Deaths worldwide among children of first cousins from all causes are estimated to be 4-5% higher than children of unrelated couples. Within any small endogamous population, cousin marriage is very likely to occur.
Traveller babies are 3x more likely to be stillborn in Ireland.
Travellers are far more likely than non-Travellers to carry the Q188R mutation that is the predominant cause of galactosemia in the Traveller community.
From www.ncbi.nlm.nih.gov/pubmed/10439960 'Anonymous population screening has shown the Q188R carrier frequency to be 0.092 or 1 in 11 among the Travellers as compared with 0.009 or 1 in 107 among the non-Travellers.' The side effects apart from death in early infancy are very serious, result in diminished capacity to be educated or employed, increased propensity to be involved in accidents due to gross motor deficiencies, and go on to adversely affect Travellers throughout their lives.
Travellers are also more likely than non-Travellers to carry:
(1) Hurler syndrome - Scroll down for 'Features' -- "Children with Hurler syndrome often die before age 10 from obstructive airway disease, respiratory infections, or cardiac complications."
(2) Fanconi's Anaemia - "the majority of FA patients develop cancer, most often acute myelogenous leukemia, and 90% develop bone marrow failure (the inability to produce blood cells) by age 40. About 60-75% of FA patients have congenital defects, commonly short stature, abnormalities of the skin, arms, head, eyes, kidneys, and ears, and developmental disabilities. Around 75% of FA patients have some form of endocrine problem, with varying degrees of severity. Median age of death was 30 years in 2000."
(3) Type II/III Osteogenesis Imperfecta -
In Type II, "Collagen is not of a sufficient quality or quantity. Most cases die within the first year of life due to respiratory failure or intracerebral hemorrhage. [Other symptoms are] Severe respiratory problems due to underdeveloped lungs [and] Severe bone deformity and small stature."
In Type III, "Collagen [is] improperly formed. Enough collagen is made but it is defective.
[Symptoms are]:
Bones fracture easily, sometimes even before birth.
Bone deformity, often severe.
Respiratory problems possible.
Short stature, spinal curvature and sometimes barrel-shaped rib cage.
Triangular face.
Loose joints.
Poor muscle tone in arms and legs.
Discolouration of the sclera (the 'whites' of the eyes), often turning blue during severe break.
Early loss of hearing possible
Type III is distinguished among the other classifications of OI as being the "Progressive Deforming" type, wherein a neonate presents with mild symptoms at birth and develops the aforementioned symptoms throughout life. Lifespan may be normal, albeit with severe physical handicapping."
So life expectancy is affected by the genetic diseases Travellers are most susceptible to, and quality of life too.
There are definitely aspects of their culture that are problematic for non-Travellers, and when it comes to shooting yourself in the foot, Travellers seem to excel.
But PrincessTamTam's question is really the only valid one to arise from this thread and its predecessor. "Where is the harm in trying a different tack, cutting them some slack no matter whether they deserve it, being the grown up and actually attempting to sort out an answer once and for all?" - as opposed to spending £18 m to evict them now and potentially even more in order to keep them moving on.