Selfish Gene

Feeling Sick? Blame Your Selfish Genes

jhalper — Thu, 07 Jan 2016 08:09:46 +0000

Feeling Sick? Blame Your Selfish Genes

Why does infection with bacteria or viruses make you feel sick? Prof. Guy Shakhar and Dr. Keren Shakhar have proposed that your symptoms are not just a byproduct of your body’s attempt to get rid of the infection. It is your genes’ way of ensuring they are passed down. The long and short of their argument is that the malaise, loss of appetite and lethargy are all ways of isolating you from your social group – so that your kin, who carry many of your genes, are not infected as well.

That means we share an evolutionary adaptation with such organisms as bees that go off to die far from the hive if they get sick. Shakhar and Shakhar note that we look, behave, sound (meh!) and even smell different when we are sick, and that these signals trigger the basic instinct in others to stay away.

Bees leave the hive when they are sick. Image: Wikimedia commons

The researchers say that their proposal is not just an interesting thought exercise. Modern medicine enables us to ignore our innate instincts when we’re sick, take a pill, and go to work. They think it might be time to start paying attention to what millions of years of evolution have written into our behavior, and maybe stop spreading our infectious diseases around the office.

And if you happen to be recovering at home (or just browsing at your office desk), you can read our other two stories today:

An atomic clock that Weizmann Institute scientists are working on for the ESA’s mission to Jupiter that will test the planet’s atmosphere and its moons’ gravity, and self-assembling nanoflasks that make chemical reactions run hundreds of times faster.

jhalper Thu, 01/07/2016 - 03:09

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evolution

genes

immunology

Research model

Gene wars across the generations

razib — Mon, 14 Sep 2009 06:36:06 +0000

Gene wars across the generations

Nearly 50 years ago W. D. Hamilton published two papers, The genetical evolution of social behaviour - I & The genetical evolution of social behaviour - II, which helped revolutionize our conception of how social and genetic process might work in concert. It opened up a field of research which was highlighted in Richard Dawkins' The Selfish Gene, and helped make inclusive fitness a general idea which allows us to view specific phenomena through a powerful theoretical lens. Hamilton's original work was broad in its implications and abstract in method, but concretely utilized various eusocial insects as biological illustrations, and in particular the hymenoptera, which are characterized by haplodiploid sex-determination.

In a haplodiploid scenario the males, the drones, are haploid. They have half the number of chromosomes as females, workers or queens, who are diploid. They receive all these chromosomes from their mother, and no genetic input from fathers. That is, drones are the products of unfertilized eggs. Females are the products of fertilized eggs, but if (as is often the case) only one male mates with the queen, then sisters will have a coefficient of relatedness with each other of 3/4, because all the genes they receive from their father will be identical. This is because he is haploid, and so contributes his total genome content to his daughters (as opposed to 50% as would be the case if he were diploid). In contrast, the mother contributes half her genome, and so there is an expectation that sisters will share only half their distinctive genes from their mother. 50% identical + 1/2 * 50% = 75% identical.

When Hamilton and his coworkers (John Maynard Smith was working in the same area of mathematical evolutionary biology, while George Williams was tearing down group selection) developed their theories genetic relatedness among hymenoptera was assumed. But with cheaper genotyping technologies over the decades evolutionary biologists have been able to look much closer in regards to the genetic structure of a colony. The reality is more complex than Hamilton's assumptions, and the colonies of eusocial insects are often diverse when it comes to relatedness. In some cases it turns out that relatedness is far less than 3/4, and that cooperation occurs even when it is below the critical threshold given by Hamilton's Rule. In other cases, there are a variety of morphs which operate in competition and cooperation in a facultative manner (sound familiar?). Some of the complexities have resulted in the emergence of group (colony) selection models to explain how unselfish behavior can persist despite the lack of the inclusive fitness context.

Hymenoptera are themselves diverse, exploring a variety of ecological niches and characterized by a range of behaviors and colony structures. A recent group has published a paper exploring (or uncovering) long term persistence of distinct lineages within a colony, The queen is dead--long live the workers: intraspecific parasitism by workers in the stingless bee Melipona scutellaris:

Insect societies are well known for their high degree of cooperation, but their colonies can potentially be exploited by reproductive workers who lay unfertilized, male eggs, rather than work for the good of the colony. Recently, it has also been discovered that workers in bumblebees and Asian honeybees can succeed in entering and parasitizing unrelated colonies to produce their own male offspring. The aim of this study was to investigate whether such intraspecific worker parasitism might also occur in stingless bees, another group of highly social bees. Based on a large-scale genetic study of the species Melipona scutellaris, and the genotyping of nearly 600 males from 45 colonies, we show that â¼20% of all males are workers' sons, but that around 80% of these had genotypes that were incompatible with them being the sons of workers of the resident queen. By tracking colonies over multiple generations, we show that these males were not produced by drifted workers, but rather by workers that were the offspring of a previous, superseded queen. This means that uniquely, workers reproductively parasitize the next-generation workforce. Our results are surprising given that most colonies were sampled many months after the previous queen had died and that workers normally only have a life expectancy of â¼30 days. It also implies that reproductive workers greatly outlive all other workers. We explain our results in the context of kin selection theory, and the fact that it pays workers more from exploiting the colony if costs are carried by less related individuals.

They sampled colonies over several years, and even managed to genotype several queens. It turns out that the genotypes of the drones who were atypical (that is, they're not from the current queen and so are not as closely to the majority of the workers) weren't so varied as one might expect from a small but diverse number of alien workers. Rather, the genotypes of the drones implied that the mothers were the daughters of previous queens! The authors note that the expectation is that workers live about 30 days, but that timing of the sampling suggested that some of the "previous generation" workers who were reproducing so to give rise to these drones were living at in excess of 100 days (which is when the previous queen had died, and so must be a peg which fixes the youngest of previous generation workers).

How could this occur? One hypothesis is that these older generation workers simply shirked their workerly duties, did not expend energy, or take risks which would increase their mortality. There are strong genetic incentives for workers who are closely related to not shirk their duties (though even they sometimes engage in selfish behavior and lay eggs, though this is generally "policed"), but for workers who are more distantly related to most of the hive there is a rational opening for parasitizing and free riding on the behavior of the colony. Shirking duties and focusing on reproduction comes at the cost of the maintenance of the colony, but if the colony is genetically rather dissimilar than the "loss" via inclusive fitness because of colonial degradation or risk of collapse are sharply reduced. The authors note that it is possible that these reproducing older workers live as long as queens, and it seems to me that what they've really discovered is an alternative behavioral morph in this species of bee. These sorts of phenomena are not limited to hymenoptera, in Demonic Males the authors report that there are two types of male orangutans, large slow ones to whom females are attracted to, and small fast ones which have to catch and rape female orangutans to reproduce.

Over the years that W. D. Hamilton's original insights and framework have turned out to just be the beginning. Social insects might not be as intelligent as humans, but the complexity of their behaviors and the subtly of their societies may surprise us yet. A through empirical mapping of their behavioral ecology may lead us to new theoretical frameworks. After all, if the adaptive landscape was characterized by a simple topology, why are there so many species?

Citation: Molecular Ecology (2009) doi: 10.1111/j.1365-294X.2009.04323.x

razib Mon, 09/14/2009 - 02:36

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There is a small typo about orang-utans, you probably mean Â«Â small fast onesÂ Â»Â (not Â«Â slow fastÂ Â»).

The Selfish Genius, mind your manners Dr. Dawkins!

razib — Mon, 24 Aug 2009 07:03:57 +0000

The Selfish Genius, mind your manners Dr. Dawkins!

A month ago Larry Moran made reference to Fern Elsdon Baker's new book, The Selfish Genius: How Richard Dawkins Rewrote Darwin's Legacy. Moran was a bit disappointed by the previews, his pet hobby-horse being the revolutionary impact of the neutral theory of molecular evolution, while Elsdon-Baker seems rather fixated on the potential of Neo-Lamarckism, especially epigenetics. Well, I've read the book, and Larry Moran would probably be disappointed, though she mentions Stephen Jay Gould and pluralism a bit, there's really very little engagement with the 20th century debates in evolutionary biology. The narrative is broken into two parts, the first half being a history of science and a general description of the current consensus and its possible future trajectory, and the second half a detailed examination of Richard Dawkins' foray into social and political advocacy, and its relationship to his philosophy of science, and the potential impact of his reputation on science education. A mouthful in less than 300 pages.

If you have read some Peter J. Bowler the first few chapters of the book won't have much new or surprising. It is mostly in the class of "facts which ignorant people should know." For example, that the idea of evolution was in wide circulation when Charles Darwin made the case for natural selection as being its primary driving engine. Or, that many progressive Christian clergy were quick to accept the fact of evolution. And so on. If you didn't know that Charles Darwin accepted some Lamarckian processes, you might pick up a book on the history of science. Elsdon-Baker's treatment is rather thin and cursory on these subjects because its primary aim isn't to educate you about the history of evolutionary thought, rather, it is to sketch out the constellations just thickly enough to illustrate how Richard Dawkins rewrote history to serve his own Whiggish narrative in a series of popularizations. This issue with Dawkins' arguments isn't particularly shocking, he famously asserted in The Blind Watchmaker that Darwinism allowed one to be an intellectually fulfilled atheist. A. N. Wilson engages this model in God's Funeral: The Decline of Faith in Western Civilization because of its widespread acceptance. As an empirical matter Dawkins is likely wrong, unless you assert anyone who was an atheist or unbeliever before Darwin's theory of evolution by natural selection was intellectually unfulfilled by definition.

A history of 19th century evolutionary thought, and Darwin's own particular ideas, are followed by a series of rapid jumps down the decades to the contemporary period. These jumps span the late 19th century debates between the classical Darwinians such as August Weismann and Saltationists, with barely a reference to the emergence of genetics due to the synthesis of evolutionary theory and Mendelism, the creation of population genetics and later the crystallization of the neo-Darwinian synthesis, and finally the emergence of the ideas of William D. Hamilton which prompted Richard Dawkins' own foray into the public sphere. I can't guess with certainty the reason one would elide so much critical historical and scientific meat, but I assume it had to do with the fact that the book was aimed at a general audience, and, that it was constrained in the material it could cover due to its page count. These rapid leaps across paradigms quickly settle upon a more thorough outline of the debate between Richard Dawkins and those who promote the possibility of processes such as horizontal gene transfer and epigenetics, which would undercut the neo-Darwinian orthodoxy of which he is the primary public expositor. There is no mention of the selectionist-neutralist debate, or the earlier disagreements within the neo-Darwinian orthodoxy (e.g., Sewall Wright vs. R. A. Fisher, Ernst Mayer vs. J. B. S. Haldane).

Obviously I was not satisfied with the survey of the scientific literature and the richly textured debates and disagreements which bubbled across conferences and decades were not even hinted at. Of course I am not likely the typical intended audience, so I will let it rest, but not before I note some issues with the substance of the science as Fern Elsdon-Baker presents them. For example, she portrays random contingency and natural selection as alternative paths, but the reality is that on even normal geological timescales selection is stochastic, more or less. With infinite time and population size one assumes that selection could explore the full sample space of fitness possibilities, but this theoretical boundary condition isn't taken seriously by most from what I know. Similarly, she asserts that Stephen Jay Gould emphasized evolution on the level of the species, but as someone who has read most of The Structure of Evolutionary Theory, I think this is not only wrong in the emphasis but misses the whole point of Gould's line of argument, that it is problematic to emphasize one level of organization or complexity as the primary target of selection. There is no symmetry between Gould and Dawkins when it comes to the levels of selection debate. Additionally, it seems to me that there is some conflation of issues such as phyletic gradualism and adaptationism, with these set against punctuated equilibrium. In fact R. A. Fisher's model of adaptation and conception of how allele frequencies change over time is totally at odds with gradualism, rather, there should be large initial changes which rapidly converge upon an adaptive optimum, which would then remained in a relatively fixed state until the adaptive landscape changed. Though I think Dawkins protests a bit too far in dismissing punctuated equilibrium as already part of the basic Darwinian framework, I do think in The Selfish Genius there is a bit excessive simplification so as to present a starker scientific narrative which makes Richard Dawkins out to be an advocate and not a scholar.

I could go on in this vein with my critiques of Fern Elsdon-Baker's description of the scientific debate, but I will concede the difficulties in appropriately condensing the nuance in a relatively short work which is frankly verging on polemic, though I won't retract my opinion that there are some serious factual issues which might lead lay readers astray. In broad-brush strokes there is truth to the portrait insofar as Dawkins is a partisan, in particular of the tradition of evolutionary biology which comes through R. A. Fisher down to William D. Hamilton, the Oxford School, which was surveyed by Marek Kohen in A Reason for Everything: Natural Selection and the English Imagination. This is not a marginal or extreme faction, as detailed in The Selfish Genius it is in many ways the main trunk of evolutionary thought from the 1930s to the present day. The issue in terms of science is whether findings in fields such as epigenetics will overturn the rules-of-thumb which were established in the middle of the 20th century. Science and time will tell. Rather, when it comes to the present day Fern Elsdon-Baker's narrative takes a tangent and shifts away from the meat of natural science to the more delicate desserts of sociology, politics and rhetoric.

Richard Dawkins is a household name not because of his science, but because of his ability as a communicator. There is no shame in this, scientists of undisputed eminence such as James Watson and E. O. Wilson are known more for their provocative public statements and social pronouncements than they are for their research (I would suggest that much of the public which is aware of "Watson & Crick" has no idea that James Watson is the Watson). In the mid-1970s Dawkins published The Selfsh Gene, which made his name as a distiller, transmitter and philosopher. Dawkins drank deeply at the well of William D. Hamilton and John Maynard Smith, and reworked their ideas into a more robust verbal apparatus, the selfish gene, the vehicle, the replicator, and so forth. His impact was great enough that a generation later his achievement warranted a festschrift, Richard Dawkins: How a Scientist Changed the Way We Think. In his later books Dawkins pushed further into the realm of popularizer, with his last scientifically oriented work, The Ancestor's Tale, being a descriptive natural history which avoids the logical and speculative tendencies of his previous projects. The original research of Richard Dawkins in ethology is a distant memory now, as he has transformed himself into a public figure and celebrity, with an actress wife to boot to round out the image. It is because of this reality that I am willing to move past the objections I entered in above in regards to how The Selfsh Gene characterizes the scientific debate and consensus; for all the talk of epigenetics most readers will be more interested in the fireworks in the second half of the book which delves into religion, philosophy and the role of public intellectuals.

Elsdon-Baker paints a portrait of Dawkins as a naive positivist, a dyed-in-the-wool believer in an objectivity to which he has clear and distinct access, an obnoxious and often offensive advocate and polemicist who suffers no fools. I think this is in the main correct. Much of what irks many about Richard Dawkins is not the content, it is the style and delivery. Carl Sagan was arguably just as uncompromising a materialist, but his congenial and affable personality had a much softer edge to it. And this razor sharpness is what also elicits in devotion to Dawkins which can verge on cultish. The problem for Elsdon-Baker, and many others, is Dawkins' dual roles as a science popularizer and prophet of the New Atheism, and, his vocal connection between his Darwinism as the acid which necessarily ate away at his theism. This is familiar ground, Chris Mooney & Sheril Kirshenbaum and Michael Ruse have opined on. The pro- and anti- Dawkins factions were out in full-force in the early days of ScienceBlogs in the wake of The God Delusion.

There is some rehashing of non-overlapping magisteria, but the more interesting bits are deconstructions of Richard Dawkins' view of science and implicit epistemology. As I said above, Dawkins seems to be a naive positivist, as are many scientists. They presume there is an objective world out there, a world that can be modeled, measured and conceived in a clear and distinct fashion. Natural scientists live in a world apart from literary essayists, who might quibble on the margins over a thousand interpretations. This is not to say that disputes do not arise in natural science, but the ability to observe and experiment, to scaffold verbs with mathematical formalism, does the endeavour much good. Science is not dependent upon the faculties of humans, rather, the world itself serves as a critical test and check upon the intuitions, deductions and inferences of the human mind.

But of course science is the enterprise of humans, and so as with all human enterprises there is a great deal of messy politics, bickering and self-dealing. Even scientists as brilliant as Fred Hoyle could not give up on their pet theory when the data began to turn against it. This messy proximate reality, the objective principles of science being suborned by self-interest and bias, ultimately gives way to truth and falsification. There is only so long you can resist the verdict of nature, but in the meantime the normal human process of paradigmatic conflict persists. The difference is that these conflicts generally conclude, either with minds changed, or holdouts dying. Fern Elsdon-Baker seems to be of the position that Richard Dawkins and his acolytes in their scientistic fervor elide all these day to day details in the interest of promoting the march of science toward truth in a straight line without deviation and human foible, and that these omissions serve to undermine Dawkins' credibility, and that of science, with the public. The genius of science is not that it is right, but that it is wrong, and often indubitably so. Richard Dawkins' pronouncements seem to go against this spirit, for their are vigorous, aggressive, assertive and without doubt. In a debate this is an asset, but in transmitting the spirit of science it can be misleading.

Additionally, Dawkins' aggressive espousal of atheism with the cudgel of science often leads him to conflating various intellectual modes. While claiming to be a rationalist he makes no distinction between philosophical rationalism of which the hallmark is deduction, and the inductive empirical workaday of normal science. This blurring leads one to easily dismiss theism on scientific grounds. Fern Elsdon-Baker rightly, in my view, points out that while some versions of theism can be empirically refuted (e.g., literalism which supports Young Earth Creationism), others can only be philosophically denied (e.g., philosophical Deism). The empirical inductive tools of science are of limited scope, and to assert that something is a scientific question does not make it amenable to scientific methods. Words are not magic.

Finally, there is the matter of Richard Dawkins' Eurocentric anti-liberal positivism. To be fair, it is not stated as such in The Selfish Genius, but the message is clear. I actually do not know where some of this comes from, though Dawkins has expressed skepticism of some aspects of liberalism, such as multiculturalism, from all I know he is a conventional Labour party supporter who exhibits the typical European intellectual contempt for American conservatism. I am no Richard Dawkins scholar, but Fern Elsdon-Baker presented little concrete evidence that the man is anti-liberal, aside from a few quotations which make it clear that the liberalism of those who inflamed him to ire was less consequential than their relativism or multiculturalism. As a point of fact I also think Dawkins is correct, though perhaps premature, to suggest that Muslims tend to be Creationist. More polls need to be done, but if Turkish and American Muslims do not support evolution, it seems implausible that Egyptian or Pakistani Muslims would. Additionally, when it comes to rejecting some of Richard Dawkins' excessively authoritative assertions, such as the idea that female circumcision is an "ethnic religious" tradition, Fern Elsdon-Baker seems to feel that a claim to objectivity is totally acceptable, as she asserts that it has nothing to do with religion. Certainly this is a defensible claim, but there are many Muslims who do claim it has everything to do with religion, as that is their interpretation of Islam. In fact Dawkins is correct, to a great extent female circumcision is justified on ethnic-religious grounds, though the particular interpretation of the religion might not be widely accepted outside of that ethnic group, the idea that there is "true religion" which one might objectively use as a judge against which to dismiss Dawkins' assertion is itself falling prey to the sort of naive positivism that Elsdon-Baker so often chides him for. The issue here is not that Richard Dawkins is wrong, it is that he is in the minority viewpoint when it comes to the proper boundaries of sensitivity.

In a world in which most people believe in God, making the necessary and essential connection between evolutionary biology and atheism may not be the best marketing ploy for the former. This is no seminal observation. Richard Dawkins aggressive, acerbic and take-no-prisoners style is a matter of taste. I am frankly skeptical that Dawkins is as consequential as his acolytes and detractors claim he is, most of the public is relatively detached from intellectual discourse, and probably are ignorant of terms such as "New Atheist." The Selfish Genius does not always play fair, as Fern Elsdon-Baker acknowledges on the first page in regards to the title, which was a gimmick rather than a description of Richard Dawkins' character. This sort of ploy seemed a bit low to me, but The Selfish Genius has a polemical flavor, and so likely such behavior should be interpreted in that light. Though Fern Elsdon-Baker writes in an engaging style which is accessible to the general reader, I believe that the complexity and subtly of some of the scientific questions which she wades into require a more well-versed audience to navigate the details with ease. The author may take a strong line against Richard Dawkins, she is no Steve Fuller, and she makes enough charitable concessions to Dawkins so that The Selfish Genius falls short of being mean-spirited. As an American I definitely learned a bit more about the intellectual scene in Britain, where Dawkins seems to stride across the landscape like a latter day giant. If you're a fan of Richard Dawkins there is enough to get you're juices flowing, but not enough for you to froth at the mouth. Fern Elsdon-Baker snipes at the intellectual edifice which Richard Dawkins constructs, but does not attack in a personalized fashion. If you're an admirer or a hater of Richard Dawkins, a worthwhile read. If you're looking for an introduction to the history of the science at issue, look elsewhere.

Addendum: Sometimes you can judge a book by its cover.

razib Mon, 08/24/2009 - 03:03

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They presume there is an objective world out there, a world that can be modeled, measured and conceived in a clear and distinct fashion.

The "objective world out there" isn't the problem, in my opinion, but the adequacy of our models and descriptions. Each model answers the questions it proposes to answer more or less well within some margin of error. If they're answering the same question, one model can be unquestionably better than another. But you can't be sure that the answer is the last word on the topic.

In large areas of science these "relatvism" questions are of not very important, but on some major questions they're very important.

"Relativism" in quotes because I think the real issue is highlighting or marking -- chosing which aspect of an actuality to investigate and foreground. "an indefinitely large number of systems can be defined on any given object".

"Sometimes you can judge a book by its cover." - or by its lack of cover! Good review. Thanks.

"While claiming to be a rationalist he makes no distinction between philosophical rationalism of which the hallmark is deduction, and the inductive empirical workaday of normal science. This blurring leads one to easily dismiss theism on scientific grounds. Fern Elsdon-Baker rightly, in my view, points out that while some versions of theism can be empirically refuted (e.g., literalism which supports Young Earth Creationism), others can only be philosophically denied (e.g., philosophical Deism)."

If the blurring you speak of refers to the example you gave via Fern Elsdon-Baker, then you have not pinned Dawkins down as a naive positivist because he has never (to my knowledge) denied deism on empirical grounds.

Moran was a bit disappointed by the previews, his pet hobby-horse being the revolutionary impact of the neutral theory of molecular evolution ...

A minor quibble. I'm an advocate of pluralism and evolution by accident. That includes a greater emphasis on the role of random genetic drift.

"Neutral Theory" is a theory about the relative fitness of various alleles. Specifically, the theory proposes that many alleles are neutral with respect to fitness. Such alleles can be fixed in a population by random genetic drift.

But random genetic drift plays a role in the fixation or elimination of beneficial and detrimental alleles as well. It would be more correct to say that one of my "hobby-horses" is the importance of random genetic drift. Neutral theory is merely part of the hobby-horse!

I wonder if Dawkins polemic is going to change in his next book. Sounds like he is going to attack/define denialism with regard to the findings of science, rather than incompatibility in methods of approach to knowledge. Could be interesting with respect to debates about accomodationism.

All pages from Why Truth Matters by Benson and Stangroom:
"I am not advocating a morality based on evolution. I am saying how things have evolved. I am not saying how we humans morally ought to behaveâ¦My own feeling is that a human society based simply on the gene's law of universal ruthless selfishness would be a very nasty society in which to live" - Dawkins (100)
"As the bumper stickers put it, 'Re-defeat Bush'. But, this time, do it so overwhelming that neither his brother's friends in Florida nor his father's friends on the Supreme Court will be able to rig the count. Decent Americansâ¦please show your electoral muscle this time around" - Dawkins (104)
"And in the second edition of The Selfish Gene, Dawkins noted that he had helped to vote in a socialist government in 1974; and said that of Thatcherism that it 'elevated meanness and selfishness to the status of ideology'" - authors on Dawkins (104)

Adoption in Non-Human Primates

emjohnson — Fri, 17 Jul 2009 10:53:25 +0000

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 journal Primates (subscription required), Cristiane CÃ¤sar and Robert John Young report on a case of adoption among a wild group of black-fronted titi monkeys (Callicebus nigrifrons) (see right) from the rainforests of Brazil.

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:

CÃ¤sar, C., & Young, R. (2007). A case of adoption in a wild group of black-fronted titi monkeys (Callicebus nigrifrons) Primates, 49 (2), 146-148 DOI: 10.1007/s10329-007-0066-x

emjohnson Fri, 07/17/2009 - 06:53

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Callicebus nigrifrons

"Since animals, including humans, are primarily ambulatory vehicles for their selfish genes..."

Nicely put, but isn't it a matter of perspective? You can reduce it to the level of selfish genes, or expand it to the level of all titi monkeys, or all primates. From that perspective, the individual titis or primates seem to be the impetus for action, not the superorganism of all titis or primates, but it's just perspective. In this same way, couldn't adoption of an unrelated (or distantly related) individual be as unremarkable as a single gene not coding for anything inherently beneficial. As long as it doesn't kill an individual before they reproduce, any gene could conceivably pass through generations. A single pair of titis adopting an unrelated individual, may be a mis-behaving, but not detrimental gene in an otherwise completely predictable and logical superorganism that is all titis.

The problem with expanding it to the macro level of all titi monkeys is that the coefficient of genetic relatedness would shrink to almost zero (meaning it would be very unlikely that an individual you were helping was related to you). The gene is the ultimate unit of selection and, according to traditional sociobiology, any genes that encourage an individual to take a hit in order to help nonkin are reducing their fitness over the long term. Any genes that encouraged such behavior wouldn't be around for many generations before disappearing. You are correct that this would work for superorganisms. However, this only exists in Hymenoptera or in rare cases among different orders, such as naked mole rats, that are extremely inbred so that all members of the group have a coefficient as high, or higher, than their own offspring.

However, this study (and several others) suggest that traditional sociobiology is incomplete. Joan Roughgarden has proposed an alternative perspective that she calls social selection theory. I'm reading her book The Genial Gene right now and will be writing about it in the future.

Couldn't it also be that a small titi group benefits from increasing its size? That's been argued as an explanation for adoption and even kidnapping in a number of species, including white-winged choughs and banded mongooses.

For instance, see [Kidnapping and reciprocity in cooperatively breeding white-winged choughs. Heinsohn, RG. Animal Behaviour. 1991] and
[Kidnapping and infanticide between groups of banded mongooses. Mammalian Biology. MÃ¼ller, C. A. & Manser, M. B. 2008.]

Sorry for the slow response. I think this is an excellent hypothesis. However, both studies you cite are talking about cooperatively breeding species. Callicebus nigrifrons are not considered cooperative breeders (having an average group size of only 2.2 individuals). Endocrinological studies of cooperative breeders (see, for example, Ziegler, 2000) show that they are generally more tolerant than species who aren't. What would be important to look at is a metanalysis of literature on the subject of adoption or kidnapping to find out the kinds of animal societies that are most prone to this. I'm not aware of any such study but, from the literature I'm aware of, the behavior shown by C. nigrifrons remains perplexing given existing theory.

"The problem with expanding it to the macro level of all titi monkeys is that the coefficient of genetic relatedness would shrink to almost zero"

Yes, but that's still using the measurements of the micro level at the level of the macro. In order to evaluate rates of change at the macro level, you need a new metric.

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Betty

http://adoptpet.info

Betty

http://adoptpet.info