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Archive for the ‘evolution’ Category

Sequencing Neanderthals

Just out now in Cell is a wonderful article on the full sequence of mitochondria DNA from the Neanderthal. The paper is already receiving much interest in the media, and Nature has a news story somewhat misleadingly entitled “First complete Neanderthal genome sequenced“.

Using very rigorous methods for extracting DNA material from the Vindija Cave in Croatia and keeping it clean from (human) contamination, the researchers were able to analyze 35 samples. The paper abstract basically tells the main findings:

A complete mitochondrial (mt) genome sequence was reconstructed from a 38,000 year-old Neandertal individual with 8341 mtDNA sequences identified among 4.8 Gb of DNA generated from ∼0.3 g of bone. Analysis of the assembled sequence unequivocally establishes that the Neandertal mtDNA falls outside the variation of extant human mtDNAs, and allows an estimate of the divergence date between the two mtDNA lineages of 660,000 ± 140,000 years. Of the 13 proteins encoded in the mtDNA, subunit 2 of cytochrome c oxidase of the mitochondrial electron transport chain has experienced the largest number of amino acid substitutions in human ancestors since the separation from Neandertals. There is evidence that purifying selection in the Neandertal mtDNA was reduced compared with other primate lineages, suggesting that the effective population size of Neandertals was small.

But even more interesting is that a month ago, I unexpectedly met one of the co-authors on this paper. Michael Egholm had entered my wife’s gallery for a brief visit to check out her famous microscopy paintings. While it took me some time to understand who he was, and who he worked with (such as Svante Pääbo), our conversation continued after he’d left for the US. Luckily to you English-only readers, Egholm has spent too many years to feel comfortable writing science in his native Danish. He sent me the submitted manuscript with the following comment:

The somewhat simplistic grand purpose of the Neanderthal project is to figure out what makes us human – presumably our unique brain function.  By comparing the Neanderthal sequence with Chimpanzee and Human we can ideally pin point areas on the genome that has undergone rapid evolution the last 660K years (the new split time determined in the paper). It is generally accepted that something dramatic happened within the last 100K years or so which eventually let to the exodus from Africa and population of the rest of the world along with the extinction of other hominoids.  So with the Neanderthal genome we’re on the safe side but a lot closer than our divergence from Chimpanzee (est. at 6M years).  Obviously, we will be blind in areas of the Neanderthal genome that have undergone evolution since the split from modern humans.

The mitochondrial genome is an obvious first milestone in the project because of its overrepresentation and because it does not undergo recombination the analysis is a lot simpler with respect to split time etc.  Anyways, there is one big surprise and/or coincidence in the 13 proteins that are coded for by the mtDNA in that we find one gene with 4 ns changes – this is exactly what we had hoped for and while highly statistically significant within the context of the 13 proteins of the mtDNA it is not within the context of 20K+ genes.

How’s that for an explanation?

-Thomas

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Who said evolution could not happen fast? Has it not been one of the main criticisms from evolution-critics that we cannot observe evolution taking place today? Well, here is just one recent example of evolution over a few generations only.

In case you have not heard this story before, a study published in the March issue of PNAS demonstrated that the Italian wall lizard (Podarcis sicula) had developed gross morphological changes in only a few decades. In particular, the story was that in the early 1970’s the lizard was introduced by humans to the island Pod Mrcaru in Croatia (from the neighboring island called Pod Kopiste).I’ve made a map just to show where that is:

A google map of the region can be found here

Five adult pairs introduced in 1971. During the Croatian war of independence, the lizards were long forgotten, not studied again until decades after their release. At that time, the researchers were not even sure whether there would be any lizards left. Imagine their surprise, then, when they discovered the species now dominates the island in great numbers, well over 10.000!

But as if this was not a big surprise itself, the researchers discovered that the Pod Mrcaru lizards had developed morphological differences, including larger heads, broader jaws and a harder bite. In addition, the lizards had developed a completely new gut structure. Why? Because the two islands differed in what the lizards could feed upon. In a great story about this exciting finding, National Geographics notes:

Pod Mrcaru, for example, had an abundance of plants for the primarily insect-eating lizards to munch on. Physically, however, the lizards were not built to digest a vegetarian diet.

Researchers found that the lizards developed cecal valves—muscles between the large and small intestine—that slowed down food digestion in fermenting chambers, which allowed their bodies to process the vegetation’s cellulose into volatile fatty acids.

“They evolved an expanded gut to allow them to process these leaves,” Irschick said, adding it was something that had not been documented before. “This was a brand-new structure.”

Can anything be more “wow” than this?

So not only did the study demonstrate the ability of only a few number of lizards to survive and thrive in a relatively new habitat. The study also demonstrates just how fast evolutionary preassures can lead to adaptions in a much faster time than what we normally think of.

This, of course, is supportive evidence for the thought about fast evolutionary changes even in humans, as we have previously blogged about (see here, here, here, here and here).

-Thomas

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I’ve received two new books on the relationship between economics and the brain. I soon discovered that they are quite different. While the first book definitely springs out from an economic point of view, is dry and scientifically speaking to the point, the other is written as a popular science book with several allusions, anecdotes and with an emphasis on the story itself.

Unless you haven’t already guessed, I’m talking about Peter Politser’s “Neuroeconomics” and Michael Shermer’s “The mind of the market“. Both books are extremely attractive to both newcomers to the field as well as well established scholars. (I wonder who is really a “neuroeconomist” today, or anybody would call themselves this).

You’ve guessed right: Michael Shermer is the witty and alluding popular science writer that writes a book with such an energy and enthusiasm that one may become a bit envious. By drawing on life experiences as diverse as his old graduate rat-project and working with and developing professional bikes, Shermer tells the story about economics and the relationship to psychology, evolution and the brain in the most wonderful and inspiring way. One thing I found remarkable was Shermer’s ability to tell these stories in a coherent way. His digressions into his experience with bicycles got me wondering what this book was really about — a self-biography? — but I soon realized that Shermer had other plans. The idea was to present how markets and products are shaped in a way analogous to darwininan evolution (although the analogy is not complete). In a way, I think Shermer may have made a new topic of study: the evolution of markets and products, much in the same way we have seen the debate about memetics (i.e., how ideas are formed and evolve with time and within communities).

Peter Politser’s contribution could easily be seen as a dried out academic paperwork that, despite its few 150 pages, would seem endless to get through. However, if you appreciate a sober approach to neuroeconomics, with less stress on story telling and more weight on facts, theories and formulas, your inner academic economist will certainly cheer all the way through the book. And it did so for me, too. politser provides an interesting take on neuroeconomics, with what I see as an approach from the economists view. Thus, one could ask for the treatment of more neuroscience, but let’s see if there will not be a sequel, or another book with more stress on the brain side of things.

So which book should you go for? If this is your first try at neuroeconomics, Shermer’s a safe try. If you want to go straight to the topic, Politser is the guy. But why not do both? They are actually important contributions and may serve as each other’s refreshments in a combination.

-Thomas

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humphrey.JPGIt was twenty years ago today. Sgt. Pepper taught the band to play.

Actually, last year it was 30 years ago that Nicholas Humphrey published his seminal paper “The social function of intellect” (pdf). Many people see this paper as the impetus to later work on the social brain hypothesis (pdf) and Theory of Mind. Humphrey suggested that, rather than the need for technology, it was in fact the need for advanced cognitive mechanisms for keeping track of conspecifics and interacting with other members of their social group that drove the expansion of brain and intelligence in hominids. This idea has provoked research into the role of cooperation and collaboration as well as deception and competition in primate social behaviour. It has prompted research into the importance of conspecifics being able to attend to a shared mental content. (Shared attention appears crucial to the transfer of knowledge in a social group, and is therefore probably a prerequisite for the establishment of cultural traditions.) Finally, it has been instrumental in getting neuroscientists interested in the neurobiological underpinnings of social cognition, including research into Theory of Mind and mirror neurons.

To commemorate Humphrey’s paper and track the above-mentioned ensuing research, the Royal Society of London staged a Dicussion Meeting last year. The papers presented at that meeting have now been published in the latest issue of the Philosophical Transactions of the Royal Society B. It is a veritable smorgardsbord of big names: There’s papers on social intelligence in birds, hyenas, dolphins and apes by, inter alia, Nathan Emery, Nicola Clayton, Kay Holekamp, and Richard Connor. Richard Byrne and Andrew Whiten discuss the animal cultures hypothesis. There’s papers by Michael Tomasello and Daniel Povinelli on ToM in primates. Vittorio Gallese explains the importance of mirror neurons, Chris Frith reviews what we know about the social brain, and Steven Mithen speculates that farming may have arisen from a misapplication of social intelligence. Naturally, Humphrey is also given the opportunity to revisit his 1976 paper.

If you are at all interested in the question of what makes some species social beings you will want to check out this issue.

-Martin

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This week’s Nature features a nice battle between creationists and evolutionists in the correspondence section.

The debate contains the following parts:

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The gene genie

1-3-1-1-2-1-3-1-0-0-0.jpgWhen it was announced in Nature in 2001 that the linguistic disorder displayed by members of an English family known as KE could be traced back to a mutation of a certain gene, FOXP2, Steven Pinker heralded this result as “the dawn of cognitive genetics”. While we are still a long way from being able to link cognitive mechanisms to the function of specific genes, it is certainly true that researchers, these days, are coming increasingly closer to understanding how the genome interfaces with the neural processes underlying cognitive behaviour. Among the many fundamental questions genomic studies are starting weigh in on is how brains have changed in evolutionary lineages, development, and individual differences in cognitive behaviour. (more…)

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books.jpgWhile Thomas is getting his kicks off at the SfN meeting in Atlanta I am toiling away at a number of long overdue papers here in the increasingly cold Denmark. I have several longer blog posts planned, but no time to write them. So, here’s three things to read in the meantime at other venues on the net.

First, John Searle reviews a new book on consciousness by Nicholas Humphrey, Seeing Red, in The New York Review of Books. I have always enjoyed Humphrey’s work, but his new theory on consciousness sounds plain weird (at least as retold by Searle; I haven’t read Humphrey’s book). In Searle’s words:

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Many people are interested in the new, emerging field of neuroaesthetics – the attempt to use neuroscience to understand art and aesthetic behaviour. It is not an easy field to come to as an outsider, though. First of all, at the moment neuroaesthetics is not so much a coherent field (with textbooks and so on) as a collection of researchers with an individual interest in illuminating the neural underpinnings of art behaviour – and what these researchers take “neuroaesthetics” to mean differ rather widely. Secondly, although quite a lot has been written on neuroaesthetics in the last ten years, there is really no representative publication where newcomers can become acquainted with all the problems and research data pertinent to neuroaesthtics (for the reasons stated above).

I therefore thought that I should ease the way for the interested reader by listing a number of books that can serve as a first introduction to the world of neuroaesthetics. I have chosen to only list more or less popular books, not specialist papers, for two reasons: first, since this list is meant as an introduction, the material on it should not be too difficult; second, listing all relevant research papers is simply impossible within the framework of a short blog post. Choosing to highlight only some papers, leaving out others, would surely also make me unpopular with researchers around the world!

Neuroaesthetics can be thought of as a part of a more general study of art and aesthetics as a biological phenomenon. I will follow other proponents of this view (such as Tecumseh Fitch) in calling this broader approach bioaesthetics. The overall goal of bioaesthetics is to answer the three basic biological questions – what?, how?, why? – in regard to aesthetic behaviour in humans: what is art and aesthetics?; how does art and aesthetics spring from the brain?; and why did this cognitive ability evolve in humans? Neuroaesthetics is predominantly concerned with question number 2. In the list that follows below I will also mention a number of books that discuss the other two questions.

What is aesthetics?

Archaeological and anthropological research can help us answer such fundamental questions as when the first works of art appeared in the fossil record, what characterizes them, and who created them. It is of rather great importance to know what function(s) the first art objects had since that function reflects the cognitive capacities of those who created them. Randall White’s book from 2003, Prehistoric art (Harry N. Abrams), gives a fine overview of the when and what. Steven Mithen’s The prehistory of the mind (Thames and Hudson 1996) and David Lewis-Williams’ The mind in the cave (Thames and Hudson 2004) contain interesting speculation on the question of function and cognitive capabilities.

dancers1.jpgEqually important is ethnographic studies of what constitutes art in different contemporary societies. Much debate on “the nature” of art takes its departure from wholly theoretical considerations of what features define art. From a biological perspective it is much more interesting to know what people actually do when they create of experience art. Unfortunately, I know of no ethnographical survey, covering all the world’s cultures. However, in her books on the evolution of art Ellen Dissanayake has several great discussions of what art behaviour actually amounts to in different cultures. See especially her first two books, What is art for? (University of Washington Press 1988) and Homo Aestheticus (University of Washington Press 1992).

To these descriptions of art behaviour we should of course add the controlled investigations of experimental aesthetics. Sadly, most of the books trying to review of this psychological research tradition are rather old and outdated, but a short and idiosyncratic introduction to the field can be found in Robert Solso’s last book The psychology of art and the evolution of the conscious brain (Bradford Book 2003), which exclusive focus is on visual art, though. (Books on music are mentioned in the next section.)

How does art and aesthetics spring from the brain?

Neuroaesthetic research on how the brain gives rise to art and aesthetic behaviour can be divided up in three areas of interest: (1) Representation, (2) Emotion, and (3) Creativity.

Research on representation deals with the question of how the brain transforms perceptual inputs into mental representations – images, musical structures, etc. Since the different art forms – visual art, music, literature, dance, etc. – target different perceptual systems most researchers tend to focus on only one modality, especially vision or music. Good books on visual art are Semir Zeki’s Inner vision (Oxford University Press 1999) and Margaret Livingstone’s Vision and art (Harry N. Abrams 2002). An introduction to music research can be found in Isabelle Peretz & Roberts Zatorre (Eds.), The cognitive neuroscience of music (Oxford University Press 2003), and Daniel Livitin’s new book This is your brain on music (Dutton 2006). No books have yet been published on the cognitive neuroscience of literature – a great loss – but a few books on literature written from the point of view of cognitive science do exist, including Suzanne Nabantian’s Memory in literature (Palgrave Macmillan 2003) and Liza Zunshine’s Why we read fiction (Ohio State University Press 2006). This lack of books on literature written from the perspective of neuroscience is mostly due to the fact that, though there is a lot of neuroscientific research on language as such, almost no experiments yet have attempted to test specific literary questions. The same thing goes for dance and architecture as well (although some research appears to be forthcoming).

vermeer_painter.jpgResearch on emotion and art is a rather recent phenomenon and I know of only one book that explicitly deals with this topic, the book Music and emotion, edited by Patrick Juslin and John Sloboda (Oxford University Press 2001). I think there is reason to expect, though, that we will soon see several new books looking into it. (As Nancy Aiken reports in the comments to this post, her 1998 book, The biological origins of art, also deals with the question of how art elicits emotional responses. I am sorry to say I haven’t read that book yet, though.) In principle the field of emotion and art can be subdivided into two different problems: (1) How are emotions emulated by works of art? (2) How does the brain attach an aesthetic value to works of art? It is well known that a lot of art has human emotional life as its topic – think of romantic comedies, stories of vengeance and so on. Without the ability to induce these emotions in the viewer or reader such art works would simply be meaningless. So the ability of works of art to activate the brain’s emotional system is central to art. At the same time, art also activates the brain’s reward system, giving rise to such emotional reactions as feelings of beauty, ugliness, fascination, etc. Research on how such aesthetic emotions are computed by the brain is booming at the moment.

Finally, brain research on (artistic) creativity is still very much in its infancy. Several papers have been published recently investigating creative problem solving with fMRI and PET, but such research hasn’t really been translated into book presentations yet. The best new book on creativity and the brain is Kenneth Heilman’s Creativity and the brain (Psychology Press 2005). Readers interested in papers on artistic creativity will find several updated chapters in Colin Martindale, Paul Locher & Vladimir Petrov (Eds), Evolutionary and neurocognitive approaches to aesthetics, creativity and the arts (Baywood 2006) and Paul Locher, Colin Martindale & Leonid Dorfman (Eds), New directions in aesthetics, creativity and the arts (Baywood, in press).

I should also mention that in 2004 and 2005 Frank Clifford Rose and Dahlia Zaidel published two fascinating books collecting case stories and patient data casting further light on the issue of representation from the point of view of neuropsychology: Neurology and the arts (Imperial College Press 2004) and Neuropsychology of art (Psychology Press 2005).

Why did aesthetic cognition evolve in humans?

The evolutionary question of why aesthetic cognition evolved in humans is informed by several lines of evidence: archaeological findings, comparative studies of similarities and differences in cognitive behaviour between humans and other animals, genetics, etc. Researchers are often trying to identify either principles of sexual selection or natural selection as the driving force of the evolution of aesthetic cognition. The name most often associated with sexual selection – besides Darwin who first suggested it as a principle of evolution in The descent of man (1871) – is Geoffrey Miller who published the influential book The mating mind in 2000 (William Heinemann). The doyenne of adaptationist aesthetic studies (studies searching for natural selection forces) is Ellen Dissanayake who, apart from the two books already mentioned, published Art and intimacy in 2000 (at the University of Washington Press). The adaptationist approach has spawned quite a few publications in the last ten years, especially concerning the evolution of literature. Two good books on this topic is Joseph Carroll’s Literary darwinism (Routledge 2004) and the anthology The literary animal, edited by Jonathan Gottschall and D.S. Wilson (Northwestern University Press 2005).

chimp-painting.jpgIn addition to these books a number of publications dealing specifically with music have appeared very recently. The first, an anthology edited by Nils Wallin, Björn Merker and Steven Brown, entitled The origins of music (The MIT Press 2001) contains a wealth of different approaches, whereas Steven Mithen’s book The singing neanderthals from 2005 (Weidenfeld & Nicolson) promotes only one hypothesis.

As can be seen, the literature on bioaesthetics is rapidly growing and the probably only gain momentum in the coming years. It will be interesting to see if someone will attempt to synthesize research on all three questions, including research on all art forms, in one tome sometimes in the future.

-Martin

UPDATE. I have changed the embarassing mistitling of Mithen’s book pointed out by Geraldine in the comments. I have also fixed a couple of spelling errors.

There are clearly other relevent books out there which I haven’t mentioned. I encourage you all to suggest additional good titles in the comments section. I would personally be most interested in hearing of French and German books relevant to neuroaesthetics from readers speaking these languages.

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Here is a great story: human imitation has been known to be present in newborns, supporting a notion of the human race being predisposed to social interaction. However, an obvious question of whether this is also the case in non-human primates below our closest evolutionary relatives has not been asked. Until now. In an excellent study by Pier Ferrari and colleagues in PLoS Biology, imitation of facial expression is demonstrated in neonatal monkeys (that disappeared after approx. 7 days).

From ScienceDaily we can read:

Ferrari et al. tested 21 baby rhesus monkeys’ response to various experimental conditions at different ages (one, three, seven, and 14 days old). Infants were held in front of a researcher who began with a passive expression (the baseline condition) and then made one of several gestures, including tongue protrusion, mouth opening, lip smacking, and hand opening.

Day-old infants rarely displayed mouth opening behavior, but smacked their lips frequently. When experimenters performed the mouth opening gesture, infants responded with increased lip smacking but did not increase any other behavior. None of the other stimuli produced significant responses. But by day 3, matched behaviors emerged: infants stuck out their tongues far more often in response to researchers’ tongue protrusions compared with control conditions, and smacked their lips far more often while watching researchers smacking theirs. By day 7, the monkeys tended to decrease lip smacking when humans performed the gesture, and by two weeks, all imitative behavior stopped.

Here is an example from the article:

And from the abstract:

Our findings provide a quantitative description of neonatal imitation in a nonhuman primate species and suggest that these imitative capacities, contrary to what was previously thought, are not unique to the ape and human lineage. We suggest that their evolutionary origins may be traced to affiliative gestures with communicative functions.

UPDATE: Jown Hawkes has an in-depth presentation and discussion of this study.

-Thomas

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