Category: Evolution

Identical twins not… err… identical?

Although we’ve been accused of hatin’ on twin studies, I admit that I find twins pretty fascinating, mostly because they attract all kinds of magical thinking, not just within traditional Yoruba cosmology, but also in the West. My favorite pair of twins has to be the ‘Jim twins,’ a pair of identical twins discussed in an article in Time Magazine.

Like many identical twins reared apart, Jim Lewis and Jim Springer found they had been leading eerily similar lives. Separated four weeks after birth in 1940, the Jim twins grew up 45 miles apart in Ohio and were reunited in 1979. Eventually they discovered that both drove the same model blue Chevrolet, chain-smoked Salems, chewed their fingernails and owned dogs named Toy. Each had spent a good deal of time vacationing at the same three-block strip of beach in Florida. More important, when tested for such personality traits as flexibility, self-control and sociability, the twins responded almost exactly alike.

The Jim twins are great; they have given me hours of fun just going over the possible genetic roots for their similarity: ‘Oh my god, we’ve got a shared gene for naming our dogs “Toy” and another one for marrying women named “Linda” and, when that didn’t work out, marrying a second wife called “Betty.”‘ (A similarity that the Time Magazine article doesn’t explore.) I mean, I just can’t stop laughing when I think about how lovers of this sort of data actually think that some sort of gene directs people to go vacation in a particular spot or naming a son either James Alan or James Allan (Ooooh, so close… it must be shared genes!). But I digress… I just love the Jim twins’ story so much (see also Jonathan Marks’ book, What It Means to Be 98% Chimpanzee, where he writes that, ‘In the world of twin studies the unscrupulous and the credulous symbiotically plumb the depths of contemporary pseudoscience.’ He’s way funnier than I am writing about this stuff in pieces like ‘Folk Heredity,’ especially the section on ‘hereditarianism’.)

But now we’ve got an interesting piece from Scientific American, Identical Twins’ Genes Are Not Identical, which explores the possibility that identical twins aren’t perfect genetic copies of each other. As the article reports:

Geneticist Carl Bruder of the University of Alabama at Birmingham, and his colleagues closely compared the genomes of 19 sets of adult identical twins. In some cases, one twin’s DNA differed from the other’s at various points on their genomes. At these sites of genetic divergence, one bore a different number of copies of the same gene, a genetic state called copy number variants.

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Wednesday Round Up #4

Books

Dr. Ginger Campell and her Brain Science Store
Ginger provides a handy Amazon collection of the books covered in her podcasts

Greg Mortensen and David Oliver Relin, Three Cups of Tea: One Man’s Mission to Promote Peace… One School at a Time
Building schools amid the Taliban, Americans and more…  Recently covered in the Diane Rehm show.  800+ reviews on Amazon, averaging in at the max 5 stars 

Brian Fagan, The Great Warming: Climate Change and the Rise and Fall of Civilizations
Drought is our great historical enemy, especially in dense populations… Recently reviewed in the NY Times 

Sandra Blakeslee & Matthew Blakeslee, The Body Has a Mind of Its Own: How Body Maps in Your Brain Help You Do (Almost) Everything Better
One reviewer: “The brain and the body are not separate entities, but are intertwined, interdependent, and interfunctional. Understanding this fact is essential to understanding how and why body maps work. This book explains that lucidly.” 

Stephen Kern, A Cultural History of Causality: Science, Murder Novels, and Systems of Thought
Literary murder and social history—how we view the causes of ourselves

Melody Petersen, Our Daily Meds: How the Pharmaceutical Companies Transformed Themselves into Slick Marketing Machines and Hooked the Nation on Prescription Drugs
Pharmaceuticals killing people, and companies marketing them more.  See an illuminating review here  

Vision 

Cognitive Daily, Fun With Point-Light Displays—And What That Says About The Visual System
Creating order out of dots… includes some good QuickTime videos

Mixing Memory, Language, Neuroscientific Evidence for the Influence of Language on Color Perception
Critique of imaging, importance of evidence, and our visual system

General 

Cordelia Fine, Will Working Mothers’ Brains Explode? The Popular New Genre of Neurosexism
Critique of the at times popular view that gender differences are “hard wired”

Brandon Keim, Brain Scanner Can Tell You What You’re Looking At
Functional imaging and a good computational program can “decode” the different photographs people see, reconstructing the content.   Worth a look!

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Snakes and spiders on the brain

A little while ago, I wrote a piece, ‘Innate’ fear of snakes?, in which I took issue with a University of Virginia study that was described by a science writer (and perhaps by the researchers) as showing that humans have an ‘innate’ fear of snakes. At the time, I argued that what their research had shown was a propensity to pay attention to snake shapes, and not that this was an ‘innate’ fear, for reasons that I banged on about for a fair few words (go to the original if you’re a glutton for snake-related musings).

And now, vindication. Well, as much vindication as you can get considering that psychological research is liable to be undermined by another study in the next few months. According to a posting today on Science Daily, ‘Unlocking The Psychology Of Snake And Spider Phobias,’ researchers at the University of Queensland have tested both snake experts and those who are naive about the creatures to see if there is an innate fear.

In the study, researchers compared the responses to stimuli of participants with no particular experience with snakes and spiders, to that of snake and spider experts.
“Previous research has argued that snakes and spiders attract preferential attention (they capture attention very quickly) and that during this early processing a negative (fear) response is generated… as an implicit and indexed subconscious [action],” Dr [Helena] Purkis said.
“We showed that although everyone preferentially attends to snakes or spiders in the environment as they are potentially dangerous, only inexperienced participants display a negative response.”

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The history of mind-altering mechanisms

Katherine MacKinnon of St. Louis University just dropped me a line to point out a recent book review in The New York Times, I Feel Good, by Alexander Star. Star reviews the book, On Deep History and the Brain, by Daniel Lord Smail (University of California Press). Amazon raters are giving it 4.5 stars at the moment, if you want to check it out through the bookseller. Normally, I’d trust Daniel to write our best stuff about ‘mind-altering’ chemicals of all sorts, but this book review just set me to thinking, so I thought I’d put my own two cents in.

Smail wants to tell the story of humanity as a series of ‘self-modifications of our mental states,’ according to the reviewer Star:

We want to alter our own moods and feelings, and the rise of man from hunter-gatherer and farmer to office worker and video-game adept is the story of the ever proliferating devices — from coffee and tobacco to religious rites and romance novels — we’ve acquired to do so. Humans, Smail writes, have invented “a dizzying array of practices that stimulate the production and circulation of our own chemical messengers,” and those devices have become more plentiful with time. We make our own history, albeit with neurotransmitters not of our choosing.

Smail is really a historian, but his venture into a kind of neuro-history shows the robustness of the emerging awareness that the brain is shaped by what humans do. Star points out that most ‘macro-history’ these days — long, sweeping accounts of human evolution and what is sometimes called something prosaic like the ‘rise and fall of civilizations’ — is not being written by historians, but rather by folks like Jared Diamond. In contrast, Smail is a medieval historian.

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Glucose, Self Control and Evolution

Galliott et al. published a 2007 article entitled “Self Control Relies on Glucose as an Energy Source: Willpower Is More Than Self Control” (pdf here). Recently Vaughan at Mind Hacks and Dave at Cognitive Daily have taken up the topic with some creative posts.  Vaughan writes that Resisting Temptation Is Energy Intensive, focusing on the role of attention and the prefrontal cortices.  Dave posts on Practicing Self-Control Takes Real Energy, and includes a recreation of the research procedure (with video) and an informative summary.  I also mentioned some of this research in a previous post on Willpower as Mental Muscle.

What I want to add today is that this sort of research has implications for our understanding of brain evolution and for social problems like obesity and addiction.  Focusing attention and using one part of your brain against another part, that takes significant energy.  The brain is already our most energy-intensive organ, so adding the demands of “self control” on top of that is likely to have presented some adaptive issues in the past.  Put differently, it’s unlikely to expect that we’ve evolved to be able to maintain self control over extremely long periods of time (say, months), simply because such problems rarely presented themselves in the past (there were few adaptive benefits) and because the energetic costs of doing so would have been quite high.

Diets are often marked by periods of effortful weight loss, followed by a slide back, where weight is regained.  That pattern is not simply a matter of mind over matter, of willpower so we can match a cultural and cognitive ideal.  It’s hard for people to maintain sustained mental efforts, it costs energy, and there’s little evolutionary reason to expect everybody’s brains to suddenly begin cooperating with what our culture tells us we should be able to do.

‘Innate’ fear of snakes?

Live Science has a recent piece, Why We Fear Snakes, written by Clara Moskowitz. I have to admit that, well, I hate this sort of thing for so many reasons that I hesitate to write. My problem with these accounts is with ‘innate’; I think the term is, generally, poorly defined, unprovable and unproven, sloppy, theoretically suspect, and freighted with so many dangerous implications that it gives me, for want of a better word, the heebie-jeebies.

Before I get too critical, however, it’s necessary to acknowledge that some of the assumptions I’ll critique may have, likely have, arisen in the translation of a complex research project into a few hundred words for a popular press account. God knows my own work has suffered when it’s been translated into popular formats (don’t even get started about a CNN special on race that I was interviewed for…). We’re encouraged to do outreach to the community, to put our specialties up on ‘expert’ databases and basically pimp ourselves for any positive reference, so we wind up bending over backwards to make our ideas accessible. This can lead us to stumble, especially in the view of a discipline that doesn’t share our concerns. For example, if I were to try to give an accessible account of my work, a neuroscientists would likely gag on some of the explanatory shortcuts. So some of the criticisms that I will level might be better applied to the science writer rather than the researchers; we’ll know when the research findings are eventually published. Caveats in place, on with it…

Apparently, the Psychology Department at the University of Virginia has a couple of scholars studying the ‘universal’ fear of snakes. The piece says what one might expect: ‘The researchers were inspired to investigate the fear of snakes when they thought about how universally people dislike the slithering legless lizards. “This feeling is really common,” [Vanessa] LoBue told LiveScience. “We don’t see snakes all the time. There’s really no reason for this overwhelming disgust or hatred of snakes.”‘ The researchers demonstrated this universal fear by showing that both adults and children ‘could detect images of snakes among a variety of non-threatening objects more quickly than they could pinpoint frogs, flowers or caterpillars.’ And the explanation is that an innate fear of snakes would have made humans more likely to survive in the wild.

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