Science – Page 23 – Replicated Typo

Cultural innovation, Pleistocene environments and demographic change

It is well documented that Thomas Robert Malthus’ An Essay on the Principle of Population greatly influenced both Charles Darwin and Alfred Russell Wallace’s independent conception of their theory of natural selection. In it, Malthus puts forward his observation that the finite nature of resources is in conflict with the potentially exponential rate of reproduction, leading to an inevitable struggle between individuals. Darwin took this basic premise and applied it to nature, as he notes in his autobiography:

In October 1838, that is, fifteen months after I had begun my systematic inquiry, I happened to read for amusement Malthus on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The results of this would be the formation of a new species. Here, then I had at last got a theory by which to work.

The interaction of demographic and evolutionary processes is thus central in understanding Darwin’s big idea: that exponential growth will eventually lead to a large population, and in turn will generate competition for natural selection to act on any heritable variation which conferred a greater fitness advantage. Under these assumptions we are able to interpret the evolutionary record of most species by appealing to two basic causal elements: genes and the environment. As we all know, in most cases the environment generates selection pressures to which genes operate and respond. For humans, however, the situation becomes more complicated when we consider another basic causal element: culture. The current paper by Richerson, Boyd & Bettinger (2009) offers one way to view this muddied situation by delineating the demographic and evolutionary processes through the notion of time scales:

The idea of time scales is used in the physical environmental sciences to simplify problems with complex interactions between processes. If one process happens on a short time scale and the other one on a long time scale, then one can often assume that the short time scale process is at an equilibrium (or in some more complex state that can be described statistically) with respect to factors governed by the long scale process. If the short time scale and long time scale interact, we can often imagine that at each time step in the evolution of the long time scale process, the short time scale process is at “equilibrium.” A separation of time scales, if justified, makes thinking about many problems of coupled dynamics much easier.

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Phylogenetics, Cultural Evolution and Horizontal Transmission

For some time now, evolutionary biologists have used phylogenetics. It is a well-established, powerful set of tools that allow us to test evolutionary hypotheses. More recently, however, these methods are being imported to analyse linguistic and cultural phenomena. For instance, the use of phylogenetics has led to observations that languages evolve in punctuational bursts, explored the role of population movements, and investigated the descent of Acheulean handaxes. I’ve followed the developments in linguistics with particular interest; after all, tracing the ephemeral nature of language is a daunting task. The first obvious road block is that prior to the invention of writing, the uptake of which is limited in geography and history, language leaves no archaeological record for linguists to examine. One particular note I’d like to make is that when Charles Darwin first formulated his theory of natural selection, he took inspiration from linguistic family trees as the basis for his sketch on the evolutionary tree of life. So it seems rather appropriate that phylogenetic approaches are now being used to inform our knowledge regarding linguistic evolution.

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The Movius Line represents the crossing of a demographic threshold

When examining the dispersal of Pleistocene hominins, one of the more fascinating debates concern the patterns of biological and technological evolution in East Asia and other regions of the Old World. One suggestion emerging from palaeoanthropological research places a demarcation between these two regions in the form of a geographical division known as the Movius Line. Specifically, the suggestions that initially led to the Movius Line were based on observations of differing technological patterns, namely: the lack of Acheulean handaxes and the Levallois core traditions in East Asia.

Since Hallam L. Movius’ initial proposal, the recent discovery of handaxes within East Asia have led to suggestions that the Movius Line is in fact obsolete. Suggesting this may not in fact be the case is a recent paper by Stephen Lycett & Christopher Norton, which highlights three central points coming from a growing body of research: 1) “several morphometric analyses have identified statistically significant differences between the attributes of specific biface assemblages from east and west of the Movius Line”; 2) “The number of sites from which handaxes have been recovered in East Asia tend to be geographically sparse compared with many regions west of the Movius Line”; 3) “‘handaxe’ specimens tend only to comprise a small percentage of the total number of artefacts recovered, a situation that contrasts with many classic Acheulean sites in western portions of the Old World, where bifacial handaxes may dominate assemblages in large numbers”.

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The brain–artefact interface (BAI): a challenge for archaeology and cultural neuroscience

Just found an interesting paper on cultural neuroscience and the extended mind. Some of you might remember the author, Dr Lambros Malafouris, from Seed Magazine’s Revolutionary Minds series. I plan on providing a more thorough examination of paper at a later point. In the meantime, check out the abstract:

Cultural neuroscience provides a new approach for understanding the impact of culture on the human brain (and vice versa) opening thus new avenues for cross-disciplinary collaboration with archaeology and anthropology. Finding new meaningful and productive unit of analysis is essential for such collaboration. But what can archaeological preoccupation with material culture and long-term change contribute to this end? In this article, I introduce and discuss the notion of the brain–artefact interface (BAI) as a useful conceptual bridge between neuroplastisty and the extended mind. I argue that a key challenge for archaeology and cultural neuroscience lies in the cross-disciplinary understanding of the processes by which our plastic enculturated brains become constituted within the wider extended networks of non-biological artefacts and cultural practices that delineate the real spatial and temporal boundaries of the human cognitive map.

Some links #3

Of my random meanderings around the Internet, I think the coolest thing I’ve seen this past week certainly has to be the Steampunk sequencer:

With that out of the way, here are some links:

In somewhat keeping with the theme from some links 2’s look at primitive writing systems, comes a post from the excellent Not Exactly Rocket Science: An 60,000-year old artistic movement recorded in Ostrich egg shells.
More on topic of writing systems is Kevin Mitchell’s post on Why Johnny can’t read (but Jane can). Essentially, the post is asking: why dyslexia is about twice as common in boys as in girls?
Is synaesthesia a high-level brain power? I’m not sure, but that’s the question being asked over at New Scientist.
Science Daily claims: Simple math explains dramatic beak shape variation in Darwin’s finches. Key paragraph: “Using digitization techniques, the researchers found that 14 distinct beak shapes, that at first glance look unrelated, could be categorized into three broader, group shapes. Despite the striking variety of sizes and shapes, mathematically, the beaks within a particular group only differ by their scales.”
Pamelia Brown has 50 Fascinating Lectures All About Your Brain. I’ve only managed to watch one of the videos (see below), so I’m certain that there is at least one fascinating lecture…
Be sure to check out the Kahn Academy — a not-for-profit organisation that provides some great educational resources. For those of you interested in demographics and the quantitative analysis of movement, then here’s a whole section on differential equations.
Dormivigilia provides a brief overview of a paper examining the neural origins of handedness.
Razib Kahn over at GNXP has an in-depth discussion about the convergent evolution of skin pigmentation: OCA2 makes East Asians white and Europeans blue.
How reliable are fMRI results? Another question I’m not so sure about. However, Prefrontal.org has a full paper on providing something of an answer. The key sentence: “the results from fMRI research may be somewhat less reliable than many researchers implicitly believe.”
Jonah Leher has a lengthy, interesting piece over at the New York Times, asking: Is depression an adaptation? Probably not. But for a more balanced perspective, read Neurocritic’s brilliant analysis of the topic.
Laelaps writes about a paper claiming the discovery a 4,300 year old chimpanzee nut-cracking site: Uncovering the “Chimpanzee Stone Age”.
Lastly, Jeff Elman, UCSD professor of cognitive science and co-director of the Kavli Institute for Brain and Mind, presents a lecture on some of the latest research in our ability to use language and why it is so far removed from other animal communication systems:

Culture and the human genome: a synthesis of genetics and the human sciences

Humans are immersed in culture from birth. It is so fundamental to our experience, and what it means to be human itself, yet we often overlook the consideration that “cultural practices might have transformed the selection pressures acting on humans” (Laland, Odling-Smee & Myles, 2010, pg. 137).

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Some Links #2

This week we all get to learn a new word, the potential origins of the written word and killing at a distance. Enjoy!

Archaeogenetics — yet another call for multi-discipline research? Yes, and the latest issue of Current Biology has a load of free (yes, free) papers on archaeogenetics. I haven’t had chance to read all of them, but it’s certainly worth checking out these two: Archaeogenetics — towards a ‘New Synthesis’? and The Genetics of Human Adaptation: Hard Sweeps, Soft Sweeps, and Polygenic Adaptation.
New Scientist discusses research into the discovery of primitive writing systems from 35,000 years ago. Obviously, this has massive implications for those of us who thought the seeds of writing were only starting to emerge approximately 5000-years-ago. The key paragraph: “What emerged was startling: 26 signs, all drawn in the same style, appeared again and again at numerous sites (see illustration). Admittedly, some of the symbols are pretty basic, like straight lines, circles and triangles, but the fact that many of the more complex designs also appeared in several places hinted to von Petzinger and Nowell that they were meaningful – perhaps even the seeds of written communication.” They’ve also got some pretty pictures.
If you’re looking for good news regarding the economy, then don’t go over to Washington’s Blog. He has a short post on Alan Greenspan’s assertion that we’re in the worst financial crisis ever.
I’ve been reading a lot of articles over at the brilliant blog, Emergent Fool. Of particular interest are posts relating to my recent article on cumulative culture and coordinated behaviour: Rafe Furst discusses three types of cooperation, cultural agency and complex systems concept summary. Meanwhile, Plektix writes about how human cultural transformation was triggered by dense populations.
Emergent Fool also led me to an in-depth essay by Professor Yaneer Bar-Yam on emergence and complexity: complexity rising: from human beings to human civilization, a complexity profile.
Lastly, American Scientist has a podcast on the evolution of the human capacity for killing at a distance. Here’s the summary: “Duke University anthropologist Steven Churchill presents his research on the evolutionary origins of projectile weaponry, and how weapon use changed interactions between humans and other species—including, perhaps, the Neandertals.”

Cumulative Culture Evolved to Rapidly Coordinate Novel Behaviours

In the deliberations over humanity and its perceived uniqueness, a link is frequently made between our ability to support a rich, diverse culture and the origin of complex human behaviour. Yet what is often overlooked in our view of these two, clearly connected phenomena is the thread that weaves them together: the ability to coordinate behaviour. We need only look at the products of our culture, from language to religion, to see that any variant we may deem successful is contingent on coordinating the behaviour of two or more individuals. Still, what is truly illuminating about this ability is that, far from being a uniquely human feature, the ability to coordinate behaviour is ubiquitous throughout the many organismal kingdoms.

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Guns, Germs and Predictable Reviews

If, like me, you generally like the Guardian’s science features, then please avoid reading Tim Radford‘s book club discussion of Jared Diamond‘s Guns, Germs and Steel. Ever since I noticed this book was on the Guardian’s reading list, it’s been an ongoing curiosity of mine as to how they will tackle the subject. Mainly because Diamond’s book, along with Richard Dawkins’ The Selfish Gene, urged me to move into studying evolution. Sadly, and perhaps not very surprisingly, you get little from the discussion bar an unequivocal acceptance of Diamond’s central thesis: that of environmental determinism.

Nowhere is there a mention of ideas that stand somewhat in opposition to Diamond’s, such as those in the 10,000 Year Explosion. Namely, the consequences of agriculture on recent human evolution, and the growing mountain of evidence supporting the contention that different human populations have adapted to their local environments.

And just to be clear: I think Diamond’s book is a well-written, scholarly account of human history, and it’s influence is not to be understated. But I also think he overlooked a large portion of the argument.

How Culture Shaped The Human Genome

The study of culture, cultural evolution, gene-culture coevolution and niche construction have all received much more attention over the last decade. So it’s nice to see Nature taking on-board a fascinating review by Kevin Laland, John Odling-Smee and Sean Myles about how culture shaped the human genome: bringing genetics and the human sciences together. It’s really worth reading for anyone interested in the interactions between biology and culture. In particular, I was pleased to see them put forward the notion of culture having accelerated recent evolution, contra Stephen J. Gould’s claim that “there’s been no biological change in humans for 40,000 or 50,000 years”. Here’s the abstract:

Researchers from diverse backgrounds are converging on the view that human evolution has been shaped by gene–culture interactions. Theoretical biologists have used population genetic models to demonstrate that cultural processes can have a profound effect on human evolution, and anthropologists are investigating cultural practices that modify current selection. These findings are supported by recent analyses of human genetic variation, which reveal that hundreds of genes have been subject to recent positive selection, often in response to human activities. Here, we collate these data, highlighting the considerable potential for cross-disciplinary exchange to provide novel insights into how culture has shaped the human genome.