"When this happened, the male acquired a motive for keeping the female, or, speaking more generally, his sexual objects, near him; while the female, who did not want to be separated from her helpless young, was obliged, in their interests, to remain with the stronger male." Sigmund Freud Civilization and Its Discontents 1929 Book IV footnote
The family is the first unit of society. A true family involves a bond between offspring and parents who invest in offspring something other than their gametes and birthing. Animal life until the influence of culture is shaped primarily by natural selection which decides what is inherited by posterity.
Not all living things have sex. Reproduction by multiplication creates offspring with most of the same DNA as the parent. With sex, offspring have half of each parent's DNA, and the individual must find and be a partner fit enough to ensure the survival of their genes in changing environments over generations. Sexes evolved it is thought because it offers greater genetic variation relative to asexual reproduction for future generations to continually adapt to parasites, the "Red Queen" hypothesis. Why two sexes? It seems to have been the most stable arrangement due to its popularity but isn't the only way things could have gone.
Sex is the most important bond between animals besides birth, but in most animals this occurs during a small part of the year, heat season, and the male and female don't stick around with each other after that. Another bond is that between offspring and mother, but this becomes an important bond later with birds who have nests and pair bonds and mammals who give live birth and provide fluids to their young after birth. Reptiles just lay and bury eggs and leave them to hatch on their own. Giving live birth and providing milk gives mammal females a stronger bond to offspring than reptiles and their eggs.
Our distant evolutionary ancestors didn't have specialized sexual organs. They had a cloaca like birds and reptiles, a single hole for excrement and fertilization. The specialization of genitalia is a later acquisition in developmental history. Placental mammals, most mammals, don't have a cloaca. The reason is that most mammals don't lay eggs; the embryo develops internally and demands fluids provided by the mother, thus specializing sexual organs from the birthing process.
The "invention" of specialized genitals is because of the gestation and live birth of mammals. This is the first step in sexual organs becoming divorced from other bodily functions and sexual activity becoming more than a reproductive activity, leading to other bonds between sexes. Both greater mammalian maternal attachment to the child and greater sexual attachment of males to females are linked to these anatomical changes.
The major biological breakthrough was sexuality becoming continuous rather than periodic. Most animals go through seasons of heat and rut, reproducing during a particular time of the year. Human and ape females go through monthly cycles of ovulation and can have sex year round. There aren't as obvious signs for female ovulation, by "hiding" ovulation regular sexual activity is encouraged. Unlike chimpanzees and other apes however, human female sexual organs aren't on display and don't give the obvious sign of ovulation. This is the first step toward social bonding as males have a motive for being around females continuously. Continual sexual receptivity and "concealed" ovulation.
Strengthening the sexual bond is face to face sex rather than from behind, which is almost exclusive to humans. Having genitals and not a cloaca is the first reason for this, as is being bipedal with the organs on display, with greater lower limb locomotion. This creates an affective bond, individualizing the sexual experience. This would be quite adaptive to get males to stick around to invest in their offspring.
Having a big brain requires a long period of physical development outside of the womb. Our big heads wouldn't fit through the birth canal if allowed to grow any larger, and so we're born premature. It takes over a year for a baby to walk, whereas foals can get and go when they're born. Its not for 15 or 20 years that we're considered adults.
A basic sexual division of labor would emerge from differences in parental investment in offspring which would be considerable to develop those big heads; man the hunter and woman the gatherer. The father would go out and hunt/find food to provide for the child and the mother would spend time caring for the child, feeding. This would be due to a stronger bond between mother and child because she always knows the child is hers whereas the male cannot be certain. The mother's mobility is limited by the child as carrying the youngling would immobilize at least one arm and limit activity to gathering within the area. Men with less of an attachment to the child would go hunt. Since a man only invests his sperm at one moment for the development of a child whereas a woman has to carry the fetus for nine months, women should be more "choosy" when it comes to a mate. A male would have to demonstrate their commitment by provision of resources. This would be done in competition with other men who if not successful have to wait at least nine months for another chance or find another partner. In terms of children, women are guaranteed a child if pregnancy is successful.
The limited mobility of bipedal motion, with no wings, and the long time it takes to develop physically due to large heads precludes multi-generational life. Having a campsite to go home to where women and children would be would be advantageous due to limited mobility. A mother can't just fly off and start her own nest like birds. Most likely she would stay with members of the group, or possibly join another group presumably of the male partner (matrilocal versus patrilocal residence). Having a home camp would preclude multi-generational living. Though life expectancy was low, the number partially dragged down by high infant morality, some of those who survived into adulthood could assist care for grandchildren. This "investment", presumably by the mother's parents, wouldn't be as much as a mate would provide, but would certainly help. Knowledge could be passed down directly from generation to generation, a gerontocracy of knowledge.
The family is the first unit of society. A true family involves a bond between offspring and parents who invest in offspring something other than their gametes and birthing. Animal life until the influence of culture is shaped primarily by natural selection which decides what is inherited by posterity.
Not all living things have sex. Reproduction by multiplication creates offspring with most of the same DNA as the parent. With sex, offspring have half of each parent's DNA, and the individual must find and be a partner fit enough to ensure the survival of their genes in changing environments over generations. Sexes evolved it is thought because it offers greater genetic variation relative to asexual reproduction for future generations to continually adapt to parasites, the "Red Queen" hypothesis. Why two sexes? It seems to have been the most stable arrangement due to its popularity but isn't the only way things could have gone.
Sex is the most important bond between animals besides birth, but in most animals this occurs during a small part of the year, heat season, and the male and female don't stick around with each other after that. Another bond is that between offspring and mother, but this becomes an important bond later with birds who have nests and pair bonds and mammals who give live birth and provide fluids to their young after birth. Reptiles just lay and bury eggs and leave them to hatch on their own. Giving live birth and providing milk gives mammal females a stronger bond to offspring than reptiles and their eggs.
Our distant evolutionary ancestors didn't have specialized sexual organs. They had a cloaca like birds and reptiles, a single hole for excrement and fertilization. The specialization of genitalia is a later acquisition in developmental history. Placental mammals, most mammals, don't have a cloaca. The reason is that most mammals don't lay eggs; the embryo develops internally and demands fluids provided by the mother, thus specializing sexual organs from the birthing process.
The "invention" of specialized genitals is because of the gestation and live birth of mammals. This is the first step in sexual organs becoming divorced from other bodily functions and sexual activity becoming more than a reproductive activity, leading to other bonds between sexes. Both greater mammalian maternal attachment to the child and greater sexual attachment of males to females are linked to these anatomical changes.
The major biological breakthrough was sexuality becoming continuous rather than periodic. Most animals go through seasons of heat and rut, reproducing during a particular time of the year. Human and ape females go through monthly cycles of ovulation and can have sex year round. There aren't as obvious signs for female ovulation, by "hiding" ovulation regular sexual activity is encouraged. Unlike chimpanzees and other apes however, human female sexual organs aren't on display and don't give the obvious sign of ovulation. This is the first step toward social bonding as males have a motive for being around females continuously. Continual sexual receptivity and "concealed" ovulation.
Strengthening the sexual bond is face to face sex rather than from behind, which is almost exclusive to humans. Having genitals and not a cloaca is the first reason for this, as is being bipedal with the organs on display, with greater lower limb locomotion. This creates an affective bond, individualizing the sexual experience. This would be quite adaptive to get males to stick around to invest in their offspring.
Having a big brain requires a long period of physical development outside of the womb. Our big heads wouldn't fit through the birth canal if allowed to grow any larger, and so we're born premature. It takes over a year for a baby to walk, whereas foals can get and go when they're born. Its not for 15 or 20 years that we're considered adults.
A basic sexual division of labor would emerge from differences in parental investment in offspring which would be considerable to develop those big heads; man the hunter and woman the gatherer. The father would go out and hunt/find food to provide for the child and the mother would spend time caring for the child, feeding. This would be due to a stronger bond between mother and child because she always knows the child is hers whereas the male cannot be certain. The mother's mobility is limited by the child as carrying the youngling would immobilize at least one arm and limit activity to gathering within the area. Men with less of an attachment to the child would go hunt. Since a man only invests his sperm at one moment for the development of a child whereas a woman has to carry the fetus for nine months, women should be more "choosy" when it comes to a mate. A male would have to demonstrate their commitment by provision of resources. This would be done in competition with other men who if not successful have to wait at least nine months for another chance or find another partner. In terms of children, women are guaranteed a child if pregnancy is successful.
The limited mobility of bipedal motion, with no wings, and the long time it takes to develop physically due to large heads precludes multi-generational life. Having a campsite to go home to where women and children would be would be advantageous due to limited mobility. A mother can't just fly off and start her own nest like birds. Most likely she would stay with members of the group, or possibly join another group presumably of the male partner (matrilocal versus patrilocal residence). Having a home camp would preclude multi-generational living. Though life expectancy was low, the number partially dragged down by high infant morality, some of those who survived into adulthood could assist care for grandchildren. This "investment", presumably by the mother's parents, wouldn't be as much as a mate would provide, but would certainly help. Knowledge could be passed down directly from generation to generation, a gerontocracy of knowledge.
Always operating with this first unit of society is kin selection. All of this investment would be adaptive because of its promotion of inclusive fitness; propagation of genes of the individual as well as relatives sharing genes. A child shares half its genes with both parents and siblings, a fourth of genes with grandparents and half-siblings and uncles/aunts, and an eighth of genes with cousins and great-grandparents. Hunter gatherers lived in small bands of 10 to 100 people who were most likely related in some way. Sexual couples all having their kids could continually mate together. Could the children of Adam and Eve avoid incest in sufficient numbers? What effect would this level of relatedness have on social life compared to contemporary society?
Larger social groups like tribes could have emerged from the practice of exogamy, individuals leaving a group to find partners not related to them to prevent incest. Perhaps men stole women from a rival group, something that began the Trojan war in Homer's Iliad. Or men challenged the men of another group to battle and the outcome could've joined members of the two groups. The resolution of the conflict between families could've been like the wergeld payment of old Germanic law in which restitution for theft, damage, injury or murder was paid to the victim's family to prevent a blood feud between the families of the victim and perpetrator, Hatfields and McCoys style enmity. The practices of brideprice and dowry, which are different, could also be reflective of an origin to larger social organization from a merging of different families through a mutually acceptable agreement. Maybe exogamy began with men leaving the group since a surplus of men doesn't lend to as much reproductive opportunity as a surplus of women to fewer men. A polygamous situation could have sparked this male exogamy by monopolizing multiple women to a single or few men and leaving the other men with no reproductive prospects in the group.
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