« Gibbons and siamangs form the hylobatid family. Their "families" consist of a female, a male and several young. A "complete family" includes both parents, a very young unanerved child, another weaned child, a teenager and a subadult: from 2 - childless family - to 6 individuals - with all possible children. When the eldest approaches maturity, he is strongly encouraged to leave by the parent of the same sex. The gibbons fiercely defend their territory, unceremoniously hunting down any intruders. Infidelities are rare (partner surveillance). Each morning, the two adults sing powerful songs to which their neighbors respond. All these elements mean that gibbons have few social and emotional relationships. Dusting sessions remain limited between adults and children. They don't sleep in the same nest. Children do not play, and for good reason, with young people their own age. The role of the adult male is limited to the defence of the territory. There is no parental investment of the male, except in the Siamangs where fathers carry their children and dust them. Dominance relationships are balanced, with the female able to move her companion or vice versa. It seems that it depends more on the character of each other. There is no sexual dimorphism for body size or canines. However, in some species the color of the fleece differs, white for the female, black for the male. So goes life, peaceful, in gibbons and siamangs. This lineage of hominoids, separated from that of the great homoinoid apes for 19 million years in Asia, was once more diverse. But much uncertainty remains about its origins and evolution. We will note, however, that strong phylogenetic constraints are exerted on the social systems of hylobatids, whether they are frugivores such as gibbons or folivores such as siamangs. »

« (According to UN and Unicef data, one-third of women in the world are forced into marriage, with the majority still in their teens or having just left.) »

« Empirical sociosexual rules in primates - The asymmetry of parental investment is increasing, from early mammals to humans, to monkeys (to use an anthropocentric perspective) at the expense of females and women. The more asymmetry in parental investment, the more sexual coercion there is. The more complex structures and organizations species have, the more sexual coercion there is. The difference in body size between females and males, sexual dimorphism, is not correlated with the level of sexual coercion. There are phylogenetic constraints on structures (solitary, monogamous, polygynous or polyandrous, polygynandres) and social organizations (exogamie of males or females). Notwithstanding the phylogenetic constraints specific to each lineage, there is always a great diversity of organization, more rarely of structure, between the species of these lineages, with the exception of gibbons and siamangs (hylobatids). Land species tend to be more coercive than arboreal species (socio-ecology). Two major evolutionary trends differ in monkeys and great apes: one towards more sexual coercion in polygynous and polygynandre species, the other towards monogamy, sometimes polyandry, and the absence of sexual coercion. Once monogamy is acquired, there is no evolution towards other forms of sexuality and reproduction (which would explain the uniformity of monogamy in hylobatids). »