Thangal are also member of Tenyimi. And Mao and Poumai have closer resemblance with Angami and Chakhesang than even to Maram and Thangal. This is so despite the fact that in term of geneology Mao and Poumai split from Angami and Chakhesang earlier. And since this split occurred earlier, Mao and Poumai should share commonness more with Maram and Thangal. However, this is not the case. In turn, Maram and Thangal share resemblence more with Zeliangrong, another group of Tenyimi, though in term of geneological split they should share commonness more with Mao and Poumai.

How do we account for such observation? When we look at the geography of how each group is situated, Mao and Poumai share boundary with Angami and Chakhesang respectively, and also with each other;  and Maram and Thangal share boundary with Zeliangrong, and also with each other. 

Culture of each group underwent a dialectical transformation vis-a-vis their neighbour. Shepoumaramth would have one culture when the dispersion took place. But as Mao and Poumai interacted more with people in their north i.e Angami and Chakhesang, culture evolved and brought them thus far, which is a culture much closer to Angami and Chakhesang. The language is also not very different from each other and the traditional costume is almost the same. So though Mao and Poumai should have more in common in with Maram and Thangal, due to geographical location and the interaction they end up sharing closer similarities with Angami and Chakhesang. The same applies to Maram and Thangal as well. 

So we have few points. First, language evolved over a period of time depending on who the neighbour  is and where the group is located in term of weather, food item etc. Second, Custome and practices also evolved depending on with which culture a group interacts. Third, culture of a group never remain stable for a long long period of time; it has an effect on others and others have an effect on it too. 

This culturally evolution is the main reason why when British came in the 19th- 20th century to the region, Mao / Poumai and Chakhesang/Pochury were identified Eastern Angami by certain people because these groups were very similar to Angami in term of language and costume and other features. The term Eastern Angami was, however, not applied to the Maram and Thangal.

NB: This is a hypothesis. I have no expertise in this area. But I am writing this so that someone may pick up this thread and do a more detail research in the subject.