Tuesday, November 30, 2010

Open Source GIS

If you haven't tried it lately, I recommend you give GRASS a whirl. While earlier versions were a mess of imploding modules and inscrutable dialogs, Version 6.4 has many binaries for the major platforms and lots of deep functionality. Check it out at: http://grass.fbk.eu/Mac OS X binaries are available at: http://www.kyngchaos.com/software/grass (just needs GDAL, Freetype and cairo frameworks to install -- links on the KingChaos site).

You also should check out the newest version of Quantum GIS (QGIS). The latest release (1.6.0) is "Copiap√≥" is getting to be pretty solid. http://www.qgis.org/  

While you are at it, download the newest version of Google Earth (6.0) which now boasts 3D trees. Im not sure why we need 3D trees but what the heck. Actually, the better integration of historical imagery makes this a very useful release.

Monday, November 29, 2010

Fluff-heads and Anthropology

Alice Dreger made quite a bit of news last year by exposing the American Anthropological Association Executive Committee witch hunt against Napolean Chagnon.   This year, while attending the AAA meetings (to go to the Evolutionary Anthropology Society section meetings), she got wind of the "ditch science" move the Executive Committee is now undertaking. Not one to back away from saying it like it is, Dreger describes the issue as this one:

In the messages flying back and forth, I was reminded why anthropologists refer to the annual conference as "the meetings," plural: it's because they go and meet with their own actual disciplinary types, in separate groups, so that the real scientists don't have to deal too much with the fluff-head cultural anthropological types who think science is just another way of knowing.

Not all cultural anthropologists are fluff-heads, of course. You can usually tell the ones who are fluff-heads by their constant need to look like superheroes for oppressed peoples, and you can tell the non-fluff-heads by their attention to data. But the non-fluff-head cultural anthropologists are feeling utterly beleaguered in this environment that actively denigrates science and consistently promotes activism over data collection and scientific theorizing.

You can read more about Dreger's take on the debacle in her blog on Psychology Today: http://www.psychologytoday.com/blog/fetishes-i-dont-get/201011/no-science-please-were-anthropologists

Culture Evolves and Anthropology Does Not.

While the primary association for Anthropology continues to fall into a puzzlingly empty abyss, biologists expand their authority over the core concept that once defined Anthropology: culture. The recent Culture Evolves meeting in London highlights the degree to which anthropology has handed over its raison d'être. An article in the New Scientist describes the goings-on at Culture Evolves. (Note: see Mark Collard's extensive quotes...). Is the last good anthropological treatise on culture going to be Cornealis Osgood 1951?

From: http://www.newscientist.com/article/mg20827871.500-culture-club-all-species-welcome.html?full=true&print=true

From lay-a-bed meerkats to fish traditions, all sorts of animal behaviour comes from learning as well as genes. So what makes humans different?

CULTURE: the word conjures images of nights at the opera, airy art galleries and classical architecture. Whether you consider culture and all its trappings to be elitist and intimidating or enriching and the pinnacle of civilisation, there is one point on which most people agree - culture is distinctly human. So it was quite surreal to find myself, last June, in the foyer of the Queen Elizabeth concert hall in London, in a group of 700 people, discussing the cultural lives of orang-utans, meerkats and fish.

The meeting, called Culture Evolves, was held to help celebrate the 350th anniversary of the Royal Society of London. It was an indication of just how far the scientific study of culture has come in recent years. It is little more than a decade since a landmark paper in Nature identified dozens of cultural activities in chimps, catapulting culture out of the exclusively human domain. Since then, culture in non-humans has become a hot topic, with evidence piling up that it can be found right down through the animal kingdom, even as far as insects.

All of which presents an enigma. If culture is so prevalent in the animal kingdom, why are we the only creature with traditions as complex or diverse as the cha-cha or the Japanese Noh drama? This question was debated at the meeting, with interesting answers emerging, some of which even hint at where human culture will go from here. "[The research] looks set to transform our understanding of ourselves," says meeting co-organiser Andrew Whiten of the University of St Andrews, UK.

A word about definitions before genteel readers start choking on their afternoon tea: nobody is proposing that animals have anything close to what you might call "high culture". If you want to understand what biologists mean when they refer to animal culture, forget Rimbaud, classical concerts and art appreciation: think instead about all the things humans do that go under the umbrella of cultural diversity - traditions such as languages, cuisines, fashion, ritual and games. An animal species in which distinct groups display such socially learned traditions may be said to possess culture - although some biologists still prefer not to use the C word.

The idea that culture is not exclusively human has been hotly contested for at least half a century, with proponents citing classic examples, like one troop of Japanese macaques who developed a tendency to wash their sweet potatoes in the sea before eating them. Others, however, doubted whether such traditions could be equated with culture. Things came to a head in 1999 when Whiten teamed up with a group of luminaries in the world of primatology to catalogue chimp local traditions (Nature, vol 399, p 682).

Chimp customs

Trawling through reports from over 150 years of observation of chimpanzees from seven different sites, the researchers identified 65 categories of behaviour, 42 of which varied between populations. A few of these differences could be explained by ecological factors - in four sites where there was a high risk of being attacked by predators, for example, the chimps did not build sleeping nests on the ground as they did in other places. When such instances were removed, that still left 39 areas in which different communities had distinct behaviours. These ranged from the construction and use of specific tools for termite fishing or cracking recalcitrant nuts, to idiosyncratic courtship routines and particular styles of grooming - some groups do it with one arm clasped overhead, for example. Ruling out the possibility that these behaviours were either genetically predetermined or learned by individuals through trial and error, the team concluded that they must be passed on from one animal to another via social learning, and therefore constituted cultural traditions.

The combination of so much evidence, big-name authors and publication in Nature finally persuaded many animal behaviourists to embrace the idea that culture is not exclusively human. Before long, many more creatures had gained admission into the culture club. In 2001, Hal Whitehead from Dalhousie University in Halifax, Nova Scotia, Canada, and Luke Rendell from the University of St Andrews, UK, published a paper in which they identified a variety of cultural traits in whales and dolphins, including specific songs, migratory traditions and foraging techniques (Behavioral and Brain Sciences, vol 24, p 309).

Then in 2003, Carel van Schaik at the University of Zurich, Switzerland, and colleagues, catalogued 24 cultural traditions in orang-utans. These ranged from the practice of making "dolls" from bundles of leaves to blowing raspberries at each other before bedtime (Science, vol 299, p 102). The same year Susan Perry of the University of California, Los Angeles, revealed culture in capuchin monkeys in Costa Rica, which have some truly bizarre traditions, like poking each other in the eye and sniffing one another's hands (Current Anthropology, vol 44, p 241).

Orang-utan cultural traditions range from the practice of making 'dolls' from bundles of leaves to blowing raspberries at each other at bedtime

It is clear to see why social learning would be beneficial to these species. An animal that can copy behaviour already acquired by a compatriot can pick up new skills more quickly. This is particularly advantageous in fast-changing environments, where behaviours that are hard-wired into the genes would soon become redundant. But what about more "cognitively challenged" animals - would they have the brainpower to cash-in on social learning?

It has long been known that some birds learn their songs from one another, but many researchers were sceptical that they would use social learning beyond this one specific trait. There is now convincing evidence that they do. For example, Tore Slagsvold of the University of Oslo, Norway, described at the Culture Evolves meeting how he transferred the eggs of blue tits to the nests of great tits, and vice versa. He found that the fostered chicks acquired foraging behaviours characteristic of their adoptive parents. Since both species inhabit essentially the same natural environment, this indicates that the way in which they exploit it is largely determined by culture rather than a genetic predisposition (Proceedings of the Royal Society, B, vol 274, p 19).

That's not all. Fish also learn techniques from their peers to navigate many of life's problems, from deciding what to eat and where to find food, to recognising and avoiding predators. Moving even further down the animal kingdom, there is even some evidence of social learning in insects including crickets and bees, leading some to claim that they, too, may have their own cultural traditions (Behavioral Ecology and Sociobiology, vol 61, p 1789).

Within just 11 years of Whiten and colleagues' seminal Nature paper, it has now become clear that the fundamental building block of culture - social learning - is widespread in the animal kingdom. A conundrum remains, however. If a fish with a brain the size of a petit pois is sophisticated enough for social learning, how come millions of years of evolution have only produced one species with traditions as diverse as the tango, brutalism and dim-sum?

One possible explanation, explored at the meeting, springs from the growing realisation that learning by copying is not the unalloyed good it was once thought to be. Although social learning is an efficient way of picking up information, if used indiscriminately it can be arbitrary or even harmful. An inability to abandon learned traditions could mean that animals get locked into using an inefficient strategy when environmental conditions change. Worse still, local traditions may even emerge that confer no benefits and simply put you at a disadvantage, which seems to have happened among some Kalahari meerkats.

Life is tough for these animals, and pups rely heavily on social learning to work out what is edible and how to avoid being eaten themselves, but the tendency to copy also extends to another habit with no apparent benefits. Alex Thornton at the University of Cambridge has discovered that some groups consistently get up later than others, even though this lay-a-bed tradition gives less time for foraging (Proceedings of the Royal Society B, vol 277, p 3623).

Judging when and who to copy should therefore be vital. Is this where humans steal a march over other animals? Unlike many other species, we do not merely copy our parents, but instead consider everyone around us as potential role models. This should give us more opportunities to acquire useful traditions, provided that we can work out who is most likely to possess good information.

It turns out that we are particularly skilled at making this distinction. Adults are known to choose the most successful, prestigious and knowledgeable individuals to copy. Even children are highly selective of who to trust, rather than blindly copying the people they know best, as had previously been believed. "By age 5, kids prefer information from reliable informants to familiar ones," saysPaul Harris of Harvard University, who presented work on the topic at the Culture Evolves meeting.

All of this is very sensible and clever, but there's a problem: "Every single one of these effects have previously been observed in fish," says Kevin Laland at the University of St Andrews, who studies social learning in guppies. We might like to think that we are more discriminating than a fish, but perhaps what really sets us apart from other species is not who we learn from, but how we learn.

"In animals, social learning occurs through observation," says Gergely Csibra of the Central European University in Budapest, Hungary. We, however, have a more active system of instruction that includes both teachers and learners. He has dubbed this "natural pedagogy" and believes it evolved in the human line in response to technological advances. Around 2.6 million years ago, our ancestors began making tools. As tools increased in complexity the technology became more "opaque", says Csibra. This meant that learners could not simply copy by observing, so knowledge came to be passed on by explicit demonstration, either using non-verbal techniques or the evolved trait of language. As a result, he asserts, only humans are psychologically adapted to assume the roles of both teacher and pupil (New Scientist, vol 2545, p 42).

Further evidence that the complexity of human technology pushed us to become better social learners comes from another distinctly human quirk: over-imitation. Unlike chimps and other social learners, young children copy every single step performed by a demonstrator, even ones that are clearly irrelevant. Various experiments by Derek Lyons at the University of California, Irvine, have ruled out the possibilities that kids over-imitate because they think it is expected of them, or from a desire to be like the adult demonstrator, or simply because they want to. "Over-imitation is involuntary," he says. He concludes that when children are taught a new procedure they automatically encode all the actions as causally meaningful (Proceedings of the National Academy of Sciences, vol 104, p 19751). This may sometimes lead to the reproduction of irrelevant actions, but in a world where cultural artefacts are often complex, on balance it is a useful adaptation.

All of which suggests a kind of positive feedback loop, in which the complexities of early technology pushed us to evolve better methods of social learning. These improved learning abilities then accelerated cultural transmission, ultimately pushing us towards greater and greater cultural complexity.

Runaway evolution

As powerful a driver of cultural development as technology may have been, there is inevitably a great deal more to it than that. Francesco d'Errico at the University of Bordeaux, France, andChris Stringer of the Natural History Museum in London recently turned to the archaeological record to track cultural change in prehistory. They found that cultural developments such as innovations in the way stone tools are created happened in leaps and bounds, rather than in a more gradual, steady trend. That may be because our psychology also includes a strong conservative streak.

Harris finds, for example, that children will preferentially imitate people who conform to social norms. This trait makes it difficult for new traditions to get off the ground, and outside forces may therefore be required to tip the balance in favour of innovation, d'Errico and Stringer conclude. From their study, three broad factors seem to be key: changes in climate, population growth and high levels of cultural exchange. Agriculture, for instance, is thought to have emerged 10,000 years ago partly as a result of increasing population pressure in the eastern Mediterranean.

If these factors shaped cultural evolution in the past, can we make any predictions about the future? With increasing opportunities for cultural exchange via the internet and globalisation, perhaps we should expect to see runaway cultural evolution? "There are countervailing forces," says Mark Collard from Simon Fraser University in Burnaby, British Columbia, Canada, who spoke at the Culture Evolves meeting about what causes cultural complexity. On the one hand, he points out that the internet and globalisation allow social information to be shared by large numbers of people across the world who could never have connected before. That could lead to a breakdown in cultural barriers as different traditions merge together and begin to lose some of their individuality. Look at any social networking site, however, and you'll see that people still form distinct cliques - more so than ever, in fact, since it's now much easier for individuals to hook up with others who share their passions, no matter how far-out these may be. "The internet allows groupishness," says Collard.

Throughout human evolution, people have used traditions and cultural practices to distinguish themselves from other camps. "Humans have a long history of erecting barriers," says another conference delegate, evolutionary biologist Mark Pagel of the University of Reading, UK. Cliques on the internet are no different, each propagating their own distinct trends and fashions. Our tendency for groupishness may be a somewhat unappealing trait in many circumstances, but it may just be the saving grace that allows our amazing cultural diversity to flourish in the future.

Kate Douglas is a features editor for New Scientist

Friday, November 26, 2010

Whither Anthropology as a Science?

There must have been some buzz this past week at the AAA meetings in New Orleans. Peter Peregrine sent an email out to members, past and present, of the Society for Anthropological Sciences (SAS) (for which Peregrine is President). Quite rightly, he was massively alarmed about a motion the Executive Committee of the AAA has taken in revision of the Association's mission statement. In essence, the committee has expunged all references to Anthropology as a science as part of their "Long Range Plan." He has called for a response to the AAA in the form of a resolution for the SAS. I assume there will be other responses as well. Here is what is being proposed:

Mission Statement in the new LRP (additions underlined; deletions in strikethrough)

Section 1. The purposes of the Association shall be to advance anthropology as the science that studies public understanding of humankind in all its aspects, through This includes, but is not limited to, archeological, biological, ethnological, social, cultural, economic, political, historical, medical, visual, and linguistic anthropological research; The Association also commits itself and to further the professional interests of American anthropologists, including the dissemination of anthropological knowledge, expertise, and interpretation. and its use to solve human problems.

Section 2. To advance the science of anthropology the public understanding of humankind, the Association shall: Foster and support the development of special anthropological societies organized on a regional or functional basis; Publish and promote the publication of anthropological monographs and journals; Encourage anthropological teaching, research, and practice; act to coordinate activities of members of the Association with those of other organizations concerned with anthropology, and maintain effective liaison with related sciences knowledge disciplines and their organizations.

Section 3. To further the professional interests of anthropologists, the Association shall, in addition to those activities described under Section 2: Take action on behalf of the entire profession and integrate the professional activities of anthropologists in the special aspects of the science; and promote the widespread recognition and constant improvement of professional standards in anthropology.

When I first read this, I thought "well, that is at least being honest." In many ways, Anthropology has survived in some of its least flattering forms due to the impression that many people that "doing Anthropology" is somehow necessarily "scientific." One might think, for example, "why are these people 'specialists' and getting paid to do this?" if science didn't have something to do with it. Here, science is confused with "systematic" but the gist is basically the same (i.e., assuming something systematic produces some regular and recognizable product). Of course, so much of what anthropology does do really isn't science, not even in its most empiricist and "systematic" form. Looking over the set of papers presented at the AAAs, one sees largely an ad hoc assortment of viewpoints, beliefs, assertions, claims, stories, tales, re-envisionings, interpretations, polemics, rallies, hubris, hue, and so on. Little of it is even empiricist in its crass form and even less is "systematic" in any recognizable way.

But on second thought, the idea that the people who believe that anthropology cannot or should not be a science can entirely co-opt the entire discipline is pretty outrageous. This kind of gerrymandering of the mission basically makes it necessary for those who believe that there are ways of generating theory-laden falsifiable accounts of the world in terms of culture (and other basic anthropological concepts) must work under a different banner than anthropology. But why should this be - we (science focused individuals) are anthropologists in the best sense of the discipline and its tradition. The anti-science theme is something early anthropologists fought against -- and is a relative late comer to the party.

And to make things worse, this new "mission" for anthropology seems only to further its the association's self-perpetuation interests without providing any particular reason for existing in the first place. The mission statement is insular, self-fulfilling and largely pointless. Deleting the goal of "solve human problems"? Uh, isn't this defining the mission of the AAA as simply promoting anthropology to simply replicate itself in whatever random form it happens to take? While ideas are all conceptually equal, some have more use than others when goals such as "solve human problems" are explicit. So removing this clause simply means that everyone doing anything is all okay. While this might not seem like such a big deal (i.e., who cares?), the reality is that resources are always finite and decisions have to be made. Plus, the "everything goes" kind of mentality seems to breed idiotic, political minded, self-congratulatory, post-hoc rationalized initiatives like the AAA Executive Committee's earlier witch hunt after Napoleon Chagnon.

Personally, I decided long ago to never send another dollar towards the AAA -- the journal sucks, the meetings consist of endless parade of dour, self-serious blathering and the association is a platform for mindless PC agenda and attacks on the folks struggling to make anthropology have a purpose. This change in the mission largely serves to confirm my earlier feelings about the AAA. Still, I cannot help but feel even more abandoned and disrespected by many of my academic colleagues.

Related link: http://chronicle.com/article/Anthropologists-Look-for/125464/

Want to tell the AAA Executive Committee what you think about this? Email them by clicking here....

Other discussions on this issue:





Thursday, November 18, 2010

Evolutionary and Interpretive Archaeologies: A Dialogue

While I am not sure what the dialogue is going to consist of, colleague Ethan Cochrane and co-editor Andrew Gardner are on the brink of publishing a new edited volume entitled " 512w2voCzeL._SL160_.jpgEvolutionary and Interpretive Archaeologies: A Dialogue" (December 1, 2010, Left Coast Press). From what I remember, this book started as a colloquium series while Ethan was teaching at UCL. Given the radically (and explicit) different epistemologies (falsification vs. plausibility as a means of evaluation), I am not sure what the common ground for this dialogue will be (i.e., is it just claiming that plausibility is "good enough"?). If the book serves to demonstrate the critical differences between these kinds of explanatory products, it will be of use. I look forward to reading it.

Tuesday, November 16, 2010

The Statues That Walked now on Amazon (Pre-order)!

While we are still doing edits on the manuscript, our Rapa Nui/Easter Island book has now become available on Amazon for pre-orders. Pre-order your copy here! Order now and we will throw in a free set of steak knives or a personalized signed note!

Friday, November 12, 2010

Structure From Motion

Part of our interest in acquiring a UAV is to expand our ability for quickly generating high resolution topographic data. Traditionally, this process is time-consuming and (as a result) expensive. I've spent a number of summers collecting elevation data over archaeological deposits (Easter Island, Panakton, Greece, Harappa..) and even after weeks of tedious point collection (and thousands of points measured across the ground), the resulting topographic map is less-than-desirable. The problem is one of data density -- 1000 points can be collected pretty quickly (esp. with a modern total station) but over any sized area the density of the points is pretty low per unit area. Take a 100x100 meter area -- it would take 10000 points to have a point every meter. 1000 points is only a 10% sample of that. Now one can be "smart" and sample more densely in areas with greater changes in topography but then some of the algorithms for building the iso-contours will produce odd "artifacts" -- many assume even coverage of points. Even with 10000 points, you end up with a fairly crude representation of the surface - which might work at the scale of the entire deposit, but is too crude for examining any specific area. To make matters worse, in order to increase resolution by say 2x (i.e., to get 50 centimeter resolution), you have to quadruple the sample size.

New developments in laser scanning and LiDAR provide a great means for changing the data generation to cost relationship. However, the technology is pretty new and not entirely cheap. Ultimately, LiDAR provides a great solution for mapping landscape scale features (e.g., entire states) and produces information about the bare ground (so can provide topographic data under tree canopies -- often where we know the least about the archaeological record [e.g., bayous]). But for a project specific survey LiDAR can be overly expensive or simply impossible (since getting plane to some places with the right set up for laser scanning is not always possible -- e.g., Easter Island). Here, land-based laser scanners are handy but these cost about $100,000 to start and typically require trained operators. Renting them can be as much as $20K a month.

From a cost perspective, generating topographic information using "structure from motion" based techniques is quite appealing. This approach makes use of basic imagery collected from inexpensive cameras. Surfaces are calculated based on shared points in photos, determining the position of the camera from images and calculating where the points that are shared must be in space in order that they were captured by the camera. It is an ingenious technique - using some cool math. Noah Snavely, a PhD student (now an assistant professor at Cornell) at the University of Washington developed some of the basic software for doing this (originally part of a "photo tourism" project in which photos taken by tourists of locations can be combined to build a 3-D model of the scene - without knowing before hand where the cameras were placed and under a variety of lighting and other conditions). This project has morphed into Photosynth, the free Microsoft project that automates this project and is Silverlight based.

From a topographic perspective, the "structure from motion" approach is pretty slick - using just a bunch of photos made on cheap digital cameras, one can produce detailed representations of surfaces. Actually, the product is a 3D point cloud that has excellent relative accuracy. Increasing resolution simply means more photos - and whole swaths of areas can be covered with just a click of the shutter. Getting absolute position requires georectification - a separate process (which I can detail elsewhere). Commercial products, though, can take geotagged photos and create a georeferenced point cloud. We have a license for Microsoft's Geosynth - a professional version of Photosynth that can take HD video and geotags to produce high density georeferenced point clouds.

One of the problems with Geosynth, however, is that it doesn't produce some basic products such as a simple (georeferenced) photomosaic. Instead, there focus is on creating "synths" -- a cool product but entirely unintegrated with other kinds of spatial tools (e.g., GIS). Last week, we saw a demo of another software package that produces mosaics using the same kinds of algorithms as Geosynth -- 2d3's TacitView. 2d3 is a small software company located in Irvine. TacitView (and TopoMap, their 3D product). The software is slick and well-done - a great interface and the products are well-suited for integrating into GIS software. We are going to do a demo of this software soon to see how it compares to Geosynth.

Thursday, November 11, 2010


We finally made the plunge and send out a PO for a UAV (unmanned aerial vehicle). Of course, we are not talking about a GlobalHawk or a Predator drone (but man, those would be cool -- do field mapping on the other side of the planet from a desktop... drool). We are looking to get a (1) robust (2) self piloting (3) portable (4) minimally dangerous to others (5) robust (6) really robust (7) affordable platform for generating high resolution imagery of land surfaces that can be turned into georectified orthophotos (ideally with multi-spectral capability) and high resolution topographic information. The UAV we want has GPS guidance, returns to launch location, and will allow systematic coverage of a landscape. This rules out most helicopter solutions that specialize in "overhead" type coverage. While there are *many* fixed-wing based UAVs out there for potential sale, most of them tend to be military oriented and thus too expensive or unattainable (i.e., why bother with a university when uncle sam will buy a billion dollars worth of your product).

We initially had made a deal with DraganFly to buy their Tango platform. In fact, we went so far as to do a PO for their fixed wing system. However, we found out a number of details (1) DraganFly isn't really making Tango type platforms, at least for the near future as they are focusing almost entirely on the helicopter type units (2) when they list "gps guidance" in their specs what they really mean is that they have a "solution" for gps guidance provided by another company that requires an entirely separate license and other negotiation. In other words, they simply can't deliver a fixed wing system. Bogus.

We ended up going with Gatewing, a Belgian startup company that has created a UAV system ideally suited to our purposes: generating systematic imagery to be used in creating orthophotos and terrain maps. Their system is the "X100" and meets all of our requirements -- and will ship on December 13th! Whoohooo. At any rate, this platform should gives an excellent means for generating topographic maps of study areas and for producing detail photographic imagery. We look forward to working with Gatewing and exploring this UAV's capability.


Monday, November 1, 2010

Philosophical Transactions of the Royal Society B

Ethan just let me know that the special issue of the Philosophical Transactions of the Royal Society B -- edited by James Steele, Peter Jordan and Ethan Cochrane is now available online.

Cultural and linguistic diversity: evolutionary approaches

Cover image

Recent work has shown that language and other human cultural practices can be considered as evolutionary systems operating on the Darwinian principle of 'descent with modification'. An emerging field of interdisciplinary science builds on phylogenetic and other methods adopted from biology, and adapts them to explain the transmission histories of suites of cultural traits (whether languages, social structures, or artefacts). This theme issue asks what social processes lead to coupled and decoupled transmission of different cultural traits or suites of traits, and how their transmission histories can be estimated retrospectively using quantitative methods. Understanding the factors affecting descent histories is central to explaining how cultural diversity arises and how it is maintained. These questions are of interest and relevance not just to social science and evolutionary theory, but also to planners working on topics such as endangered language maintenance.