I am a Muslim woman and have Christian friends, who often ask about the prohibition of pork in Islam. Could you give me a scientific explanation of this prohibition?

At the outset, it needs to be understood that the basic objective of Islam is purification -- both physical and spiritual. Therefore, it only prohibits things that are unclean and hinder purification. Certain edibles are also prohibited because of this very reason.

The second thing which needs to be appreciated is that in case of most edibles, human nature is well equipped to know for itself which food stuff is inedible1 It is only in a very small sphere that human nature is unable to pronounce a clear verdict on edibles that are unclean, and it is in this sphere in which the Sharī‘ah has guided man. Consequently, where this guidance is stated, the words of the Qur’ān subtly allude to the fact that this guidance is being provided about edibles. The prohibition of animals or stuff which is non-edible is not mentioned for the simple reason that human nature has already pronounced them to be inedible:

Say: ‘I find not in the Message received by me by inspiration forbidden to a person who eats things which are edible, unless it be dead meat, or blood or the flesh of swine ….’ (6:145)

Human nature has always remained averse to eating beasts. No one generally eats carnivores (animals that feed on meat) like lions, tigers, elephants etc. Such animals were never liked by man for eating. On the other hand, herbivores (animals that feed on plants) like goats, cows and camels have always been relished by human nature. The meat of such animals has always been eaten.

Consider now the pig. We know that besides being a herbivore it is also a carnivore. Such an animal we know is called an omnivore. In other words, since the pig simultaneously belongs to both categories2 it would have been difficult for human beings to class it in either. Its herbivorous nature could have impelled some to eat it while its carnivorous nature could have dispelled some from eating it. So man could have faltered in grouping it in either of the two categories. It is here that the Almighty told us that its carnivorous nature (and therefore its beastliness) is dominant over its herbivorous nature, and therefore it should be avoided.

Consequently, in the Old Testament, the prohibition of pork is mentioned in words which subtly allude to this double nature of the animal:

The pig is also unclean; although it has a split hoof, it does not chew the cud. You are not to eat their meat or touch their carcasses. (Deuteronomy, 14:8)

1.There may be slight differences among human beings in classifying something as inedible, but, by and large, the dividing line is pretty clear. For example we know that once in the time of the Prophet (sws) the meat of a certain type of lizard was brought before the Prophet (sws). He felt an abhorrence for it and refrained from eating it. When the celebrated warrior, Khālid Ibn Walīd (rta) asked whether it was prohibited in Islam, the Prophet (sws) replied in the negative and said that he personally disliked it. (For details see Bukhārī, Kitābu’l-Atimah)

2. It belongs to the genre of Artiodactyls and is omnivorous. (See Encyclopaedia Britannica 15th ed., vol 2,  [USA: Helen Hemingway Benton Publishers, 1979], p. 79)