We are not the boss of natural selection. It is unpwnable.

We came, we saw, we conquered natural selection.

It should come as no surprise that I didn't actually speak to David Attenborough* recently. I'm just here writing about what I read about what he said about human evolution...

"We stopped natural selection as soon as we started being able to rear 90-95% of our babies that are born. We are the only species to have put a halt to natural selection, of its own free will, as it were," he tells this week's Radio Times. [source: The Guardian]

I think a lot of these conversations come about because people like to ask people like David Attenborough (and even me!) what will happen to us in the future. And instead of saying that it's impossible to predict the future of evolution (because it depends on so many probabilistic, seemingly random, and maybe truly random events, big and small), many public intellectuals please the crowd by offering some kind of speculation. Often the questions are about whether we'll grow tails or larger brains; whether our brains will shrink because of computers; whether our wisdom teeth, pinky toes or appendix will completely disappear. And often the experts play along with tongue in cheek, or sometimes seriously, building future scenarios.

The problem with Attenborough's answer--which might be aimed at avoiding this sort of speculation about the future--is that natural selection cannot possibly actually stop, not even at the hands, the hearts, the minds of humans. We're pretty amazing, but not that amazing.

Jeepers. What are we even looking at here? (source)

To start, natural selection doesn't just enable the most obvious, visible, awesome changes to our bodies over time.  To be sure, natural selection explains adaptations of all sorts--from fur to feather, prehensile tail to flagellum, macro to micro. (Ahem... as long as we're sure whether what we're covered with, dangling from or whipping around is actually an adaptation.)

But natural selection also explains how we are here, alive and working well enough to be here, alive. In that sense, in its purifying sense, natural selection's at work, if you will, on practically everything about us and on practically everything about everything else that's alive now or that's ever been alive. Natural selection is always happening. Always. Culture or no culture... and because of culture!

Furthermore, even if we could consider all environments (and our cultural abilities to adapt to them) to be equal and constant, there will always be both new combinations of old genes and new mutations in each and every person (100+ brand new base changes to each person’s code compared to mom and dad)--some of which will cause human lives to end before they've passed on those combinations and those new mutations.

That each of us is unique, demonstrates that evolution is always occurring even though scientists prefer to think of it as change over time at the population level. Regardless, and this is very important, natural selection allows for most of this perpetual change in lineages and in populations, which is why so much life on the planet is humming and thrumming away, and has for the last 4 billion years.

http://evolutionpsa.tumblr.com/

However, any genetic-based infertility, any genetic condition that directly or indirectly inhibits procreation, or any genetic disorder or disease that ends a person's life before they pass it on will disappear due to natural selection, along with their entire genome, including everything that had little to do with early death or infertility. So regardless of medicine and birth control, there will always be lineages that are more prolific than others (i.e. differential reproductive success) and there will always be lineages that disappear--both due to constant natural selection. The same is true about differential reproduction due to constant genetic drift--that is, chance change in a gene or trait’s frequency over time or differences in a gene or trait’s frequency between populations due to chance differential reproduction and other evolutionary processes occurring differently in those populations. Like selection, drift is always occurring, but it can escalate in intensity, for example, after a tsunami.

Teddy Roosevelt conquering a moosevelt. (via @HistoryInPics)

So, it may be true that, generally speaking, humans today have more egalitarian reproductive "success" compared to our ancestors who were arguably more vulnerable to nature red in tooth and claw.

And it may be true that the odds are greater for any one human to produce offspring that go on to bear their own offspring than for an individual in another, and maybe many many other, species—those that are, arguably, more vulnerable to nature red in tooth and claw.

And it may be true that because we birth relatively few offspring--compared to, for example, octopuses that bear thousands and thousands at once--that there's not a whole lot of difference between Alex's fitness, having 3 kids and 3 grandkids, versus Alice's having 3 kids and 2 grandkids.

And furthermore, it may be true that compared to innumerable species, we have more lineage continuance and less lineage extinction due to fewer juvenile deaths per birth thanks to opposable thumbs, throwing ability, weapons, medicine, extended family, extended love, extended memory, food storage, food production, cooking, sanitation, and so much more that contributes to or falls under the “culture” umbrella.

Classic examples of recent and potentially currently occurring natural selection that people call on in discussions like this are lactose tolerance and malaria resistance. Both are usually used to argue that natural selection has not stopped. But leaning on them can give the impression that we know of only two ways humans are presently adapting. There are others, like amylase and immune system genes, which are potentially powerful too, but again, examples of human biological adaptation in present or near-present times are not exactly overwhelming us. No matter! Because there are, unfortunately, myriad mutations (individually rare, but not so rare in total), both de novo and inherited, that are selected against every day, all around us, too numerous to list. This is natural selection.

So it's just wrong to say that natural selection has stopped unless to "stop" is a relative term. And even then, saying natural selection has relatively stopped or has effectively stopped in humans is making an assumption about what's good for humanity (that will sadly never evolve) and what's bad (that we're so busy propagating). It's also making an assumption about the relative strength of selection for forming adaptations out there in the "wild"--one that isn't grounded in firm understanding or consensus among many thoughtful scientists.

If we're going to consider natural selection to be so strong an evolutionary mechanism, then we have to consider mutation and genetic drift to have the potential to be just as strong--depending on the snapshot in time/space/organism and there have been many of these snapshots, to put it mildly. Further, to ignore the potential for gene flow to spread and to create new combinations of genes with potential to create new phenotypes that fail or flourish (i.e. under natural selection and/or genetic drift) in different circumstances is to lack an imagination--and a guttery one at that.

And these assumptions about selection's great strength relative to other mechanisms of evolution illustrate our biases and fashions, as well as the limits of our observations, our methods, and Science. These major issues in evolutionary biology are real and they're certainly not respected by statements like " We stopped natural selection." For a public that often mistakenly equates evolution with natural selection, it’s just reinforcement. And, no, evolutionary understanding isn’t just about being academically correct; many of us strongly believe that how we understand or misunderstand evolution affects how we think about social inequality, race, other organisms, caring for the environment, etc and, therefore, how we behave regarding those issues.

I’ve written a few posts that speak to the importance of evolutionary understanding, like:

• Evolution is the only natural explanation. And it’s all we need.
• The F-words of Evolution
• Another F-word of Evolution
• Evolution’s got a P.R. problem
• Taking our (lovely lady) lumps
• Luck of the draw
• Please make us teach creationism

And, granted, Attenborough admits he’s privileged so this isn’t a comment aimed at him, but. … Isn’t it just a bit soon to be including the entire human species in such a healthy, well-nourished, low youth mortality, long life expectancy state of nature that has “stopped natural selection” on ourselves? I think we have a long way to go before such a definition of humanity can be granted to all of us. And even if or when we, as a whole, achieve such a comfy state, we still won’t be able to say that natural selection has stopped for the reasons I discussed above, and for others that I didn't.

What’s more, if we did achieve the kind of wizardrous skills that deem us impervious to natural selection, it couldn’t have occurred until recently. So it’s probably a bit premature, based on our limited observation, to conclude that’s where our species is.

I'm right there with Attenborough in sharing his astonishment at how we affect our own evolution, and that of other species, in ways that might not have unfolded if our cognition and culture had not evolved first. In fact, I think it's so fascinating that I'm writing a book about it right now. But if we claim that human cognition and culture have ended natural selection, we're denying our place in a universe that we cannot completely control. We are not immune to effects of the world around us, no matter how masterful we are at manipulating it. Climate, weather, geological processes, disasters, infectious diseases, parasites, symbionts (we're full of 'em and covered in 'em!)… these are just some of the things that affect our evolution through natural selection (and other means) as well as all the evolution of the species we depend on for food and all the species besides us that our food depends on. Evolution that's occurring just as constantly in everything around us and on us and inside us as it is in our own genomes will directly and indirectly affect our future evolution.  There are few blanket rules in biology but here’s two: Evolution of an organism is always happening and always will. Evolution in one organism is affected by evolution in another.

Conquering a sperm whale.

So, sure! I can speculate about our future just like anyone else. Here’s how natural selection will affect human evolution at some point in the future. It's not so much a tale of our interconnectedness with other species as a tale of our interconnectedness with the planet. Everyone knows that heat is bad for sperm production. It’s possible that the earth will eventually get so hot (thanks to our cognition and culture???) that sperm production ceases in many men living in the hottest parts of Earth and that it only persists in the men who live in cooler regions and in the men with mutations for overcoming the obstacle. As a result, we’ll lose lineages evolving in the tropics and maybe all lineages. And if the warming occurs quickly and uniformly, and if there are no mutants already alive who can make sperm in the heat, global warming will certainly cause human extinction. There. See how easy it is to speculate about future human evolution? You can’t prove me wrong.

And, like our speculation about the evolutionary future, many of our hypotheses for the evolutionary past are nearly as unpwnable as natural selection and evolution are.

***

Thanks to Barbara J. King for sparking me to think about these things. Her reflection, including some of my input, is up on her blog at NPR. 

*I don't know him, but like many of you, I have admiration and maybe even a little (or a lot of) affection for David Attenborough. So this isn't about reacting to a popularizer of science, as a person. These are just my thoughts about something he said about how evolution works. This isn't about Attenborough, it's about us.



Thanks to the folks at io9 for reposting this on their site! http://io9.com/we-are-not-the-boss-of-natural-selection-it-is-unpwnab-1325126849

lolhumans

"This pelican looks like a urinal. 
Go home, evolution, you are drunk." 
(wtfevolution.tumblr) 

Urinalification is so lol.

But it's calling evolution drunk that really got you, isn't it?

Steven Pinker (as of the late 90s) might say that personifying evolution's funny because it juxtaposes or mixes up what are normally separate rules or domains of our intuition. Personification's funny the way slapstick comedy's funny: Without any warning (but with a well-placed banana peel) a guy goes from being a dad to being a bag of molecules.When we give nonhumans human potential, Pinker says that we’re marrying “our intuitive psychology to our intuitive biology.” [1]

Personification is the same sort of thinking that enables us to discover, to know, to understand how the world works. It’s story, analogy, metaphor, unseen imaginative b.s. that we misfire like crazy. And even though we've overcome much of our reliance on it, we tend to preserve the spirit of it anyway. 

The powers of life, death and destruction aren't the only things worthy of personification. We'll give agency to a triangle or square. Just shapes. Being two-dimensional and moving around is all it takes. We are constantly up to this and as Dawkins said, 

“The reason we personify things like cars and computers is that just as monkeys live in an arboreal world, and moles live in an underground world, and water striders live in a surface-tension dominated flatland, we live in a social world. We swim through a sea of people. … We are evolved to second guess the behavior of others by becoming brilliant intuitive psychologists. Treating people as machines may be scientifically and philosophically accurate, but it’s a cumbersome waste of time if you want to guess what this person is going to do next. The economically useful way to model a person is to treat him as a purposeful goal seeking agent with pleasures and pains, desires and intentions, guilt and blameworthiness. Personification and the imputing of intentional purpose is such a brilliantly successful way to model humans, it’s hardly surprising the same modeling software often seizes control when we’re trying to think about entities for which it’s not appropriate, …”[2]

Although many other animals have desires and pleasures and pains and generally have experiences—at least they do as long as we assume we do—we should extend Dawkins’ reflection to our personification of nonhuman animals. There's very good reason we do this as scientists. It's not a terrible null hypothesis that if you observe an animal behaving like a human could, then it might be thinking like a human could. This is the argument by analogy or as I call it doing demonstrates knowing. How else could you reverse engineer cognition? You're a human, you think like one, you know how humans think from a scientific perspective better than you know how any other animal thinks. This makes sense. It's a good default. But that's all it is. And scientists get that. They taught me all this after all. (Reading a lot of Shettleworth, Povinelli, and Tomasello lately.) But the rest of us who don't work on animal behavior and who have very little experience with real animals at all are taking this perspective literally without caution. For example, maybe we should perk our ears but cock our heads skeptically when the website for Dognition (a service rooted in good science that sells cognitive testing for your furry friends) says, “Learning who your dog is as a ‘person’ will help you make the most of the time you spend together.”

Sometimes anthropomorphism smells like money and sometimes it makes us angry for no good reason. For example. Ed Yong wrote a piece "Male frog extracts and fertilises eggs from dead female" about an Amazonian frog that bleeps to death and still procreates. (No survival necessary--take that, Darwin!) Yong didn't personify the frogs but that didn't stop a reader. 

And thanks to the delightful woman who accused me of misogyny for my piece on the necrophiliac frogs. They. Are. Frogs.
— Ed Yong(@edyong209) March 1, 2013

I have a hunch that our habit of anthropomorphizing (combined with some empathic and also narcissistic tendencies) makes it much harder for us to understand reality, to understand scientific explanations for the universe, and to stumble onto new ones.

I wonder a lot about how our language encourages these mistaken habits. I've written before about how I don't use "force" to describe processes and mechanisms of evolutionary change. It's one of my f-words of evolution.

I've got similar concerns about our language that describes animal behavior. Take for example this fascinating paragraph written by the primatologist Toshisada Nishida about the chimpanzees he studied at Mahale, Tanzania:

“In an effort to maximize their reproductive output, males and females may cooperate when it is to their mutual advantage. However they may also control, manipulate, betray and even attack each other when they have conflicting interests. Chimpanzees maintain a promiscuous mating system, for which females develop a huge swelling of sexual skin and males large scrota. These morphological features make sperm competition the characteristic features of chimpanzee sexual activity. Males are expected to mate with as many females as possible, while female are expected to be more choosey because reproductive output over their lifetime is more limited. A powerful constraint on female chimpanzees is the need to consider males’ tendencies toward infanticide.”[3]

I added those italics to emphasize the language that could be interpreted to give chimpanzees more cognitive ability and more agency than the author intended or has evidence for. That paragraph, re-written to avoid any overstatement of chimpanzee cognition and any hint of calculated intention by chimps or by Mother Nature, could look like this:

In a system where higher reproductive output means more of whatever traits lead to it in future generations, males and females may behave cooperatively because it has been perpetuated by higher reproductive output in the past and will continue to do so until something changes. However, depending on the circumstance, they may also control, manipulate, betray and even attack each other if cooperation is supplanted by another behavior that is and has been perpetuated due to its increase of reproductive output, instead, in that sort of circumstance in the chimpanzee’s life. Chimpanzees maintain a promiscuous mating system and, because higher reproductive output of females with huge sex swellings and males with large scrota, females have huge sex swellings and males have large scrota. These morphological features exist, as hypothesized, because sperm competition has been occurring over chimpanzee evolutionary history. Males that mate with as many females as possible have, and have had, higher reproductive output, while females mate less frequently and have much more limited procreative potential over their lifetimes, so they appear to be choosier than males about their copulatory partners because doing so (assuming they are actually choosier than males) has and does increase reproductive output. A powerful influence on female chimpanzee mating behavior is males’ tendencies toward infanticide because females who have babies that are killed have lower reproductive outputs.

There. I managed to suck all the fun out of chimp sex. Not only that, but if you made it far enough you must be wondering how I could be so circumspect about female mate choice. That’s something for another day, but let’s just say that we should be circumspect about male choosiness too since they can’t decide which females (or males, or other circumstances) will give them erections.

Oh, hello! Now you’re awake! Why did my translation of Nishida’s paragraph fail to engage you? Here’s a try: Because it wasn’t a narrative and there were no interesting actors with calculating minds raging with intentions. There was nobody to figure out, to empathize with, to love, to fear, to root for. You just don’t tell stories without those kinds of characters.

But listen up close: that’s the true story of most of Earth’s evolutionary history. Agency evolved (maybe), but evolution itself did nothing purposefully, or even whimsically, to cause it.

Left to our naïve devices, how we talk and write about animal behavior affects how we think about their truths, their essences. The animals we put on the big screen are now just CGI manipulated reality--no cartoon drawings necessary for a pig like Babe to politely request sheep to scram, or for the pups in Space Buddies to bark interstellar commands. If only they had our mouths and throats these creatures could tell us about all the complex thoughts and feelings they experience! My mom has named this the Disney Syndrome. Some might blame the fertile “lolcats” and other such memes. We don’t just anthropomorphize animals, though, we personify oak trees, grandfather clocks, and toenail fungus.

Let's not pile all the blame our limited language, our love of agent-driven narrative, our teachers, scientists and Disney. Because how removed we are from “nature” probably affects our perceptions of animals too. Urban and suburban Americans might be the worst about this. In a piece about Joe Henrich's work, Watters writes,

“While studying children from the U.S., researchers have suggested a developmental timeline for what is called “folkbiological reasoning.” These studies posit that it is not until children are around 7 years old that they stop projecting human qualities onto animals and begin to understand that humans are one animal among many. Compared to Yucatec Maya communities in Mexico, however, Western urban children appear to be developmentally delayed in this regard. Children who grow up constantly interacting with the natural world are much less likely to anthropomorphize other living things into late childhood. Given that people living in WEIRD societies don’t routinely encounter or interact with animals other than humans or pets, it’s not surprising that they end up with a rather cartoonish understanding of the natural world.”

Nobody's saying to give it up completely. It's adorable.It's funny. It's lovely, actually. But if we coddle it like crazy in our children and if we don't check it once in a while in ourselves, this cultural phenomenon is going to continue to contribute handily to the scientific challenges that we face with increasing urgency.

Before submitting a scientific manuscript about animal behavior, evolution, climate, or any process that tempts us to infuse agency, make sure it's not drunk.

---

[1] From Pinker's lecture "How the mind works" published in the Annals of the New York Academy of Sciences

[2] Richard Dawkins's TED talk at about 21:00 - http://www.ted.com/talks/richard_dawkins_on_our_queer_universe.html

[3] Nishida, T. (2012) Chimpanzees of the Lakeshore (Cambridge University Press), p. 201

Science vs "Science"

It's got a lot to do with how you get your information, whether you trust science or not. And it's got a lot to do with whether you're exposed to real science or "science."

Like this "science"...



This product has been "proven by science," so we're fools not to buy it! I find that if I'm not watching a Nova or Nature or an episode of anything with Morgan Freeman or Stephen Hawking, most everything else that talks of science on the television is trying to sell me something. Most everything else is "science."

It seems like every beauty product advertisement is using "science" to convince me that I'm butt ugly and that to fix it (or prevent it from worsening) I should give them my perfectly good dollars. It's "science" after all.

I'm kind of stunned that it's legal for for-profits to cry "science" when it's their own study, when they merely asked opinions as evidence for effectiveness, or when they didn't do any studies at all. Science isn't allowed to be so biased. Science is supposed to want to improve your life first and foremost, not con you out of your money.

I'm not just thinking about this today because I've been hibernating this February, plopped in front of the tube, absorbing horrifying beauty ads through my aging, sagging wrinkled face. (I really should take care of it better by smearing money all over it.) I'm thinking about all this right now because of my friend Alice Roberts's nice piece "Childbirth: why I take the scientific approach to having a baby" posted on the Guardian Saturday.

Trends to move childbirth out of the hospital setting have put pressure on mothers and fathers to make decisions about what to do when it's time for theirs. You'd assume that because there's a movement to move things home that it's because some smart, science-minded, compassionate folks have figured out that it's healthier. If you can't stand the draconian and bloated government/insurance mogul-run healthcare system, a movement might feed your existing suspicions or opinions that there could be better ways to have a baby than by blindly following orders that these profit-motivated fascists at hospitals bark at us. 

But why assume that home childbirth folks are any less biased, less vested, less driven by self-interests? I don't know but it just seems so common for people to give rebels the benefit of the doubt more often than tradition, than institutions. (Something about "honest signaling" might have just popped into your mind if you've been trained in evolutionary theory.) What Alice found is that information on, that is, data or evidence for, what's healthiest--home or hospital or otherwise (birthing centers, for example)--is kind of difficult to come by!

For starters, she writes, 

"This is partly because the overall risks of maternal and neonatal death are now very small (about five per 100,000 women die in childbirth and four per 1,000 babies), so large numbers of mums are needed to assess relative risks. Maternity provision differs between countries, so looking at risks in other countries, even in Europe and the US, may not be terribly helpful."

Within that small risk there is a lot of jockeying for your support. So the second reason, she says, that makes it hard to find information is, 

"the politics of birth. It can be quite hard for mums-to-be to access impartial evidence and advice when it seems there are plenty of people wanting to influence your decision in one way or the other. Evangelical advocates of home birth often talk about the importance of women's choice and empowerment, as well as instilling distrust in obstetricians. For me, being empowered to make a decision requires access to good evidence and the freedom to make up my own mind. And whilst "maternal satisfaction" is often put forward as an important factor to be taken into consideration, I want to know what the relative risks are. And if there's not yet enough evidence to assess that – I want to know that too."

You'd think we all do. You'd think we all want to know the answer to "where and how will the risks be lowest for having my baby?" But we don't all hold  the belief that it's our right to know the answer to that, the way Alice knows it is, the way Alice demonstrates that it is. And it's not just an issue about the dissenters and the movements spinning information and evidence so we'll see things their way--a very real problem that Alice walks us through in the article. It's the doctors too.

Since the article's been posted in various places I've seen commenters complain how they asked their doctors for papers and numbers to help them make their birth plans and the doctors wouldn't go there. I've never had to make a birth plan but I've had similar experiences with doctors like when, for example, I asked for non-hormonal birth control options because I saw no reason to continue ingesting the stuff when the risks for long-term use aren't known and I was now married and ready to stop taking the pill. My doctor laughed at my question, laughed when I asked for a diaphragm or anything like it, and tried to convince me without any scientific evidence that the pill was fine to take your whole life.

Do I think medical decisions should lie completely in patients' hands? Of course not. We can't all be doctors. But they've got to be better ambassadors of science. They've got to be the best. They've got to be science.

It can't be up to us to figure it out for ourselves, not just because we shouldn't have to but because some of us are terrible at it when we try. This includes bright young people at my university, one for example who had a whole textbook on reproductive biology to answer this homework essay question: Write the life story of an egg. Because she cited it, I know that instead of using her high quality resource, she went straight to livestrong.com for all of her information.

Because of movements like the anti-vaccinators and all the people without celiac disease who won't eat gluten, it's easy to worry that unscientific trends with birth will dial back mortality rates to medieval ones. Heck, it's tempting to worry that when videos like this get around to some people who love all things PALEO, they will make it so.

No wonder so many of us can't trust climate scientists and evolutionary scientists. When it comes to our health, "science" has an agenda that's not always first and foremost what's best for us. When it comes to our beauty, "science" smells like money. If this is all we know of "science" then I'm less surprised of the push back against biology, ecology, climate, space exploration, etc... that to us scientists seems downright ridiculous.

If we're going to get non-scientists on board with real science, we need to take the word back.

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.

The F-words of Evolution

Religion is commonly pegged as the biggest obstacle to teaching the backbone of biology – a.k.a. evolution.

But there’s also a formidable secular issue in evolution education and I think it’s far too often overlooked and underestimated:

Even after evolution’s accepted, it’s commonly misunderstood, mistaught, and misapplied.

Getting things wrong is bad enough, but scarier ramifications occur when wrong-headed evolutionary thinking, based on what or who is "favored" or "fittest," is used to support apathy or to justify hateful and violent behavior between humans.

So let’s think about how we throw around those f-words. Especially in the presence of children!

Let my people evolve
Whether or not they realize it, people speak of a trait or an individual being favored by Mother Nature (a.k.a. “selected for”) in the same way that religious folks talk about some people being "chosen" by God.

No, I don’t think it’s intentional.

But I do think that there's a real link: Whether or not you believe that there's a God and s/he favors people, it's easy to transfer that thinking onto Mother Nature and to have her favor things too.

Something must be doing the selecting... natural, sexual, or otherwise. Something with agency.

And not only that, but that something might like me a whole lot! And it may like me more than my drunk, tacky neighbor! Because that's logical. I really am better than my drunk, tacky neighbor. And something bigger than me should recognize that.

Whether it’s God or Mother Nature or the universe or whatever you want to call it, that agent deems me better than someone else and I love that. And I neeeeeed that.

If you cling to this belief that only the favored are special in the eyes of a God-like Mother Nature, then evolutionary thinking can give rise to the same sorts of tribal and societal conflicts that derive from religious beliefs.[1]

We need to disassociate nature from "Mother Nature" which is an entity with agency and intention.

Nature can’t favor anything. It’s our limited vocabulary that leads us to say so. And saying so tempts us to think so.[2]

Any which way but lose
Darwin incorporated Spencer’s phrase “survival of the fittest” into his work, which helped him to paint the evolutionary landscape as one rife with conflict and combat. And it certainly has a lot of that.[3]

"Survival of the fittest" brings to mind the fastest gazelle or the tallest giraffe or the busiest bee or the spiniest sea urchin or the pinchiest lobster. But that’s an extremely limited view of the world.

Most organisms are not the _____-est!

Are you the _______-est in anything or at anything?

I'm not.

Now, okay, you got me fair and square: I’m a tree-hugging liberal.

But I’m also a highly competitive person who was raised in the southern U.S. in the 1980s, who is a former captain and coach of various sports teams, and who doesn’t believe in giving every child a ribbon at a track meet.

So hear me as the latter when I say…

Evolution isn’t about the winner.

The winner? The fittest? Nope. Think “survival of the fitter.”

Many individuals, not just the winner, the best, or the ____-est, pass on their genes to the next generation. Those individuals that do not pass on their genes (the evolutionary losers, if you must), those individuals are out of the game, along with their genes. All the rest, not just the ________-est or the winner, are still in the game!

We're used to games like running races or basketball with one winner or one winning team. This analogy doesn't apply to evolution.

Instead of “survival of the best” think “survival of the good enough.”

This change in wording can change your thinking and it reminds me of the difference between saying “early man” and “early humans.” When I hear “early man” I imagine only prehistoric adult males[4] and "early humans" fixes that by adding females and juveniles to my head movies.

“Survival of the fittest” may be even more accidentally exclusive than “early man.”

***

So let's phase out “fittest” and let's phase out "favored."

Let's work on censoring these f-words and, when they must be used in historical contexts, let's be mindful of their power to not only mislead and limit our evolutionary understanding but to also support racist beliefs and behaviors.

Just because Darwin said these f-words, does not mean that they're necessary or correct. Origin of Species should not be treated as holy text.[5] There’s no such thing as blasphemy in science.[6]

And I bet Darwin, as sensitive as he was, would have dreamt up a better language for evolution and selective mechanisms by now. But since he can't, why don’t we?


Coming soon... another f-word: Forwards (a.k.a. progress)


[1] Have you seen this map of the hate groups in the U.S.? Have you studied history? Religion isn’t the only route to superiority. Among these hate groups, you're bound to find misapplications of evolutionary theory, like "social Darwinism" and the like.

[2] This is similar to how our limited vocabulary leads us to say that silverback males are "securing paternity," which then leads us to incorrectly assume that they know the concept of fatherhood in the sense that humans do. Read more here.

[3] But none of any of this would be here today if there wasn’t also very powerful cooperation at all levels of size and complexity within the biosphere. For more on cooperation, see the book The Mermaid’s Tale by Ken and Anne (of this very blog!)

[4] There's that tree-hugger rearing her frizzy-haired head.

[5] No text should be treated as holy.

[6] Even the f-words of evolution could be rescued from cuss-dom if the evidence supported it.

Culture, evolution, eugenics, and the nature of people

There was a story in the NYTimes yesterday that reports on work showing that humans have evolved in the context of culture. The story reports culture as an 'evolutionary force' in human evolution. Reference is made to a recent review of this subject in Nature Reviews Genetics.

Humans have evolved in the context of culture -- material, psychological, social, and symbolic. That has of course affected our genes. The ability of adults to digest the milk sugar lactose in populations that have depended on dairying for thousands of years, or of malaria resistance in people whose cleared agricultural fields have provided breeding grounds for mosquitoes are well-known examples. But the phenomenon is much more than that, and indeed is pervasive in humans.

Many aspects of culture protect us from what would otherwise be physical weakness that selection might otherwise have weeded out of our population. Eyeglasses, medicine, social care for the infirm, weapons, social hunting and harvesting and defense, clothing and fire, and the enabling power of language are examples.

Darwin and others worried that the protections of society would lead to the pollution of our gene pool. This was one of the motivating factors of the eugenic movement, as we discussed in a recent post. That movement aimed to remove the 'unfit' (in the Darwinian sense, but often equated to what scientists felt were undesirable in their local social sense).

This is all true and the paper referred to in the news story is a good and informative one that shows how genetic technology has made it possible to find some specific responsible genes, even if one can debate the strength of evidence for some of its examples. But as so often happens with media reports, there is a problem, and the story is misleading in that it seems to suggest that the molding effects of culture are recent (say, post-agricultural), or enumerable (only a few traits molded that way), or that this is a new discovery.

Instead, there is nothing whatever new about this except the identification of specific genetic examples. Once again, it's misleading media-hyperbole. A better understanding of human nature, and an antidote to eugenic-like thinking, or ethnocentrism with the problems that causes, would result from the realization that is not at all new to anthropology, that humans have always been, from the beginning of our divergence from common ancestry with chimps and other apes, the cultural species. From upright posture, to opposable thumbs, language, hairlessness, our physical helplessness relative to other species (no claws, fangs, wings, etc.), and so much else, this has always molded our way of life. As CL Brace, a leading anthropologist put it way back around 1970, culture was humans' ecological niche -- culture is why are here. Indeed that was offered as the reason there is only one human species here today--what was called the competitive exclusion principle in population ecology: only one species can occupy any given ecological niche.

Yesterday there was also a BBC story about the ancient nature of human culture, showing that at the time we were emerging as our current species, as long as 100,000 years ago, even art was already with us.

This fact was routinely known to any anthropologist paying attention, perhaps back to the 19th century when the field more or less became a professional one. And it's not exactly that new, either. To pick but one example, we have two recent posts on Ibn Khaldun who recognized our adaptation to environment and culture in the 13th century. Why can't we learn to be more aware of history and less melodramatic about our own time? Maybe it's in our nature to take our own lives and times too seriously -- maybe it gives our lives meaning. Maybe it's just to sell magazines and promote careers.

The protective effects of culture are vital to human existence and evolutionarily adaptive. And they always have been.