Over time, the Bedouin developed several sub-types or "strains" of Arabian horse, each with unique characteristics, and traced through the maternal line only. According to the Arabian Horse Association, the five primary strains were known as the Keheilan, Seglawi, Abeyan, Hamdani and Hadban. Carl Raswan, a promoter and writer about Arabian horses from the middle of the 20th century, held the belief that there were only three strains, Kehilan, Seglawi and Muniqi. Raswan felt that these strains represented body "types" of the breed, with the Kehilan being "masculine", the Seglawi being "feminine" and the Muniqi being "speedy". There were also lesser strains, sub-strains, and regional variations in strain names. Therefore, many Arabian horses were not only "Asil", of pure blood, but also bred to be pure in strain, with crossbreeding between strains discouraged, though not forbidden, by some tribes. Purity of bloodline was very important to the Bedouin, and they also believed in telegony, believing if a mare was ever bred to a stallion of "impure" blood, the mare herself and all future offspring would be "contaminated" by the stallion and hence no longer "Asil."