Humans definitely do not have the social organization of gorillas. All human societies are multi-male in the sense that several adult males live together, form bonds, and cooperate among themselves. Neither do we have the organization of chimps.
In stark contrast to chimps, human females form strong bonds with one another and human males can have strong bonds with human females. Bonobos also have flexible bonding, but we differ from bonobo social organization in terms of our flexibility. Human cultures can have the male-dominated social structure of chimps, an egalitarian structure, or possibly even strong matriarchies.
Our mating behaviour differs from our ape relatives in two important ways. The first is our flexibility. Our cultures can be monogamous, polygamous, or polyandrous. They can either permit or strongly proscribe promiscuity.
The second difference between us and apes is marriage. All human societies that have ever been described recognize marriage, although the form of marriage may differ from our Western view of the institution.
Anthropologists disagree about the universals in marriage, but the following characteristics are typically present:
(I) Marriage is socially recognized. That is, the members of a village, tribe, or state recognize the union.
(II) Marriage has the expectation of generating offspring.
(III) Marriage is associated with kinship. While kinship ties can happen outside of marriage, marriage always involves the right of the offspring to be socially recognized as the kin of the parents and of the parents’ kin.
(IV) Marriage has relative permanence. The marital state is entered into for a long, as opposed to a short, time period (i.e., a brief sexual encounter, a night, a week, or a breeding season). The length of the time period is, of course, variable.
(V) Marriage involves some degree of sexual exclusivity. The partners in a marriage have the right to have sex with each other. Also one or both partners are often socially admonished not to have sex with certain others. The degree of sexual exclusivity is variable across cultures.
(VI) Marriage involves the transfer of property and/or title. Again, exactly what is transferred and the degree to which it is transferred varies, but most societies that have personal property recognize that it can be bestowed on offspring.
Affective bonding is a reason for marriage. Love and romance may be the most variable characteristic of marriage. Many cultures condone arranged marriages between people who may have never even met. Typically, such marriages are entered for the purpose of establishing kinship and/or property ties.
However, every culture either overtly recognizes romance as a legitimate reason for marriage or has myths or stories about couples in love who want to enter the state of marriage and consider it tragic if they cannot fulfill their desires.
While there are legitimate reasons to disagree with this list or to argue that other factors should be added to it, it is quite obvious that gorillas, chimps, and bonobos do not have the institution of marriage as we humans do.
Humans can and do mate without marriage and can even have children, the recognition of kinship, and the transference of property outside of the institution. But virtually every human culture recognizes a special union between one (or more) male(s) and one (or more) female(s) that gives them the right to have sex, bear children, etc.