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Jul 25 2014

I like this hypothesis

But we have to be clear that it is only a hypothesis at this point. I was reading about domestication syndrome (DS) — selecting animals for domestication has a whole collection of secondary traits that come along for the ride, in addition to tameness. We are selecting for animals that tolerate the presence of humans, but in addition, we get these other traits, like floppy ears, patchy coat color, shortened faces, etc.; the best known work in this area is by Belyaev (YouTube documentary to get you up to speed) who selected silver foxes for domesticity, and got friendly foxes who also had all these other differences from their wilder brethren. Similar changes have been seen in rats and mink, so it seems to be a mammalian characteristic that all these differences are somehow linked. Here’s a handy list of the changes in domestication syndrome.

List of traits modified in the “domestication syndrome” in mammals

Trait Animal species Location/source
Depigmentation (especially white patches, brown regions) Mouse, rat, guinea pig, rabbit, dog, cat, fox, mink, ferret, pig, reindeer, sheep, goat, cattle, horse, camel, alpaca, and
guanaco
Cranial and trunk
Floppy ears Rabbit, dog, fox, pig, sheep, goat, cattle, and donkey Cranial
Reduced ears Rat, dog, cat, ferret, camel, alpaca, and guanaco Cranial
Shorter muzzles Mouse, dog, cat, fox, pig, sheep, goat, and cattle Cranial
Smaller teeth Mouse, dog, and pig Cranial
Docility All domesticated species Cranial
Smaller brain or cranial capacity Rat, guinea pig, gerbil, rabbit, pig, sheep, goat, cattle, yak, llama, camel, horse, donkey, ferret, cat, dog, and mink Cranial
Reproductive cycles (more frequent estrous cycles) Mouse, rat, gerbil, dog, cat, fox, goat, and guanaco Cranial and trunk (HPG axis)
Neotenous (juvenile) behavior Mouse, dog, fox, and bonobo Cranial
Curly tails Dog, fox, and pig Trunk

(Hah, reduced brain size. I have a cat, I believe it.)

We have a very good idea of the proximate cause of tameness: the animals have reduced adrenal glands, which means their stress response is reduced, they’re generally less fearful, and they are more open, in early life at least, to socialization. But why can’t genetic mutations that reduce the size of the adrenal gland occur without also changing the floppiness of the ears? There isn’t an obvious physiological link between the two, or other traits in that list.

One idea is that there is a Genetic Regulatory Network (GRN). A GRN is a set of genes that mutually regulate each other’s expression, and may be controlled by the same set of signals. Imagine a lazily wired house in which the lights in the kitchen and the living room are on the same circuit, so you use one switch to turn them both on and off. Or perhaps you’ve cleverly wired in a simple motion sensor, so that when you trip the living room light, the changing shadows concidentally trigger the kitchen light too. Everything is tangled together in interacting patterns of connectivity, so you often get unexpected results from single inputs. The mammalian GRN works, though, so it’s been easier to keep it for a few tens of millions of years, rather than rewiring everything and risking breaking something.

More evidence that there’s a network involved is the fact that these domestication changes can happen incredibly rapidly — Belyaev was getting distinctive behaviors with only decades of selective breeding. What that means is that we’re not dealing with the sudden emergence of mutations of large effect, but with many subtle variations of multiple genes that are being brought together by recombination. This also makes sense. Rather than gross changes that change the entire GRN, what you are doing is tapping into small differences in a number of genes that individually have little or no effect, but together modify the target organ. So in order to change the size of an adrenal gland, you gather together an existing mutation that makes a tiny change in the size while also making ears floppier, and another one that also makes a tiny change in size while also shortening the snout, and another that makes a tiny change while modifying pigment cells.

That’s a very nice general explanation, but in order to advance our understanding we need something a little more specific. What genes? What links all these traits together?

Wilkins and his colleagues have suggested an obvious starting point: it’s all neural crest. Neural crest cells (NCCs) are an early population of migrating cells that infiltrate many tissues in the embryo — they form pigment cells, contribute to craniofacial cartilages, supporting cells for the nervous system, and just generally are found in precisely the places where we see the effects of domestication. So one reasonable hypothesis is that when you’re selecting for domestication, you’re actually selecting for reduced adrenal glands, which is most easily achieved by selecting for retarded or reduced or misdirected NCC migration or increased NCC apoptosis (multiple possible causes!), which has multiple effects.

nceffects

In a nutshell, we suggest that initial selection for tameness leads to reduction of neural-crest-derived tissues of behavioral relevance, via multiple preexisting genetic variants that affect neural crest cell numbers at the final sites, and that this neural crest hypofunction produces, as an unselected byproduct, the morphological changes in pigmentation, jaws, teeth, ears, etc. exhibited in the DS. The hypothesized neural crest cell deficits in the DS could be produced via three routes: reduced numbers of original NCC formed, lesser migratory capabilities of NCC and consequently lower numbers at the final sites, or decreased proliferation of these cells at those sites. We suspect, however, that migration defects are particularly important. In this view, the characteristic DS phenotypes shown in parts of the body that are relatively distant from the sites of NCC origination, such as the face, limb extremities, tail, and belly midline, reflect lower probabilities of NCC reaching those sites in the requisite numbers. The stochastic, individual-to-individual variability in these pigmentation patterns is consistent with this idea.

They document all the phenotypic changes associated with domestication, and strongly correlate them with neural crest mechanisms. It’s a mostly convincing case … my major reservation is that because NCCs are ubiquitous and contribute to so many tissues, it’s a little bit like pointing at a dog and predicting that its features are a product of cells. It’s a very general hypothesis. But then they also discuss experiments, such as neural crest ablations or genetic neurocristopathies that directly modify the same processes involved in domestication syndrome. So it is a bit helpful to narrow the field from “all cells” to “this unique set of cells”.

I have a similar reservation about their list of genes that are candidates for the GRN — they list a lot of very familiar genes (PAX and SOX families, GDNF, RTKs) that are all broadly influential transcription factors and signaling molecules. Again, it helps to have a list of candidates, it’s a starting point, but in an interacting network, I’d be more interested in a summary of connections between them than in scattered points in the genome.

You need a diagram to summarize this hypothesis, and here it is, featuring the important distinction between selected and unselected traits.

ncsummary

I do have one question that wasn’t discussed in the paper, and would be interesting to answer with better genetic data. We talk about domestication syndrome as if it all goes one way: wild predator becomes more tolerant of humans. But it seems to me that it’s a two-way process of selection, and humans also had to be less stressed out and tolerant of sharing a space with an animal that would like to eat them, or compete with them for resources. Are humans self-domesticated apes? Were we selected for reduced neural crest input? If we figured out the changes in genes involved in domestication, it would be cool to look at dogs and cats and foxes, and then turn the lens around and ask if we experienced similar changes in our evolution.


Wilkins AS, Wrangham, RW and Fitch WT (2014) The “Domestication Syndrome” in Mammals: A Unified Explanation Based on Neural Crest Cell Behavior and Genetics. Genetics 197(3):795-808.

Jul 25 2014

Go ahead, let me plan your wedding

It’ll be cheap, there won’t be much ceremony, and I’ll yell at you to get over yourselves. Matthew Yglesias cites me…for good advice on wedding planning, which is not quite what I would have expected. But that’s OK, the Mediocrity Principle applies to everything.

Jul 25 2014

He will devour Mary Worth and Rex Morgan, MD last

It’s all over the news that Archie Comics is killing off Archie (sounds like a desperate bid to draw attention to a line that has been boring and moribund for decades). But why aren’t these same media outlets talking about the fate of another major character, Sabrina the Teenage Witch?

It’s a bit dark. She casts a spell that starts the zombie apocalypse, and then Dr Lovecraft marries her off to…Cthulhu.

sabrinasfate

brideofcthulhu

Did I say a bit dark? I meant very, very dark. Riverdale must be built over a hellmouth.

Jul 25 2014

Friday Cephalopod: Not a bird with a curved beak, or a curvy flower

But still curvy.

Jul 24 2014

Is Ted Nugent still a darling of the Republican party?

I knew Ted Nugent was a nasty piece of work, but this…can he possibly be a bit more blatantly racist? He’s had a couple of shows cancelled at Indian casinos — first by the Coeur d’Alene tribe in Idaho, and most recently by the Puyallups in Washington — and I guess it made Nugent a mite testy.

“The Coeur d’Alene Tribe has always been about human rights — for decades, we have worked individually and as a Tribe to make sure that each and every person is treated equally and with respect and dignity,” said a statement from the tribe.

A spokesperson for the casino said that the company didn’t want to provide a platform for the “racist attitudes and views that Ted Nugent espouses.”

Nugent responded to the cancelation by calling the Coeur d’Alene Tribe unclean vermin.

By all indicators, I don’t think they actually qualify as people, but there has always been a lunatic fringe of hateful, rotten, dishonest people that hate happy, successful people, he continued. I believe raising hell and demanding accountability from our elected employees is Job One for every American. I am simply doing my job.

Brilliant: fired for racist remarks, so he calls the whole tribe “vermin” and questioning their status as humans, perfectly confirming the accusation.

Jul 24 2014

A nice quote from Harry Harrison

Via Daz:

Stated very simply, I face reality and admit that not only isn’t there anyone at home upstairs, there isn’t even any upstairs. I have one life and I intend to make the most of it. Therefore it follows naturally that if I firmly believe this, why then I cannot deprive another person of their turn at existence. Only the very self-assured political and religious zealots kill people in order to save them.

It takes a real shallow thinker to claim that atheism has no consequences. It actually says that there is no escaping the consequences — you aren’t going to get a lollipop in heaven if you say the right words on your deathbed. You have one life and you have to live with it, and then you die, and there are no take-backs or resurrections or rewards or punishments.

Jul 24 2014

Ouch, anti-feminists, you made me sad

The latest noise the MRAs have been pouring into my mailbox has actually been effective in their goals: I find it very depressing. If your intent is to fill me with despair, you win!

First, some background. Y’all have heard of Cathy Young, right? She’s one of those anti-feminists who claims to be a True Feminist™, like Christina Hoff Summers. She’s one of those people who seems to hate the idea of consent, and spends most of her time writing about evil, man-hating feminists — she’s one of the sources of mischaracterization of feminism, of the sort that misogynists love to regurgitate.

Barry Deutsch takes her to task on her weird definitions of feminism.

The Oxford English Dictionary defines an anti-feminist as “One opposed to women or to feminism.” Cathy doesn’t oppose women, but you’d have to impossibly distort her work to argue that she doesn’t oppose feminism; virtually all her writings on feminism are attacks on feminists and feminism. The OED offers a second definition: “a person (usu. a man) who is hostile to sexual equality or to the advocacy of women’s rights.” Cathy isn’t hostile to equality (and she’s not a man!), but her writing clearly is “hostile to… the advocacy of women’s rights.” She thinks women already have virtually all the rights they need, and therefore further advocacy is unnecessary.

In the introduction to her book Ceasefire!, Cathy concedes that in one area – the family/work balance – women might still have a legitimate complaint. But virtually all other concerns that justify a “case for continued feminist activism,” she dismisses as illegitimate. There’s a big difference between criticizing some feminist views, and denying that there’s a legitimate need for a women’s movement at all. How can anyone who doesn’t see a need for a movement for women’s equality, be a feminist?

Deutsch also wonders about this myth of man-hating feminism, which Young tends to favor.

But this brings up something I’ve wondered about for quite a while. When I read MRAs, as well as “conservative feminists” like Christina Hoff Sommers, a narrative history of feminism tends to emerge, which goes something like this: Once upon a time there were the suffragettes, who were libertarian or conservative and they were Good. Then came the second wave feminists in the 60s and 70s, who fought for equal pay and the like, and they were Good. But in the 1980s came the Evil “gender feminists” or “victim feminists,” who turned feminism into man-hating victimology, and feminism has been Bad ever since.

But curiously enough, when reading Sommers and others, it quickly becomes apparent that most of their examples are from 60s and 70s feminism. And so Sommers makes a big deal of the word “ovulars,” a term from the 1960s that no one but Sommers herself uses nowadays. Dworkin, Young’s example, peaked in influence and prominence in the 70s, became a hugely controversial figure within feminism in the 80s, and pretty much faded from prominence after that. Most of the feminists I see quoted as proof of how awful and man-hating feminists are (Robin Morgan, Germaine Greer , Marilyn French, etc) came into prominence in the 60s and 70s.

Are we all up to speed, then? If you’ve ever heard MRAs pontificate sagely about how they are “equity feminists” but not “gender feminists”, terms that Sommers popularized, or accuse feminists of hating men, or of being professional victims, you’ve been hearing the echoes of conservative anti-feminists like Cathy Young. Their claims are nonsense, but they resonate well with the men who like their sexism endorsed.

That’s familiar. It’s a bit sad. But here’s the article I find most discouraging, an old review of one of Cathy Young’s books…a very positive review.

"Girls are not silenced or ignored in the classroom," Young writes. "Medicine has not neglected women’s health. Abuse by men is not the leading cause of injury to American women; the courts do not treat violence toward women more leniently than violence toward men. Gender disparities in pay and job status are not merely a consequence of sex discrimination. The ’80s were not a "backlash decade’ but a time of steady progress for women and, generally, of strong support for women’s advancement."

Young spends much of the book proving these assertions in a way that makes you want to cheer aloud. Finally someone has shed light (and reality) on all those bogus and overstated women-as-victims-of-patriarchy claims.

One just has to sigh at the misrepresentations and dishonesty. But this is what really gives me little hope: that article is by Robyn A. Blumner. This Robyn Blumner.

The Richard Dawkins Foundation for Reason and Science U.S. today announced that Robyn Blumner has been named Executive Director, effective February 5, 2014. Blumner will replace the interim Director, Edwina Rogers, who also serves as the Executive Director of the Secular Coalition for America. 

Blumner is a longtime columnist and editorial writer for the Tampa Bay Times in Florida. She has an extensive background as a public advocate for church-state separation, the rights of atheists and other nontheists, a spectrum of civil liberties and civil rights causes, economic and racial justice and other progressive causes. Her nonprofit experience includes having led two statewide affiliates of the American Civil Liberties Union.

“I am delighted to have Robyn Blumner leading the Foundation in the U.S,” said Richard Dawkins. “Her published writings show her to be a strong, unapologetic atheist with the vision to pursue the imaginative aims of the Foundation, while her legal background and non-profit experience equip her to put them into practice.”

You win, MRAs, misogynists, and other pig-like beings, you win. I’m going to curl up in a corner somewhere and weep for a while. Go celebrate.

But I’ll feel better later, and get back to fighting.

Jul 24 2014

That went in an unexpected direction

Everyone knows the “12-inch pianist” joke, right? Here’s a retelling that changes it in a much more interesting way.

Jul 24 2014

[Lounge #469]

iguana

This is the lounge. You can discuss anything you want, but you will do it kindly.

Status: Heavily Moderated; Previous thread

Jul 24 2014

It’s mayfly season!

Every year around this time, we can expect a sudden eruption of clouds of mayflies to emerge, as Gwen Pearson describes. There have been a few times I’ve been out driving when caught in it, and the car gets coated with brown dead bug smears, to the point where visibility is a serious problem.

But she also shows a video I found even more terrifying: this is a dying mayfly floating on the water, and she constantly dribbles out eggs, making a big pool of them on the bottom. And then one minute in, they start hatching!

Now I study an animal which develops very rapidly, the zebrafish, but this was shocking — you mean they go on a mating flight, drop to the water, and spew out eggs that develop into larval hatchlings in minutes? Impossible! Laws of thermodynamics! Cellular interactions and pattern forming mechanisms! The biochemistry couldn’t go that fast! Cell cycle times must be in milliseconds! Inconceivable! My brain is melting!

Fortunately, I read more closely.

Most mayflies lay their eggs immediately after mating; the eggs then take anywhere from 10 days to many months to hatch. Cloeon cognatum is an exception. This species is ovoviviparous, which means that a mated female holds her eggs internally until embryonic development is complete (about 18 days), after which she lays them in water and they hatch immediately. This female was dropped onto the water surface moments before the video started.

Whew. That’s better. And 18 day development time? Easy peasy. I guess I don’t have to hover around the margins of local lakes trying to catch a few minutes of development, once a year, after all.


By the way, here’s a photo of my car from last year, when I got caught driving by Lake Minnewaska one night:

mayflycar

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