Archives for posts with tag: the domestication syndrome

the idea that humans have self-domesticated themselves (ourselves!) is definitely in vogue: here’s a recent irl+online symposium held on the topic.

domestication in mammals results in a specific suite of traits known as the “domestication syndrome”:

“[I]ncreased docility and tameness, coat color changes, reductions in tooth size, changes in craniofacial morphology, alterations in ear and tail form (e.g., floppy ears), more frequent and nonseasonal estrus cycles, alterations in adrenocorticotropic hormone levels, changed concentrations of several neurotransmitters, prolongations in juvenile behavior, and reductions in both total brain size and of particular brain regions.”

humans — in some cases some human populations — appear to exhibit many, if not all, of these traits: increased docility, skin color changes, reduction in tooth size, craniofacial feminization, more frequent/nonseasonal estrus cycle, neotenous gene expression in the developing human brain, prolongation in juvenile behavior, and reduction in total brain size.

much of the current thinking seems to be centered on the idea that humans self-domesticated “in the more distant past,” but the fact that humans have been able to dwell together at all in ridiculously large numbers beginning around the time of the agricultural revolution suggests that human self-domestication did not stop “in the more distant past” and is probably even ongoing. this is 10,000 Year Explosion territory, and cochran and harpending have been here already [pgs. 110-113 — my emphases]:

“If your ancestors were farmers for a long time, you’re descended from people who decided it was better to live on their knees than to die on their feet.

“Farming led to elites, and there was no avoiding their power. Foragers could walk away from trouble, but farms were too valuable (too important to the farmers’ fitness) to abandon. So farmers had to submit to authority: The old-style, independent-minded personalities that had worked well among egalitarian hunter-gatherers (‘A Man’s a Man for a’ That’) were obsolete. Even when some group had a chance to refound society on a more egalitarian basis, as in the case of the medieval Iceland republic, elites tended to reappear.

“Aggressive, combative people may also have experienced lowered fitness once ruling elites began to appear. With strong states, the personal payoff for aggression may have become smaller, while law and order made combativeness for self-defense less necessary. Sheer crowding must also have disfavored some personality traits that had worked in the past. Intuitively, it seems that a high level of aggressiveness would be less favored when encounters with strangers were frequent. Fight too often and you’re sure to lose. Moreover, although the winner of a deadly struggle between two peasants might conceivably gain something, his owners, the elites who taxed both of those peasants, would not, any more than a farmer benefits when one bull kills another.

“Farmers don’t benefit from competition between their domesticated animals or plants. In fact, reduced competition between individual members of domesticated species is the secret of some big gains in farm productivity, such as the dwarf strains of wheat and rice that made up the ‘Green Revolution.’ Since the elites were in a very real sense raising peasants, just as peasants raised cows, there must have been a tendency for them to cull individuals who were more aggressive than average, which over time would have changed the frequencies of those alleles that induced such aggressiveness. This would have been particularly likely in strong, long-lived states, because situations in which rebels often won might well have favored aggressive personalities. This meant some people were taming others, but with reasonable amounts of gene flow between classes, populations as a whole should have become tamer.

“We know of a gene that may play a part in this story: the 7R (for 7-repeat) allele of the DRD4 (dopamine receptor D4) gene. It is associated with Attention-Deficit/Hyperactivity Disorder (ADHD), a behavioral syndrome best characterized by actions that annoy elementary school teachers: restless-impulsive behavior, inattention, distractibility, and the like.

“The polymorphism is found at varying but significant levels in many parts of the world, but is almost totally absent from East Asia. Interestingly, alleles derived from the 7R allele are fairly common in China, even though the 7R alleles themselves are extremely rare there. It is possible that individuals bearing these alleles were selected against because of cultural patterns in China. The Japanese say that the nail that sticks out is hammered down, but in China it may have been pulled out and thrown away.

Selection for submission to authority sounds unnervingly like domestication. In fact, there are parallels between the process of domestication in animals and the changes that have occurred in humans during the Holocene period. In both humans and domesticated animals, we see a reduction in brain size, broader skulls, changes in hair color or coat color, and smaller teeth. As Dmitri Belyaev’s experiment with foxes shows, some of the changes that are characteristic of domesticated animals may be side effects of selection for tameness. As for humans, we know of a number of recent changes in genes involving serotonin metabolism in Europeans that may well influence personality, but we don’t know what effect those changes have had — since we don’t yet know whether they increase or decrease serotonin levels. Floppy ears are not seen in any human population (as far as we know), but then, changes in the external ear might interfere with recognition of speech sounds. Since speech is of great importance to fitness in humans, it may be that the negative effects of floppy ears have kept them from arising.

“Some of these favored changes could be viewed as examples of neoteny — retention of childlike characteristics. Children routinely submit to their parents — at least in comparison to teenagers — and it’s possible that natural selection modified mechanisms active in children in ways that resulted in tamer human adults, just as the behaviors of adult dogs often seem relatively juvenile in comparison with adult wolf behavior.

“If the strong governments made possible by agriculture essentially ‘tamed’ people, one might expect members of groups with shallow or nonexistent agricultural experience to be less submissive, on average, than members of longtime agricultural cultures. One possible indicator of tameness is the ease with which people can be enslaved, and our reading of history suggests that some peoples with little or no evolutionary exposure to agriculture ‘would not endure the yoke,’ as was said of Indians captured by the Puritans in the Pequot War of 1636. In the same vein, the typical Bushman, a classic hunter-gatherer, has been described as ‘the anarchist of South Africa.'”

what i’d like to draw attention to is the idea that there have been multiple (probably multiple multiples of) human self-domestication events which occurred at different places and at different times — all sorta within the broader human self-domestication project which began back in some stone age or, perhaps, even before. one of these, i propose, was the manorialism/outbreeding/execution-of-violent-criminals combo of medieval europe which left “core” europeans with a very specific set of behavioral traits. another might very well be whatever domestication package went along with rice farming in southern china as peter frost has discussed. others undoubtedly include the sorts of civilizations described by cochran & harpending in the passage quoted above — those “strong, long-lived states” — like those found in ancient egypt, ancient china, and ancient india.

just like how we (prolly together with dogs themselves) domesticated dogs thousands of years ago, but then continued and honed the process by selecting for specific traits in specific breeds, i think we should consider that, not only did humans start self-domesticating themselves a very long time ago so that there are common domestication traits in (nearly?) all humans populations, but also that there have been more localized self-domestication events which selected for somewhat different behavioral traits depending on what sort of selection pressures were present in these various events.

(note: comments do not require an email. domesticated foxes!)

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Bayesian analyses of Yemeni mitochondrial genomes suggest multiple migration events with Africa and Western Eurasia

37,000-year-old Russian skeleton has Neanderthal DNA that’s gone missing“Sequences present in its genome haven’t been found in modern human populations.” – see also Remix from greg cochran. – see also Genome of Kostenki-14, an Upper Paleolithic European (Seguin-Orlando, Korneliussen, Sikora, et al. 2014) from dienekes.

Humans Would Beat Neanderthals in Marathon

Different Ways to Color a Cat – from razib. – h/t billare! who tweeted: “Progenitors of modern Europeans were fairly light-skinned–why did a 2nd bout of selection leave its tell-tale marks?”

Admixture in the Americas: Introduction, partial correlations and IQ predictions based on ancestry – from emil kirkegaard.

Our Futile Efforts to Boost Children’s IQ“How can parenting and socioeconomic status play such minor roles in determining IQ, when scholars on all sides of the nature-nurture debate agree that somewhere around half of the variation in IQ is environmental? The short answer is that the environment that affects IQ doesn’t consist of the advantages that most people have in mind — parents who talk a lot to their toddlers, many books in in the house for the older children, high-quality schools and the like. Instead, studies over the past two decades have consistently found that an amorphous thing called the “nonshared” environment accounts for most (in many studies, nearly all) of the environmentally grounded variation. Scholars are still trying to figure out what features of the nonshared environment are important. Peers? Events in the womb? Accidents? We can be sure only of this: The nonshared environment does not lend itself to policy interventions intended to affect education, parenting, income or family structure.” – from charles murray. – h/t mr. mangan, esq!

Results of a “GWAS Plus:” General Cognitive Ability Is Substantially Heritable and Massively Polygenic – h/t emil kirkegaard!

Does neural crest development drive domestication syndrome?“Altered neural crest development could be the reason mammals change in oddly consistent ways during domestication. As first noted by Darwin more than 140 years ago, domestic mammals tend to share certain characteristics—a suite of traits called the domestication syndrome.”

‘Darwin’s Dilemma’ May Be Solved“Scientists following two different lines of evidence have just published research that may help resolve ‘Darwin’s dilemma,’ a mystery that plagued the father of evolution until his death more than a century ago. Biologists and geologists have been puzzled for decades over why life began so early on this planet, and then took so long to get interesting.”

A new study pieces together the puzzle of insect evolution“A new study of insect evolution — the largest of its kind ever undertaken — has uncovered some surprising new information, confirmed some long-held hypotheses and may lead researchers toward a more comprehensive understanding of evolution. One hundred scientists from 10 countries worked together to examine 144 insect species. Their goal was to create an insect ‘family tree’ and establish a timeline of insect evolution. Their results were published recently in the journal Science.” – cool!

More evidence that certain versions of some genes can encourage violence

Facial structure predicts goals, fouls among World Cup soccer players“The scientists studied the facial-width-to-height ratio (FHWR) of about 1,000 players from 32 countries who competed in the 2010 World Cup. The results, published in the journal Adaptive Human Behavior and Physiology, showed that midfielders, who play both offense and defense, and forwards, who lead the offense, with higher FWHRs were more likely to commit fouls. Forwards with higher FWHRs also were more likely to score goals or make assists.”

Mental health: Depression needs large human-genetics studies“To understand the molecular mechanisms of depression, collect genetic data from more than 100,000 people, says Steven Hyman.”

Geneticists tap human knockouts“On average, every person carries mutations that inactivate at least one copy of 200 or so genes and both copies of around 20 genes.”

The Inexorable Progress of Science: Archaeology“With a very limited set of clues, smart guys managed to get key facts about European prehistory roughly correct almost 90 years ago . With tremendously better tools, better methods, vastly more money, more data, etc, archaeologists (most of them) drifted farther and farther from the truth.” – from greg cochran.

How Your Facebook Updates Reveal Your Personality“Extroverts tend to use words like love, tonight, party, excited and amazing. Several length variants of the word soooo and ‘text speak’ terms like lovin and ur, are more often found on extroverts’ updates. In general the extrovert word cloud is sloppy enough to make any ‘Grammar Nazi’ red in the face. When we come to introverts, use of the word computer was one of the biggest giveaways. Posting status updates about Internet, and to a lesser extent anime, doctor who, and books, were also predictive of introversion.” – from neuroskeptic.

The contribution of additive genetic variation to personality variation: heritability of personality“[W]e found that approximately 52% of animal personality variation was attributable to additive genetic variation.”

The genetics of impulsivity: evidence for the heritability of delay discounting – h/t ben southwood! who tweeted: “Impulsivity is 55% heritable at age 18.”

We are not equally empathic – from peter frost.

He’s Definitely a Liberal—Just Check Out His Brain Scan“[W]e’ve had solid indications for a while now that our ideological biases are based, in large part, on the biology of our brains…. Of course, we’d like to think we came to our core beliefs through a process of rational reflection and discussion — or, at the very least, as a psychological reaction to the influence of our parents and peers…. But the profound influence of basic brain biology has just been re-affirmed in a new research paper, which found liberals and conservatives can be easily identified through fMRI scans…. ‘Remarkably,’ writes a team led by P. Read Montague of the Virginia Tech Carilion Research Institute, ‘brain responses to a single disgusting stimulus were sufficient to make accurate predictions about an individual subject’s political ideology.'”

The Most Heritable Gut Bacterium is… Wait, What is That?“By studying 416 pairs of British twins, Julia Goodrich and colleagues from Cornell University have identified the gut microbes whose presence is most strongly affected by our genes.”

Microbiome science threatened by contamination“Non-sterile sequencing returns rogue results in dilute microbe samples.”

Global IQ and health – from dr. james thompson.

Book Review: The Ten Thousand Year Explosion (2009) by Greg Cochran and Henry Harpending – from staffan.

The ecology of religious beliefs“Both comparative and experimental evidence indicate that beliefs in moralizing high gods promote cooperation among humans, a behavioral attribute known to correlate with environmental harshness in nonhuman animals. Here we combine fine-grained bioclimatic data with the latest statistical tools from ecology and the social sciences to evaluate the potential effects of environmental forces, language history, and culture on the global distribution of belief in moralizing high gods (n = 583 societies). After simultaneously accounting for potential nonindependence among societies because of shared ancestry and cultural diffusion, we find that these beliefs are more prevalent among societies that inhabit poorer environments and are more prone to ecological duress.”

Edvard Westermarck on Morality: The Light Before the Darkness Fell and Post-Darwinian, “Evolutional” Theories of Morality in the 19th Century – from helian.

Genes contribute to behavior differences between fierce and friendly rats“Genes active in the brain implicated in differences in rats selected for aggression or tameness”

Intimidating chimpanzee males are more likely to become fathers – ruh roh. – h/t steve stewart williams!

Marriage Records Reveal Patterns of Korean Migration Through the Centuries

What Edward Luttwak Doesn’t Know About Ancient China (Or a Short History of Han-Xiongnu Relations), pt. 1 and What Edward Luttwak Doesn’t Know About Ancient China (Or a Short History of Han-Xiongnu Relations), pt. 2 – from t.greer.

There’s Something About Teutonics – from those who can see.

An extremely low-density human population exterminated New Zealand moa“Here we show that the Polynesian population of New Zealand would not have exceeded 2,000 individuals before extinction of moa populations in the habitable areas of the eastern South Island. During a brief (<150 years) period and at population densities that never exceeded ~0.01 km(-2), Polynesians exterminated viable populations of moa by hunting and removal of habitat. High human population densities are not required in models of megafaunal extinction."

A Gene by Any Other Name“What is the logic in naming human genes?”

bonus: Keeping Mates Close and Competition Out in an Ocean Sponge

bonus bonus: Here’s Why Other People’s Farts Smell Way Worse Than Your Own – we cover *all* aspects of human biodiversity here on the hbd chick blog! (~_^)

(note: comments do not require an email. an ocean sponge.)