The Sinister Reason Why People Fall in Love

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The Sinister Reason Why People Fall in Love

Romance may have existed in some form long before the origin of humanity, and some believe it was born out of death and violence

By Melissa Hogenboom
15 February 2016

Your heart beats a little faster, glands open to secret tiny dribbles of sweat, and your body starts producing hormones, which make you feel a bit giddy and warm inside.
These are some of the biological processes that occur as you are thrust into the early throes of love – or infatuation, it can be hard to tell which it is.
Love is such a pervasive part of our humanity that art and culture is filled with references to love won and love lost. Libraries have shelves of books filled with romantic prose. "Love is not time's fool," wrote Shakespeare in sonnet 116: "Love alters not with his brief hours and weeks / But bears it out even to the edge of doom."
It seems Shakespeare was more correct than he could have known. Peer into the evolution of love in the animal kingdom and it becomes apparent that love had its beginnings long before the advent of humanity. What's more, it could have been born out of something quite sinister.
The journey to love as we know it today began with sex, which was one of the first things life on Earth figured out how to do. Sex began as a way to pass on an organism's genes to the next generation.
To love, life first needed a brain that could deal with emotions. It was not until a few billion years after life began that the brain began its journey to existence. At first it was only a small clump of cells.
Fast forward to around 60 million years ago, when the first members of our family, the primates, appeared. Over millions more years of evolution, some primates would evolve ever bigger brains, eventually producing modern humans.
But there was a problem. As our brains grew, our babies had to be born earlier in development. Otherwise their heads would be too big to pass through the birth canal.
As a result, baby gorillas, chimps and humans are almost entirely helpless. Their parents therefore had to spend ever more time caring for them.
This prolonged childhood created a new risk.
In many primates today, a mother with a dependent infant is unavailable to mate until her infant is weaned. To get access to her, a male would first have to kill her child. This sort of targeted infanticide goes on in many species, including gorillas, monkeys and dolphins.
This led Kit Opie of University College London in the UK and his colleagues, to propose a startling idea. Almost a third of primates form monogamous male-female relationships, and in 2013 Opie suggested that this behaviour had evolved to prevent infanticide.
His team peered back into the family tree of primates to reconstruct how behaviours like mating and parenting changed over the course of evolution. Their analysis suggested that infanticide has been the driving force for monogamy for 20 million years, because it consistently preceded monogamy in evolution.
Other species found different solutions, which is why not all primates are monogamous. For instance, chimps and bonobos minimise the risk of infanticide by being highly promiscuous. The males do not kill babies because they do not know which are theirs.
But in those species where males and females started bonding strongly, their offspring's chances of survival improved because the males could help out with parenting. As a result, monogamy was favoured by evolution, says Opie.
This process may have been a one-way street, says Robin Dunbar of the University of Oxford in the UK. It could have resulted in major changes in the brain, "to keep the pair-bond together for life". This includes a preference for your partner and antagonism towards potential rivals.
This in turn could have been the "kick" that changed human evolution, says Opie. Extra male care helped early human societies grow and thrive, which in turn "allowed our brains to grow larger than our closest relatives".
There is evidence to back this up. As brain size started to expand, so did cooperation and group size. We can see a trend towards larger groups and more cooperation in the early-human species Homo erectus, which lived almost two million years ago.
What's more, it seems that aspects of love depend on regions of the brain that only appeared quite recently in our evolutionary history.
Stephanie Cacioppo of the University of Chicago in Illinois, US, scoured the scientific literature to find fMRI brain imaging studies that examined the parts of the brain involved in love. She found that the most intense and "abstract" states of love rely on a part of the brain called the angular gyrus.
This is known to be important for certain aspects of language, like metaphors. This makes some sense, as without complex language we cannot express the more refined and intense aspects of our emotions. Conceivably, Shakespeare's angular gyrus was active when he penned his love sonnets.
The angular gyrus is only found in great apes and humans.
We do not actually know what role it plays in apes' emotions, says Cacioppo, because "complementary fMRI experiments have not been performed on apes". So we do not know what chimpanzees feel about their mates. Obviously they do not write sonnets, but neither do most humans.
Still, Cacioppo's findings offer some support to the idea that our growing brains helped love to flourish.
However, Opie's idea that infanticide kick-started this process is controversial. Not everyone agrees it played any role in the development of monogamy.
Anthropologist Robert Sussman of Washington University in St Louis in Missouri, US is one of the sceptics. He says that both monogamy and infanticide are such unusual behaviours that they are unlikely to be linked.
There are alternatives. A 2014 study suggested monogamy evolved as an outgrowth of a "mate guarding strategy": that is, males staying with a female to ensure that no one else mates with her.
One year later, another study reconstructed the evolution of another group of primates called lemurs. It found that female competition could have encouraged pair bonds.
Opie disagrees. He says the methods in these studies "cannot be used to determine the switch to monogamy".
What is certainly true is that many primates get by just fine without pair-bonded parents, and presumably without anything akin to romantic love. But there is one thing all primates do have in common: a strong mother-child bond.
This is true, "even in the nocturnal primates that live solitarily," says Sussman. He suggests that the brain processes underlying the mother-child bond were "hijacked" to create romantic love.
There is evidence from neuroscience to suggest he is right.
Love is hard to define, but neuroscientists agree that there are several overlapping stages.
The first stage is sexual desire: we feel attracted to another person. Touching them releases feel-good chemicals and we experience an intense longing to be with them.
Parts of our limbic system, one of the more ancient bits of the human brain, are active during this stage. This includes the insula, an area known to be involved in intense emotional experiences. The ventral striatum is also in overdrive. It is the hub of the brain's reward system, and when we see an attractive face it lights up: we are rewarded simply by looking at the person we desire.
As desire moves onto the next stage – romantic love – the limbic system again plays a key role. It pumps out the feel-good chemical dopamine and the hormone oxytocin, which binds people together.
This progression implies that intense pleasure from the sexual desire stage can lead directly to love, says Cacioppo. "Love tends to grow out of desire. You cannot passionately love someone you never desire."
At the same time, other more advanced areas of the brain are suppressed. For instance, research has shown that parts of the prefrontal cortex are deactivated. This is an area involved in rational decisions.
In this stage, we are literally "crazy in love". People in love do not process the world around them, says Thomas Lewis, a neuroscientist at the University of California, San Francisco in the US. "They're not evaluating the person critically or in a highly cognitive way."
Serotonin, which usually helps us feel calm, is also suppressed. This makes some sense when you consider how obsessed we can become when in love. Serotonin levels are also low in the brains of individuals with psychological disorders like obsessive compulsive disorder.
"What evolution wants from the falling in love state is for the two individuals to spend a lot of time together… in order to get a pregnancy going," says Lewis.
But once the deed is done, couples do not stay bound together in such an intense, obsessive state for long. After several more months, sometimes after an intermediate "honeymoon period", the companionship stage begins.
Now the serotonin and dopamine levels normalise. But there is still a feeling of closeness, helped along by more oxytocin. If you suppress oxytocin in a monogamous species, such as a prairie vole, the animals stop being monogamous.
"The bonds that hold people together are not dopamine-driven or by intense delirious excitement," says Lewis. "There is reward there but it's more sedate."
This brings us back to Sussman's suggestion that romantic love evolved out of mother-child bonding. The bonds of long-term couples are similar to those between mother and child, and rely on similar hormonal processes.
In both animals and humans, research has shown that separation from a "loved one" creates similar feelings of emotional pain. It makes sense that we want to avoid the pain of separation by staying together.
These feelings seem to have deep roots in evolutionary history.
The limbic system plays a key role in all the known stages of love. Many other mammals, and even reptiles, have some form of limbic system. This area of the brain was around long before the first primates.
"The oldest parts of the brain are involved in attachment, in pair-bonding, and these areas are activated in many species," says Cacioppo.
In other words, animals' brains have been primed for at least some forms of love for hundreds of millions of years. Along the way, other factors pushed our ancestors to evolve ever bigger brains, allowing romantic love to get its claws into us.
Whether it was infanticide or a mother's attachment to her infant that pushed us to get close, we can be thankful that something did. We owe much of our success as a species to that crazy little thing called love.
Melissa Hogenboom is @melissasuzanneh on Twitter. Follow BBC Earth on Facebook, Twitter, and Instagram

fonte: [Tens de ter uma conta e sessão iniciada para poderes visualizar este link]

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Why paring up for life time is hardly ever a good idea

Many animals engage in long-term relationships, but a closer look reveals infidelity, illegitimate offspring and even infanticide – and humans may be no different

By Josh Gabbatiss
13 February 2016

For many of us, marriage is special. The idea of a lifelong bond between two people is accorded legal, spiritual and cultural significance throughout much of the world. Whether we are religious or secular, a permanent monogamous relationship can feel sacred.
So when we hear about animals that form lifelong bonds, our "aww" factor goes into overdrive: "How adorable! Gosh, we could all learn a thing or two from those shingleback lizards".
But for all the romantic novels, love songs and soppy greetings cards, monogamy remains more of an ideal than a reality. Even in seemingly monogamous human societies, infidelity is common, and the same is generally true of monogamous animals. There are a few that do remain faithful, but the underlying reasons are anything but romantic.
Understanding why monogamy sometimes works for animals, and why it so often fails, can tell us about the nature of our own relationships. So cast aside your romantic ideals, and enter a world of amorous parasitic worms, adulterous songbirds and thoroughly naughty monkeys.
In nature, reproduction is everything. All creatures are ultimately trying to pass on their genes to their offspring. Monogamy is just one of many strategies, and there are two inescapable pressures that drive animals to mate more freely.
The first point is that genetic variation is good. A female who mates with several different males will have more genetically diverse offspring, boosting the chances that at least some of them will thrive.
Secondly, as the English geneticist Angus John Bateman pointed out, there is a fundamental difference between males and females when it comes to making sex cells. Put simply, sperm are cheaper to produce than eggs.
This means a typical male animal has enough sperm at his disposal to fertilise countless females, whereas beyond a certain point females will not produce any more offspring by mating with extra males.
Put these two points together, and both sexes have incentives to find multiple mates. As a result, monogamy is only a sensible strategy under very specific circumstances, many of which will seem eerily familiar. The first is simply proximity.
If the members of a species live great distances apart, they will tend to take a "love the one you're with" attitude. They pair up with the first mate they can find, and stick with them.
One animal that takes this to its logical conclusion is the intestinal parasite Schistosoma mansoni.
Reviled for causing schistosomiasis in humans, these worms live very intimate lives: males and females spend the entirety of their adult lives locked in a tight embrace. Each male has a "gynaecophoric canal" in which the female nestles while she churns out hundreds of eggs into the host's intestines.
The human digestive system is not the best place to pick up hot dates, so when a worm encounters a member of the opposite sex, it is quite willing to tie the knot for good.
The other key reason animals opt for monogamy has to do with good parenting.
If a species inhabits an environment that is fraught with danger and lacking in resources, their offspring are at great risk of dying young. In such situations, "staying together for the kids" can help ensure their progeny survive to adulthood.
This was demonstrated in 2010 by Kyle Summers and his colleagues at East Carolina University in Greenville, North Carolina, USA. They discovered the first known monogamous amphibian: the mimic poison frog.
The team was able to directly link this mating strategy to the fact that these frogs raise their tadpoles in tiny, nutrient-poor pools of water. Owing to their inhospitable nurseries, the tadpoles require the assistance of both parents to get enough food to reach adulthood.
"We were able to tie the evolution of monogamy and the evolution of biparental care to variation in a single ecological factor, and that's rare," says Summers.
But these monogamous animals are the exception. For many species, reproduction consists of squirting out a few thousand eggs or sperm and hoping for the best, so they could not be monogamous even if they wanted to.
If we want to learn something from nature, maybe we should look to the masters of monogamy: birds.
An estimated 90% of bird species are monogamous. At least, they are on paper. But bird love lives contain more drama than your average soap opera, with storylines involving jealous spouses, unfaithful partners and illegitimate children.
There are two possible levels of monogamy. "Social monogamy" refers to a male and a female who are spatially close together, having sex, and cooperating in tasks like parenting. But it does not necessarily mean they are not sleeping around. Such exclusivity is called "sexual monogamy" and it is much rarer.
A cynic would say that many human relationships are social monogamy masquerading as sexual monogamy. In this respect, we have a lot in common with birds.
For a long time, scientists thought the bonds observed between bird couples during the breeding season meant that sexual monogamy was a given. But this turned out to be naïve. Genetic and behavioural studies have revealed a world of avian scandal featuring cheating buntings and cuckolded warblers.
These misdemeanours are called, in delightfully euphemistic tones, "extra-pair copulations". They can account for up to 75% of the offspring in a population. Even birds known for their loyalty are prone to betrayal.
Every other year, wandering albatrosses return from months at sea to rekindle their relationship with the same lifelong partner. But they are far from sexually monogamous. Genetic techniques suggest that 14-24% of albatross chicks are fathered by a male who is not their mother's life partner.
With such a high rate of infidelity, you might wonder why the birds stay together at all. The answer is the same as for the mimic poison frogs: parental responsibility. Baby birds are helpless lumps of skin and fluff, and they need two doting parents to ensure that they are well fed.
The albatrosses' lifelong partnerships are exceptional. In most bird species partnerships do not last much longer than a single breeding season.
But compared to the mammals, the group to which we belong, birds are paragons of monogamy.
The reason for this is partly physiological. By definition, mammalian parenting is dominated by females, because they suckle their young with milk. This means that the division of labour seen in bird pairings simply cannot exist to the same degree.
Nevertheless, around 3-5% of mammal species practise social monogamy, ranging from bats to wolves. These marital mammals limit their mating for many different reasons.
For example, beavers have to maintain their dams as well as caring for their offspring, so they benefit hugely from working together. However, the tiny dik-dik antelope does not share parental duties, but still pursues exclusive relationships. Needless to say, neither of these species is beyond a spot of extra-pair copulation.
The dik-diks hint at an explanation for monogamy that is less than endearing.
In an ambitious study published in 2013, Tim Clutton-Brock and Dieter Lukas of the University of Cambridge in the UK analysed over 2,500 mammal species to find out why some of them have become monogamous. They concluded that males will only accept monogamous pairings if they cannot dominate the females of their species.
If females are widely dispersed, as with dik-diks – or indeed Schistosoma worms – then males will make the evolutionary transition from free-spirited bachelors to doting husbands. This helps them ensure success with at least one member of the opposite sex.
Among one group of mammals, social monogamy is more common. Around 27% of primates – the group that includes monkeys, apes and humans – practice social monogamy.
To find out why, a team led by Kit Opie of University College London in the UK studied all primate species, from hairy-eared dwarf lemurs to chimpanzees. They noted each species' preferred mating systems, as well as many other behaviours.
Then they mapped all the known traits onto an evolutionary tree. This allowed them to figure out when different behaviours arose over the course of primate evolution. Their results, released at the same time as Clutton-Brock and Lukas's, are rather shocking.
Shared parental care and wide female ranges did both correlate strongly with monogamy, suggesting they were linked. But only one factor appeared to actually precede the evolution of pair-bonds: infanticide by males.
It is quite common in some species for males to kill offspring that do not belong to them. This strategy may strike us as unpleasant, but it eliminates the children of rival males and prepares females for another bout of mating.
Now consider the position of a male whose offspring are not yet grown up. Such males might well form pair-bonds with females, if that is what it takes to prevent the murder of their offspring.
"Our analyses clearly show that infanticide is the trigger for monogamy in primates," Opie says assuredly.
He goes on to suggest that the risk of infanticide may be the basis for our own fondness for partnering up. This may be true, but it clearly has not gone as far as it might, because humans are far from strictly monogamous. Quite apart from promiscuous individuals, there are plenty of societies for which monogamy is not the norm – some estimates place the figure as high as 83%.
This suggests that the value we place on monogamy is more cultural than biological. The "natural" state of human relationships may be quite different. Once again, our evolutionary cousins offer clues.
Apes are our closest living relatives. There are only a handful of species, but they show great diversity in their mating systems.
Gibbons are monogamous, pairing for life barring the occasional infidelity. Chimpanzees live in multi-male and multi-female communities, promiscuously mating with each other. Gorillas live in polygynous groups in which several females are dominated by a single male.
These differences are reflected in the bodies of males and females. In some species, males and females look quite different: they are "sexually dimorphic". For example, males may grow huge appendages such as the antlers of a moose.
The more sexually dimorphic a species is, the less likely it is to be monogamous. If males must compete to mate with multiple females, this can drive them to grow to great sizes or develop ridiculous appendages. If each male tends to settle for a single female, competition is less intense.
This explains why gibbons, which pair-bond, show very little sexual dimorphism. Gorillas show a lot: silverback males are huge compared to females. Humans fall somewhere in the middle, not far from chimpanzees.
Similar clues can be found in the males' testicles.
If males often find themselves mating with females who have recently mated with another, they tend to grow large testicles. This allows them to produce lots of ejaculate to wash away the sperm of other males. If the male has a regular, exclusive mate, he has no need for large testicles.
Chimpanzees tend not to have exclusive mates, and are massively well endowed in the testicle department. Gorillas and gibbons are spectacularly un-endowed. Again, we fall somewhere in the middle.
This, combined with our sexual dimorphism, has led some scientists to suggest that our original mating strategy was more like that of promiscuous chimpanzees, or even the "free love" mating practices observed in bonobos, and less like monogamous gibbons.
So where does this leave the human desire for life-long exclusive relationships?
In the animal kingdom, monogamy in the strictest sense of sexual exclusivity is largely a myth. Where it does occur, the factors underpinning it are either coldly pragmatic, or bloodcurdling.
However, this does not tell us anything about how the animals involved actually feel about each other. The ultimate evolutionary reason for pair-bonding might be the avoidance of infanticide, but the animals involved may well not be thinking about that. For all we know, they are experiencing an emotion akin to love, if they have some level of consciousness.
Perhaps it is also true that humans are not naturally monogamous. But if there is one thing that makes us human, it is that we try to act against our instincts when it seems like a good idea.
There are plenty of excellent reasons to give monogamy a go. Just because the bonds you cherish are ultimately nothing more that the product of unfeeling evolutionary processes, that does not make them less real.

Fonte: [Tens de ter uma conta e sessão iniciada para poderes visualizar este link]

Não postei as imagens das notícias dessa vez para evitar a fadiga.
Mas nem há nada nelas tão relevante assim para as notícias.
Devo dizer que li mesmo só a primeira.
Postei a segunda para para me lembrar de lê-la depois.
...
Quer dizer então que uma das hipóteses para o surgimento do amor entre macho e fêmea é que ele teria sido uma espécie de usurpação entre o amor entre mãe e cria?
(Tenho que reler a notícia para ver se não a interpretei de forma incorreta.)
Bem...
Doutor Frêudi gostaria de saber dessa.
É engraçado que essas psicologias ditas evolucionistas criticam muito outras mais ligadas ás ciências humanas que eles, mas no fundo fazem o mesmo que elas, ou seja, uma hermenêutica.
Aonde está a cientificidade dessas reconstruções de como teriam surgidos determinados aspectos da mente humana?
Cara, isso é hermenêutica.
A diferença é que isso é mais palatável para mentes cientificistas por causa do prestígio da teoria da evolução.
Aliás, esses artigos são muito legais para a compreensão de aspectos pontuais.
Ciência humana não é ciência como a físcia ou a química o é, mas isso que que dizer que ela seja palpite.