The Sacrifice of Admetus

How the evolution of altruism reveals our noblest qualities

Heracles battles Death for generosity's sake
* This piece has been included in the 2007 Open Laboratory: The Best Science Writing on Blogs. For information on how to purchase or download a copy click here.


Whereas great scientific theories stand the test of time when they accurately predict the natural world through repeated empirical trials, great literature transcends the ages when it speaks to universal qualities of human experience. Such inspirational works can also, without the authors realizing at the time, reveal the sublime beauty and tragedy of our evolutionary drama. Few classical authors have tapped into this zeitgeist of biological experience as the Greek tragedian Euripides. The conflict between male and female reproductive strategy and the horrific choice of maternal infanticide is powerfully presented in the story of Medea (which waited some 2,400 years before being elucidated as an adaptive strategy in primates by the incomparable Sarah Hrdy). Electra chronicles the bitter feud between parent and child that would later be revealed as encompassing a biological reality by Robert Trivers in Parent-Offspring Conflict Theory. And Helen, the haunting tale of Helen of Troy's fateful decision, evokes the evolutionary importance of female mate choice revealed through Darwin's theory of sexual selection.

However, despite his focus on tragedy, Euripides could also reveal what we as a species have long prided ourselves as a uniquely transcendent gift: generosity even amidst the most terrible of circumstances. In his lesser-known work Alcestis, Euripides has the great hero Heracles (the Greek Hercules) arriving to the home of Admetus, the King of Pherae in Thessaly. Not realizing that his wife and true love, Queen Alcestis, has just been snatched by Death at a young age, Heracles asks his dear friend for harbor and a reprieve from his many adventures. Though wrought with grief, the tenderhearted Admetus cannot deny his friend the generosity of his home and so hides his mourning for the benefit of the visiting demigod. Ignorant of the great pain felt throughout the household, Heracles unwittingly offends his hosts with his Dionysian joviality only to be clued in by one of Admetus' less obedient servants. Overwhelmed by his breach of such generosity, Heracles descends to the Underworld to confront the "black and wingèd Lord of Corpses" and wrestle the dearly departed Alcestis from Death's icy grasp. Heracles understood the depth to which Admetus had sacrificed his own well-being for the sake of hospitality, and not even Death would prevent him from honoring his debt.


Alfred Russell Wallace and Charles Darwin
Such beneficence, in a decidedly less epic but nonetheless important way, has likewise been shown in the life of the great bard of biology himself. Having spent more than twenty years privately exploring the evidence for evolution, only mentioning his heretical research to his closest friends, Charles Darwin was faced with one of the great moral challenges in the history of science. In the summer of 1858 Darwin's collected work on the topic of natural selection exceeded a quarter of a million words (roughly five hundred pages), and was only half completed, when a parcel arrived from a young naturalist working in Borneo by the name of Alfred Russell Wallace. To Darwin's surprise he found that Wallace had independently developed a theory of natural selection (which he referred to as "progression") that outlined what Darwin had spent countless hours elucidating. Scientific culture places a premium on primacy of authorship and here Darwin was holding in his hand a document that could undermine the originality of his life's work.

Darwin knew what was at stake when he wrote to his friend and mentor Charles Lyell that Wallace "could not have made a better short abstract! Even his terms now stand as Heads of my Chapters. . . So all my originality, whatever it may amount to, will be smashed." But in an act that evokes Admetus' generosity, Darwin continued by stating that, "he does not say he wishes me to publish, but I shall, of course, at once write & offer to send to any Journal." And so Wallace's outline was included alongside an abstract of Darwin's theory and presented jointly before the Linnaen Society on July 1, 1858. On the Origin of Species was published just over a year later, the first edition selling out on the day of its release.

Ironic though it may be, the very act of generosity which gave origin to the Origin has posed tremendous difficulty to evolutionary biologists ever since. What Martin Luther King, Jr. described as a "walk in the light of creative altruism" has seemed, to many, contradictory to the "selfish gene" approach of natural selection. From a gene's-eye view of the world only those traits that are successful for an individual organism and allows the maximum level of reproductive success will live on in subsequent generations. Any trait that influenced one to benefit others at their own expense would be at a disadvantage compared to individuals who merely accepted the assistance and failed to reciprocate. The schoolyard dictum that "cheaters never prosper" wouldn't seem to have any place in such a system.


Chimpanzees show spontaneous altruism
Much ink, and many hours in the field, have been spent working to resolve this seeming conflict. The latest papers to do so, hitting the presses back-to-back and reinforcing each other in a fitting metaphor of the mutual assistance they document, highlights how this perceived conflict is really no conflict at all. The first to be published (on June 26, 2007 in the public journal PLoS Biology) was by Felix Warneken, Brian Hare, Alicia P. Melis, Daniel Hanus and Michael Tomasello of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. In their study they compared the innate predisposition for generosity in wild-born adult chimpanzees (Pan troglodytes, named for another Greek demigod) and human infants (aged 18-months).

The researchers set up identical conditions by which their Pan and Homo subjects observed an unfamiliar person stretching to reach an object just beyond their grasp. In multiple individual trials the researchers recorded the frequency at which each group of 36 subjects would offer their assistance by retrieving the desired object and handing it to the stranger. Contradicting previous studies of chimpanzee altruism, the researchers found no significant difference between us and our evolutionary cousins. This result was upheld even when the subjects had to put in some effort, climbing over a series of obstacles, in order to deliver the object. In a variation on these initial trials the researchers also offered the subjects a reward to illicit their assistance (toy blocks for the infants and bananas, of course, for the chimpanzees). In both cases the only significant factor was whether the subjects observed the stranger attempting to reach the distant object; a factor that chimpanzees and infants both responded to selflessly. Offering a reward for their assistance had no effect on this display of generosity. Service, it seems, was its own reward.

However, perhaps the chimpanzees had previously learned to obey human researchers in their time spent under semi-wild conditions? Would chimpanzees go out of their way to help other chimpanzees? To test this possibility the researchers constructed a door that could be opened by pulling a chain in order to access food on the other side. The researchers fastened this chain to a peg that could only be removed by a second chimpanzee in an adjoining room. In order to access the food the first chimpanzee would have to rely on assistance from the second, who gains nothing in the bargain. As before, 8 out of 9 individuals consistently helped a stranger (this time of their own species) if they saw they needed help. This, the authors reason, suggests that "the roots of human altruism may go deeper than previously thought, reaching as far back as the last common ancestor of humans and chimpanzees."

But could the roots of altruism go back even further? Apparently yes, as suggested by an additional study appearing in PLoS Biology on July 3 by Claudia Rutte and Michael Taborsky at the University of Berne, Switzerland. In a study entitled "Generalized Reciprocity in Rats" the Swiss biologists constructed a similar cooperative task as used for the chimpanzees. A baited tray was attached to a stick that one rat could pull in order to bring food within range for a second, unrelated rat's benefit. Rutte and Taborsky then conducted subsequent trials to see how often rats who had benefited in the past would be willing to help other rats in the future, the Rattus norvegicus version of the movie Pay It Forward. On average rats were 21% more likely to help strangers if they had received such help themselves.


Maasai pastoralists share meat throughout the community
These findings seem to fly in the face of previous theory suggesting that individuals wouldn't perform an altruistic act unless they could expect such acts to be repaid. Known as reciprocal altruism, it has traditionally been held that an individual (human and non-human alike) would only be likely to help another if the recipient had previously shown they wouldn't take advantage of such generosity. This meant that only group residents whom the individuals had previous experience interacting with would warrant their aid. It was solely among kin members, depending on the frequency of shared genes, that individuals would behave altruistically without reciprocation. However, in both PLoS Biology papers, altruism was being displayed for the benefit of total strangers. And in the case of rats the decision to offer anonymous help was determined by how much anonymous help they'd already received. Rather than contradicting reciprocal altruism, what these studies instead suggest is an expansion of the evolutionary social contract. In an environment of cooperative strangers it pays to be cooperative yourself.

While much has been made of the Darwinian phrase "survival of the fittest" suggesting that natural selection operates purely through aggressive competition, credit for the term must go to the British sociologist Herbert Spencer who had a dubious political ax to grind ("Social" Darwinism remains as his misguided legacy). However, Darwin's Origin preferred the more neutral "struggle for existence," which evokes a race against the elements rather than between individuals. It is only through Spencer's understanding of natural selection that cooperation and altruism pose a problem. For Darwin, cooperation between individuals could be an adaptive strategy in many environments as individual reproductive success increases through the safety and support of the group. Such group dynamics have been examined in detail by Robert Sussman and Audrey Garber published in the edited volume The Origins and Nature of Sociality (which Sussman also co-edited). In their metanalysis including seventy-eight published studies that covered twenty-five genera and forty-nine species of non-human primates they determined that prosimians, monkeys and apes spend the vast majority of their social lives in cooperative interactions. The study also showed that the amount of social aggression was statistically insignificant, concluding that "affiliation is the major governing principle of primate sociality and that aggression and competition represent important but secondary features of daily primate social interaction."

It was in Darwin's second great treatise on natural selection, The Descent of Man, that he offered this very line of reasoning that would wait 130 years to return full circle. With the knowledge that human and non-human animals alike were often illuminated by such walks of creative altruism, Darwin suggested that "those communities which included the greatest number of the most sympathetic members would flourish best and rear the greatest number of offspring." It is this relatively unacknowledged aspect of Darwin's theory that offers us hope in troubled times. For as surely as aggression and greed are part of our human character, so also is our capacity for cooperation and generosity.


Such an evolutionary legacy is rightly explored and celebrated through our great works, scientific and literary alike. In this way a chimpanzee reaching across species lines to help a human stranger in need can be viewed with the same appreciation as a Samaritan woman reaching out to offer water to a traveling Jewish mystic in breach of the social customs of her time. And, just as a notoriously self-indulgent demigod will transcend the boundaries of the living to repay his host's hospitality, so will a beady-eyed vermin transcend its (clearly unjustified) reputation to help a stranger with food. Through this very idea of generosity we witness how evolution can reveal our noblest of attributes. As Euripides expressed in his play Temenidae (of which, like the fossil record, only fragments remain), "When good men die their goodness does not perish, but lives though they are gone." The sacrifice of Admetus persists today as our evolutionary inheritance thanks to an unbroken chain of cooperative ancestors, who even Death himself could not prevent from sharing their gift with us.

For more on this topic see my posts here and here.


References:

Felix Warneken, Brian Hare, Alicia P. Melis, Daniel Hanus, Michael Tomasello (2007). Spontaneous Altruism by Chimpanzees and Young Children PLoS Biology, 5 (7) DOI: 10.1371/journal.pbio.0050184

Claudia Rutte, Michael Taborsky (2007). Generalized Reciprocity in Rats PLoS Biology, 5 (7) DOI: 10.1371/journal.pbio.0050196

Sussman, RW, Chapman AR (2004) The nature and evolution of sociality: Introduction. In: The Origins and Nature of Sociality. Ed. by RW Sussman and AR Chapman. Aldine De Gruyter: New York, pp. 3-19.

[Read more →]

You Groom My Back, I’ll Groom Yours

Tit-for-tat a common pattern across primate species

Grooming reciprocity common in our evolutionary cousins.

Image: Unattribated
It is one of the oldest questions of philosophy: why are people good and why should we be kind to each other. Research with nonhuman primates is beginning to bring an answer to this age-old question: return benefits.

Thirty years ago Robert Trivers developed the framework of reciprocal altruism. His hypothesis predicted that social organisms would benefit others if the cost to themselves was less than what the expected returns were likely to be. This hypothesis has been successfully tested for species ranging from ants to lions, and now a new analysis can confidently add primates to this list.

Writing in the journal Biology Letters, Gabriele Schino and Filippo Aureli report that across 22 different species and 12 genera of primates females will preferentially groom others that preferentially groom them. Previous studies have suggested that primates will direct their grooming up the hierarchy, in the nonhuman version of social networking. However these studies suggest that a trusted grooming companion was more important in the decision of whom to groom in return than was rank or relationship.

Imagine that? Fairness and gratitude as a common tactic in nonhuman primates? Meanwhile our country is vetoing health care for poor kids because we’d prefer that every family of four dole out $20,000 per year for our war in Iraq (roughly $800,000,000 total). It appears we’re lacking the basic decency found in our primate relatives. We’d better find a way to get it back and construct a more cooperative society, otherwise you may find yourself one day with no one willing to come to your aid during a time of need.

[Read more →]

Adoption in Non-Human Primates

How genes for altruism can benefit strangers as well as kin

The generosity of adoption has long been considered a unique human hallmark.

Image: Shadows of Forgotten Ancestors
For decades it was conventional dogma that humans were the only species that used tools. “Man the Toolmaker” was our celebrated designation. The hominin fossil Homo habilis (or "handy" man) was even defined within our genera primarily because the skeleton was associated with stone implements. However, when Jane Goodall discovered chimpanzees using modified sticks at Gombe to “fish” for termites, Louis Leakey famously cabled her that:

“Now we must redefine man, redefine tool – or accept chimpanzees as human.”

By now people should stop insisting on singling out specific human behaviors and declaring them to be unique in the natural world. Invariably, whatever special attributes humans possess, other primates do in some form as well. For many years it’s been argued that humans are the only primates that will adopt unrelated individuals to care for as their own. This has been conventional wisdom because it doesn’t make intuitive sense according to the rigid definition of biological fitness.

Since animals, including humans, are primarily ambulatory vehicles for their selfish genes, it would be to one's benefit to care for a niece or cousin that lost their mother but not for a stranger of which there was no genetic relation. This is because any genes that promoted such altruism towards unrelated individuals would end up losing out by using up resources that didn’t perpetuate themselves. However, these “altruistic genes” would be passed on and thrive if they were helping a kin member with similar genetic makeup. In the currency of reproductive fitness, nepotism pays.

However, in the early edition of the journal Primates (subscription required), Cristiane Cäsar and Robert John Young report on a case of adoption among a wild group of black-fronted titi monkeys (Callicebus nigrifrons) from the rainforests of Brazil.


Titi monkeys found to adopt abandoned orphans.

Image: Luiz Claudio Marigo

Since July of 2005 the team has been studying this largely unknown species, when, much to their surprise, they witnessed a new infant traveling with the group that wasn’t there previously (the authors subsequently determined that a nearby group was missing an infant). Presumably the infant got lost from its former group and ended up being saved by the latter. Even more remarkably, it was the male in the new group that provided much of the adoptive care:

“Observations of the adoptive group confirm that it was being cared for by the adult male, and initially the group’s adult female was nursing the infant alongside her biological infant. . . Thus, in the case of adoption by C. nigrifrons there is an argument to include male primates in the definition of adoption.”

This would appear to undermine the notion that only related individuals would be adopted and cared for by others. However, the authors speculate that the two groups might be distantly related, thus suggesting kin altruism as the explanation for this unique occurrence. While this could be, the coefficient of genetic relatedness would likely be much too low for such a large investment to be in the genetic interests of the adoptive parents. Furthermore, any genetic mechanism involved (let alone an epigenetic one) would be unlikely to be so precise as to differentiate a kin member from a stranger. Since any orphan they come across would have a higher chance of being from their own group (and thus closely related), a genetic “rule of thumb” would be to provide assistance to all abandoned infants so long as resources were available.

Much the same has been argued for the origin of human altruism. Since most modern hunter-gatherer populations (and presumably our hominin ancestors) live in small groups of closely related individuals, the chances of helping a kin member by behaving altruistically are very high. Our genes today are descended from such close knit communities and don’t realize that we now live in enormous populations of strangers where being generous doesn’t directly improve our reproductive fitness.

By this simple act of adopting a strange infant, these titi monkeys are teaching us an important lesson about evolutionary strategies. While the net sum of behaviors in the natural world is for the perpetuation of their genes, such mechanisms can’t always differentiate the forest for the trees. Genes that evolved for one set of environmental constraints (in this case helping the infant of a kin member) could promote behaviors for another (helping the infant of a stranger). This should give us some hope as political commentators suggest that our world is spinning out of control as the result of factionalized groups based around instincts for kin networks. If we can extend our notion of kin from our local population to the global community, then perhaps we’ll find a way to help one another. Our genes are already primed to benefit their close relations, we just need to find a way to put them to use for the benefit of the human family.

Reference:

Cristiane Cäsar and Robert John Young (2007). A case of adoption in a wild group of black-fronted titi monkeys (Callicebus nigrifrons). Primates, published online Oct. 16. doi: 10.1007/s10329-007-0066-x

[Read more →]

The Genetics of Politics

New study breaks the silence and suggests voter apathy could be explained by the genes.

Front page from the 1914 American textbook Eugenics by Professor T.W. Shannon


Genetics and political science have had an ugly association in the past. Arguments that certain people were biologically “unfit” for the political process led to an official eugenics policy in the United States that continued up until the Second World War. This was based largely in prevailing views about racial inferiority.

For example, writing in 1907 Davis Rich Dewey notes (p. 163):

The white population of the South honestly believed that political activity and privilege was bad for the colored race. . . The inferiority of the negro was still held to be a demonstrated fact.

This “demonstrated fact” motivated the Jim Crow voting exclusion laws and anti-miscegenation legislation such as the Racial Integrity Act of 1924.

Given this history you’d suspect few political scientists would be willing to link the fields of genetics and politics, even if they’re clearly separated from the racist views of the past. However, political scientist James Fowler and colleagues have suggested just such a connection in a study they reported on at the American Political Science Association.

In trying to predict who will vote and who will stay home, researchers have tried in vain to find any patterns in age, gender, race, income, or level of education. This is a question of some urgency since fewer than 50% of US citizens regularly vote in presidential elections. In order to determine if genes played any role the researchers collected voting data on 442 identical and 364 fraternal twins and found that 72 percent of the differences in voting turnout and around 60 percent of the differences in political activity could be explained by genetics alone (though those numbers are disputed).

According to a review in the current issue of Scientific American:

If genes do in part control voting, a single gene is unlikely to be responsible—hundreds of genes are probably involved, suggests behavioral geneticist Robert Plomin of King’s College London. Fowler hypothesizes that because “we obviously did not vote in large-scale elections in the Pleistocene,” the drive to vote or participate in politics may be linked with genes underlying more ancient behaviors, such as innate dispositions toward cooperation. The search for any such genes in our primate relatives could help determine “whether we share the neurobiological underpinnings of cooperation or whether humans are unique in this respect,” Fowler adds.

This study doesn’t suggest that genetics can account for political differences (though another study tries to make that claim), merely a willingness to engage in the political process. As it happens, studies on such neurobiological underpinnings of cooperation in non-human primates have been undertaken, including with our closely related cousins the chimpanzees and bonobos.


Bonobos sharing cantaloupe

Image: David Eppstein
According to research by Brian Hare and colleagues published in the journal Current Biology (subscription required) bonobos were found to be more successful than chimpanzees in cofeeding trials that tested their emotional reactivity. Bonobos were shown to be consistently more tolerant, were able to cooperate more effectively and, as a result, ended up receiving a greater food reward than the more individualistic chimps. While it’s a far cry from representative democracy, what the bonobo study demonstrates is that neurobiological processes (and potentially even genetic differences) can go a long way in promoting cooperative behavior and social engagement.

So perhaps Fowler’s study isn’t as far fetched as it may initially appear. However, there are numerous additional factors that should be considered before throwing up our hands and blaming our faulty genes. For example, the International Institute for Democracy and Electoral Assistance has demonstrated that since WWII Western Europe has had the largest voter turnout in the world while North America has had the third lowest. Would anyone seriously suggest that genetic factors account for this difference? Certainly higher education standards, a news media that informs rather than provokes and greater worker participation in collective bargaining play some role. Understanding genetic factors can provide some interesting insights into political motivations but, like those who challenged injustice in our nation’s past, in order to turn our broken election system around we’ll need to follow our bonobo cousins and work together to achieve a larger reward.

[Read more →]

The Bonding Brain

How the evolution of primate sociality is linked to brain networks for pair bonds.

Social conservatives are fond of linking morality with monogamy and will be quick to condemn the moral crimes of adulterous felatio while ignoring the moral crimes of cutting social programs for poor mothers. However, in a bizarre twist, it seems that morality and monogamy are closely intertwined, though it’s doubtful many conservatives will champion the reasons why.

Those of you who are regular readers of these pages know that I’ve touched on the issues of evolution, cooperation and altruism on several occasions (for example see here and here). In the latest issue of the journal Science, Robin Dunbar revisits this question with a unique perspective on why some species (including humans) succeed so well as members of a group.

While it may come as a shock to the Milton Friedman’s of the world (proponents for the brand of capitalist theory often referred to as “free market fundamentalism”) human beings are a distinctively socialist species. While we come nowhere near the extreme for the natural world (the eusocial bees, ants and termites win the Karl Marx utopian award for selfless behavior on that one) we humans are far and away the most social species of the most social order of the most social class in the animal kingdom (for those of you not up on your Linnaean terminology I refer to primates and mammals respectively). How can I claim such a thing? A very simple measure will suffice: social group size.

Humans have the largest group sizes of any primate. Baboons are known as having the largest group sizes of all non-human primates with an average of about 40-50 individuals and only approach as many as two hundred under extreme circumstances. Humans, in contrast, have an average group size of about 150-200 individuals in hunter-gatherer societies and a maximum group size in the millions under the unique conditions we experience as the result of industrial agriculture. And these large social groups require substantial brain power. All organisms need to successfully predict and navigate their environments and this becomes far more complicated when there are multiple actors interacting in the same social circle.


In the 1990s Robin Dunbar championed an idea known as the Social Brain Hypothesis. He found that mammals who lived in the largest social groups often had the largest neocortex to brain ratio. Since the neocortex is associated with complex and abstract thought he suggested that the demands of group living selected for an increase in neocortex size. In his latest paper in Science he and Susanne Shultz have suggested that there is even more than simply group size that may have influenced this selective process. When the authors analyzed the mating strategies of those highly social mammals that had the largest neocortex they found that pair bonds were significant in all groups except primates.


All social mammals except primates show connection between brain volume and pair bonding
Pair bonds occur when an animal stays with their partner for extended periods rather than simply meet up during the mating season. Pair bonds are cognitively tricky because monogamy is a risky business. In order to avoid getting stuck with a bad partner (either one with bad genes or one who won’t share the costs of reproduction) individuals have to be careful in choosing a good-quality mate. Also, pair bonded individuals have to carefully coordinate their activities to be in synchrony with the other. This may require substantial brain power to predict the other’s behavior and adjust your own behavior accordingly. But why is it significant that the social primates don’t show this connection between a large neocortex and pair bonding like other mammals do? Well, whenever there is a consistent pattern in nature that is violated in a single case a good scientist will want to know why. Primates are already unique among mammals, so any unique qualities that jump out could help us understand the evolution of our lineage.


As mean group size rises so does neocortex ratio
What Dunbar and Shultz have suggested is that the social brain that was selected under conditions for pair bonds in other species has been coopted and utilized for strangers in primate social groups. As the authors state in their paper:

This would explain why, as primatologists have argued for decades, the nature of primate sociality seems to be qualitatively different from that found in most other mammals and birds. The reason is that the everyday relationships of anthropoid primates involve a form of “bondedness” that is only found elsewhere in reproductive pairbonds.

Primates, and humans in particular, are such good social cooperators because we can empathize with others and coordinate our activities to build consensus. Rather than natural selection being a process of selfish individuals maximizing their own fitness, this “bonding brain” hypothesis suggests that natural selection, at least in primates, was a process of maximizing individual fitness through the promotion of the group as a whole. There is already a vast literature on the proximate mechanisms (the hormonal and neurobiological aspects) that promote both pair bonding and affiliative behavior. While there are still many more questions that need to be answered, this research is a promising candidate for understanding the evolutionary origins of primate sociality and human morality itself.


This research doesn’t imply that monogamy causes increased social cooperation, merely that the brain mechanisms selected for in the evolution of pair bonds have been extended to additional members of the primate order. But it’s unfortunate that so many conservatives are adamantly opposed to understanding evolution. Finally a connection between morality and monogamy has been established by Science and their refusal to understand means they'll miss a terrific opportunity to pound the bully pulpit.

Reference:

R.I.M. Dunbar and Susanne Shultz (2007). Evolution in the social brain. Science 317:1344-47. DOI: 10.1126/science.1145463

[Read more →]

The Sacrifice of Admetus

How the evolution of altruism reveals our noblest qualities


Heracles battles Death for generosity's sake

* This piece has been included in the 2007 Open Laboratory: The Best Science Writing on Blogs. For information on how to purchase or download a copy click here.

Whereas great scientific theories stand the test of time when they accurately predict the natural world through repeated empirical trials, great literature transcends the ages when it speaks to universal qualities of human experience. Such inspirational works can also, without the authors realizing at the time, reveal the sublime beauty and tragedy of our evolutionary drama. Few classical authors have tapped into this zeitgeist of biological experience as the Greek tragedian Euripides. The conflict between male and female reproductive strategy and the horrific choice of maternal infanticide is powerfully presented in the story of Medea (which waited some 2,400 years before being elucidated as an adaptive strategy in primates by the incomparable Sarah Hrdy). Electra chronicles the bitter feud between parent and child that would later be revealed as encompassing a biological reality by Robert Trivers in Parent-Offspring Conflict Theory. And Helen, the haunting tale of Helen of Troy's fateful decision, evokes the evolutionary importance of female mate choice revealed through Darwin's theory of sexual selection.

However, despite his focus on tragedy, Euripides could also reveal what we as a species have long prided ourselves as a uniquely transcendent gift: generosity even amidst the most terrible of circumstances. In his lesser-known work Alcestis, Euripides has the great hero Heracles (the Greek Hercules) arriving to the home of Admetus, the King of Pherae in Thessaly. Not realizing that his wife and true love, Queen Alcestis, has just been snatched by Death at a young age, Heracles asks his dear friend for harbor and a reprieve from his many adventures. Though wrought with grief, the tenderhearted Admetus cannot deny his friend the generosity of his home and so hides his mourning for the benefit of the visiting demigod. Ignorant of the great pain felt throughout the household, Heracles unwittingly offends his hosts with his Dionysian joviality only to be clued in by one of Admetus' less obedient servants. Overwhelmed by his breach of such generosity, Heracles descends to the Underworld to confront the "black and wingèd Lord of Corpses" and wrestle the dearly departed Alcestis from Death's icy grasp. Heracles understood the depth to which Admetus had sacrificed his own well-being for the sake of hospitality, and not even Death would prevent him from honoring his debt.


Alfred Russell Wallace and Charles Darwin

Such beneficence, in a decidedly less epic but nonetheless important way, has likewise been shown in the life of the great bard of biology himself. Having spent more than twenty years privately exploring the evidence for evolution, only mentioning his heretical research to his closest friends, Charles Darwin was faced with one of the great moral challenges in the history of science. In the summer of 1858 Darwin's collected work on the topic of natural selection exceeded a quarter of a million words (roughly five hundred pages), and was only half completed, when a parcel arrived from a young naturalist working in Borneo by the name of Alfred Russell Wallace. To Darwin's surprise he found that Wallace had independently developed a theory of natural selection (which he referred to as "progression") that outlined what Darwin had spent countless hours elucidating. Scientific culture places a premium on primacy of authorship and here Darwin was holding in his hand a document that could undermine the originality of his life's work.

Darwin knew what was at stake when he wrote to his friend and mentor Charles Lyell that Wallace "could not have made a better short abstract! Even his terms now stand as Heads of my Chapters. . . So all my originality, whatever it may amount to, will be smashed." But in an act that evokes Admetus' generosity, Darwin continued by stating that, "he does not say he wishes me to publish, but I shall, of course, at once write & offer to send to any Journal." And so Wallace's outline was included alongside an abstract of Darwin's theory and presented jointly before the Linnaen Society on July 1, 1858. On the Origin of Species was published just over a year later, the first edition selling out on the day of its release.

Ironic though it may be, the very act of generosity which gave origin to the Origin has posed tremendous difficulty to evolutionary biologists ever since. What Martin Luther King, Jr. described as a "walk in the light of creative altruism" has seemed, to many, contradictory to the "selfish gene" approach of natural selection. From a gene's-eye view of the world only those traits that are successful for an individual organism and allows the maximum level of reproductive success will live on in subsequent generations. Any trait that influenced one to benefit others at their own expense would be at a disadvantage compared to individuals who merely accepted the assistance and failed to reciprocate. The schoolyard dictum that "cheaters never prosper" wouldn't seem to have any place in such a system.


Chimpanzees show spontaneous altruism

Much ink, and many hours in the field, have been spent working to resolve this seeming conflict. The latest papers to do so, hitting the presses back-to-back and reinforcing each other in a fitting metaphor of the mutual assistance they document, highlights how this perceived conflict is really no conflict at all. The first to be published (on June 26, 2007 in the public journal PLoS Biology) was by Felix Warneken, Brian Hare, Alicia P. Melis, Daniel Hanus and Michael Tomasello of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. In their study they compared the innate predisposition for generosity in wild-born adult chimpanzees (Pan troglodytes, named for another Greek demigod) and human infants (aged 18-months).

The researchers set up identical conditions by which their Pan and Homo subjects observed an unfamiliar person stretching to reach an object just beyond their grasp. In multiple individual trials the researchers recorded the frequency at which each group of 36 subjects would offer their assistance by retrieving the desired object and handing it to the stranger. Contradicting previous studies of chimpanzee altruism, the researchers found no significant difference between us and our evolutionary cousins. This result was upheld even when the subjects had to put in some effort, climbing over a series of obstacles, in order to deliver the object. In a variation on these initial trials the researchers also offered the subjects a reward to illicit their assistance (toy blocks for the infants and bananas, of course, for the chimpanzees). In both cases the only significant factor was whether the subjects observed the stranger attempting to reach the distant object; a factor that chimpanzees and infants both responded to selflessly. Offering a reward for their assistance had no effect on this display of generosity. Service, it seems, was its own reward.

However, perhaps the chimpanzees had previously learned to obey human researchers in their time spent under semi-wild conditions? Would chimpanzees go out of their way to help other chimpanzees? To test this possibility the researchers constructed a door that could be opened by pulling a chain in order to access food on the other side. The researchers fastened this chain to a peg that could only be removed by a second chimpanzee in an adjoining room. In order to access the food the first chimpanzee would have to rely on assistance from the second, who gains nothing in the bargain. As before, 8 out of 9 individuals consistently helped a stranger (this time of their own species) if they saw they needed help. This, the authors reason, suggests that "the roots of human altruism may go deeper than previously thought, reaching as far back as the last common ancestor of humans and chimpanzees."

But could the roots of altruism go back even further? Apparently yes, as suggested by an additional study appearing in PLoS Biology on July 3 by Claudia Rutte and Michael Taborsky at the University of Berne, Switzerland. In a study entitled "Generalized Reciprocity in Rats" the Swiss biologists constructed a similar cooperative task as used for the chimpanzees. A baited tray was attached to a stick that one rat could pull in order to bring food within range for a second, unrelated rat's benefit. Rutte and Taborsky then conducted subsequent trials to see how often rats who had benefited in the past would be willing to help other rats in the future, the Rattus norvegicus version of the movie Pay It Forward. On average rats were 21% more likely to help strangers if they had received such help themselves.


Modern hunter-gatherers share meat throughout the community

These findings seem to fly in the face of previous theory suggesting that individuals wouldn't perform an altruistic act unless they could expect such acts to be repaid. Known as reciprocal altruism, it has traditionally been held that an individual (human and non-human alike) would only be likely to help another if the recipient had previously shown they wouldn't take advantage of such generosity. This meant that only group residents whom the individuals had previous experience interacting with would warrant their aid. It was solely among kin members, depending on the frequency of shared genes, that individuals would behave altruistically without reciprocation. However, in both PLoS Biology papers, altruism was being displayed for the benefit of total strangers. And in the case of rats the decision to offer anonymous help was determined by how much anonymous help they'd already received. Rather than contradicting reciprocal altruism, what these studies instead suggest is an expansion of the evolutionary social contract. In an environment of cooperative strangers it pays to be cooperative yourself.

While much has been made of the Darwinian phrase "survival of the fittest" suggesting that natural selection operates purely through aggressive competition, credit for the term must go to the American sociologist Herbert Spencer who had a dubious political ax to grind ("Social" Darwinism remains as his misguided legacy). However, Darwin's Origin preferred the more neutral "struggle for existence," which evokes a race against the elements rather than between individuals. It is only through Spencer's understanding of natural selection that cooperation and altruism pose a problem. For Darwin, cooperation between individuals could be an adaptive strategy in many environments as individual reproductive success increases through the safety and support of the group. Such group dynamics have been examined in detail by Robert Sussman and Audrey Garber published in the edited volume The Origins and Nature of Sociality (which Sussman also co-edited). In their metanalysis including seventy-eight published studies that covered twenty-five genera and forty-nine species of non-human primates they determined that prosimians, monkeys and apes spend the vast majority of their social lives in cooperative interactions. The study also showed that the amount of social aggression was statistically insignificant, concluding that "affiliation is the major governing principle of primate sociality and that aggression and competition represent important but secondary features of daily primate social interaction."

It was in Darwin's second great treatise on natural selection, The Descent of Man, that he offered this very line of reasoning that would wait 130 years to return full circle. With the knowledge that human and non-human animals alike were often illuminated by such walks of creative altruism, Darwin suggested that "those communities which included the greatest number of the most sympathetic members would flourish best and rear the greatest number of offspring." It is this relatively unacknowledged aspect of Darwin's theory that offers us hope in troubled times. For as surely as aggression and greed are part of our human character, so also is our capacity for cooperation and generosity.



Such an evolutionary legacy is rightly explored and celebrated through our great works, scientific and literary alike. In this way a chimpanzee reaching across species lines to help a human stranger in need can be viewed with the same appreciation as a Samaritan woman reaching out to offer water to a traveling Jewish mystic in breach of the social customs of her time. And, just as a notoriously self-indulgent demigod will transcend the boundaries of the living to repay his host's hospitality, so will a beady-eyed vermin transcend its (clearly unjustified) reputation to help a stranger with food. Through this very idea of generosity we witness how evolution can reveal our noblest of attributes. As Euripides expressed in his play Temenidae (of which, like the fossil record, only fragments remain), "When good men die their goodness does not perish, but lives though they are gone." The sacrifice of Admetus persists today as our evolutionary inheritance thanks to an unbroken chain of cooperative ancestors, who even Death himself could not prevent from sharing their gift with us.

For more on this topic see my posts here and here.


References:

Warneken F, Hare B, Melis AP, Hanus D, Tomasello M (2007) Spontaneous Altruism by Chimpanzees and Young Children. PLoS Biol 5(7): e184 doi:10.1371/journal.pbio.0050184

Rutte C, Taborsky M (2007) Generalized Reciprocity in Rats. PLoS Biol 5(7): e196 doi:10.1371/journal.pbio.0050196

Sussman, RW, Chapman AR (2004) The nature and evolution of sociality: Introduction. In: The Origins and Nature of Sociality. Ed. by RW Sussman and AR Chapman. Aldine De Gruyter: New York, pp. 3-19.

[Read more →]