On a side note, this is one of the reasons I'm skeptical of believing travellers are genetically distinct from the rest of the population, as it assumes that the entire "settled" population is a genetically homogeneous entity that you can separate yourself from, but this seems unlikely due to the uneven geographical distribution of people who settled here in the past (Normans, Anglo-Saxon planters, Vikings etc.), and the localised nature of Gaelic clans in the past, e.g. The McCarthy clan in Kerry/Cork and the O'Neill's in Donegal were there for 100's or even thousands of years. Considering they say Travellers became noticeably distinct due to inbreeding in only 200-300 years, wouldn't there likely be some small genetic variation between the people at one end of the country from the other if separated for a much longer time period? And if that is the case, we could potentially have Cork, Donegel, and Dublin etc. claiming that they're distinct ethnicities (and culturally you could argue this too), which wouldn't make the traveller case unique.

In the paper linked here recently about how travellers are different genetically, they only used a sample of 50 travellers, and about 2000 'settled' people, but they didn't say if they if they were distributed across the whole country. I suppose I would need to know that if I were to believe it.