You keep citing our paper. I don't think it means what you think it means.

Quote here
(image: princessbride.wikia.com)

I haven't published much. Activity in my scholar.google profile isn't so hectic and exponential that I can't dig into things a little more than your more prolific scholar.

So as I continue the line of research kicked off by our paper (Metabolic hypothesis for human altriciality), I naturally want to read the articles that cite it. Scholar.google is great for showing me those. And while I dig around, I also have the opportunity to see why these authors cited our paper.

For background, here's a short synopsis of our paper that I'm Google-stalking:
Humans are thought to be born when we're born to escape the bipedally-adapted, gestation-constraining birth canal ("obstetrical dilemma"), but it's more likely that we're born when we're born because that's all the fetal tissue our mother can grow ("EGG: energetics of gestation and growth"). 

That's it. There's a lot more in the paper but that's the gist. Now, how's it being cited?

Let's go paper by paper. Don't worry. There are only five.

***

Increased morphological asymmetry, evolvability and plasticity in human brain evolution
Our paper is #69 in this one.Here's where it's cited:

"Biomechanical [68] or metabolic [69] constraints causing human altriciality may have provided another key preadaptation for the evolution of modern human cognition by allowing an increased period of postnatal modelling of the developing brain via the interaction with complex social and cultural environments [70]."

Considering the results of energetic limits and metabolic constraints to be adaptive ranks pretty far up there on the Panglossian scale. Regardless, this is a perfectly good citation of our paper. Thanks to the authors for not citing us later in the sentence.

Good? Yes. 

*** 

Global Geometric Morphometric Analyses of the Human Pelvis Reveal Substantial Neutral Population History Effects, Even across Sexes

Our paper is #90 in this one. (OoA = Out of Africa) Here's where it's cited:

"Our analyses testing for obstetrical constraints in shape variation indicated no difference in the neutral OoA pattern between males and females, a difference that would be expected if constraints were stronger in females than in males. This result is consistent with Tague’s [51] finding that males are not necessarily more variable in pelvic morphology than females. It is also consistent with recent suggestions that the obstetric dilemma may be influenced more by maternal energetics than pelvic morphology per se [90,91]."

Good? Yes.

***

Many ways to die, one way to arrive: How selection acts through pregnancy
Our paper is #23 in this one. (GDM = gestational diabetes mellitus.) Here's where it's cited:

"GDM and preeclampsia are common diseases, with grave consequences in pregnancy, and thus may strongly impact upon reproductive fitness. GDM affects 4–20% of pregnancies in different populations worldwide [19]. It can cause macrosomia, in which the fetus grows too large to fit through the maternal pelvis [20–23]."

Here is the only part of our paper that mentions diabetes:

"uncontrolled gestational diabetes is commonly associated with postterm parturition (Langer O, Kozlowski S, Brustman L. 1991. Abnormal growth patterns in diabetes in pregnancy: A longitudinal study. Isr J Med Sci 27:516–523.)"

Notice how our paper talks about postterm parturition and neither fetal size nor fetal size relative to maternal pelvis. Maybe the paper we cite does.

Good? No.

***

Bony pelvic canal size and shape in relation to body proportionality in humans
 Here's where it's cited:

"This “obstetric dilemma” (Washburn, 1960) has recently been questioned on biomechanical (Warrener, 2011; but see Whitcome et al., 2012) and energetic grounds (Dunsworth et al., 2012)."

Good? Yes. Although it could also go under the biomechanical part of that sentence.

***

Teaching the principle of biological optimization
Our paper is #4 in this one. Here's where it's cited:

"It has been hypothesized that the timing of human birth optimizes the ability of cognitive and motor neuronal development in the child by allowing the child to maximize the absorption of important cultural information (memes) in its environment [4]." 

Yes it has, but not by us. Here's what our paper says (by the way, we were forced to address this by reviewers):

"Finally, a fourth possibility, originally proposed by Portmann (5), is that the timing of human birth and degree of neonatal brain development optimizes cognitive and motor neuronal development (50)."

Our paper points to others which should be dug up when possible and, if not, then it should be explicit that the author means to point readers to references within ours, not to ours itself.

Good? No. 

***

Sure it's a small sample size but people aren't as good as they should be at citing our paper.  I know I've made these same mistakes and I know there's no way coauthors and reviewers can catch all of them especially in interdisciplinary works, but I just thought I'd pipe up and go through with this exercise here to remind myself and others to do our homework better.

But beyond a nice little reality check, there's a larger issue...Can I really consider all these citations as meaningful indicators of my research's value? Are citations truly reflecting the impact of my work if they misrepresent it? Should I include this little expose in my portfolio come promotion and tenure time to demonstrate how I should, in reality, have a lower citation count... that I should have fewer points in this game?

Inconceivable!

Here's why I won't be revealing any of this to my evaluators: I'm being compared against others whose citation totals are also padded with misrepresentation. It's only fair that I assume the same advantages that everyone else does. Who cares about all the larger implications for Scholarship, Evidence, and Knowledge when my job is on the line? I need those points.

So I change my tune. I don't care how you cite our paper. Thank you for citing! Cite as you wish.

***

Note: Earlier in 2013 I read The Princess Bride for the first time and YOU ARE MISSING OUT if you haven't.

Taking our (lovely lady) lumps

Of course I'm still talking about our PNAS paper. Wouldn't you, in my shoes?

Since getting the back story, the story, and the implications for your pregnancy out of the way, I can finally talk about some important cultural and philosophical implications of our paper.  

Aw. The poor girl's compromised. 

Are ladies' hips compromised?
Women aren't called broads for nothing. We have, on average, larger dimensions of the pelvis that comprise the birth canal (linked into broader hips) than men do and this is not just relatively but absolutely and this is not just in the U.S., this is species-wide (1).

There is no better explanation for this than it's due to selection for successful childbirth.

But somehow with the combination of classic biomechanical theory, plus obvious performance differences between the sexes, it has become ingrained in our thinking that wider hips make women athletically inferior to men. In this line of thinking, the  male pelvis is the human ideal because it's part of a superior athlete's body. The female pelvis, therefore, is second-rate--compromised for necessary reasons to do with childbirth.

But recent research by Anna Warrener--which she was so generous to contribute to our paper--shows that hip breadth fails to predict the biomechanical values that are used to calculate walking and running economy. There's support, too, from prior studies that used different or less complex models. So the notion that wide hips are worse at walking and running is not supported by current evidence.

He must be the fastest swimmer alive because of his man hips.

Not only does Anna's research call into question whether women's hips are to blame for our failure to dominate sports, but it also lends strength to any doubt that slightly wider hips that could better accommodate a neonate or that could birth a more developed neonate (i.e. one that is more precocial like all the other primates) are being selected against in favor of proper walking and running ability.

Of course, there could be alternative explanations. Selection could be keeping wide hips from getting wider because of some yet to be understood horrible side effect of too-wide hips. It could be that wider hips than we have now would increase the stress on the hips, knees and ankles to the point of immobility. It could mean that the soft tissues of the pelvic floor would be stressed beyond their mechanical properties and strained to failure. It's also possible that pregnancy itself requires a narrow-enough pelvis to carry the fetus above it, and that getting any wider down there in the swimsuit area would mean the fetus literally falls out before it's ready. But to my knowledge, we don't have good understandings of any of this, at least not in evolutionary terms.

Given research like Anna's, it's much harder to support this idea that we're at the perfect balance now in the ladies' pelvis: With pelvic width (despite all the variation) thanks to childbirth keeping it perfectly wide but bipedalism keeping it perfectly narrow.

But that's--as I'm finding more and more with this research--what many people support. There's this thinking that humans are presently at this perfect balance and that everything would fall to pieces if we weren't. From the childbirth side of the scale it's true: Gotta be big enough! (But that's true for all animals that give birth through a bony birth canal.) However, it's not clear why it's true from the bipedalism side of the balanced equation.

And if turns out to be true that narrow hips do not contribute to male domination in sports (assuming male sport domination is on mother nature's radar), then tell me what is ideal about the male pelvis? Maybe you never thought about it that way, but by assuming that the female is compromised, the "ideal" status for males is implied.

Neither the existence of sexual dimorphism in pelvic dimensions, nor anything else that I can think of supports a tradition of placing suboptimal value on the female form. The female births the babies so if (iff) there’s an "ideal" it’s female. Selection maintains its adequacy for locomotion and for childbirth. If it didn’t, humans would have gone extinct.

To some that may still mean the female pelvis is compromised. To me, it's a multi-tasker and a good one.

Always look on the bright side of life. But up to a limit, please. 
A popular reaction to our paper is, But why the tight fit at birth? It's impossible to ignore! Why should childbirth be so difficult?

Answers of "because the baby is big and the birth canal is not" or "it's a coincidence that might mean nothing because clearly we overcome it just fine" or "I like to think it's just a coincidence that my finger fits perfectly into my nostril" ... these sorts of replies rarely appease a protester.

We already discussed adaptationism in this context, but it's fun to consider it further in more Panglossian terms.

When I imagine what it was like to first hear about the obstetrical dilemma back in the 1950s and '60s when it was first suggested, here's what I think my reaction would have been:

Hooray! The pains of childbirth (2) and the curse of helpless babies (3) are no longer Eve's fault but Evolution's! This is great. Eve was framed! Point for evolution AND point for feminism. Woot!

And what I've been yapping away about for four posts is not refuting that evolution's the process behind all this. Of course it is. Everything in biology is either evolution or it's magic.

However, evolution isn't always unicorns and double rainbows. Sometimes life just sucks.

For example, I'm going to die. I could look on the bright side and say that my decomposing carcass will nourish myriad life forms in the complex web of life that lives beyond my death in amazing and beautiful ways. And I often like to think about my molecules living on in a narwhal or a mango tree. But c'mon. Death sucks.

That's an extreme example, but I sense a similar need to make lemonade out of painful and dangerous labor and needy babies.  There must be some good reason...

As if the simple observation ...that childbirth works warts and all... is insufficient reason.

With everyone who was born to a mom who was born to a mom who was born to a mom, etc..., with all the billions of us here today, why are we refusing to accept human reproduction as adequate?

We are nothing less than a raging evolutionary success, just like nearly everything else that is alive right now.

Instead, the downsides to reproduction mean to some that it's deficient, leading them to seek reasons or evolutionary upsides: It's okay ladies, childbirth sucks because humans have such big wonderful brains! It's okay ladies, childbirth sucks so we can walk and run properly! It's okay ladies, babies are so needy and helpless so they get out into the environment where there's proper stimulation for learning and development!

But why do we need any other reason or evolutionary upside than the cute little bundle of joy?

http://blogs.smithsonianmag.com/hominids/2012/08/timing-of-childbirth-evolved-to-match-womens-energy-limits/

References/Notes
1. Simpson SW, Quade J, Levin NE, Butler R, Dupont-Nivet G, et al. (2008) A female Homo erectus pelvis from Gona, Ethiopia. Science 322:1089–1092.

2. The Book of Genesis (See where it all goes wrong after Eve first ate fruit with the serpent then ate it with Adam.)

3. Influential fourth century orthodox Christian, Augustine bishop of Hippo, called upon the fact that infants are born helpless to support his description of the sinful, suffering, terrifyingly vulnerable natural state of the human species. In Pagels, Elaine (1988) Adam, Eve and the Serpent. New York: Vintage.

***

And for your Friday happiness...this never fails to crack me up into all kinds of stitches... Jeff Tweedy reads "My Humps" (the song that my title of this post riffs on) by the Black-Eyed Peas.

How to apply an evolutionary hypothesis about gestation to your pregnancy

To get up to speed, click on Part 1 here and Part 2 here to learn about the paper I'm writing about below...Or read it for yourself in early view here at PNAS. 

There have been some very personal reactions to the press that came with our recent paper on the evolution of human gestation length.

And I don't mean this kind:

I mean the what about my short/ long/ weird pregnancy? kind.

Result of googling "weird pregnancy"

This research has always been wrapped up in questions about human variation and even draws upon observations of human variation in gestation length. So I'm not surprised it's causing people to reflect on their own experiences. And I'm also not totally surprised because I've been on the planet long enough to know that if you claim to know anything about pregnancy, you get all the stories.

But I didn't fully anticipate how strongly our work about humans as a species would be seen as work about "me." I guess we're only human.

So today's post is for all the people who read media about our paper and are dying to know what it's got to do with their own pregnancy.

Some things first.
1. I see the world through evolution goggles. Take that as close to literal as you can.

2. I have more scholarly experience with skeletonized (dead) and fossilized (extremely dead) humans than living ones.

3. I am not trained in medicine or health sciences.
4. I will not give medical advice.
5. I do not know what doctors are, or should be, telling pregnant women about eating and exercise.
6. It took me five years to write this paper from first notes to publication and I needed the help of brilliant experts to make it as strong as it is. I do not expect to fully appreciate its implications on the week it is published--not for human evolution, not for pregnant human mothers, not yet! If you have ideas... go on with your bad self and test them! I'll try to do the same.

Here we go, then...

How to apply an evolutionary hypothesis about gestation to your pregnancy

#1 thing to think about. 

Evolution is everything about you, but it is not all about you.

When reports of our research say "moms" we're not talking about you in particular. We're talking about "moms" in a general comparative evolutionary context, species-wide, primate-wide, mammal-wide.

#2 thing to think about. 

The EGG hypothesis explains species-level phenomena

Many evolutionary papers like ours are about understanding species level phenomena and comparing differences and similarities between species to better understand those phenomena, to explain whether patterns exist and, if they do, how or why.

So using the EGG hypothesis to explain why you gestated 9 days past your due date is a little bit like this: Try using the broad ecological and biological rules and patterns that explain variation in body size across mammals to explain why Fred the elephant is 9 cm taller than Frank the elephant. That's a challenge. That's what you're attempting to do if you read our paper (or reports on it) and think of yourself first rather than your species.

Here's another way to think about it. You might have seen our paper described as finding, "Metabolism, not the hips, limits gestation."  Metabolism might get you thinking of yourself but the hips hypothesis (obstetrical dilemma; OD) never did right? I could be so so wrong but nobody thinks that there's some way the fetus can sense when its head or shoulders are about to be too big to fit through the birth canal and then initiates labor so it can escape. Nobody thinks that the mom's body can detect when the baby is about to get too big to pass through her birth canal and initiates labor so it can escape. Nobody really thinks that these sorts of mechanisms exist in mothers do they? (It's possible but I don't know of any literature suggesting this.) So the hip constraint hypothesis (OD) was never about individuals, it's about our species over evolutionary history, with hips shaping our gestation length to be the right length for babies to escape in time. Generations over deep time... that's where your brain needs to be with this EGG idea too.

Sure, we need to consider individual human variation, like yours and mine. To formulate the EGG hypothesis we drew heavily upon Ellison's (2001; and in our paper) metabolic crossover (MC) hypothesis for the timing of human birth: Babies are born when they begin to starve in utero. This happens when the needs of the fetus surpass the mother’s ability to meet them or, in other words, cross over to become larger than what the mother can provide. Labor is then triggered and carried out by a complex biochemical process. Some of the evidence he provides includes:

Gestation length can be truncated according to metabolic parameters.

• Gestation is shorter in mothers with lower body fat composition and lower metabolic rates (Klein et al., 1989; Ellison, 2001)
• Mothers living at high altitude can give birth earlier than counterparts at low altitude (Lichty et al., 1957)

Gestation and fetal growth can be increased according to metabolic parameters.

• Fetal brain size pathology à longer gestation (Higgins, 1954)
• Increase maternal caloric intake à neonatal increase (Prentice et al., 1981)
• Increase maternal caloric intake à preterm births decrease (Prentice et al., 1981)

The MC is very much about individual within-species variation and it's possible that the MC explains all individual variation in gestation length among humans, however, that's uncertain right now. Since it's specific to the biochemical pathways of humans, the details of the MC don't apply to other species with different physiologies. However, the idea that human gestation is limited by mother's metabolism--the cornerstone of the MC-- is what EGG applies to human/hominin evolutionary history and to gestation in other primates and other mammals as well, since a mother's body size (a nice proxy for metabolism) predicts fetal size and gestation length across mammals.  This is really not news to a lot of researchers considering the body of research supporting it.

It's a useful method in evolutionary biology to look at variation within a species and use it to hypothesize why variation exists between species. That is what we have done with EGG. Mother's body sizes differ between species like say, humans and orangutans, and so do their metabolic traits! EGG suggests variation in metabolism between species explains variation in gestation length. It predicts that species do not exceed their species specific metabolic ceiling during pregnancy. It will be exciting to find out whether some species give birth well before they reach their metabolic capacity!

#3 thing to think about. 

Evolution is about common ancestry and change over time. "Ideals", "optimization," "standards," "greater value in this form, lesser value in that one"... these do not exist in nature except in our minds.

You worrying that you gestated too long or too little compared to the species average is a bit like you worrying that you're shorter or taller than average, have a larger or smaller head than average, have more saliva than average, or that you can't intentionally fart. Stop worrying about your normal variation. Variation exists because it works. There's safe wiggle room around most traits and sometimes there's even full-on spasmodic dancing room. We'd be extinct if there wasn't any room for variation in how to survive and reproduce. Celebrate your weirdness, your slightly long healthy gestation, your slightly short healthy gestation, your big healthy baby, your small healthy baby, your freckles, your asymmetrical face, your hairy knuckles, your lack of wisdom teeth, your pterodactyl toes. Who cares! If life's getting on with your weird ass, then you can certainly get on with life.

Further, it helps if you don't require EGG to be all about adaptation. It could be. But it's easier to think of it as just the way it is. Mothers can only gestate so long. Period. The mechanism that initiates labor based on those metabolic cues (MC)... totally adaptive! The process the EGG explains? Not really ... a limit's a limit! How could it surpass it? It would be physiologically  impossible. Adaptive ideas aren't necessary for EGG unless it's somehow adaptive to keep the fetus inside mother right up until that threshold. Which is possible. But it could also just be the only way to trigger labor. And so we're back to the EGG being just how it is.

***

So how should you apply this evolutionary hypothesis to your pregnancy?

It sheds light on why it's difficult to give birth. It sheds light on why babies seem so helpless compared to other primates.

But regarding your specific individual details that differ compared to other human mothers and their babies?  Please talk to your doctor who's your main brain on this. And read read read read read, if you're interested.

There are some pretty cool cultural and philosophical implications of our paper. I'll save those for tomorrow's post.


References
Ellison, P. 2001. On fertile ground: A natural history of human reproduction. Cambridge: Harvard University Press. [link to book on amazon]

Higgins LG. 1954. Prolonged pregnancy (partus serotinus). Lancet 2: 1154.

Klein, J, Stein Z and M Susser, (1989) Conception to Birth: Epidemiology of Prenatal Development. New York: Oxford University Press.

Lichty JA, Ting RY, Bruns PD, and E Dyar. 1957. Studies of babies born at high altitude. Part I. Relation of altitude to birth weight. American Journal of Diseases in Childhood 93: 666-669.

Prentice AM, Whitehead RG, Roberts SB, and AA Paul. 1981. Long-term energy balance in child-bearing Gambian women. American Journal of Clinical Nutrition 34: 2790-2799.

That [obstetrical dilemma] really tied the [human evolution] together. Part 2.

Update (Aug 30, 6:41 am): Paper's up. Here.

Update (Aug 28, 3:32 pm):  Jeepers, if I'd have known readership (err, clickership) was going to jump way above normal with this post, or that writers would lift quotes from here, I'm sure I would have crafted it better. 

Note: We're past our embargo, so I'm posting this now even though it doesn't appear that the article is posted on-line yet. I'll update this post and link to it once it is.

Some colleagues and I have a paper this week in early view at PNAS (1). I already told a big part of the story here.

In our paper, we show how weak--given current evidence--the popular obstetrical dilemma hypothesis (OD) is for explaining human gestation length. And, we offer up an alternative hypothesis as well.

It gets a lot bigger than this, doesn't it moms!  
(image: http://classes.biology.ucsd.edu)

The EGG hypothesis
What limits fetal growth during pregnancy? The OD says it's the pelvis--implying it's a unique constraint due to bipedalism. But the EGG hypothesis suggests that the primary constraint on fetal growth and gestation length is maternal metabolism (energetics, growth, gestation). Mothers give birth when they do because they cannot possibly give anymore energy into gestation and fetal growth. And when you look at the data available on pregnancy and lactation metabolism in humans... it shows that right around 9 months of gestation, mothers reach the energetic throughput ceiling for most humans.

Here's Herman's Figure 3 showing the EGG for humans, plotted with real metabolic data. Circles are the offspring, squares are the mother. Notice how fetal energy demands increase exponentially as the end of a normal human gestation period approaches. To keep it in any longer, mother would have to burst through her normal metabolic ceiling. Instead, she gives birth and remains in a safe and possible (!) metabolic zone.

The starred dot is a human infant at the developmental equivalency of a newborn chimpanzee. This is the thought experiment that Stephen Jay Gould famously wrote about. That's the age you'd have to birth a human baby to be like a newborn chimp, since we're born born more helpless than chimps. Keeping a fetus in this long--that is, adding 7 or more months to our gestation--would be physiologically impossible because it would require a mother to exceed 2.1x the basal metabolic rate, bursting through the ceiling for most humans. We actually gestate as long or maybe a little longer than you'd expect for a primate or a mammal, not shorter! So our relative helplessness at birth is indicating how much more neurological growth we have to achieve during our lives, after birth, than chimps and other relatives.

The EGG is a more general incarnation and a broader application of Peter Ellison's "metabolic crossover hypothesis" for the timing of human birth. The EGG branches out beyond our species, considering humans to operate within the physiological confines of other primates and mammals. But comparable data for other species, for testing the EGG, are not yet available to our knowledge.

Why do we grow babies that seem too big to fit through our birth canals? A strong hypothesis is that it's our diets that have radically changed compared to most of our evolutionary history. Many humans have constant and easy access to high calorie foods while pregnant and they can grow bigger babies over longer pregnancies. Very much related to this idea, check out Herman's recent NYT article about how our energy intake affects our health: "Debunking the Hunter-Gatherer Workout."

***

We named the hypothesis for ease of communication, not because we're eggomaniacs. We were tempted to call it HAM (humans are mammals) but felt that EGG better described the idea and was also adorable considering how babies are made.

HAM and EGG, or EGG and HAM, to me, is the ideal name but try saying that without going all Dr. Seuss on a wumbus full of thneed-suited who-scientists.

And that goes for here too. Your pop culture references best remain R-rated if you're to retain an ounce of R-word. And because it's just so enlightening, we'll continue to employ the very mature and refined Lebowski theme from Part 1 in our discussion here.

Call me Maude.

“The [species] abides.”
Part of the trouble I and others have with the obstetrical dilemma is this: We do just fine in the face of the tight fit at birth. Just because there's a tight fit, just because childbirth is terrifying, just because it's not an easy or enjoyable experience, that's not necessarily a "bad" thing evolutionarily. Clearly it's the opposite. It's a good thing. We're here to think about it! It can't possibly be "bad" if we keep having babies despite the hellishness of childbirth. This perspective was one of the contributions of "The obstetrical dilemma revisited" (2): Our behaviors, our aiding of women during childbirth, have probably reduced selection pressures against the tightness of fit, or other contributors to childbirth difficulty and danger. The species abides.

When you look at childbirth not as a biological failure, or as God's plague on lascivious women invited by Eve, but when you see it instead as a raging success, the obstetrical dilemma hypothesis is much easier to doubt.

The picture of evolutionary success. (source)

"Say what you like about the tenets of [Natural Selection], Dude, at least it's an ethos."

The widespread popularity of the OD may well be rooted in its adaptationist appeal, where nonoptimality (e.g. human altriciality, or helplessness and relative underdeveloped-ness at birth) is explained as a contribution to the best possible design of the whole (e.g. big brain and efficient bipedalism). Gould and Lewontin (3) famously criticized the “adaptationist programme” by cautioning that “organisms must be analyzed as integrated wholes” that are “constrained by phyletic heritage, pathways of development, and general architecture” and that “the constraints themselves become more interesting and more important in delimiting pathways of change than the selective force that may mediate change when it occurs.” They faulted this approach for failing to “consider alternatives to adaptive stories” and for its “reliance on plausibility alone as a criterion for accepting speculative tales.”

From this perspective, it's inappropriate to root the evolution of human altriciality in a compromise between adaptations for big brains and adaptations for bipedalism when there are most likely more basic, conserved, phyletic constraints on pathways of development and general architecture (e.g. gestation, pregnancy and fetal growth) at play.

“Yeah, well, that’s just like, uh, your opinion man.” 

Over the last five years as I’ve been thinking about this, specifically, I've had a teeny tiny bit of resentment creep up now and again towards the field that coaxed me into buying this OD as dogma. But I have nobody to blame but myself! A hypothesis is just that and why I just swallowed it whole without doubt is partly because it's a cool idea! And partly because an alternative idea just wasn't as well-known yet! Our paper is not attacking anyone, despite the guilt we've induced in folks who have been treating the OD as fact and teaching it to hordes of students for the last 50 years. To those researchers and teachers who came before us, we’re grateful! And to anyone who thinks of our paper as gotcha or an attempt at it: Please remember how science works and how knowledge accumulation works. That's all this is. It's just a little more hyped because it's about humans, not sea squirts.

The OD is not dead. It's just put in a less omnipotent place. The heaviest burdens should always be on supporting hypotheses for human exceptionalism; we should never default to them. Humans are animals/mammals/primates/hominoids and when we fail at that default view, that's when we can claim human exceptionalism.


References

1. Dunsworth HM, Warrener A, Deacon T, Ellison P, and H Pontzer (2012) Metabolic hypothesis for human altriciality. PNAS on-line early view.

2. Rosenberg K, Trevathan WR (2002) Birth, obstetrics, and human evolution. BJOG 109(11): 1199–1206.
3. Gould, SJ and RC Lewontin (1979) The spandrels of San Marco and the Panglossian paradigm: A critique of the adaptationist programme. Proceedings of the Royal Society of London, Series B 205(1161): 581-598.

Note
Please do look to the PNAS paper to read about the EGG or to see how we've exposed the challenges to testing the traditional OD. I did not write this post to stand for anyone's sole source. If you cannot access the paper once it's posted on-line, then please email me and I'll happily send the paper to you.

Another Update (Aug. 30, 6:41 am)