Thursday, August 21, 2014

An infantile hypothesis for Mandrillus sphinx coloration

Tomorrow, Friday August 22, is the deadline for submitting your bad ad hoc (bah) hypotheses for consideration to be presented at BahFest 2014

I've been chewing a bit on an idea about mandrill coloration and it's just not at all ready, so I'm not going to submit it despite my desperate desire to participate. And I'll just hope that by next year's submission deadline I'll have a much better idea, one that I've had time to actually and properly research and to build strong with data, one that's funnier, one that doesn't require me to read Freud, and one that's wackier since plausibility is not permitted. 

But since I've got the outline for this mandrill idea, of course I want to share what I've got here. Who knows, maybe it will spark someone to submit their own bahfest hypothesis or to think about why mandrills are colored like they are or how we could ever know. 

So here it is... my bad, bad ad hoc hypothesis... an infantile hypothesis for mandrill coloration... which follows in the tradition of the wonderfully infantile ones to be born at Bahfest exemplified by this one from organizer Zach Weinersmith and also last year's winning hypothesis from Tomer Ullman. (Maybe don't watch those amazing ones until after you've suffered through mine?)

An infantile hypothesis for 

Mandrillus sphinx coloration

Holly M. Dunsworth, B.A, M.A., Ph.D.

“No other member in the whole class of mammals is coloured in so extraordinary a manner as the adult male mandrill.”  
Charles Darwin, The Descent of Man, 1874

Male mandrill at Singapore Zoo (Robert Young, Wikipedia
Darwin was famously astonished by the extraordinary coloration of the mandrill monkey, Mandrillus sphinx. Because males are more striking than females, evolutionary explanations have focused on the adult male. And, as the thinking goes, it's the adult male face that's been the primary focus of selection, with duller female faces and the colorful rumps of both sexes being secondary, in evolutionary terms. 

One explanation for the colorful male mandrill face is sexual selection. Males with healthy, robust physiologies capable of building and maintaining that rainbow visage are the sexiest. And because coloration isn't as pronounced in females, that's an indication that it's less crucial for their reproductive success. But their ability to choose male mates based on good looks is, and the particular genetic mechanism which beautifies the male carries some of that beauty along in females. So that sufficiently, albeit vaguely, explains the mandrill face.

But for many of us an even more urgent question is, Why did the mandrill rump evolve to resemble the face? 

And there are a few possible answers.

There's the more-is-better explanation: those with colorful faces are seen, socially and sexually, as all right, but those with colorful faces and butts are all that. They're the real peacocks of the troop. 

There's also a potential social benefit to being visible and, better yet, identifiable, both coming and going in the dark dense forests where mandrills live. 

Then there's a strength-in-numbers sort of idea, where other groups or predators, even, will see twice as many of you. 

Alternatively, the development of rump color could be genetically linked to face color, so it could simply be an accidental byproduct of selection on the face. 

But what if we flip our view around and assume that the monkeys' rainbow hinies are the primary focus of selection? After all, we find colorful bums and privates across the primates, and in both males and females, and in species without much to match on the face. (Yet.)  This alternative perspective could free us to arrive at the real explanation for mandrill coloration. 

And this means we should ask, Why did the mandrill face evolve to resemble the rump?

Dear Reader, I'm sure you can think up all sorts of advantages to having a face that looks like a butt. 

For instance, by appearing to groom your ass, rather than eat food, you might not attract competitors to your precious food source that you can now enjoy all to yourself.

And there's always the Handicap Principle:  He’s got a face like a butt, but he’s still got it going on. And if males are choosy (it's possible!) it could go the other way too.  

Or we could go with the Cyrano de Bergerac Principle: His nose looks so much like his junk. He’s so cute!  Again, if males are choosy, this goes both ways.

It's highly possible that having one rear-end and another end that looks like a rear-end causes confusion, on the part of the male, during copulation, that can accidentally lead to some innovative, pleasurable positions that strengthen social bonds (@ElroyBeefstu, personal communication).

Relatedly, having a face like this could be a nice way for females to test male intelligence and choose intercourse partners accordingly: If he can't distinguish which end is the business end, then no way am I making this transaction. 

What about lowering standards?  Wouldn't a decrease in mating restrictions increase reproductive success for those who've had less of it? This might entail something along the lines of, wow I totally expected his face which looks like a butt to smell like a butt, but it doesn't! I guess I'll make a baby with him. Unfortunately, to my knowledge, no one has published on the relevant odor preferences of mandrills.

There's great possibility that this coloration is a sort of menage-a-trompe-de-l'oeil. Females are more attractive if they're not one but two! And to any onlookers, this threesome is quite impressive. 

It could be as simple as mandrills getting along better with mandrills with faces look like butts because that's just, pure and simple, the very best part of a mandrill, to a mandrill. This applies beyond the sexual and into the general social realm.

One, some, or all of the above hypotheses, and many others that I'm sure you've already thought of, could easily explain mandrill face coloration. But I now offer what I think is the best rump-first, then-face explanation of them all. 

The Perinatal Imprinting Hypothesis
When it comes to infants, selection pressures are on hyperdrive, so our adaptive hypotheses about babies are essentially iron-clad. Nature’s got to get infancy right for evolution to continue and nature’s got a genius way to get it right in mandrills and it’s why mandrills are colored the way they are.  

Mandrill coloration is an adaptation to infant perception.

As mandrill neonates slowly emerge from their mothers’ bodies during parturition, they are gobsmacked by the electric coloration of her rump.

Simulation of mandrill birth. 
Sure, female mandrill rump coloration is not as striking as males', but imagine if it's the first color you ever saw... in your entire life. So, from a neonate's perspective, this welcome sign to the world may as well be as striking as the males' tookus is to adults, and to us.

Female of breeding age. Look closely and you'll see the same color pattern of the male rump is there, just muted. (captured from Arkive film)
Think about how much monkeys love colors. If you saw that upon your arrival on Earth, you'd be enchanted. You'd want to keep looking at it, wouldn't you? 

And if it weren’t for the mother’s colorful face proximal to her teats, mandrill infants would be dangerously inclined to literally hang around at the abysmal end of their source of food and social development, and these, of course, are their requirements for life. 

The colorful bum, alone, is just too distracting. So, mothers with color faces to match their butts have more surviving offspring, that go on to have surviving offspring, than others. They can even get away with those boring whitish nipples because their faces are so pretty.


So that explains mandrill female faces but what about the male rumps and faces? Especially since they’re even more colorful?

This crucial and intense early experience, which selects for colorful mother’s faces, affects mandrill phenotypic preference throughout their lives. 

All social and sexual realms are better with color because of these individuals born literally to color and raised by moms with colorful faces.  Colorful males are adaptive in this situation because youngsters fall in love with how they look too, ingratiating themselves with what could be a killing machine, softening his heart and preventing him from ending lineages of mothers with colorful faces who birth babies through their colorful places. 

Young male grooming adult male. (source)
And this could explain, in turn, why male faces look so much not just like male genitalia but also so much like female genitalia, especially at their peak attractiveness.  (See photo of fertile female's rump, above.) Males with these features that are arousing to males are attractive to other males, which promotes group cohesion. And males with these features are attractive to females because it makes them less threatening. 

So that first splash of color that neonatal mandrills experienced was such a technicolor Oz, that they grow up preferring not just color but the most electric adults out there… Runaway selection at its finest! 

To test whether the rump or the face is the driving phenotype…
Dye the butt hairs of all the mandrills to match the rest of their olive-colored bodies. All future mandrill babies will be born to a dull mother's rump. And then if selection is relaxed on the face coloration, as predicted by the rump-first approach, mutations should take over and remove the color from the face. Then next, stop dying the butt hairs of the mandrills and selection should bring back the colorful face again. Unfortunately this will only answer the question as to which end, the face or the bum, is driving the appearance of the other. 

To test the Perinatal Imprinting hypothesis….

Dye the butt hairs of pregnant drills (the boring-looking cousins of mandrills) to match female mandrills' and see if (a) drill neonates spend too much time hanging around mom’s distractingly colorful butt, (b) there are negative consequences of this, and (c) mother drill's faces evolve coloration in future generations and, also, coloration evolves in drill males too. Easy.

Drill. Mandrillus leucophaeus (source)
But remember, one of the most compelling aspects of the Perinatal Imprinting hypothesis is that it cannot be proven wrong, even if other explanations are better supported. 

Concluding Remarks
Not only is adaptive coloration of the mandrill face secondary to the primary adaptive value of the coloration of the butt, but the adaptive coloration of the males is actually secondary to the primary adaptive value of the coloration in the females!  

Colorful female rumps, and the infants who love them, are responsible for the extraordinary coloration of mandrills. Everyone, especially Darwin, was thinking about this all wrong!

Note: I recently donated to Arkive because I heavily rely on it for teaching, writing, and learning. I hope that if you use it like I do, that you'll do the same so that it continues to thrive as a resource. 

Wednesday, August 20, 2014

Blogging isn't catastrophic, but the opposite could be.

Ken and I just had an article published in Evolutionary Anthropology:

Catastrophes in evolution: Is Cuvier's world extinct or extant?

It's open access, so no need for a subscription to read it.

It's the second one we've done (first one is here). The piece is largely the product of many discussions we've had, mainly over email, and these discussions were sparked by posts we had each written for the MT.

Beyond how satisfying it was to have these discussions with Ken and to write this paper with him, it was a great excuse to read Elizabeth Kolbert's articles in The New Yorker (here and here) as well as her wonderful book that accompanies them:

Although the subtitle's irksome if you're not keen on separating human behavior from nature, the book's incredibly insightful. And, it's captivating if you just love tales of exploration and discovery, and if you eat up details about kit, gear and extraordinary travel conditions. It was sometimes difficult to read through my jealousy, and I consider that reason alone to recommend this read, regardless of the compelling scientific history, the exciting albeit depressing cutting-edge knowledge, as well as the important political message that only peeks out, from under the enormous pile of scientific evidence, in her final paragraphs.

It's because of our ongoing discussions and writings and then also Kolbert's, that Ken and I got to thinking about whether and how extinction, background and mass extinctions, and especially Cuvier's pre-Darwinian notions of "catastrophism" are playing out in paleoanthropology right now. This is the overall theme of our piece linked above.

Kolbert deals briefly with Neanderthals near the end of her book. However, Ken and I weren't so much concerned with what happened to the Neanderthals as whether, for instance, we could fairly consider what happened to them to be "extinction" given what we know about their DNA living on inside, probably, billions of us today. And, because of those genetic circumstances, it naturally made us wonder whether anything we call "extinct" truly is and if it is, how could we know? This of course begs for a thoughtful consideration of species and adaptation and, seemingly, all the ol' evolutionary chestnuts that are terribly difficult to crack.

I don't think that what Ken and I contributed in Evolutionary Anthropology was far different from anything that could have occurred before blogs were invented, but blogging certainly did facilitate it. What's more, if I didn't have The Mermaid's Tale, if I wasn't routinely reading it and writing for it, I probably wouldn't be thinking this regularly and this deeply about many of these marvelous things in the first place, especially not with the unimaginably wonderful benefit of engaging with Anne and Ken.  What a catastrophe that would be.

Tuesday, August 19, 2014

Nominate a blog post for the 3 Quarks Daily science writing prize

If you write about science or if you read about science, and if you like making new friends, earning praise and winning money, or if you would like science writers to make new friends, earn praise and win money, then you should definitely, by the August 22 deadline, nominate something for this:

The 5th annual 3 Quarks Daily science writing prize!

Information here:

3QD editor Abbas Raza says:
We are very honored and pleased to announce that Frans de Waal has agreed to be the final judge for our 5th annual prize for the best blog and online writing in the category of science. Details of the previous four science (and other) prizes can be seen on our prize page.

What a fantastic judge they scored this year.

Last round of this contest--thanks to readers of the MT who voted and to the 3QD editors and that year's judge, Sean Carroll--I won the Charm Quark for "Forget bipedalism, what about babyism?"*

It's a wonderfully inspiring thing to experience and I'm so excited for the writers who will win this year's contest. Please help to make it a good contest by nominating what's turned you on, lit you up, wizened, informed, enlightened, or inspired you.  All you have to do is choose something about science that you like, dating back only as far as August 10, 2013, and then post the URL to it in the comments section HERE.

Each person can only nominate one link, which encourages writers to nominate one of their own. So don't be humble or shy or insecure. Do it!

And if you're not a writer, nominate a link that you've really enjoyed reading. Support your science writers in this often thankless service!

This isn't a ploy to get you to nominate one of mine. For good fun, I already nominated this one anyway:

But if Ken, Anne, Dan, Jim, Reed or another guest writer posted something here, or if another writer posted something anywhere else in the last year that stuck with you or that struck you, then for the love of science and science writing, please nominate them before the August 22 deadline!

*Which now has deadlinks to cute photos because back in 2012 I didn't know what the hell I was doing with images in blogger.

Monday, August 18, 2014

Logical Reasoning in Helsinki

Ken and I are in Finland this week co-teaching the Logical Reasoning in Human Genetics course that Ken and Joe Terwilliger have taught a number of times in a number of places over the last 10 years.  People in the class, and/or I, may do some live tweeting at #lrhg14.

We'll be away for another week or so after the course.  We will do some blogging this week or next if we find the time.  If not, we'll be back the first week of September.

Helsinki: Wikipedia

Friday, August 15, 2014

The abbatoir, the lab, and pre-medieval behavior

It's a lazy August day and one wonders what to write about.  So I took a walk with my constant companions--sadly, not a dog, but my iPod.  I was listening to one of the BBC Radio4 program podcasts that we like, and I thought it would be worth putting down some thoughts, hoping to make them relevant.

Abbatoirs, or slaughterhouses, are among the most sensitive kinds of industrial plants.  This post was stimulated by the  BBC story I was listening to (File on 4: Inside the Abbatoir, June 17, 2014).  A standard protocol for killing mammals is to stun them with an electric shock to the brain, knocking them out to they'll feel no pain or terror, and then quickly killing them by, for example, stringing them up, slitting their throat, and letting the blood drain. Then they are butchered. The treatment of food birds is something like this, as I understand it, but the birds are first hung up by their feet, so they probably feel more terror before the deed is done.  Of course, all of this may be more gruesomely done on the farm, for both birds and mammals, though there are certainly farmers who work hard to ensure that their animals are calm until their sudden end.  But an abbatoir does it to numbers that would match a WWI battlefield--every day.

A properly run abbatoir, gruesomely, uses the same idea we have with human execution: a nice last meal, and a blindfold or for those to be done in with chemicals, a tranquilizer first.  Similar considerations are given to pets who are put 'to sleep' by a vet when they are old and suffering.

In the slaughterhouse, Lovis Corinth, 1893; Wikipedia

The BBC story described how this killing is done when done right.  It's properly supervised, sanitary, and the like.  If an animal has to go, well, it's better than how most wild animals have had to make their exit, being torn apart by a predator while alive or suffering an injury or disease without medical care or even (with some exceptions) sympathy from friends or relatives.

But the BBC story also describes how some Jews and Muslims are excused from this humaneness, and allowed to engage in pre-medieval slaughtering techniques (i.e., no stunning first), because, apparently, God (the loving one, that is) apparently said we have to torment animals to please Him.  That doesn't seem very different from Aztecs cutting out the hearts of their living victims (although, I vaguely recall their victims were at least intoxicated on something first).  I only pick these examples because I am too ignorant to have any idea how much other savagery we humans allow today in the name of other Gods or for what rationales.

If stunning is humane and if we are to eat meat, the killing is probably not exceptionable.  However, the BBC story reports various lapses in the system, disturbing instances of lax inspection, and cheating for sport, anger, or for convenience. Even in this sensitive context, are the insensitive among us.

What about fish?  We are generally quite happy with dragging them up from hearth and home, by the net-full, only to suffocate en masse, not so different from, say, the gas chambers, I guess.  Or, when undertaking mere individual slaughter, by hooking them (for sport) in the mouth before asphyxiating them.  Fortunately, thanks to research in part by faculty here at Penn State that shows that fish are not just automatons, there are growing numbers of human fish abbatoirs, that use altered water or stunning to lull the animals to their doom, as humanely at least as the fate we dole out to mammals.

Our concern for doing our killing gently is clearly inconsistent even when applied to other humans. Just look at the latest news. Bombing of children and hospitals, beheading or crucifying captured people because our God (the loving one, that is) says it's the thing to do and (we say) doesn't like their God. He must be a blood-sport fan.  In that regard, it is interesting to read, as perchance I've been doing, Milton's Paradise Lost, in which there's a Hollywood-like tale of wars among the 'angels' in that Heaven we so aspire to attend.

We justify at least instant killing on the grounds that we have to eat and that, given those conditions, instant killing is at least terror and pain-free.  But one reason vegetarians believe as they do is that killing sentient animals (some would, properly, include all animals) is in itself cruel no matter how kindly done, and since we can live perfectly well, and more economically sustainably, on plants, that's what we should do (though, personally, I question the plant exceptionalism since plants clearly respond to environmental trauma and threats).

Experimental abbatoirs
But MT is generally a science blog.  So let's talk about what goes on in the animal research lab.  IRBs (Institutional Rationalizing Boards) generally approve research procedures as being useful to human knowledge, and good for the research business, so long as they don't outright torture the animals. There are at least some limits.  But speaking of things pre-medieval, the reality is closer to saying that, as God (the loving one, that is) pronounced, the rest of animals and plants are just here for us to exploit, and we countenance a lot of things being done to animals, effectively under such an implicit assumption.

For example, what about, say, flies?  Here, the rationalizing gets even more contorted, or perhaps less. Insects and such simple creatures are said either not to feel pain or experience terror.  The way they're sometimes treated flies must absolutely like to have their body segments altered, or electrodes stuck into their brains.  Observations of insects in nature suggests they do sense and recoil from danger, and experience distress.

The arguments justifying research-based experimenting with animals is that that's how we learn about the world (and there's the widespread treatment of science as a largely unquestioned good), or that making countless animals experience a nasty disease or experimental 'procedure', often the only life they'll know, will eventually prevent humans from having to suffer in the same manner we make the mice suffer. We at least claim to try to minimize the trauma, but many in science know the more grim reality.  It's human exceptionalism, but since we're the ones in charge it's no surprise that we behave that way.

Just as we give life and then taketh it away from cows and chickens, so do we for lab mice.  They have their day (in the artificial light of the mouse room), at least, existence they'd not experience were it not for our NIH grant.  Some even get to have a rather active sex life (though, if female, usually they are killed while pregnant, so we can study their not-yet-offspring).

If we accept the reality and inevitability of mortality, then one can accept the killing for food as well as research. But need we accept the torment?  Could we at least have more stringent limits? Animal rights lobbyists, descendants of anti-vivisectionists, are irritating to those running research labs, but perhaps at least help keep things somewhat tempered.  After all, this is nothing new:  The great Roman physician Galen was famous for doing dissections on live unanethesized animals--in the name of science, and indeed somewhat theatrically.  We're not as savage as that!

We can always make up a rationale about human good or basic knowledge, or that the animals don't really suffer; but the fraction of lab animals who shed much light on scientific knowledge is small, and what we're allowed to do to them not so small, even though certainly many lab animals do 'contribute' to ultimate human good.  These are not easy issues (and I say this not in an accusatory way: I worked on developmental genetics of mice for many years).

We all have to die, humans as well as other animals.  The pre-scientific belief systems promise something better afterwards, and if you believe that kind of thing, then lucky you!  But we can at least do our best to make the exit of those enslaved by us a painless one......I had intended again to say a 'humane' one, but that now somehow seems an inappropriate word.  Thinking about the abbatoir, and other aspects of human behavior, puts these issues in stark perspective.

Thursday, August 14, 2014

Anthropology's troublesome arguments

By Anne Buchanan and Ken Weiss

These last few months have been strange ones for anthropology.  So much linen being aired so prominently, dirty and otherwise.  First we had a best-selling book by science journalist Nicholas Wade that in effect defines the field as the science of genetically determined traits, declaring among other things that there are five human races and that anyone who doesn't accept the biological basis of race is motivated not by science but by politics -- unlike his own stance. Then we had two papers (here and here) in PNAS suggesting that one of the now extinct short people on the Indonesian island of Flores had Down syndrome. And now we have a paper, albeit in a less visible journal than PNAS, but nothing's invisible to Twitter, declaring that premenstrual syndrome evolved to keep women from staying with partners with whom they are infertile.

The Wade book, of course, has gotten a lot of press, both positive and negative, including a letter in the New York Times last week refuting Wade's use of population biology by a long list of population biologists, many of whom are authors of the work Wade cites in support of his own political views, although of course he doesn't see it that way.  The PNAS papers got huge amounts of publicity around the world, but very accepting, none that we saw questioning the hypothesis. The PMS hypothesis, on the other hand, has been critiqued as nicely as 140 characters allow (including by Holly, who red-inks it below (it's a Twitter thing), and blames PLS (pre labor syndrome) for any perceived snark).

Each of these publications happens to bring up deep and long-standing issues in anthropology.  The issues involve the usual scientific food fights, but over and above the specific details, there are problems, and it's these that we want to discuss today.

Troublesome arguments
We'll take these issues one at a time.  Enough has been written about Wade's book that there's no need to look at the specific arguments again.  It's a continuation of retailing Just-So stories and selective reporting and misreporting, that he's been doing for many years; it sells well and he serves a surreptitious audience that includes various shades of racist enmity, as well as readers who have no way to know better, including many anthropologists.

Fine.  What's interesting to us, in terms of the broader field of Anthropology, is that it has clarified how deeply politics affects what we all make of scientific 'facts'.  You've got your genetic determinists on the right and your gene/environment interactionists on the left, and if you know how someone feels about genetic determinism -- that what and who you are is basically set the moment you are conceived -- then you know a lot about how s/he feels about IQ, scientific racism, natural selection vs drift, the importance of adaptation in evolution, and indeed about immigration, Obama, economic inequality, and so much more.  Sociopolitical views are correlated with what one seeks, accepts, or promotes when it comes to science -- not just some purportedly objective truth.

Genetic determinism is an interesting hot button issue.  Too often, people believe either that it explains virtually all traits or explains none, but of course it's some of both.  Some diseases, e.g., are caused with high predictability by a genetic variant, some diseases are due to gene/environment interaction, and some 'causal' variants are fairly useless for disease prediction.  Even infectious diseases that can affect almost anyone, that is, almost any genotype, do so in concert with genes.  Genes contribute to every trait, directly or indirectly: without genes we would not be here, and genetic variation can affect almost anything.  But that is not the same as saying that they determine, or specify, every trait.

There are academics who have trouble accepting strongly genetic arguments, because they believe they are, as the phrase goes, 'politically incorrect'.  But behind the political incorrectness smear is of course a dark history of eugenics, lynchings, the slaughter of 11 million people during World War II, including Jews, homosexuals, disabled people, and more.  But further, even if all of genetic-deterministic arguments were fully supported by the science, and we all were to accept that, for example, 'race' is a clear-cut biologically determined category of humans, why would that justify unequal, and worse, treatment of groups we (those in decision-making positions) deem unequal to ourselves?  Unequal because science tells us so.  Science doesn't make value judgements -- people do.  That is why the assertion of such points, or even the funding of studies to find them, is itself a political act.

To the people whose politics are supported by the new 'genomic' version of scientific racism (the latter term, we think, was invented in pre-Nazi Germany), of course, those arguments are 'politically correct' and their generally left-leaning proponents are just idiotic know-nothings.  Not in science, but in scientific racism, it's perfectly fine to cherry-pick the data when making an argument -- and the argument is supported by white supremacists, people who see genes behind everything, people who believe that every trait is here because it was naturally selected, and so on.  Genetic determinism and other labels have become code for accepting inequality, for hording resources, for rationalizing us having and them not having, and this often goes hand-in-hand with racism and hate (often not openly stated, of course, but sometimes it is). It's hard to argue that's science, not politics.  And, the disagreement won't be solved by science.

The problem here is simply the facile telling of stories without anything close to a sufficient understanding of the available information, the mixing of how things are today with how they got here, the assumption that how they are today is driven by genes rather than by much stronger and more ephemeral cultural factors, and the simple assumption that everything simply must be simply explained by genetic natural selection above other evolutionary paths.  In these conditions, a measured discussion of the issues is not possible -- and by the conflicting parties with their agendas, perhaps not even desired.

Getting to now may have nothing to do with then
The PMS paper is interesting for a number of reasons.  First, the author is a biologist who, at least judging from his web page, works on genetic variation in non-human organisms.  Mostly not even mammals.  So it's curious that he's decided to, er, wade into the evo psych realm.  Evo psych can be troubling enough when the arguments are coherent, so this one is particularly troublesome. In "Were there evolutionary advantages to premenstrual syndrome?" Gillings repeats and then discounts a number of previous evolutionary arguments about PMS, and then argues that premenstrual syndrome or premenstrual dysphoric disorder are essentially universal and experienced by all women, so there must be an adaptive explanation for such a maladaptive trait.  And of course it has a genetic basis.
Ongoing bonding between humans is complex, depending on sexual and nonsexual behaviours, and on previous experience in the relationship. Where such relationships do not result in pregnancy, premenstrual hostility may cause varying degrees of rejection, both sexually and of the relationship in more general terms. It might then be conjectured that infertile pair bonds are more likely to break down, freeing both partners to pursue fertile mates (Morriss and Keverne 1974).
Women suffering from PMS are likely to direct their anger at current partners, Gillings suggests, but most often it is when they have no children, that is, when one of the pair is infertile (or the pair, together, is infertile), that this will result in the dissolution of the pairing.

So, PMS evolved to dissolve infertile couplings.  But Gillings then says that this wasn't a problem in hunter gatherer times because women then weren't cycling nearly as frequently as women today -- they were pregnant or lactating, or poorly enough nourished that they didn't menstruate.  In that case, it's hard to understand how this evolved.  Gillings argues, though, that modern cycling is maladaptive, and that it causes health problems, as well as disrupts family dynamics with this genetically driven monthly bearishness of women.  He goes on to suggest that women should consider using cycle-stopping contraception (rather than, say, suggesting men should offer chocolate and not take it so personally).

But wait a minute.  First, a trait can only be selected if it's visible to natural selection.  It has nothing to do with whether people are paired up or happy (unless these are requirements for reproductive success, and the former is, according to some widely held evo psych-type assumptions), and it must be based on genetic variation, not cultural patterns.  If women weren't cycling regularly, and there's a lot of evidence that they weren't until modern times, how could PMS adaptively evolve if it didn't exist in any significant form?  And second, as Ken pointed out in his series a few weeks ago on the mythology of natural selection, there are many other ways that traits can evolve, including a series of reasons we might have no ability to guess, and including by drift relative to any Just-So story we reconstruct as if we got here in a straight adaptive line from then to now.

Like Wade's book, this paper makes the all-too-frequent mistake, in evo psych yes, but in anthropology -- and increasingly in other fields as well -- of assuming that every trait is adaptive, is here because of natural selection, and is thus genetically determined.  And that if we can build a plausible argument, it must be true.  And that the way it functions today is the reason for its evolution.  But, let's call this the geodesic fallacy.

SpaceTime trajectory real and imaginary (modified from GoogleImages)
See Ken's final post on the mythology of natural selection for the details, but here's the gist:
Even if the implicit complete determinism of Darwinian assumptions were true, the complex dynamic nature of earthly ecologies means that an evolutionary geodesic need not follow a retrospectively reconstructable path from then to now. A species or trait need not have evolved 'for' its current use, not even in stages aimed in a particular direction, not with its various components evolving synchronously or even sympatrically. Indeed, if and where ecologies are complex and dynamic, the meanderings of our object--a trait or species--may be essentially indistinguishable from random movement relative to any long-term 'purpose'.
It's very easy to make up adaptive scenarios.  That's why they are called Just-So stories.  And they are seductive.  But elegance or cleverness doesn't make them right.  Indeed, most often we have no idea if they are right, or even how to test them.

Again, the problem here is simply the facile telling of stories without anything close to a sufficient understanding of the available information, the mixing of how things are today with how they got here, the assumption that how they are today is driven by genes rather than by much stronger and more ephemeral cultural factors, and the simple assumption that everything simply must be explained by genetic natural selection.

Lumpers and splitters
The Flores controversy, of course, well-known in anthropology, has been ongoing since the first report of the findings of bones in Liang Bua Cave on the Indonesian island of Flores ten years ago.  The bones were from individuals obviously much smaller than other known hominids of the time, prompting the discoverers to declare them to be representatives of a species of human new to science.  The authors of the current re-interpretive papers on Flores at the time argued that no, these bones didn't represent a new species, but instead at least the one intact skull that was found represented an individual with microcephaly.  Now, it's an individual with Down syndrome.

LB1 skull: Wikipedia
 (associated postcranial remains can be seen here)

However, the argument is based on assuming that it's possible to definitively diagnose Down syndrome in a skeleton (among the many possible skeletal indicators of Down syndrome, most are not found exclusively in people with DS)  and that the asymmetry in the skull was present before the individual died, and not the result of thousands of years of burial, that this individual reached adulthood, and without modern medical care, that's less likely, all at least questionable assumptions.

But suppose LB1 really did have Down syndrome, then what?  Then it is completely irrelevant to any population or evolutionary argument.  One can argue about the Down diagnosis, a subject best left to actual experts of which there are many, but it matters not to the issue of whether the population experienced the very commonly observed evolutionary phenomenon of island dwarfism.

Cave where the bones were found: Wikipedia
This then gets into a very long-standing argumentation between those who tend to name each new fossil with a separate species designation (often called 'splitters' in evolutionary biology), and those who see a range of variation within species and argue that what we have found in the fossil record are representations of that variation, not of different species.  The latter are the 'lumpers'.  The snide and over-puffed Flores papers seem to be at heart a jab at those who see the Flores specimens as representative of a different species from the southeast Asian mainland.

Of course, 'species' is itself a largely subjective subject.  Even the idea of reproductive isolation is very hard to prove.  How many matings does one need to try to show that they never produce fertile offspring?  Usually, of course, and certainly with fossils we cannot do that directly!  The species problem has been debated for more than a century.

Were Neanderthals and early 'modern' Homo sapiens separate species?  Many would say so.  Are the recently prominent 'Denisovans', fossils from a region in Northwest Asia, a separate species?  They have separate names, after all!  Yet because they are recent enough, and perished under fortuitously helpful conditions, we have DNA from them.  And to date, the evidence suggests admixture between them (with remnants of both in modern humans today).  So: separate species, or not?

The arguments are heated among anthropologists about these sorts of issues and the more-heat-than-light regarding the Flores material reflects that.  There is, after all, a whole lot of publicity in the media for stories that sell, like tales of human fossils.  Anthropologists, whose field is often not all that rigorous given the problems of reconstructing the past, are particularly vulnerable to promoting their finds as different, or blasting their peers for doing so.  The media circus loves anthropologists, and anthropologists love it!

In these areas, the controversy is stirred up by the journals and the media.  Every week outrageously poorly supported evolutionary stories appear in journals and are eaten up by media reporters who either don't know the science, don't probe as they should, or don't care to be informed because the objective is to sell copy, and to do that content must be found.

Whether we'll see a day when appropriately measured questions can be asked and discussed, even if they can't really be 'answered', isn't clear.  Probably not in our lifetimes.

Monday, August 11, 2014

The Leaning edge: strange meat allergy

Despite decades of extensive study at the molecular level, many fundamental issues remain unexplained about the adaptive immune system.  We have two types of immunity, adaptive immunity whose genetic basis originated in jawed fish 500 million years ago, and is now shared by all jawed vertebrates. This system uses scrambled coding sections that generate randomly configured proteins to produce an open-ended repertoire of antibody and related molecules that quickly 'learns' to recognize and how to fight unknown pathogens as we meet them.

In addition we have an 'innate' immune system that generates predetermined responses, for example to general inflammation and some basic structures of bacteria.  We share this system with all other organisms.  Even plants can mount immune responses to pathogens and other kinds of assaults, including repertoires that are largely open-ended -- that is, that did not evolve in a Darwinian way one-by-one to respond to specific pathogens.  Adaptive systems of these sorts are terrific because they can evolve within organisms as fast as bacteria or viruses and so on can mutate.

However, one major unknown is why we can develop allergic responses to what, for most people, are entirely benign molecules.  It's one thing to be able to attack and destroy viruses or bacteria that would kill us if we didn't, but why some of us become hypersensitive to substances like bee venom or cow milk or dust mites -- or sometimes even our own tissues and organs, in autoimmune responses -- is not understood.  Thus there's a lot that can still surprise researchers in allergy and immunology.

Last week's story about a recent upsurge in red meat allergies was interesting.  In case you missed it -- though with those glaring photos of the culprit, it was hard to miss -- first in the southwestern US and now up the US Eastern seaboard, people have been developing a severe allergic reaction to red meat in droves, induced by the bite of a lone star tick.  The same syndrome is occurring in Europe and Australia as well.

Lone star tick; CDC Public Image Library
In general, the reaction is developing in people who have been eating red meat all their lives, but the bite of one of these ticks can change that fast.  The thinking is that the tick's saliva contains a carbohydrate, called galactose-α-1,3-galactose (α-gal), which is also found in red meats like beef, lamb, pork, venison, and so on.  When the tick bites, it injects enough α-gal into its blood source to cause the victim to create antibodies to this carbohydrate.  Then, upon next consuming meat, the immune system is primed to overreact to the α-gal in the meat.  Essentially, and ironically, while we may think we are preying on the cow or pig, they are treated as if they're preying on us!

The reaction usually occurs 3-6 hours after the meal, so the connection between the meat and the reaction isn't always immediately made when someone is trying to understand what they could possibly be allergic to.  And this kind of a delay is unusual for an allergic response.

The story is just hitting the news but in fact it's not a new story.  The first paper to describe delayed anaphylaxis after red meat consumption appeared in 2009 ("Delayed anaphylaxis, angioedema, or urticaria after consumption of red meat in patients with IgE antibodies specific for galactose-a-1,3-galactose," Commins et al., Allergy Clin Immunol. 2009;123:426–33.).  The association between α-gal and allergic response was first noticed, and explored by Commins et al., because of a geographically localized cluster of anaphylactic reactions to the monoclonal antibody cetuximab, a cancer drug. People who reacted to the drug were found to have antibodies to α-gal, and maps of the prevalence of allergic response to the drug were a close match to prevalence of Rocky Mountain Spotted Fever. This suggested a strong likelihood that one of the two ticks that cause RMSF, D. variabilis or A. americium, also were causing the allergic response.

The authors documented allergic reaction to red meat with skin prick tests in 24 people, and found raised IgE (immunoglobulin E, which indicates an immediate allergic response) antibodies to α-gal.  The association with tick or mite bites was proposed in that paper, and Commins et al. confirmed in a paper published in 2011 that the cause of the raised IgE antibodies in the USA at least is bites from the lone star tick Amblyomma americium.  In the 2011 paper, they wrote:
The evidence comes from i) prospective studies of the response to tick bites in three subjects, ii) epidemiological evidence that these IgE antibodies are present in areas where tick bites are common, iii) correlation between IgE antibodies to tick proteins and IgE antibodies to alpha-gal, and iv) evidence for an expanding range of the lone star tick, Amblyomma americanum.
Documented occurrences of this reaction now number in the thousands, and Commins et al. suggest they may be seeing the beginnings of an epidemic.  They relate this to an increased number of ticks and thus tick bites with the increasing population of deer around urban areas, although the tick host includes small mammals as well, and the increasing range of the A. americanum.

Hamburgers on the grill; Wikipedia
This is a nice piece of medical detective work, but not all has been explained.  It seems that the reaction is worse after consumption of fatty meat, and there may be no reaction at all if the meat is lean.  The reaction isn't always severe, even in the same person, ranging from a few hives to severe anaphylaxis.  Why ticks induce this response isn't yet entirely clear.  And, most food allergy reactions are immediate, or within minutes of consumption of the allergen, but this one is delayed by hours.  That may be because the offending allergen is a sugar, while most food allergens are proteins.  Or, it may be the lipid connection, as Commins and Platts-Mills wrote in 2013:
The reason(s) for the 3–6-h delay in this IgE-mediated food allergy has not yet been elucidated. Given the apparent role for lipids in producing the clinical reaction, it may well be that absorption of lipid is the rate-limiting step in the delay. Biochemically, fats are absorbed and processed much differently than are carbohydrates and proteins. Fats ultimately enter the bloodstream via the thoracic duct 3–4 h after a meal. The conversion and processing of fats to chylomicrons and then further in LDL particles of various sizes may also explain a portion of the delay. Alternatively, chylomicrons themselves may transport alpha-gal antigens from the gut and intestinal epithelium via mesenteric lymph nodes to the circulation. Intestinal epithelial cells have been postulated to secrete antigen on newly formed chylomicrons, a process that could also help to explain the delayed response to mammalian meat in patients with IgE Ab to alpha-gal.
Unexplained, or idiopathic hives are a common reason for people to see an allergist.  And most commonly, people leave the allergist without an answer.  Commins and Platts-Mills are hoping that explaining the reason for the delay in the response to red meat may help elucidate aspects of allergic reactions that aren't yet understood.  And one can ask if something like this is also the story that may explain the apparent recent high rise of allergies to peanuts, gluten, and others.

Allergists and immunologists are responding to this increasing outbreak with surprise.  As food allergies go, meat allergies have been fairly uncommon, so the rapid increase in allergy to red meat is interesting enough.  But the delayed response is also unusual.  Or so they have thought -- when so many cases of chronic or recurrent hives are unexplained, it's hard to know whether they represent delayed or immediate responses.  If this is indeed an epidemic, it may teach immunologists a lot about a system about which much remains a mystery.