Monogamy is the most natural form of matrimony. In monogamy the spirit of special exclusiveness exists, that is to say, of individual and particular “having”, which is, of course, different from the feeling of the possession of material things. In monogamy both the wife and the husband consider the sentiments, affections and sexual advantages from the other as his or her own and special to him or her.
The converse of monogamy is polygamy or the shared condition of being a wife or husband. Polygamy, or the shared condition of being a wife or husband, can be envisaged in several forms.
One of these forms is that there is no special exclusiveness on either side; no man has an exclusive relationship with any particular woman, and no woman is exclusively tied to any man. This imagined situation is the very one which is known as sexual communism. This form pre-supposes the rejection of family life. Neither history nor even guesses and theories concerning pre-history give any clue of a time when human beings had absolutely no family life at all and when sexual communism prevailed. The way of life which they call by this name and which they claim existed among some primitive peoples was really a middle stage between an exclusive family system and sexual communism. It is said that in some tribes several brothers would marry several sisters jointly, or that a group of men from one tribe would jointly marry a group of women from another tribe.
In the first volume of The Story of Civilization, Will Durant writes: In a few cases we find “group marriage,” by which a number of men belonging to one group married collectively a number of women belonging to another group. In Tibet, for example, it was the custom for a group of brothers to marry a group of sisters, and for the two groups to practice sexual communism between them, each of the men cohabiting with each of the women. Caesar reported a similar custom in ancient Britain. Survivals of it appear in the “levirate,” a custom existing among the early Jews and other ancient peoples, by which a man was obliged to marry his brother’s widow”
According to what can be inferred from Plato’s Republic, and from what historians in general confirm, it seems that he, in his theory of philosopher- kings and king-philosophers, proposed a shared family for this class of citizen. As we know, some communist leaders of the nineteenth century also made the same proposal, but, according to the book Fru’id va tahrim-e zanashu’i ba maharim (Freud and the Forbidding of Incest)  as a result of numerous bitter experiences, the law of monogamy was recognized as the only official law in 1938 by some of the powerful communist countries.
Another form of multiple partnerships is that of polyandry. In other words at one time a woman may have more than one husband. Will Durant writes: “This state of affairs can be observed in the tribe of Tuda and in some of the tribes of Tibet.”
In Sahih al-d-Bukhari,  A’ishah (the Prophet’s wife), is reported to have related that “In Arabia in the pre-Islamic period four kinds of matrimony were practised: One kind was the same as that which prevails at present, that is, a man, through the father of the girl, asks for girl’s hand in marriage and after settling the dower marries her. As the child, born to that girl after marriage is of determined parenthood, the father’s responsibilities towards that child are clear. In another kind, the man, at the same time as he is married to a particular woman, transfers or entrusts her wifehood to some other man for a limited period for the purpose or having noble children trough him. The custom was that he himself kept away from his wife and advised her to surrender herself to that particular man, as long as she had not become pregnant by that man, while he himself continued to keep him self away from her. As soon as it was established that she was pregnant, he renewed his sexual relations with her. They did this with those men whom they considered worthier than themselves to make the woman pregnant. In all good faith they took this step for the improvement and welfare of their progeny and the improvement of their stock. This kind of matrimony, which was matrimony during the period of matrimony to another man, was called as “nikahu l-istibda ‘” (i.e., marriage pact from which some benefit is sought). Another kind of matrimony was that a group of men, less than ten in number, used to arrange to have sexual relations with a particular woman. When the woman became pregnant and a child had been born to her, the woman summoned all the members of that group, and, in conformity with the convention of that period, none of them could refuse to be present at her call. Everyone used to turn up and on that occasion that woman made a choice of a father for her child from amongst that group according to her own inclination. That man, however, was not entitled to refuse to acknowledge that child as his own. Thus, the child was considered to be the legal and official child of that man.
“The fourth form of conjugal relationship was that the woman was officially a kind of prostitute. Any man, without exception, could have sexual intercourse with her. Women of this class used to set up flag on the top of their house, and by that sign they could be distinguished. Whenever a child was born to a woman of this class, the women gathered together all the men with whom she had sexual intercourse and then fortune-tellers and physiognomists were called in. In the light of the distinctive marks and features of the child, the physiognomists declared their expert opinion as to whom the child belonged, and that chosen man was obliged to accept the view of the physiognomists and had to consider that child his official child.
“All these systems of conjugal relationship existed in the pre-Islamic period till Allah chose Muhammad (s.a.w.a.) for the Prophethood, and he annulled all these customs except the one which is at present in practice.”
By this it is evident that the custom of plurality of husbands existed among the Arabs of the pre-Islamic age. In The Spirit of Laws, Montesquieu  wrote:
“Albuzeir-el-Hassen (Abu az-Zahir al-Hasan) one of the Mahomedan Arabs who, in the ninth century went into India and China thought this custom (i.e., polyandry) a prostitution (vol.1, p.272)
He also wrote:
“In the tribe of the Naires, on the coast of Malabar, the men can have only one wife, while a woman, on the contrary, may have many husbands. The origin of this custom is not I believe difficult to discover. The Naires are the tribe of nobles, who are the soldiers of all the nations. In Europe soldiers are forbidden to marry; in Malabar, where the climate requires greater indulgence, they are satisfied with rendering marriage as little burden-some to them as possible: they give one wife amongst many men, which consequently diminishes the attachment to a family, and the cares of housekeeping, and leaves them in the free possession of a military spirit.” (ibid. p.273)
The difficulty with polyandry:
The greater difficulty that lies with polyandry, and which has been the cause of this custom not being successful in practice, is that there is a problem because the parentage of the children is not known. In this kind of conjugal relationship the connection between a father and his children is unspecified. Just as sexual communism could not find a foot-hold, so also polyandry could not make itself popular in any society worth the name. The reason is that, as we have pointed out in one of the preceding articles, family-life, which is the establishment of a secure shelter for the next generation and a definite attachment between the previous and the future generations, is an instinctive demand of human nature. If, incidentally, and as an exceptional case, polyandry happened to exist among certain categories of men, it does not serve as an argument for the theory that the setting up of one’s own family is not the result of an instinctive human urge; just as preference for an unmarried life, and a dislike for setting up a family among a section of men or women is only a kind of deviation and cannot be adduced as an argument to show that human beings are not inherently disposed to living in families. Polyandry is eventually not only inconsistent with man’s innate desire for exclusivity and love for his children, but it is against the nature of woman also. Psychological research has proved that women are in favour of monogamy more than men.
The other form and the other kind of multiple partnerships is polygyny. Polygyny unlike polyandry and sexual communism is more usual and has a comparatively more accepted status. It does not exist only in savage tribes, but many civilized nations have also adopted it. Leaving aside the pre-Islamic Arabs, the custom existed also amongst the Jews, amongst the Iranians in the Sassanid period, and in some other nations.
Montesquieu wrote: “This law (equality in behaviour towards all wives in polygyny) is also in force in the Maldivian Isles, where they are at liberty to marry three wives.” (The Spirit of Laws, vol.1, p.274)
He also wrote: “Some particular reasons induced Valentinian to permit polygamy in the (Roman) empire. That law, so improper for our climates, was abrogated by Theodosius, Arcadius and Honorious.” (ibid. p.271)
Islam and polygyny:
Islam did not completely do away with polygamy, although it did do so as far as polyandry was concerned. Instead, it limited and restricted it. It abolished its non- restrictedness and confined it to a maximum of four wives. Islam, moreover, laid down conditions and restrictions, and did not allow everybody, to have several wives. We shall comment upon those limits and restrictions in the coming sections, and shall likewise throw light upon the reasons why Islam did not absolutely abolish polygyny.
It is strange that in the Middle-ages, among all the propaganda that was carried out against Islam, it was alleged that it was the Prophet of Islam who introduced polygyny into the world for the first time, and it was claimed that the foundation of Islam lay in polygyny. It was asserted that the cause of the speedy conversion to Islam among the various nations and peoples of the world is the permissibility of polygyny, and it was also given to be understood that the prime cause of the decline of the east was again polygyny.
In the first volume of his The story of Civilization Will Durant writes: Medieval theologians thought that Mohammed had invented polygamy, but it antedated Islam by some years, being the prevailing mode of marriage in the primitive world. Many causes conspired to make it general. In early society, because of hunting and war, the life of the male is more violent and dangerous, and the death rate of men is higher than that of women. The consequent excess of women compels a choice between polygamy and the barren celibacy of a minority of women; but such celibacy is intolerable to peoples who require a high birth rate to make up for a high death rate, and who therefore scorn the mateless and childless woman.
“Doubtless polygamy was well adapted to the marital needs of a primitive society in which women outnumbered men. It had a eugenic value superior to that of contemporary monogamy; for whereas in modern society the most able and prudent men may marry latest and have least children, under polygamy the most able men, presumably, secured the best mates and had most children. Hence polygamy has survived among practically all mature peoples, even among the majority of civilized mankind; only in our day has it begun to die in the Orient. Certain conditions, however, militated against it. The decrease in danger and violence, consequent upon a settled agricultural life, brought the sexes towards an approximate numerical equality; and under these circumstances open polygamy, even in primitive societies, became the privilege of the prosperous minority. The mass of the people practised a monogamy tempered with adultery, while another minority of willing or regretful celibates, balanced the polygamy of the rich.”
In La Civilization des Arabes, Gustave Le Bon  writes: There is no custom more despised and on which more erroneous ideas have been pronounced than polygamy. For the most serious of historians, polygamy has been the corner-stone of Islamism, the principle cause of the spread of the Koran, and at the same time of the decadence of the Orientals. These peculiar assertions are generally followed by indignant tirades on the unfortunate lot of the miserable women confined to the far reaches of the harem, guarded by ferocious eunuchs, and killed without pity when they no longer please their master.
“Such a picture is the opposite of the truth, and the reader who wishes to read this chapter putting aside his European prejudices will, I hope, be convinced that oriental polygamy is an excellent institution which greatly raises the moral standard of the peoples who practise it, gives much stability to the family and, as a final result, renders the woman infinitely more respected and more happy than in Europe.
“Before embarking on the proof of this, I will recall, firstly, that polygamy is completely independent from Islamism, for it existed before Mahomet among all the peoples of the East: the Jews, the Persians, the Arabs, etc. Those nations who adopted the Koran, therefore, had nothing to gain on this score by adopting polygamy. There has never been a religion, anyway, strong enough to transform traditions to the point of creating or preventing a similar institution. It is simply the consequence of the climate, of race and the various conditions of existence particular to the Orientals …………..
“In the West, where the climate and the temperament are however very much less demanding, monogamy is no longer to be found except in the law, and no one will contest, I think, that it is very rarely to be found in the behaviour of people. I cannot see in what way the legal polygamy of the Orientals is inferior to the hypocritical polygamy of the Occidentals; rather, I can, on the contrary, very well see in what way it is superior. One can therefore perfectly well understand how the Orientals who have visited our great cities find our indignation towards them to be most strange and judge it most unfavourably.” (pp. 421-2)
Truly, Islam did not initiate polygyny but limited its number, and at the same time laid down stringent conditions for it. Amongst most of the peoples and the communities which accepted Islam, this practice was customary, and under the commandments of Islam they had to comply with the limits and the conditions ordained by Islam.
Polygyny in Iran:
The Danish Pahlavi scholar Arthur Christenson wrote: (In Sassanian Iran) the family was based on polygamy. In practice, the number of wives a man had been related to his means, and, in general, the less well-off probably only had one wife. The master of the house the kadhagh-khvadhay, enjoy the right of patria potestas (sardarih-i dudhagh). The principle wife, zan-i padheshayiha, the “privileged” wife, was distinct from the “second-rank” wife, the “servant wife.” (Zan-i tchghariha). The legal situations of the two classes of wives were different. It would appear that bought slaves and women plundered in war were in the second class. We do not know if the number of “privileged” was limited, but the case of men who had two principle wives is often mentioned in matters of law. Every privileged wife was “woman of the house” (kadhagh-banugh), a household being specially set aside, it seems, for each one. The privileged wife had the right to be fed and kept by the husband for all her life; the same right belonged to her son up to the age of majority and to her daughters until marriage. As for a “servant-wife”, only her male children were adopted into the father’s family.”
In Tarikh-e ijtima ‘i-e Iran az inqirad-e Sasaniyan ta inqirad-e Umawiyan (The Social History of Iran from the Fall of the Sasanids to the Fall of the Umayyids) written by late Sa’id Nafisi, it is stated that: “The number of wives that a man could have was unlimited and in Greek documents it has been found mentioned that a man sometimes had several hundred wives in his house.”
In The Spirit of Laws Montesquieu relates from the Roman historian Agathias that: “In the reign of Justinian, many philosophers, displeased with the constraint of Christianity, retired into Persia. What struck them most ……was that polygamy was permitted amongst men who did not even abstain from adultery.” (vol.1, p.274) 
It should not be passed over unmentioned that the philosophers of Byzantium took refuge in court of Anüshiravan, King of Iran, and not in the court of Khusru Parviz. Montesquieu mistakenly wrote the name of Khusru.
Amongst the Arabs there was no limit to the number of wives. The restrictions ordained by Islam, and the laying down of a maximum limit in the number of wives was a difficult problem for a number of Arabs who had more than four wives. There were certain individuals who, it so happened, had ten wives, and they were obliged to give up six of them.
So it is clear that Islam did not introduce or originate polygyny. It has, on the other hand, laid down restrictions and limitations on it, but of course, it by no means abolished absolutely or annulled it. In the coming chapters we shall examine the causes of polygyny among humans and shall look into the question as to whether the cause of it is the high-handedness of man and his domination over woman, or whether there are some special necessities that have produced it. We shall examine those necessities and shall see whether certain factors are geographical and relate to particular regions or whether they are universally applicable. We shall look closely into the question of why Islam did not abolish this custom and also the limits, restrictions and conditions that it has laid down in connection with polygyny. We shall examine what, after all, the reasons are that human beings, men and women, are against polygyny. Does it have its root-cause in any human or moral reason, or are some other factors at work? These are the points which we shall discuss in the forthcoming chapters.
 Translated from the Persian, original untraced, (tr.)
 The first of the Kutub as-sittah, or “six” correct books of hadith transmitted in Sunni Islam. Compiled by Abu Abdillah Muhammad ibn Ismail al-Bukhari (194/256-810/870).
 Montesquieu (1689-1755) took fourteen years to write L’Esprit des lois. It was translated into English as The Spirit of Laws. (tr)
 Gustave Le Bon (1841-1931), doctor, psychologist and sociologist, travelled in North Africa and subsequently in India. Apart from La civilisation des Arabes he also wrote many other books, the most famous being Les Lois Psycologiques de Revolution des Peuples. (Tr.)
 A.Christenson: L’Iran sous les Sassanides. (2nd ed. Copenhagen, 1944) pp. 322-323 (translated from the French)
 In the French original, unlike the Persian translation, Khusru Parviz is not mentioned; the reference is only to “La Perse”. The Arabic translation has Kasra, seemingly on the correct assumption that the reference was to the time of the Khusru, Anushiravan. The Persian translator seems to have thought the reference was to Khusru II, Khusru Parviz. See what fellows. (Tr.)