information

Simon Armitage and colleagues [1] describe archaeological remains from Jebel Faya, in the United Arab Emirates. The assemblages come from a rock shelter in the mountain, which is around 100 km south of the Straits of Hormuz, entry to the Persian Gulf. Below Bronze Age and later remains, are three Paleolithic units. The oldest (assemblage C in the paper) is dated by OSL to the last interglacial, around 125,000 years ago. My comments here are more note-like than usual; this topic opens a window into some work we've been recently doing.

The authors' main conclusion is that the oldest assemblage displays technical similarities to East African archaeological assemblages, which are not present in the archaeology of the Levant either before or after this time. We have to dig into the supplementary material to the paper to get a good account of the technical similarities:

Technologically, this assemblage has general links to East Africa (S3 S4) while showing none of the technological traits characteristic in the contemporaneous Levantine Mousterian (S5). As in the early Middle Stone Age (MSA) of East Africa, Assemblage C exhibits three profoundly different reduction strategies: bifacial, volumetric blade, and radial Levallois. This combination is unknown in the Levant after about 200 ka, where there is no bifacial reduction and the Levallois method is largely limited to unidirectional converging. The latter produced large numbers of Levallois points, which are absent from Assemblage C.

For a layman's description of the result from coauthor Anthony Marks, I can recommend Katherine Harmon's account at Scientific American's website.

I like the observation, but I think we should be cautious about it. The basic idea is that African assemblages display three different strategies early in the reduction sequence, none of which are evident in Levantine assemblages of equivalent age.

Reduction sequences and conservatism

Yesterday I talked over this concept with my graduate student Marc Kissel. I find it very interesting that the authors focused on initial reduction stages as elements of technical similarity. They thereby assume much about the cultural transmission of the reduction sequence.

It seems reasonable that the initial steps of a reduction sequence -- from quarrying through early core shaping -- should be conservative. Early stages necessarily constrain the later steps toward finished tool production, so that a skilled toolmaker who wants to carry out the later stages of a reduction sequence has first to get the early steps right.

Paradoxically a naive learner may be ill-equipped to attend to the importance of these first steps, compared to later steps where the preform is more readily identifiable by its physical configuration. Within a social group, the early steps of reduction may well be carried out by other people, including less-skilled artificers. The best toolmaker may go to the quarry himself, but often he may call on someone less skilled to carry out the initial reduction, or may be forced to work with partially exhausted cores from earlier attempts.

I'm willing to hazard a guess that the social learning that enables tool manufacture would exert a bias toward low error rates early in the reduction sequence. We can consider a biological analogy -- early embryonic development is more strongly conserved across taxa (and phyla) than later development. Changing something early in a developmental sequence may make later events impossible. If I'm right, the argument by Armitage and colleagues should have some force -- finding that the early stages of the reduction sequence are shared among sites should be a better indicator of relationship than most archaeological indicators.

But Armitage and colleagues' conclusion has force just to the extent that we accept two proposals: (1) that we understand the technical variation in the Levant, and (2) that independent development of the early-stage reduction strategies in the Jebel Faya assemblage is unlikely.

These proposals hang together. The Levant is richly documented across the period before and after the last interglacial, moreso after OIS 6 (around 130,000 years ago) than before. These assemblages were directed toward convergent removal of Levallois points. I'm not immediately in a position to discuss the variation within these assemblages, but the question strikes me as crucial. Although the archaeological record from this area is relatively dense, like all places it samples only a small fraction of the actual groups that must have existed at the time -- to use a genetic comparison, the record has high coverage over a very small fraction of the regional behaviorome.

Was independent invention of these early-stage reduction strategies likely? The answer depends on whether a particular early-stage reduction strategy is merely rare in the large Levantine sample, or entirely absent. If such a strategy (in this case, foliate reduction) occurs at all, we can infer that its invention was possible, if not likely. With assemblage C at Jebel Faya, we are considering the cultural tradition represented by 500 artifacts. If we treated these as a random sample of the Levantine record, they are exceedingly unusual, no doubt. But random sampling across an entire record isn't the correct comparison; we want some equivalent sampling of the cultural information in terms of time and space.

The paper's conclusion that Jebel Faya represents an incursion of African-derived technical traditions into the Arabian peninsula depends on these assertions. I don't have strong feelings about them, but I think we should work to get a better statistical understanding about the issue. I am singularly unimpressed when archaeologists assert that one assemblage "resembles" another on purely typological grounds. Typological similarities may result from many constraints other than cultural information, and rare appearances actually carry a lot of information about them.

Out of Africa early

Now, what about this "southern route" business? I say it's a year behind the times. The entire reason for the "southern route" hypothesis was to explain how Africans could have left Africa 70,000 years ago without being stopped by Neandertals in the Levant. Sail them around the southern coast of Asia, and you can get them early into SE Asia and Australia without mixing with those darned Neandertals.

We obviously don't need to rule out Neandertal interbreeding anymore. We know it happened, most likely in West Asia. Putting Africans into the Levant during the last interglacial isn't a bug, it's a feature. We need contact between moderns and Neandertals in this area to explain the genetic data.

The dates may seem like more of a stumbling block. If we accept that a major out-of-Africa movement was underway by 70,000 years ago, we are going to have a hard time explaining why the Levant seems to have been entirely uninfluenced by it.

But a 70,000-year-long chronology, based on estimates of mtDNA haplogroup divergences, is already out of kilter with the majority of evidence. Nuclear DNA suggests a substantially longer timescale, which would derive non-African and sub-Saharan populations from common ancestors before 140,000 years ago. Depending on the amount of mixture among these populations and the mutation rate we adopt, these populations may have begun to differentiate very early in the Middle Stone Age.

It's hard to account for the diversity of people outside of Africa with a short migration timescale. People outside Africa are around 20 percent more inbred than sub-Saharan Africans, but they don't look like they underwent any sudden severe bottleneck. Even accounting for the mixture with archaic people like Neandertals and Denisovans, much of the variation of Middle Pleistocene humans (still present in Africa) just didn't get into non-Africans.

I would propose a movement of MSA Africans into West Asia before the last interglacial as a model that provides a good fit to these data. An early movement followed by long interactions in this limited area would explain so much of the population structure and morphological variation of MSA Africans wasn't represented in the people who peopled Eurasia. A substantial delay between the initial entrance into West Asia and the dispersal to Europe and the rest of Asia would explain why the later archaeological transitions in those regions have no sign of immediate technical or cultural links to the MSA. It would also explain why the initial "modern" humans outside Africa share few if any derived morphological features with Africans after 100,000 years ago.

The anatomy of the Skhul and Qafzeh samples suggests that an African incursion into the Near East did occur before 100,000 years ago. Many paleoanthropologists have supposed that this early incursion did not persist, even locally. The later Levantine sample includes individuals with more Neandertal resemblances, chiefly Amud and Kebara. But each of the later specimens shares several traits with early modern humans from Skhul or Qafzeh. Indeed there is no clear constellation of derived traits that sorts the Skhul-Qafzeh sample cleanly from Tabun 1 and the later Levantine specimens. I just don't think this skeletal record poses any problem for the idea of a long interaction of populations in this area -- especially if we extend the focus from the Levant into the Arabian peninsula and Persian Gulf region.

The strongest reason to suppose that an African incursion was extinguished is not the skeletal record but instead the mtDNA timescale. I can refer readers to the paper by Endicott and colleagues [2], which discusses a range of mutation rate estimates and their effects on the origin of macrohaplogroups M and N, the key ancestral non-African lineages. Current estimates unanimously suggest that these clades originated within the last 75,000 years. By itself, this would suggest that the mtDNA common ancestors of non-Africans and sub-Saharan African populations diverged shortly before that time.

I keep coming back to this, because the mtDNA just seems so out of line with the autosomal and X-chromosome picture. I regard this as a serious sticking point and hesitate to just wave it away. As I suggested to Charles Choi, the resolution may involve a time of isolation outside Africa during which the ancestors of non-Africans lost heterozygosity (and became enriched for the later mtDNA clades M and N). Or maybe we just have the mtDNA clock wrong -- the large revisions of the Neandertal-human mtDNA divergence in the light of developing evidence don't inspire confidence about the timing of internal nodes to the human mtDNA tree.

The early archaeological assemblage from Jebel Faya strikes me as consistent with a model of early dispersal from Africa, but not especially good evidence for it. The outstanding question is whether the early reduction strategy is a behavioral trait that provides good evidence about biological relationships. I see the logic but think that it is tenuous.

The model obviously is relevant to the question of an early presence of African-derived modern humans in India. If we combine the presence of an African-derived population in eastern Arabia with the large exposed Persian Gulf region during the last interglacial, this begins to look like a large habitable region with easy land connections to the Indus River valley. But the Indian subcontinent would potentially have been home to a very large population of ancient humans. I doubt that an occupation across the large area of West Asia plus the Indian subcontinent would have enabled the substantial reduction of heterozygosity that we see in present-day non-Africans.

References

I read Chris Anderson's book because it was, well, "Free". The book's thesis is simple: Sometimes people profit by giving things away.

I have been, for several years now, making scientific knowledge available for no cost to any readers who care to come by my site. In academic circles, this practice is ordinarily considered to be insane. Therefore, whenever I come across anything explaining why blogging isn't such a stupid idea, I put it right into my files. That's for Luddites on future promotion committees.

How do I review the book without making points like a Slashdot comment thread?

Somewhere in the book, Anderson wrote his plan for making money from Free: Get businesses to pay for the Chris Anderson "Free" seminar. The short business profiles and catchy anecdotes in the book were pretty well crafted as advertisements for the seminar. But beneath the chrome, there are some interesting -- sometimes wacky -- ideas about the nature of human economic interactions.

Anderson describes the $10,000 wager between economist Julian Simon and Paul Ehrlich. Simon believed that commodity prices would not rise over the long term, betting that the "substitution effect" would spur people to find new technological solutions to replace expensive raw materials, thus lowering the commodity prices. Ehrlich believed that resource shortages were inevitable as population and economic pressures grew. In 1990, Simon collected on the bet, as the five commodity metals chosen by the two had all fallen, many substantially.

Others have cast this story as a parable about bad predictions, or the inherent fallacy of future pessimism. Anderson gives the story a sociobiological spin:

Humans are wired to understand scarcity better than abundance. Just as we've evolved to overreact to threats and danger, one of our survival tactics is to focus on the risk that supplies are going to run out. Abundance, from an evolutionary perspective, resolves itself, while scarcity needs to be fought over. The result is that despite Simon's victory, the world seemed to assume that Ehrlich, on some level, was still right.

As [Wired's Ed] Regis noted, "Simon complained that, for some reason he could never comprehend, people were inclined to believe the very worst about anything and everything; they were immune to contrary evidence just as if they'd been medically vaccinated against the force of fact." Ehrlich's gloomy predictions continued (and continue) to have influence. Meanwhile Simon's own observations seem to be of interest only to commodities traders (49-50).

If we really want to explain the phenomenon of "Free", we need to turn to psychology and sociology. At several points in the book, Anderson does connect to these fields -- mentioning the "Dunbar number" in the context of MySpace "friends", Lewis Hyde's work The Gift in the context of non-monetary economies, and Abraham Maslow's "Theory of human motivations" in the context of why bloggers write for free. But Anderson's goal is not to explain, but to popularize. So his use of academic sources is, well, eclectic. The "Dunbar number" is mostly an anthropological urban myth. There's a very deep literature on the gift in ethnology. Sure, there's no market for Mauss seminars on Anderson's lecture circuit, but there are some entertaining classic stories about confusion, gifts, and cross-cultural contacts.

Anderson's theme simplifies this complexity of social interactions into a binary:

There is a reason why economics is defined as the science of "choice under scarcity": In abundance you don't have to make choices, which means that you don't have to think about it at all (50).

There's an anthropological claim -- that humans are "wired" as a "survival tactic" to perceive scarcity. It makes a good story. But is it true?

Human lives are long. Sure, there are some essential resources so abundant that we don't need to think about them -- air, for example. But most resources vary over time or space. People have always needed to consider whether to stay or move, whether to hunt today or wait until tomorrow, to gather more firewood or risk the cold. It's the ant and the grasshopper.

We might imagine a version of the Ehrlich-Simon bet during the Pleistocene. Imagine humans occupying a few abundant habitats with plenty of food. As the population grows, they put pressure on these habitats. What happens? On the Ehrlich side, resource scarcity might trigger a demographic crisis, with hunger, warfare, and a population crash. On the Simon side, people might expand their behavioral niche, moving into less favorable habitat with more complex cultural adaptations.

Humans are tricky creatures, and our potential for increasing complexity depends on the level of complexity we've already reached. Only some parts of a complex system may be amenable to measurement. Anderson points out this problem from the standpoint of business information technology:

When your phone company tells you that your voice mail box is full, that's artificial scarcity -- it costs less than a nickel to store one hundred voice messages, and the average iPod could store thirty thousand of them (voice messages are recorded at lower quality than music, so they take less space). By forcing subscribers to take the time to delete voice mails, the phone companies are saving a little money in storage costs by spending a lot of consumer time. They managed the scarcity they could measure (storage) but neglected to manage the much larger scarcity of their customers' goodwill. No wonder phone companies are second only to cable TV companies in the "most hated" rankings (191).

Reading this made me think of behavioral science in the role of the stupid phone company. Natural selection optimizes fitness, that much is algorithmic. But how does this optimization process affect any given behavioral trait? That depends how the trait is connected to fitness, how heritable it is, and whether anything else correlated with the trait exerts its own independent negative effect on fitness. It's a mess, and we generally can't figure it out. So, we measure what we can. The fallacy is that what we can measure may have little connection to the important output -- for the phone company, profit per customer; for the biologist fitness.

Today with an embarrassment of abundance of food and goods, people still agonize over choices. From one point of view, this is just a waste of time -- why argue over arbitrary markers of status, when the essential resources are super-abundant?

But from a social point of view, seeking out limited information may be in our nature. This leads me to question whether Anderson is right about the value of information itself. Does it really trend toward free?

Humans evolved to be users (and broadcasters) of social information, but in the past our communication was limited by many of the same constraints that other animals face. Animal communication is not free -- it comes with direct and indirect costs. The direct costs are energetic and developmental -- animals have to build and maintain the organs of communication, and supply the power to run them. The indirect costs are the perils of advertising: an animal that reveals itself runs a greater risk of predation. Worse, the peril of honest advertising is that potential mates may see what a loser you really are.

The Internet might have enabled more complex systems of information presentation, but for the most part, people use it for old-fashioned reading. At its best, it has enabled a social transformation, empowering millions of people to use very simple means of information transfer -- from short-form blogs to messaging in World of Warcraft.

That's "messaging", not "massaging".

If the cost of information appears to be trending downward, it may be that's because the production of information is increasing with a lot higher slope than the production of money that might purchase it. Consider genomics: What would you be willing to pay for your genome today? Whatever your answer, you can expect that you would be willing to pay even less 10 years from now, unless the health value of that information radically increases.

[T]he more products are made of ideas, rather than stuff, the faster they can get cheap. This is the root of the abundance that leads to Free in the digital world, which we today shorthand as Moore's Law.

However, this is not limited to digital products. Any industry where information becomes the main ingredient will tend to follow this compound learning curve and accelerate in performance while it drops in price. Take medicine, which is shifting from "we don't know why it woks, it just does" (there's a reason it's called drug "discovery") to a process that starts with the first principles of molecular biology ("now we know why it works"). The underlying science is information, while observed efficacy is just anecdote. Once you understand the basics, you can create an abundance of better drugs, faster.

DNA sequencing is falling in price by 50 percent every 1.9 years, and soon our individual genetic makeup will be another information industry. More and more medical and diagnostic services will be provided by software (which get cheaper, to the point of being free) as opposed to doctors (who get more expensive) (84).

Once upon a time, the only diagnostic service was a doctor. Doctors offloaded some of their diagnostic effort as lab tests became more and more important. Nowadays, one of the major reasons for the increase in health care costs is the routine ordering of expensive tests. Doctors order these tests because they reduce risk -- risk of bad outcomes, and risk of malpractice suits. Risk is money.

The least satisfactory chapter for me was about science fiction and abundance. Anderson argues throughout the book that humans are "wired" for scarcity; that we just don't understand abundance. In chapter 15, he turns to fictional worlds -- from E. M. Forster to Cory Doctorow -- in which some machine (or other invention) had created endless abundance. Invariably, these works describe how society degenerates when freed from scarcity -- freed from "striving", people are robbed of purpose.

Anderson misses a darker connection. The people who worried about the degeneration of human moral purpose in the face of abundance also worried about our genetic degeneration. The eugenics movement was born in the same post-industrial society as science fiction, and for the same reason. Later in the book Anderson references the similarity:

[R]eplace "free" with "steam" and you can imagine the Victorian concern about flabby muscles and minds (229).

I wonder whether there is something inherently dystopian about a society where genetic information is too cheap to meter. In a world where risk is money, and very small risks are increasingly quantifiable, it is not hard to imagine an inexorable process toward removing freedom and imposing control. Certainly that has been the theme of many science fiction works.

But rather than end on that depressing note, I'll point instead to a happy consequence of free information exchange: the creativity expressed in online communities:

RuneScape, yet another Web-based world of orcs and elves, counts more than 1 million subscribers (out of more than 6 million users) paying $5 a month, creating a $60 million annual business. As a point of reference, that's about the same size as the subscriber user base and annual revenues of the Wall Street Journal's subscription-based Web site, which is the biggest paid site of all the world's newspapers. It's also larger than the New York Times's paid online subscriber base was before the paper dropped the model in favor of Free in 2008. It appears that people would rather pay to cast pretend spells than to read Pulitzer Prize-winning news. (I'll leave whether that's a good thing or a bad thing to others.) (150).

People are using their power to make new things -- sometimes frivolous, fictitious things, but things that make them happy. It's possible that genetic information can serve this purpose, too -- a point I'll return to on a different topic tomorrow.

I'm a big booster of the idea that human demographic expansion helped drive our recent evolution. So you might expect me to like the new paper by Adam Powell, Stephen Shennan and Mark Thomas, titled, "Late Pleistocene demography and the appearance of modern human behavior." Yet, I see a lot of weaknesses in the paper. I think the paper tries to sidestep several issues about "modern human behavior" that ought to be tackled head-on. In the end, the model in the paper can't describe the data the authors want to consider. Maybe they should have adopted a different model; maybe different data.

I've taken a lot of notes about this -- too many for me to share, but I wanted to review the basic exposition of the paper, including why the authors think demography may determine technological change during the Late Pleistocene. I might post other notes later on the issue of genetic modeling of demography and its relevance for archaeology.

The authors describe a model in which the density of a metapopulation determines the rate of increase (or decline) its cultural evolution, using simulations to extend analytical results from Henrich (2004). Follow their assumptions and you arrive at the conclusion that population density can, under certain conditions, constrain the trajectory of cultural change.

The question is whether the model's assumptions can apply to the real world. Here's the abstract of the paper:

The origins of modern human behavior are marked by increased symbolic and technological complexity in the archaeological record. In western Eurasia this transition, the Upper Paleolithic, occurred about 45,000 years ago, but many of its features appear transiently in southern Africa about 45,000 years earlier. We show that demography is a major determinant in the maintenance of cultural complexity and that variation in regional subpopulation density and/or migratory activity results in spatial structuring of cultural skill accumulation. Genetic estimates of regional population size over time show that densities in early Upper Paleolithic Europe were similar to those in sub-Saharan Africa when modern behavior first appeared. Demographic factors can thus explain geographic variation in the timing of the first appearance of modern behavior without invoking increased cognitive capacity.

You can always tell what's supposed to be bad, it's the thing that you're not supposed to to "invoke". You know, like witches and vampires.

The model

In fact, "cognitive capacity", as a continuous, one-dimensional variable, underlies the model. In a nutshell, the model assumes that people learn behaviors by instantaneously absorbing the "skill" (which I'll call "mojo") from the best (highest "mojo") individual in their population. But they don't learn perfectly; their mojo ends up varying.

Nevertheless the whole population is choosing one individual to copy, so what happens over time is that the population changes in one direction or the other. If the distribution among individuals includes a few with higher mojo, then the average amount of mojo should increase over time. Imagine if the whole population copied the running style of the best 100 m runner. The world record might reduce over time; and then people copy the new world record holder, and the average speeds up again, ad infinitum. There is stochastic variation from one step to the next -- sometimes it will increase more, sometimes less, and sometimes it may shrink a little. But the model is deterministic: depending on the distribution of mojo, it will either trend upward or downward.

I picked the analogy because it points out a weakness of the model. There's no possibility of reaching an optimum, or a stasis. In fact, the survival value of "mojo" simply isn't part of the model, nor is the cost of developing mojo.

OK, it's a simple model -- too simple to capture most aspects of reality. What value can it possibly have?

The assumption is that some behaviors take more mojo than others. Some behaviors then will lie near a threshold where the population is just at the border between gaining or losing mojo over time. The fastest runner in the population might still be slower than last year's champion. If the population models the new winner, they might lose mojo on average.

So the change in mojo doesn't depend on the current average; it depends on the distribution of the highest-mojo individual. That's an extreme value, and extreme values depend on the total number of individuals. There's some chance that the Jamaican national champion will be the Olympic gold medalist -- like last year. But on average the world champion is faster than the champion of any single country; the champion of a country is faster than the champion of any average local track club, and so on. Numbers make a difference. Add more individuals, and you have a better chance of a high extreme value -- a better chance in the model that mojo will increase.

Again, the analogy shows the model's deficiencies. Local track clubs don't vary randomly. There are some local track clubs where the average 100 m time is pretty close to the Olympic champion's. In part this is because information isn't shared instantly and universally. There are both explicit dynamics and path-dependence: Jamaica's running team has been so successful in part because of recent investments in infrastructure, in part because of leadership from a few gifted coaches. And in large part it's because talent matters. Some people just have more running mojo.

But the model does show that for a limited range of behaviors, population size (in Powell and colleagues' simulations, local population density) can exert a deterministic effect on the behavior of the population. Outside that range, the behavior will be dominated by non-demographic factors, such as intrinsic qualities of the learners.

Deterministic versus stochastic models

The question is whether the limited range of behaviors that might respond to demography are actually relevant to the archaeology. Unfortunately, there's no way to predict which behaviors ought to respond to demography in this way. You might find a really clever way to test the hypothesis, even without knowing -- that was one of the features of Henrich's (2004) paper that first presented the model. I think in the current case, we can start here: If the authors' model were true, then demography would exert a deterministic effect on technology. A larger population would have a higher average "skill" level, which (by the authors' model) would allow the development of more complex culture.

When it comes to individual artifacts, demography's effect is stochastic. The development of technology has been path-dependent, with different populations following different paths. Sometimes those paths have included similar features, sometimes not. The same idea that spreads in some populations may fail to spread in others, despite the same demographic conditions.

For example, the Aurignacian split-based bone point is an intrinsically unlikely artifact. Most people in the world did not produce them, even though bone points were fairly common, especially in groups who used small-projectiles. Carved ivory figurines, on the other hand, are not nearly so unlikely; many peoples in the world have produced them. But some populations did so at very low population sizes and densities, while others have made carved ivory figurines only after reaching very large population sizes with highly specialized division of labor. Large populations make it more likely that we'll see carved ivory figurines, among other things, but they do not determine that such figurines will be present. In other words, population size is one factor affecting the stochastic appearance of these artifacts.

OK, but what if we try to generalize beyond individual artifacts or traditions and consider "modern human behavior" as a whole? Isn't there some general and abstract factor that might change deterministically with demography? To test that hypothesis, we need to (a) develop some accurate measure of the abstract factor, and (b) observe it to be deterministically influenced by demography.

Here's an example: For our work on the acceleration of recent adaptive evolution, our hypothesis was that a deterministic model based on recent demographic expansion could describe the number of new selected mutations in human populations. We tested the hypothesis by developing a measure for selection, and by showing that the numbers of variants matched the predictions of the deterministic model. This global conclusion about the number of variants holds despite the fact that any particular case of selection on a gene depends on many stochastic factors, including the occurrence of a favorable mutation, its escape from genetic drift when rare, and the function of the gene relative to recent human ecological changes. In the limit of large numbers, these random processes do not obscure the deterministic effect of population size.

Now, for archaeological observations, we could in principle follow the same procedure. If there is an abstract factor of "modern behavior", we might develop an accurate measure of it by understanding the relationship of the abstract factor and particular artifact types. That's the reason why archaeologists have devoted such extensive effort to defining "modern human behavior." The entire goal of defining "modern human behavior" is to make archaeology an instrument for measuring the cognitive advancement of prehistoric groups.

Yes, there's some irony here. Many archaeologists don't want to "invoke" cognitive capacity, even as they define "modern behavior" as a proxy for it. Artifacts certainly change stochastically. If we wanted to test a stochastic model of change, we might as well use artifacts directly. But that might not allow us to test whether the demographic factor was more important than other factors, such as developmental or ecological ones. Can we expect some combination of artifacts to behave deterministically?

The current paper chooses a simple threshold definition for the abstract factor: the Blombos incised ochre artifacts and pierced shells define the same level of "modern behavior" as the early Aurignacian of Europe. Why those two populations? Why those two behaviors? Why ignore much earlier engraved lines from other places, or pierced artifacts made by Neandertals? The paper doesn't make any serious effort to defend this measure of an abstract factor underlying "modern behavior".

I think at a minimum, the authors need to show that their measure of "modern behavior" is replicable and predictive outside the context of these two populations. If engraved lines can be a threshold measure of "skill", then they should reliably appear in some contexts and not others. If pierced shells can stand in for other elements of behavior, like small game exploitation or projectile use, then show the strength of the correlation. If they can't stand in reliably for their abstract factor, then they need to find some combination of observations that can. If there is no combination of observations that proves reliable, then their model cannot validly apply.

The second necessary element for testing the deterministic model is to show whether the measure is deterministically affected by demography. On this score, the paper is much more convincing: Their demographic model cannot explain the distribution of their measure of "modernity".

Oh, I know, the conclusion of the paper says the opposite. But look at the data: The model predicts that southern Asia should have Upper Paleolithic-like industries beginning long before they appeared in Europe, and that southern Africa should have retained Upper Paleolithic-like behaviors throughout the last 90,000 years or more. Neither of those predictions holds up. The authors don't consider the mtDNA evidence for population growth in the New World (where art and ornamentation are rare among Paleoindians) or Australia (which underwent substantial complexification during the Holocene). The comparison of Europe and South Africa is an assumption of their measure, not a prediction or conclusion.

The model really only gets one prediction correct: The West Asian record undergoes an Upper Paleolithic transition at around the same time as Europe. And even on that score, one may quibble: was the Levantine initial Upper Paleolithic earlier than Europe or later? Does the European mtDNA expansion, which mainly consists of mtDNA lineages derived from West Asia, record European demography or West Asian demography?

They're left making a variety of ad hoc arguments to explain why the model doesn't fit the demography: maybe the mtDNA samples don't represent Late Pleisocene populations exactly; maybe the population really shrank in post-Howieson's Poort South Africa even though the mtDNA (and a lot of archaeology) say it didn't; maybe there were recurrent bottlenecks and expansions not covered by the mtDNA demographic models. When ad hoc hypotheses add up so quickly, there's often much more parsimonious option: maybe the model is wrong.

If you're looking for a way to waste your time today, you might check out The Economist's online debate, which focuses on the question of whether the world is getting more or less cultured. Or as they put it, "smarting up or dumbing down":

Intelligent Life, The Economist's quarterly sister magazine, has been looking into what is happening to culture in Britain. The editor, Tim de Lisle, presents a mass of evidence that makes a seemingly irrefutable case: all over the country, more people are going to museums, visiting literary festivals and listening to classical music than ever before. If that isn't wising up, it is hard to know what is.

Susan Jacoby, a scholar whose career began as a reporter on the Washington Post and whose writing now focuses on American intellectual history, sees no reason for Westerners to pat themselves on the back. The education bar, in the Anglo-American world, at least, she says, is being set lower and lower. Fewer and fewer people read books; instead they just hoover up information on the internet. After she wrote an article for her former paper on the decline of reading, she received a deluge of emails from people who said they were proud that they never read books at all. They couldn't see the point.

The recurring issue in the debate seems to be whether people are using information in a deeper or more superficial way. Since both these terms are laden with moral value (always better to be deep than superficial, right?), one may wonder whether the real question isn't whether we feel better about ourselves or not.

Indeed, the two participants devolve immediately into schoolmarmy arguments about whether "high culture" is thriving or not. So we have "increasing attendance at museums" on one side the balance and "decreasing market for hardbound fiction" on the other. Blah.

It would be more interesting to consider the biocultural question: If our culture presents us with more information, do we actually get better at using it over time? There's no mention of the Flynn Effect in the debate, but it seems very relevant -- especially considering the worry that the Brits are "dumbing down".