Many anthropologists take the view that religions are adaptive. Some theorists argue that religion helps individuals reduce anxiety and uncertainty. Others stress societal needs of solidarity and cooperation. These are general needs, and it is easy to imagine why reducing anxiety or increasing cooperation would be important.
But some particular customary aspects of religious belief, at least on the surface, do not appear to be adaptive. For example, the Hindu belief in the sacred cow has seemed to many to be the very opposite of a useful or adaptive custom. Their religion does not permit Hindus to slaughter cows. Why do the Hindus retain such a belief? Why do they allow all those cows to wander around freely, defecating all over the place, and not slaughter any of them? The contrast with our own use of cows could hardly be greater.
Marvin Harris suggested that the Hindu use of cows may have beneficial consequences that some other use of cows would not have. Harris pointed out that there may be a sound economic reason for not slaughtering cattle in India. The cows, and the males they produce, provide resources that could not easily be gotten otherwise. At the same time, their wandering around to forage is no strain on the food producing economy.
The resources provided by the cows are varied. First, a team of oxen and a plow are essential for the many small farms in India. The Indians could produce oxen with fewer cows, but to do so they would have to devote some of their food production to feeding those cows. In the present system, they do not feed the cows, and even though poor nutrition makes the cows relatively infertile, males, which are castrated to make oxen, are still produced at no cost to the economy. Second, cow dung is essential as a cooking fuel and fertilizer. The National Council of Applied Economic Research estimated that an amount of dung equivalent to 45 million tons of coal is burned annually. Moreover, it is delivered practically to the door each day at no cost. Alternative sources of fuel, such as wood, are scarce or costly. In addition, about 340 million tons of dung are used as manure—essential in a country obliged to derive three harvests a year from its intensively cultivated land. Third, although Hindus do not eat beef, cattle that die naturally or are butchered by non-Hindus are eaten by the lower castes, who, without the upper-caste taboo against eating beef, might not get this needed protein. Fourth, the hides and horns of the cattle that die are used in India’s enormous leather industry. Therefore , because the cows do not themselves consume resources needed by people and it would be impossible to provide traction, fuel, and fertilizer as cheaply by other means, the taboo against slaughtering cattle may be very adaptive.
James Frazer – totemic origin -> Cooperative Theory