Relatedness is relative: How can I be 85% genetically similar to my mom, but only related to her by half?

First of all, no. I am not the lovechild of star-crossed siblings, or even cousins, or even second cousins. 

This is a gee-whiz kind of post. But the issues are not insignificant.

Hear me out with the background, first, before I get to the part where my eyes bug out of my head and I pull out my kid's Crayola box and start drawing.

If you've learned about sociobiology, or evolutionary psychology, or inclusive fitness, or kin selection, or the evolution of cooperation and even "altruism," or if you've read The Selfish Gene, or if you've been able to follow the debate about levels of selection (which you can peek at here)...

... then you've heard that you're related to your parents by 1/2, to your siblings by 1/2 as well, to your grandparents and grandchildren by 1/4, to your aunts and uncles and nieces and nephews by 1/4 as well, and to your first cousins by 1/8 and so on and so forth.  (Here's some more information.)

So, for example. For evolution (read: adaptationism) to explain how cooperative social behavior could be adaptive in the genetic sense, we use the following logic provided by Bill Hamilton, which became known as "Hamilton's Rule": 

The cost to your cooperation or your prosocial behavior (C) must be less than its benefit to you (B), reproductively speaking, relative to how genetically related (r) you are to the individual with whom you're cooperating. That could have come out smoother. Oh, here you go:

C < rB, or B > C/r

If you're helping out your identical genetic twin (r=1.0), then as long as the benefit to you is greater than the cost, it's adaptive.

C < B, or B > C

If you're helping out your daughter (r = 0.5) then as long as the benefit to you is greater than twice the cost, it's adaptive.

C < (1/2)B, or B > 2C

So already, the adaptive risk to helping out your daughter or your brother is quite higher. And it's even harder to justify the cooperation between individuals and their sibs' kids, and grandkids, especially ESPECIALLY non-kin. But, of course creatures do it! And so do we.

As relatedness gets more distant and distant, we go from 2 times the cost, to 4 times, 8 times, 16, 32, 64 etc... You can see why people like to say "the math falls away" or "drops off" at first or second cousins when they're explaining where the arbitrary line of genetic "kin" is drawn.  If you offer up a curious, "we're all related, we're all kin," someone out of this school of thought that's focused on explaining the evolution of and genes for social behavior may clue you in by circumscribing "kin" as the members of a group that are r = 1/8 or r = 1/16 but usually not less related than that.

This has long bothered me because we're all genetically related and so much cooperation beyond close kin is happening. And it's been hard for me, as someone who sees everything as connected, to read text after text supporting "kin selection" and "kin recognition" (knowing who to be kind to and who to avoid bleeping), to get past the fact that we're arbitrarily deciding what is "kin" and it seems to be for convenience. I'm not doubting that cooperation is important for evolutionary reasons. Quite the contrary! It's just that why is there so much math, based in so many potentially unnecessary assumptions about genes for behavior, gracing so many pages of scientific literature for explaining it or underscoring its importance? 

(It could just be that as an outsider and a non-expert I just don't understand enough of it and if I only did, I wouldn't be gracing this blog with my questions. But let's get back to my reason for posting anyway because it's potentially useful.)

Right. So. Even for folks who aren't part of evolution's academic endeavor, it's obvious to most that we're one half dad and one half mom. The sperm carries one half of a genome, the egg another, and together they make a whole genome which becomes the kid. Voila!

There's even an adorable "Biologist's Mother's Day" song about how we've got half our moms' genome... 

... but there's biology above and beyond the genes we get from mom (and not from dad). And that song is great for teaching us that the rest of the egg and the gestational experience in utero provide so much more to the development of the soon-to-be new human. So "slightly more than half of everything" is thanks to our mothers. Aw!

But, genetically, the mainstream idea is still that we're 50% our mom. 

I teach very basic genetics because I teach evolution and anthropology.And I'm not (usually) a dummy.* I get it. It's a fact! I'm half, genetically, my mom and I'm also half my dad. 

r = 0.5

Okay! But, given these facts about relatedness and how it's imagined in evolutionary biology, facts that I never ever questioned, I hope you can see why this report from 23andMe (personal genomics enterprise) blew my mind:

Percent similarity to Holly Dunsworth over 536070 SNPs (single nucleotide polymorphisms or, effectively/rather, a subset of known variants in the genome; Click on the image to enlarge).
I am 85% like my mom and I am at least 76% like my students and friends who are sharing with me on 23andMe. Names of comparisons have been redacted. As far as I know, this kind of report is no longer offered by 23andMe. I spat back in 2011/12 and the platform has evolved since.

Okay, first of all, it is a huge relief that, of all the people I'm sharing with on 23andMe, the one who squeezed me out of her body is the most genetically similar to me. Science works.

But that number there, with my mother, it is not 50%. It's quite a bit bigger than that. It says I'm over 85% the same as her.

What's more, I am also very similar to every single person I'm sharing with on the site, including example accounts from halfway around the world. Everyone is at least 60-ish% genetically similar to me, according to 23andMe. I know we're all "cousins," but my actual cousins are supposed to be 1/8th according to evolutionary biology. How can my mom be related to me by only one half? How can my actual cousins be only an eighth (which is 12.5%)? 

What is up with evolutionary biology and this whole "r" thing?

Hi. Here is where, if they weren't already, people just got really annoyed with me. Evolutionary biology's "relatedness" or "r" is not the same as genetic similarity like that reported by 23andMe.

Okay!

But why not? 

Let me help unpack the 85% genetic similarity with my mom. Remember, it's not because I'm inbred (which you have to take my word for, but notice that most everyone on there is over 70% genetically similar to me so...).

It's because my mom and dad, just like any two humans, share a lot in common genetically. Some of the alleles that I inherited from my dad are alleles that my mom inherited from her parents. So, not only is everything I got from her (50%) similar to her, but so are many of the parts that I got from my dad. 

Let me get out my kid's arts supplies.

Here is a pretty common view of relatedness, genetically. In our imagination, parents are not related (r = 0) which can lead our imagination to think that their alleles are distinct. Here there are four distinct alleles/variants that could be passed onto offspring, with each offspring only getting one from mom and one from dad. In this case, the sperm carrying the orange variant and the egg with the blue variant made the baby.

1. (Please, if you're horrified by the "r" business in these figures, read the post for explanation.)

But few genes have four known alleles, at least not four that exist at an appreciable frequency. Some could have three. What does that look like? 

The green allele doesn't exist in the next example. As a result of there being only three variants for this gene or locus, mom and dad must share at least one allele, minimum. That means, they look related and that means that, depending on which egg and sperm make the kid, the kid could be more related to mom than to dad. 

2. (Please, if you're horrified by the "r" business in these figures, read the post for explanation.)

Now here's where people who know more than I do about these things say that the kid is not more related to mom than dad because she got only one allele from mom and that keeps her at r = 0.5. 

Well, that's just insane. What does it matter whether she got the allele from mom or dad? I thought genes were selfish? (Sorry, for the outburst.)

Again, I realize I'm annoying people and probably much worse--like stomping all over theory and knowledge and science--by mixing up the different concepts of genetic similarity (e.g. 50%) with "r" (e.g. 0.5) and horribly misunderstanding all the nuance (and debate) about "r," but I'm doing it because I'm desperately trying to know why these two related ideas are, in fact, distinct. 

One last pathetic cartoon. 

In this third example, as is common in the genome, there are only two alleles/variants in existence (at an appreciable frequency, so not accounting for constant accumulation of de novo variation). An example of such a gene with only two known alleles is the "earwax gene" ABCC11 (there's a wet/waxy allele and dry/crumbly one). Here, the two alleles are orange and blue. Most humans in the species will have at least one allele in common with their mate for a gene with two alleles, and it's not because most humans are inbred, unless we want to redefine inbreeding to include very distant relatives (aside: which may be how the term is used by experts). 

3. (Please, if you're horrified by the "r" business in these figures, read the post for explanation.)

But as a result of the chance segregation of either the blue or orange allele into each of the gametes, two people with the same genotype can make a kid with the same genotype. 

And of course, making a kid with your same genotype is the only possible outcome if you and your mate are both homozygous (i.e. where both copies are of the same variant so that leaves no chance for variation in offspring unless there is a new mutation). 

So, I wandered a little bit away from my point with these drawings, but I had to because I wanted to get down from where my imagination has me (us?) with "r" versus how things really are with reproduction. We are baby-making with vastly similar genomes to ours, so we are making babies with vastly similar genomes to ours. 

So, I do see why biology says I'm related to my mom by one half. But, on the other hand, what does it matter if I got the thing I have in common with my mom from my mom or whether I got it from my dad? Because I got it. Period. It lives. Period. 

[Inserted graf January 20, '17] Saying it matters where I got the similarity to my mom keeps us at r = 0.5. Saying it matters only that I inherited DNA like hers keeps us always, all of us, at r > 0.5 with our parents and our kids because any two babymakers share much of their genome.

And the fact that this (see 2 and 3) happens so often is why I'm a lot more than 50% genetically like my mom, and the same can be said about my genetic similarity to my dad without him even spitting for 23andMe. 

So, here we are. I don't understand why our relatedness to one another, based on genetic similarity, is not "r."

I hope it's for really beautifully logical reasons and not something political. 

Because...

If "r" was defined by genetic similarity, then would cooperating with my 76% genetically similar students and friends be more adaptive than the credit I currently get from evolutionary biology for cooperating with my own flesh and blood son? 

If "r" was defined by genetic similarity, then could we use the power of math and theoretical biology to encourage broader cooperation among humans beyond their close kin? 

So many questions.

Maybe I should re-learn the math and learn all the other math.

Nah. Not myself. At least, it wouldn't come fast enough for my appetite. Maybe someone who already knows the math could leave a comment and we could go from there... 

And it would be worth it, you know, because despite my relatively weaker math skills, I bet we're more than 50% genetically similar.

*from 23andMe: "You have 321 Neanderthal variants. You have more Neanderthal variants than 96% of 23andMe customers."

Cooperation might actually be ... cooperation

Cooperation, altruism, anything but self-interest, have long been perplexing to true Darwinians.  According to theory, cooperation can't happen unless it has a payoff in terms of increased fitness because it's costly to the donor.  So, cooperation is redefined as ultimately just a form of competition, or as selfish only being done when those who cooperate can expect reciprocity, or only practiced among kin.

A new paper in Current Biology, Social Evolution: Reciprocity There Is, Taborsky, challenges the idea that cooperation only happens among kin, supporting instead the idea that it is evidence of reciprocity; you pat my back and I'll pat yours.  But such arguments basically make the competition viewpoint a tautology, an assumption, from which any explanation can be -- must be -- just a kind of mathematically different way to express competition.  However, cooperation is so ubiquitous, at all levels of life, that it should stand alone, without being remolded and forced to fit classical Darwinian theory.

Vampire bat; Wikimedia

Taborsky cites a recent paper on food sharing among vampire bats.  These animals often feed roost-mates by regurgitation of a blood meal, and the question has been why such behavior would have evolved. 

The original explanation for this costly helping behaviour invoked both direct and indirect fitness benefits. Several authors have since suggested that food sharing is maintained solely by indirect fitness because non-kin food sharing could have resulted from kin recognition errors, indiscriminate altruism within groups, or harassment.

The authors tested these alternate explanations by looking at food-sharing over several years among a group of bats.  They determined that sharing was initiated more often by the donor than the recipient, so clearly it wasn't due to harassment.  And, they found that bats who were given food were more likely to share, and that this reciprocity was more often involved in sharing than was relatedness between bats.  Food sharing was also correlated with social grooming.  The authors conclude that food sharing has direct, mutual fitness benefits that is more about reciprocity than kinship. 

Questionable assumptions
Well, maybe.  The assumption underlying the idea that cooperation, or altruism, are in fact selfish behaviors is that everything organisms do must be optimized to reduce energetic costs and to increase fitness.  This in turn largely also implies the assumption that evolution arrives somewhere, that organisms have finished evolving, and that energy expenditure for a given lifestyle must be as low as it can be and fitness as high as it can be.

There are problems with these assumptions.  The first is that evolution never arrives, organisms are always in process -- there is clear-cut genetic evidence for this. Dead genes, called pseudogenes, litter most genomes, relics of gene duplication events in the distant past, or functions the organism no longer has (chickens still have genes that could produce teeth, if asked to at the right time and place in development, e.g.).   

And, whether you come down on the ENCODE end of the "junk DNA" debate and accept that 80% of non-coding DNA has function, or the Dan Graur side of the debate and accept that most DNA is in fact junk (that is, doesn't do anything relevant), there does seem to be at least some of the genome of most species that has no function, whether or not it once did.  The point is not to rehash the junk DNA debate, but instead to point out that whether it's 20% or 95% of our genome, we seem to be spending a significant amount of energy making DNA that has no function.  That's not optimal.

Further, we've got a lot of DNA repair enzymes floating around in our cells, and the reason is that the processes of chromosomal replication, DNA transcription and translation are not error-free.  When the wrong nucleic acid is incorporated in a new stretch of DNA or mRNA, the cell has ways to detect this, and then correct it.  Why should these error-prone mechanisms have been maintained by selection, if optimal energetics is its goal?

There are numerous examples of imprecision at the cellular level.  Gene transcription can be stochastic, somatic mutations occur and proliferate, during development superfluous cells and tissues are made, such as webbing between the digits, and then programmed to die before birth, and so on.  If energetic optimization were a rule that evolution was supposed to be following, evolution didn't get the message.

Similarly with cooperation -- if  cooperation were only competition or selfishness in disguise, it's hard to know what to make of the interaction between cellular organelles, genes, gene products, cells, tissues, organs, organisms.  Sexual animals can't even reproduce themselves alone.  We're dead without our microbiomes.  Ecosystems are built upon cooperation.

The slime mold Dictyostelium discodeum, collections of cooperating amoeba: The Mermaid's Tale

The selectionist problem
As we've been discussing recently, this relates to the selectionist assumption, that there must be a selective reason, that is, one based on raw competition, for everything organized about life.   If cooperation leads to proliferation of whatever is responsible for it, then that means something isn't proliferating and that implies competition -- or, rather, that is an instance of redefining cooperation as just another form of competition.

Since differential proliferation is a fact of life, and proliferation is necessary for a species or lineage to persist over time, one can take a cold mathematical view and say that it is perfectly legitimate to show that everything can be translated mathematically in to proliferation based on competition.  This is not really accurate, but is actually beside an important point here.

That point is that cooperative interactions at various levels from genomes to cells to organs to individuals in a species and species in ecosystems, are how life works on a daily basis. Even if one were to grant that this arose because of some version of competition, that doesn't help understand how or why the cooperative organization works today.  Yes, there may always be a Darwinian component of variation and behavior, but that won't help understand the 'emergent' nature of the cooperative interactions.

Cooperation in the sense we're talking about is so ubiquitous that it is at least as important a feature of life as the competition that occurs.  Indeed, natural selection, as Darwin clearly noted, is usually very very slow, almost undetectably so.  But cooperation is manifest all around us all the time.  It deserves more careful attention on its own terms.

Darwin vs Wordsworth: Is Nature cruel or beneficent?

In what looks an awful lot like cooperative behavior, groups of birds often get together to 'mob' a predator.  That is, they swarm predators together, in an attempt to chase them away from nests or from a food source, and so on.  Birds often make mobbing calls, that alert nearby birds to danger, and solicit their aid.




A new paper in Biology Letters suggests that "long-term familiarity" is a factor in whether or not birds choose to help each other when faced with threat from a predator.  A.M. Grabowska-Zhang et al. show that "neighbours that shared a territory boundary the previous year are more likely to join their neighbours' nest defence than neighbours that did not share a boundary before."

Predation is a major cause of death in nestlings, so driving predators from an area in defense of the nest is crucial.  And, the more birds that can mob a threatening predator, the more likely they'll drive it away, so soliciting the help of neighboring birds is also crucial.

Grabowska-Zhang et al. "tested the hypothesis that long-term familiarity between territorial neighbours is positively related to joining behaviour in predator mobbing."  They did this in a population of great tits breeding in next-boxes in Oxfordshire, in the UK. These birds have been tagged and followed in previous years, so that their ages and familiarity are already known.  The researchers served as predators, by approaching a nest and making noise, and then assessed the birds' response.

For pairs of nests where each contained at least one familiar individual, in 12 out of 16 trials (seven out of eight nest pairs), at least one neighbour joined the mob. Individuals from the unfamiliar group joined the mob in just two out of 16 trials (one out of eight nest pairs). No neighbours joined the mob in first-years' nest.

That is, they report that they've demonstrated a significant influence of familiarity on taking part in solicited mobbing behavior.  The idea that birds decide who to cooperate with is interesting one -- apparently, they don't help just anyone.  But, what interests us more is that the authors conclude that they can't tease out from this study whether the birds cooperate because they are good neighbors (altruistically), or because they figure they'll get help from their neighbors when they need it themselves (selfishly).  The same behavior can be interpreted in two very different ways.

This is not new to this study, of course -- altruism has long been explained away as selfish.  And similarly, cooperation as competition.  There is a danger in reading ourselves into what we see in Nature.  It's a problem of subjectivity intruding where we hope and strive to be objective to the extent possible.  The issue first of all can affect study design itself, and then the interpretation of results.  Thus, if competition is the lens of your view of Nature, you can design studies to find competition or evaluate organisms' success in comparative terms.  If cooperation is your bent, you can study what happens when organisms work together for whatever reason.   The truth, as this study shows, is typically a mix.

The danger extends to reading other work, in science but even in other areas.  One can mine important thinkers for statements supporting one's bias, just as can be done with Biblical exegesis.  For example, at about the same time, and totally unbeknownst to each other, two famously brilliant authors wrote about the awesome splendor of Nature.  Darwin looked upon Nature's 'grandeur' (his word) and saw beneath it a relentless, impersonal, and savage 'struggle for survival' against limiting resources.  In an 1838 notebook, he denigrated philosophers who were trying to understand life by saying that one would learn "more towards methaphysics than Locke" by understanding baboons.  But last night Ken was writing on something for Evolutionary Anthropology that referred to Darwin's quote.  He has also been reading the famous pastoral poems written at almost the same time by the poet laureate William Wordsworth.  Like Darwin, Wordsworth denigrated stuffy academics, remarking that one who wished to understand life should turn not to the work of philosophers but to Nature's magnificent panoply reflecting God's beneficent intent.

Birds may not think about competition vs cooperation in ways that we do, but in their own way they show us the nuances of Nature.

The importance of cooperation in life: second installment

Back in June, we posted what we called a first installment on the importance of cooperation in life. Distracted by other issues and subjects, we never got around to posting a second installment. Here it is, and rather timely at that, as cooperation seems to be having its day, with entomologists and primatologists, sociologists and political scientists, among many others, now addressing this often slighted aspect of life. We, too, consider cooperation to be fundamental, even describing it as a principle of life in our book.

An essay in a recent Science by science writer Elizabeth Pennisi takes up the subject (On the origin of cooperation, Science, 4 September 2009: Vol. 325. no. 5945, pp. 1196 - 1199). Pennisi reminds us that Charles Darwin was perplexed by the existence of altruism--why would an individual help another at cost to him or herself?

Cooperation has created a conundrum for generations of evolutionary scientists. If natural selection among individuals favors the survival of the fittest, why would one individual help another at a cost to itself? Charles Darwin himself noted the difficulty of explaining why a worker bee would labor for the good of the colony, because its efforts do not lead to its own reproduction. The social insects are "one special difficulty, which first appeared to me insuperable, and actually fata to my theory," he wrote in On the Origin of Species.

And, biologists have been perplexed by this ever since, because it doesn't fit easily within the prevailing evolutionary framework.

And yet, [Pennisi continues] cooperation and sacrifice are rampant in nature. Humans working together have transformed the planet to meet the needs of billions of people. Countless examples of cooperation exist between species: Cleaner fish pick parasites off larger fish, and nitrogen-fixing bacteria team up with plants, to name just a few.

The usual discussions about cooperation, as above, are about social cooperation, among individuals in a population. Widespread as such examples are, they don't even hint at the extent of the cooperative nature of life, which is true at all levels, as our book is largely about. Genes cooperate with other genes, organelles with each other inside cells, receptors on and in cells cooperate with their ligands, cells with cells, tissues with tissues and organs with organs. Organisms cooperate with others of their own species (sexual reproduction being the quintessence of co-operation), and members of different species with each other. So, if cooperation is so all-pervasive, why has it been so consistently overlooked in favor of competition and selfishness?

The word cooperation may be denigrated from a fundamentalist Darwinian point of view as soft-headed goody-goody thinking. 'Cooperation' is indeed a culturally loaded word. But it is no more so than 'competition'! A 'selfish' gene is not competing in the same aware sense that a marathon runner is. Neither are two molecules aware of cooperating in the way members of a soccer team are.

We mean co-operation literally, that is, operating at the same time and place and in appropriate amounts and ways. That includes social cooperation. It might be better to call this 'interaction', as another way to stress that the elements of life don't act alone. But we want an antidote to the very loaded term 'competition', until the mainstream of biology changes that term to something like, say, 'differential proliferation'.

We aren't the first to point out that the idea that life is all about competition fits neatly with the history and politics of the culture within which evolutionary theory developed and grew. Historiographic context analysis is often written as if it shows the falseness of the idea being discussed. That doesn't necessarily follow, but it does seem correct that the words used and the approaches taken reflect social context whenever human affairs are the subject. In this case, our contention is that a cultural obsession with individual-based competition, which was shared by Darwin (but less so by Wallace), affects what we see and focus on and how we interpret it.

The focus on competition is one of the consequences of viewing life on the compressed evolutionary scale. Darwin himself understood that it was impossible for us to understand the immensity of time over which life evolved. Thinking in evolutionary terms makes it easy to forget that life is actually lived from moment to moment, and needs to be understood on that scale as well. When seen at the level of daily life, cooperation is omnipresent, and far more important than competition.

Nor are we the first to point out that even when cooperation is undeniable, it's often quickly redefined as competition--people are only altruistic because they get something out of it, or to help their kin, and so on. Why people help non-kin is easy to explain when you acknowledge the role of culture in what we do. If you filter everything through a strictly Darwinian lens, where reproductive fitness is the ultimate measure of success, and we're all in competition with each other, driven by natural selection, it is indeed impossible to understand why people would jump off a bridge to save a drowning stranger, or choose to limit their number of offspring (even if you explain this with r and k strategies, this only kicks the question back a step), or invent the concept of socialism, or, the ultimate inexplicable action in Darwinian terms, detonate a suicide belt in the service of religious conviction.

But, if you allow that culture can drive what we do, in perhaps biologically inexplicable ways, and not simply our sex drive, or the fact that helping our cousin favors some of our own genes, these actions don't then have to be explained in terms of competition or survival of the fittest or optimal energy expenditure or whatever. A Darwinian purist's post hoc explanations are, for example, to invoke 'reciprocal altruism'. In the moment of truth before you swim to the drowning stranger's aid, somewhere deeply in your reptilian brain is the little message "Do it, because if they survive they may save you some day!"

Baloney! One of us has had this exact experience, and there was no little Devil on the shoulder whispering in the ear.

The fundamentalist view of social behavior rests on the important, automatic, but erroneous assumption that cooperation always involves a cost of sufficient magnitude to be detected by selection and that the act has to be seen in terms of selection and the latent assumption is that the mechanism must be related to altruism itself. That's an industrial-age's argument for 'efficiency' as the Law of Life that justifies harshness towards workers in manufacturing companies.

We suggest to the contrary that cooperation is so fundamental to life that it needs to be accepted on its own terms, and need not even be specifically 'programmed' (or such program specifically reinforced by selection). If anything, for many species the cost is for not cooperating, and translating this into Darwinian terms only distracts from what is important.

What we see and how we view it have implications for what we don't do or don't see in science, even if the latter is there unmistakeably. We think that, regardless of the aspects of differential proliferation that were involved, a focus on the nature and extent of cooperation in its many forms of equal grandeur to anything Darwin ever remarked on, and would be healthy for biology to concentrate on.