Homosexuality in animals and humans

Interesting ops piece I just ran across while studying about homosexuality and animals and humans...
http://www.themalaysianinsider.com/opinion/article/it-is-homophobia-that-is-unnatural

-RYAN GUPTA

Being insecure: how bad is it?

Today there is plenty of information on “unhealthy” relationships and how to build secure and stable attachments to people.  However, despite it being so good, a large portion of the human population do not form “healthy” relationships.  How does this fit into an evolutionary perspective?

A paper came out by Ein-Dor et al. trying to address a proposed paradox, that individuals who form secure attachments have an evolutionary advantage but almost half of the human species can be classified as insecure in attachments.  This group proposed that while insecure individuals have a lower fitness, mixed groups of individuals are better adapted for survival than groups of only secure individuals.  Their hypothesis depends on the assumption that these traits evolved in closely related groups, and that forming insecure attachments is always detrimental to the individual.  Frankenhuis published a response arguing against this hypothesis, or at least in favor of further testing.  According to him, the tendency to form insecure attachments could have developed as an individually advantageous trait in environments where help is less often offered.  He argues that there are several holes in Ein-Dor et al.’s hypothesis.  For one, they tested homogeneously secure groups and heterogeneous groups, not homogeneously insecure groups.  They also did not consider the effect of the kinds of environments where insecure attachment patterns are more prevalent or provide evidence that social groups were comprised of individuals closely related enough to support a group benefit hypothesis.  In more simple terms the debate is whether “unhealthy” relationships can be traced back to a time and place in human history where people who tried to create “healthy” relationships were hurt and trust was a disadvantage.


The original paper:
http://pps.sagepub.com/content/5/2/123.short
Commentary by Frankenhuis:
http://www.frontiersin.org/Evolutionary_Psychology/10.3389/fpsyg.2010.00172/full


- Nicole Scott

Morality: Where did it come from?

            A debate is raging between philosophers and biologists. As we learn more about the evolution of morality, some evolutionists are staking claim to the topic of morality as a biological one, not a philosophical one.

            The idea that morality is derived from our primate predecessors dates back to the 70s and it hinges on the idea that our human morality stems directly from the primates’ sociality tenants: empathy, the ability to learn and follow social rules, reciprocity and peacemaking.

            These fundamental virtues drove the actions in primate communities that from a humanistic perspective seem quite “moral.” For example, chimps share food more often with other chimps that have groomed them. Chimps will also make up and console the loser after fights. Often, female chimps will even prevent a fight from happening.

All of these moralistic sorts of actions ultimately stem from an innate fitness advantage. Maintaining a happy and unified community is important in working together for survival. Thus these exhibitions of morality by primates may be driven by a necessity for survival, yet they are nonetheless, the precursors to what humans call morality.

Human morality seems to be driven by more of an innate sense of righteousness than any sort of urgent necessity for survival, but the parallels between primate and human morality are evident.

Perhaps philosophers and biologists need not work separately on the topic of morality but instead simply acknowledge that one field is able to describe the origins and history of morality while the other field is equipped to focus on the uniquely human aspects of morality.

            Check out this article on the evolution of morality: http://www.nytimes.com/2007/03/21/health/21iht-snmorals.4978821.html?_r=1

-RYAN GUPTA

The ant equivalent of our cattle industry

There is a very interesting phenomenon afoot in the tiny world of ants. It seems that much as human culture has developed a strong agricultural system, so have certain species of ants. In a manner similar to humans’ herding and maintenance of herds of cattle, ants also keep and farm groups of aphids.

The behavior is beneficial for both species. The ants are able to keep a sustainable and constantly available food source with the sugary and edible secretions of aphids, while the aphids, as a community on the whole, receive protection from outside prey.

Developments have been made in understanding how ants maintain these colonies specifically. According to research from the Royal Holloway University of London, the ants disperse small quantities of tranquilizer in each step. Thus areas where the ants walk the most as a population have the highest concentration of tranquilizer. This tranquilizer affects the aphids and slows their movement. In fact, the researchers found that aphid movement was measured to be slower on paper that ants had previously walked on, when compared to control paper that ants had not previously walked on. Using this tranquilizer methodology, the ants can rely on each other to keep the boundaries of aphid movement quite limited.

The researchers speculate that by releasing tranquilizers from their feet, ant populations are better able to control the movement of aphids and make sure that they don’t stray too far; in doing this ants are ensuring the continuity of their honeydew food source. From the aphids’ perspective, its not a bad deal either, because as long as they stay in the proximity of the ants, they are less susceptible to predation, as ants will fend away another potential predators such as ladybugs.

Check out the article here: http://www.sciencedaily.com/releases/2007/10/071009212548.htm




-RYAN GUPTA

Storytelling for survival

Were kids who listened to their bedtime stories better at being adults?  According to a paper by Michelle Scalise Sugiyama, storytelling may have developed as another aspect of parental care and the preparation of offspring for the challenges of a forager.  Language conferred evolutionary advantages to our foraging ancestors, as more information could be shared that was dangerous to find out first-hand.  In addition to helping out kin, sharing information with those who could reciprocate in the future helped minimize risks associated with finding resources, etc.  These are all benefits of sharing among active adults who were involved in foraging.  However, there is also a strong old to young oral tradition, whether by children overhearing stories of the hunt or direct storytelling, that could have conferred additional advantages.  In addition to resources, an important part of parental care was the passing down of knowledge.  Warnings and advice would have been one aspect.  The narrative would have been another important way of transmitting knowledge and increasing offspring survival.  Specifically, the main hypothesis explored was that the vicarious experience of stories prepared offspring to plan, a cognitive process important to foraging lifestyles, through increasing episodic memory.  The paper combines anthropology, cognitive studies in development, and evolution for evidence.
http://www.frontiersin.org/Evolutionary_Psychology/10.3389/fpsyg.2011.00133/abstract


-Nicole Scott

Is Kin Selection Wrong?

In a stunning example of the inevitable marching forward of science, prominent ecologist E.O. Wilson, famed for helping lay the groundwork for modern theories which explain the genesis of social evolution, is now rejecting his own work. Originally, the favored explanation for altruistic behavior - one of the foundations of sociality - was kin selection. Kin selection is an evolutionary theory which asserts organisms can increase their fitness through actions which harm them individually. As long as their actions benefit other organisms which share, or are likely to share their genes, the altruist increases its inclusive fitness.

This was widely supported in the ecological community, because many of its predictions were born out. Organisms which resided in community nests developed sociality faster than organisms which lacked them. Organisms with strong family-rearing instincts formed into colonies of social organisms more frequently than lone wolf species.

However, according to Wilson, all that is circumstantial. In his new paper, Wilson cites group selection as the driving force behind altruism and, by extension, sociality. Group selection differs from kin selection mostly in the level of selection. Kin selection takes place at the genetic level, because inclusive fitness can increase and decrease regardless of which individual organism carries the genes. Even if an allele codes for a suicidally altruistic behavior, if that behavior causes enough relatives to survive and thereby increase the frequency of the gene in the next generation, it is still a beneficial trait. In contrast, group selection takes place at the level of organism group. Competition between groups of organisms puts a separate set of selective pressures on the individuals in the groups, promoting behaviors like selflessness and altruism, because groups made of those types of individuals out-compete groups of selfish jerks. Wilson asserts that in this scenario, high relatedness within groups is a symptom of close proximity for some time, no a cause of group formation in the first place.

Wilson’s new theories are extremely controversial within the scientific community - many ecologists consider him to have lost credibility for suggesting that kin selection is false. As for myself, I don’t think that Dr. Wilson should lose credibility, but I am not sure if I believe his assertions. His theory of group selection does not adequately explain why groups of cooperating organisms formed in the first place. Furthermore, kin selection makes several predictions which group selection does not, which nature has proven to be true. For example, kin selection implies that organisms with higher relatedness should be more social. Lo and behold, order hymenoptera, a haplodiploid gender determinant group, has a higher proportion of eusocial organisms than any other order. Given that one quirk of haplodiploid sex determination is a higher relatedness to one’s siblings than to one’s own children, it is easy to see how this supports kin selection.

You can read E.O. Wilson’s entire paper at http://www.biology.ed.ac.uk/archive/conferences/evolbiol2006/papers/Wilson.pdf and come to your own conclusion about this large debate.

-Adam Geiger

So That’s Why They Call it Humanity

Biologists have long been fascinated with the interactions between animals, both inter- and intra-species relations, studying everything from parasitisms to mutalisms, sexual selection to family groups to true eusociality. Yet the one constant that remains through the vast amounts of diversity when you get to the root of all actions is selfishness. Every action that every organism willingly performs benefits the actor in some way, otherwise it would be selected out. Every organism, that is, except for humans. We humans have found a way to defy natural selection (wouldn’t Darwin be disgusted?) through acts of compassion.

There is evidence that as early as six million years ago, human ancestors began displaying the first hints of empathy. An article published in Nature titled A Possible Case of Hypervitaminosis A in "Homo erectus" implies that even Homo erectus displayed feelings of compassion by feeding, protecting and caring for a woman who developed a paralyzingly painful condition. DiscoveryNews published an article a year-and-a-half ago that outlines the proposed evolutionary model for the development of human compassion. This is hugely exciting! As far as I can tell, Homo sapiens is the only extant species that forms such strong bonds of friendship and even cares about the general well-being of total strangers. Chimpanzees, our closest living relative, certainly do not exhibit the same kindness. Jane Goodall recounts in her reports the fate of an older male chimp named McGregor who suffered from polio. The paralyzed chimp was shunned, attacked on multiple occasions, and excluded from social activities despite efforts to join.

Perhaps some would consider compassion a frail trait, seeing as how it is only present in one species. They may even say it is maladaptive – after all, it tends to lower fitness. But I say we humans thrive on compassion. It may not be personally beneficial, but it benefits the species as a whole. No other species is capable of such a global perspective. So next time you hear someone talk about ‘losing their faith in humanity’, just remember that compassion has been around for millions of years. I don’t think it’s going anywhere any time soon.

-Elizabeth Richardson

Getting Sick Of It: How Caterpillars Try To Cheat the Group Protection System (and Fail)

Group protection is probably one of the most basic goals of social interaction between organisms. As the old adage goes, "there's always safety in numbers". But what if this social theory is wrong? How do you explain that? 

A recent study looked at a species of caterpillar called Pieris brassicae which when attacked by a predator will regurgitate its last meal, producing a foul smelling compound that often causes the predator to avoid the caterpillar. However, by doing this, the caterpillar loses out on valuable nutrients from the meal and often experiences stunted growth as a result. As a result, the caterpillar only employs this defensive mechanism when it is absolutely necessary because the individual cost to doing so is very high.

For a previously unknown reason, it has been shown that forming groups of these caterpillars for the purpose of protection does not result in a greater chance of survival on an individual basis. To explain this, the study looked at the individual behavior of the caterpillars alone and in groups. What they found was that when in a group, the caterpillar's rate and volume of regurgitation decreased significantly as opposed to in an isolated environment. This shows that the caterpillar is able to modulate its response based on if there are other individuals who are capable of performing the same act. This also shows that each individual reduces their contribution towards group protection, which in this case is enough to cancel out the supposed benefit that group formation gives for fitness. 

The full article can be read at http://onlinelibrary.wiley.com/doi/10.1111/j.1461-0248.2012.01770.x/full

-Eric Baeuerle

Other species have best friends too!

Turns out humans aren't the only species that benefit from making friends with non-kin!  As humans, we benefit from having close friends in that they help us manage stress which can help lead to a longer life.  Turns out that, in other species, having a close friend can actually be an evolutionary advantage: organisms with close friends are more likely to reproduce and are better at fighting diseases.  Some male chimpanzees spend significantly more time with certain other chimpanzees; they groom each other, share meat, and even hunt together.  Some female baboons groom certain other baboons much more than others and are more likely to help out a baboon that has recently groomed them.  If a fight ensues shortly after the grooming, having that extra baboon friend to help out could almost certainly mean the difference between life and death.  These baboons that form close bonds have more surviving offspring and live longer.  These results have also been found in other monkeys, lions, elephants, dolphins, and rodents.  It was recently discovered that female horses in New Zealand tend to form friendships with non-relatives in order to keep aggressive stallions at bay.  Mares risk their lives to help their friends with the expectation that the same help will be given if they ever need help with aggressive stallions.  Researchers are currently trying to understand how this occurs physiologically.  Thus far, they have pinpointed both a particular social-bonding hormone and oxytocin in monkeys; monkeys with more of these hormones are more generous.  Hopefully, further research in this area will help us to understand how human's tendency to form such close bonds with unrelated individuals evolved.

Here's the link to the article, check it out!

http://www.sciencenews.org/view/feature/id/339326/title/Furry_Friends_Forever

-Cristina Terhoeve

Eusociality of termites

An article was very recently published called "Brood care and social evolution in termites." The full text of this article is still not yet available at Rice, but the study presents some intriguing findings. The evolutionary community has always assumed that cooperative brood care was a necessary component for eusociality and a driving force of social evolution. However, this study looked at four different species of termites and found that cooperative brood care was common in only one of them. It appears that the evolution of eusociality in termites may have actually been driven by increased defense!

The abstract of the article can be found at http://rspb.royalsocietypublishing.org/content/early/2012/03/01/rspb.2011.2639.abstract

-Elizabeth Richardson

Is there an evolutionary basis to being nice to old people?

Humans, by nature, are an altruistic species. Unless we're affected by a mental illness, most of us feel bad about doing bad things and good about doing good things. We live by morals and we help our own, and this is especially true regarding our treatment of our elderly. We do our best to make sure Grandma and Grandpa are comfortable and taken care of, if not in our own homes, than with trusted medical staff. We don't always succeed in getting them the best treatment, but we try our hardest, with the best intentions. The topic on my mind today is, is this exclusively a human behavior, or is it a 'thing' across the animal kingdom? And if so, why? We have seen in class that animals have developed altruistic behavior in order to help relatives reproduce, but that is a different scenario. I'm not saying we should neglect old people; that would be terrible, but what, if it exists, is the advantage of altruism toward members of the species that are no longer reproductive?

After Googling around, I stumbled upon the expert opinion of evolutionary biologist Dana Krempels, who confirms that this behavior is indeed rare. Humans live in relative luxury and have no natural predators, so we can afford to practice behaviors that would be maladaptive in a hostile environment where the danger of predators lurks around every corner. Interestingly, though, in some cases altruism towards the elderly does develop in animals that have a sophisticated social order. Read more about it here.

-Mindy MacKay

The Evolution of Kissing

Unless you're this guy, you probably know that kissing does not make babies. So what, you might wonder, caused kissing to evolve as part of the human sex act?

Well, researchers suspect that kissing evolved as a means to immunize women against illness prior to pregnancy--read the full article here.

-Mindy MacKay

The Evolution of Sociality in Primates

Why are primates so social?  Also, more specifically, why are humans so social?  With the exception of primates, very few mammalian orders contain species that exhibit social behavior.  Shultz et al. have provided several clues as to why primate social behavior is so different from other mammalian orders by examining data from the past 74 million years!

They discovered that the most crucial step towards sociality occurred when primates began to become diurnal rather than nocturnal.  When primates were nocturnal, they tended to be solitary foragers that could avoid detection by hunting quietly in darkness.  When primates began to hunt during the day, their activity became more recognizable to predators simply because they could now be detected more easily in the light.  Primates who travelled and hunted in packs were more likely to survive, and thus more social primates evolved by means of natural selection.  These primates were less likely to become victims of predation because each predator would only kill one or two primates in a group and, as a result, the vast majority of the organisms in the group would survive each predator attack.  Also, having more primates to compete in each predator attack increases the likelihood that the predator will either die or retreat.  The research suggested that these social groups were only loosely bound: members could come and go as needed.  Behavior similar to this is present today in lemurs.  Primates did not begin to form small groups with close social links until millions of years later.

Unlike all other primates, humans have the ability to cope in numerous different social settings.  Over time, we have functioned in many complicated social settings: monogamous versus polygamous societies, nuclear family versus extended family groups, various work settings, etc.  Our social flexibility both in groups and in wider society is unmatched by any other species.  Shultz et al. discovered that this is a result of increased brain power (humans have more brain power than any other species).  This makes perfect sense: increased brain power allows us the ability to adjust to changes in our environment.  No other organism has the mental complexity to surmount this obstacle.  How cool is that?

Link: http://www.sciencedaily.com/releases/2011/12/111220205212.htm

-Cristina Terhoeve

Share the Love: A closer look at polygamy

When you’re little, everything seems so simple. You grow up. You fall in love. You get married. You have a family. At least that’s what I thought life was like, but I would soon come to find out that, for better or for worse, nothing in the world is that straightforward. “Alternative” types of relationships are getting increasing media attention. TLC broadcasts Sister Wives, a reality television series featuring the polygamist Brown family, and open relationships and open marriages are not unheard of. But such does not come without criticism. In his book, Opening up: a guide to creating and sustaining open relationships, author Tristan Taormino claims some of the most common criticisms to polygamy include “the monogamous person is being taken advantage of,” and “the non-monogamous person wouldn’t be doing this if she really loved the monogamous person”. Words like “sexist”, “coercive” and “patriarchal” have even been thrown around, and many groups, including numerous churches, claim that polygamy is an “abomination”. But what makes it so detestable? Can polygamy really be considered unnatural?

No. In fact, it’s quite the opposite. Cases where polygamy has naturally evolved are widespread and incredibly diverse. A vast number of species, we know, are promiscuous, meaning any male will mate with any female. But there are also many polygamous species, where a single individual maintains relationships with multiple mates. LiveScience published a list they call the “Top 10 Swingers of the Animal Kingdom”, species that break so-called norms. As one might assume, included on the list are lions, which are largely known to live in prides in which few males have mating rights to a large number of females. But also making appearances are (among others) walruses, African blue-headed lizards and bronze-winged jacanas, a tropical species in which females maintain a harem of males to raise her many clutches of eggs. Although not polygamous like the previously listed species, bonobos also make the list for their unique approach to sex. These promiscuous primates have been known to form short-term heterosexual, homosexual and even incestuous unions, and live in relatively peaceful societies. The frequent sex in bonobo societies is thought to “strengthen social bonds and resolve conflict”. Taking a look at the animal kingdom quickly shows us that monogamy is not the only answer, and promiscuity and polygamy are far from unnatural.

Now for my two cents. Individuals cannot choose to be a certain way, just like species cannot choose to evolve in a specific direction and what works for some is not necessarily what’s best for others. So ignore what your neighbor’s doing. Every human, just like every species, is unique and has their own way of doing things. That’s what makes life so fascinating.

The full LiveScience article can be found at: http://www.livescience.com/12963-top-10-polygamous-animals-bonobos-hyena.html

-Elizabeth Richardson

Putting the Ant in Infanticide

When thinking about sociality and how it evolved, ants are some of the first examples to spring to mind. Not only does each individual share resources, there is an entire caste of sterile females who never breed at all. The existence of sterile castes in ants and other eusocial insects is curious, because a mutation which removes the ability of the workers to breed seems obviously deleterious: no breeding, no fitness. The mechanism which brought this sterility about had historically been under some debate. Opinions were split between kin selection (improving the fitness of other, genetically related individuals improves your fitness as well), or some form of parental modification in which the queen actively suppressed the development of her daughters. To settle this debate, researcher Joan M. Herbers reasoned that studying the sex ratios of a colony would provide the data to conclude one way or another.

The premise of her idea is that each evolutionary mechanism would effect the sex ratio in different ways. Supposing the queen is in total control, and suppresses her workers, the sex ratio would reflect the optimum fitness ratio for the queen’s genes: a even distribution of males and females. However, if kin selection is the mechanism behind the development of sterile worker castes, the sex ratio would be approximately three females to every one male. This is because ants, like all hymenopterans, have a haplodiploid sex determination system. Instead of combinations of X and Y chromosomes determining gender, male ants emerge from unfertilized eggs, and are haploid, while females emerge from fertilized eggs, and are diploid. Assuming the queen mates once, that means that each of her daughters will share an average of 75% of her genetic material with her sisters, but only about 25% with her brothers. Because sisters share more genes with each other than with their brothers, kin selection results in strong selection towards a 3-1 female to male sex ratio.

Armed with this knowledge, Herber started gathering sex selection data for the ant species Leptothorax longispinosus, controlling for other variables that can alter sex ratios. What she found was that queens actually do produce an even ratio of male and female children. However, the measured worker sex-ratios were always around 3-1. The answer to this puzzling contradiction? Far from being developmentally and behaviorally suppressed by the queen, workers were actively killing and eating their infant brothers, enforcing the sex ratio in their favor. Thus, Herber concluded that kin selection is the primary mechanism of eusocial evolution in the species.

The full article can be found here: http://www.jstor.org/stable/2408712?seq=2

-Adam

Well I guess that’s why they’re called fruit bats.

Homosexuality has sparked scathing debates in modern society, not only in a religious setting, but in the politics that keep our everyday lives running. The argument rages between people who would eradicate discrimination in the workplace, military, and education system, and those who believe love between two people of the same sex is an abomination. One popular argument against homosexuality is that it “goes against human nature” in that it does not lead to reproduction. However, observations by zoologists suggest that this argument is evolutionarily unsound.

Scientists have observed individuals in several species, including penguins, ostriches, and even monkeys, both in the wild and in captivity, that will display interest only in their own gender even in the presence of potential opposite-gender mates. It may be surprising to some that this behavior serves a variety of purposes in the animal kingdom, including playing a role in reproductive success.

For example, primatologist Amy Parish postulates that female macaques engage in homosexual behavior to increase their social status, thus increasing their chances of breeding. By taking control of a resource—in this case, other females—a female macaque makes herself a favorable partner in an alliance or potential mate. Other proposed motives for homosexual behavior in animals include means of resolving tension (in bonobos) and friendship bonding (in dolphins). Despite progress in the field, though, animal homosexuality remains a misunderstood subject because many scientists are afraid to ‘get in trouble’ socially and politically.

What do I think? Well, first, a disclaimer: I hold myself to no particular religious belief. I don’t know and honestly couldn’t care less about what’ll happen to me when I die. That doesn’t mean I don’t have my own set of naïve, inflexible beliefs, though. Personally, I hold love, whether homosexual or heterosexual, as something pure and sacred. It unsettles me to think of it in cold and clinical terms, as a mechanism for reproductive success rather than just ‘that warm fuzzy feeling when nothing matters and you can do anything’, even though that notion is juvenile and the reproductive success thing actually has validity. But then, just because I don’t particularly like the facts doesn’t mean I should disregard them.

In conclusion, we may never know the truth behind why people, or animals, love who they do, but for now, we have patterns, theories, and facts.

Read more about it at National Geographic:http://news.nationalgeographic.com/news/2004/07/0722_040722_gayanimal.html

-Mindy MacKay.

Prehistoric Chirping: How Crickets Have Kept Their Call

            One of the difficult things about trying to determine behavior and interactions between species that have gone extinct is that, for obvious reasons, there aren’t any living members of that species to observe. However, a research group in China has managed to do the next best thing: Take the fossilized remains of a Jurassic-era katydid namedArchaboilus musicus and reconstruct the type of chirp that it would have made to communicate with others of its species. By looking at models of the stridulating wings and comparing to species alive today, the group was able to determine the frequency at which the cricket would have to stridulate in order to produce its characteristic chirp.

            The most interesting this about this is that in the 165 million years since this species existed, there are still many species of cricket that maintain this same method of communication, with almost no change in the actual mechanism of stridulating. This means that the katydids of the Jurassic era were already capable of communication in this manner, and that natural selection favored this method of chirping enough so that the mechanism survives in descendant species to this day. The paper can be found at http://www.pnas.org/content/early/2012/02/02/1118372109.full.pdf+html, and they even have a short soundfile of their predicted sound of the katydid in question at  http://www.pnas.org/content/suppl/2012/02/03/1118372109.DCSupplemental/sm01.mov

-Eric Baeuerle

Early Evolution of Eusocial Organisms

I’ve always thought that eusocial organisms, like termites, ants, and some bees, were rather fascinating to study, but no one really knows how eusociality developed because these advanced taxa evolved so long ago. What’s cool now, though, is that Bryan N. Danforth has started looking at halictid bees, which are primitively eusocial, and has found that studying their behavior gives some insight into the early evolution of the advance eusocial taxa. If you want to learn more about this, you should read his paper.

-Elizabeth Richardson

http://www.pnas.org/content/99/1/286.full.pdf+html

Singing Mice

Singing mice? That sounds like something from a fairy tale! Indeed, Disney’s portrayal of musical mice, from the singing friends of Cinderella to the whistling Steamboat Willie, seems far from accurate. Interestingly enough, however, new research shows that mice actually do have their own courtship songs using ultrasonic frequencies, which may even rival the complexity of bird song. What’s even more interesting is that females can tell the difference between the songs of brothers and those of unrelated males! You can follow the link to read the full article, it’s pretty cool. Check it out!

-Elizabeth Richardson

http://www.msnbc.msn.com/id/46184222/ns/technology_and_science-science/#.Tym8jlyXTBg

Current Social Networks Older than We Think

http://arstechnica.com/science/news/2012/01/studying-people-of-the-past-with-people-from-the-present.ars

New research suggests that current humans share many elements of their sociality with hunter-gatherer societies from the late Pleistocene era. By polling the Hadza, a present-day hunter-gatherer society in Tanzania, researchers found that the ways in which the Hadza relate to each other are quite similar to how people living in industrialized communities interact. The distance between the homes of individuals influences whether or not they will become friends, as do similarities in physical appearance. Perhaps most relevant is the finding that people who cooperate and share resources are more likely to be friends - the same is true for “non-cooperators”.

-Kendall Post