Why is Ruku amazed and perplexed by the Muslim women?

"The village portrayed in this novel must have been extremely isolates since Ruku was amazed by the Muslim women whose husbands worked at the tannery. Muslims were common in India at the time. One reason why the Muslims rather than Hindus worked in the tannery might have been that they have no aversion to handling cow hides. To Hindus, the cow is sacred, revered, and sometimes worshipped. Hindus generally do on eat beef and do not handle a cow after it has been slaughtered. Nathan's two sons violated this religious practice by working in the tannery. In addition, they probably violated the caste system since each caste is associated with a certain occupation, and they were born into the agricultural caste."