Tag Archives: cultural evolution

Culture wars

August 2015 – October 2016

Since 1981, the World Values Survey Association has been carrying out surveys around the world regarding people’s values, asking respondents, for example, whether most people can be trusted, and whether they are proud of their country. A lot of the variation in values across countries falls along two axes, call them Survival versus Well-Being/Self-Expression, and Traditional Authority versus Secular Rationality, shown as the x and y axes in the chart below.

world-values-values

In societies high on Survival and low on Well-Being/Self-Expression (left on the x axis), people tend be less trusting and less happy, and to value money and material well-being more than emotionally rewarding careers. In societies high on Traditional Authority (low on the y axis), people are more patriotic and more religious.

We can also plot countries around the world by their positions on the two axes, as in the chart below.

world-values-countries

A few observations: Confirming everyone’s stereotypes, Sweden is extreme both in post-materialism, and in post-traditionalism. Overseas Europe is more traditional than the Continent: the Anglosphere is more traditional than the Continental Protestant world, and Latin America more traditional than the Continental Catholic world. And it looks like Soviet Communism did a moderately effective job of destroying traditional values, and a really good job of leaving people miserable.

Values change over time. They constitute a mediating link between economic and political change: economic changes tend to result in changing values, while changing values tend to result in changing political institutions. More specifically:

  1. The growth of industrial employment tends to move societies up the y axis, away from traditional values, without shifting them much on the x-axis. The history of rapidly industrializing late nineteenth- and early-twentieth century Europe reflects this value shift, with new ideologies and leaders bypassing or assaulting traditional hierarchies of aristocracy and Church while fighting ruthlessly to make sure their followers came out on top in the struggle for existence.
  2. More recent economic changes, toward post-industrial employment, tend to move societies rightward on the x axis. The declining levels of violence documented by Pinker, as well our halting progress toward a more democratic world, are reflections of this. These are encouraging developments, but matters are complicated by the fact that this movement is highly uneven, both across and within countries. We no longer see the stark divisions of the Cold War era. But in many areas around the world, people find themselves in a house divided against itself on cultural matters, and the resulting culture wars can make for more conflict. Political scientists have coined a label for this, Center-Periphery Dissonance, and many of the revolutionary political struggle of the last several years have pitted a modernizing center against a more traditional periphery.

Muslim majority

933-993 A. D., 311-371 A. H.

Muslims were initially a small minority in the lands they conquered. But over the course of centuries they came to be a large majority of the population in the Middle East and North Africa. Strikingly, it may be possible to quantify, at least roughly, the progress of conversion.

A major production of Islamic society, from the earliest days until recently, is the biographical dictionary. As befits a patrilineal society, many of these dictionaries provide a nasab, or genealogy, for their subjects, a list of ancestors similar to the begats in the Bible, as well as a nisba, an affiliation, most often a geographic affiliation. An individual might be listed as Muhammed son of Ahmad son of Rustam, affiliated with Nishapur (a city in Iran). Note that the first two names (Mohammed, Ahmad) are clearly Muslim, while the name of the grandfather (Rustam) is Persian. This is probably telling us that Rustam was the first member of his family to convert to Islam, and that he initiated a sequence of Muslim names among his descendants. It’s possible to use this information, along with some reasonable demographic assumptions, to construct a graph showing the course of conversion to Islam among a large group of biographic subjects. Here’s what we get for Iran:islam convert iran

The points fall nicely along a logistic curve. A logistic curve is what we often see with the spread of an infection, where the y-axis shows the number of people infected. Logistic curves also commonly show up when we look at memes rather than germs, where the y-axis might show how many farmers have adopted a new strain of corn. In either case, the rate of growth of the “infection” is proportional to the product of the number already infected and the number not yet infected. So conversion to Islam in the medieval period may fit a simple model of cultural transmission. (Note however that this method does not tell us about people who never converted to Islam during this period, like the ancestors of present day Christian Copts in Egypt.)

This exercise is presented by Richard Bulliet (he also wrote about wheels). He makes some further observations.

  • Conversion seems to proceed more quickly in Iran than in other areas of the Arab empire (Iraq, Syria, Egypt, Tunisia). It looks as if the Christians who were the majority of the population in the latter areas are more resistant to Islam than the Zoroastrians in Iran.islam convert iraq
  • Converts, especially in the early stages, often leave behind their native communities and settle with other Muslims. This helps drive urbanization, with new cities growing up around Muslim military cantonments; Baghdad and Cairo get their start this way. The wave of urbanization following the Arab conquests contrasts sharply with the ruralization which follows the end of the Roman Empire in western Europe.
  • The early period when converts make up less than half the population coincides with a period of anti-Islamic revolts. As the Islamic fraction grows, these revolts move from more central to more peripheral regions. They eventually cease altogether as Muslims attain a secure majority.
  • In the early period, local Muslim rulers are too insecure to risk rebelling against the central authority of the Caliph. It is in the later period, with local Muslims securely in the majority, that regions assert their independence, and the ummah (community of the faithful) fragments.
  • Rather than assimilate to the locally dominant version of Islam, later generations of converts often carve out cultural space for themselves by adopting variant versions. Much of the sectarian segmentation of the Islamic Middle East today, between different legal schools and sects, traces back to differential timing of conversion during the medieval period.

First signs

In July and August, this blog covered one of the great revolutions in information transmission, the evolution of language.  And as we move into September, we will consider another, the invention of writing. But in between these two great revolutions, there are tantalizing hints that people were experimenting with other techniques for enhancing social memory.

Genevieve von Petzinger has made an extensive study of cave paintings from Ice Age Europe, 40,000 to 10,000 years ago; her results are presented in a recent book. The most famous cave paintings are pictures, sometimes of extraordinary quality. But von Petzinger has been interested in something else, in the geometric signs that often accompany these paintings, or stand on their own.  These are not random doodles. A limited number of different signs – she lists just thirty two – is found repeatedly. Some signs, like the Spanish Tectiform, are limited in geographic distribution. Some appear early and disappear later, some do the reverse, others persist through the whole period.

ice age signs

These signs would seem to be some kind of symbolic code. But not, yet, a writing system. Perhaps some of them represent astronomical phenomena, like modern astrological symbols:

astrological signs

or perhaps they represent the terrestrial natural world, or social divisions, or all of the above. At this point we don’t know.

Toba? or the sperm whale effect?

74 thousand years ago, a big chunk of the island of Sumatra blew up. It was the biggest volcanic explosion in the past two million years, expelling 2800 times as much debris as the Mount Saint Helens eruption in Washington State in 1980. Ash from the super-eruption is found all the way from Lake Malawi to the South China Sea. The resulting Toba caldera measures about 20 by 60 miles.

toba

The Toba eruption coincides with a shift back to glacial conditions, and it may be that there’s a connection, that Earth went through a long volcanic winter after the eruption, which shifted climate to a colder equilibrium.

Did Toba have an effect on human evolution? Somewhere between 100 and 50 thousand years ago, human populations went through a bottleneck: modern humans are descended from just 1,000 to 10,000 breeding pairs from that period. It’s been argued that Toba wiped out the majority of Homo sapiens around at the time, leaving only a small group of survivors.

But the evidence that Toba is responsible for the bottleneck is equivocal. In some places humans seem to have passed through the period of the eruption without major disruptions. Also, there’s a point that gets missed in a lot of popular reporting: just because a species went through a bottleneck doesn’t necessarily mean that the population of the whole species ever shrank to that size. In the case of Homo sapiens it could be that the total population was always many times larger than 1,000-10,000. It’s just that the other tens or hundreds of thousands got replaced. In other words, we may not be looking at an external catastrophe wiping out most of humanity, and a few groups of survivors recovering. Instead, we may be looking at a small population of our eventual ancestors expanding and outcompeting other populations, so that it was our ancestors, not a volcano, who made sure that most human beings alive 74,000 years ago didn’t leave descendants.

bottleneck

This may reflect something special about human evolution: human beings typically belong to tribes and ethnic groups defined by distinctive cultures, and cultural boundaries (including language boundaries) often act as barriers to interbreeding. Several authors have suggested that this may make human beings unusually susceptible to population replacement via “cultural group selection,” and that this might account for humans having unusually low effective population size, as genes “hitchhike” along with expanding cultures. Interestingly, sperm whales, which live in populations defined by different song dialects (and other cultural differences) may show the same genetic pattern. And here’s me on kin selection and ethnic group selection, related.

In May 2015, the Toba volcano grew more active than usual, producing large emissions of steam and foul gases. Locals were reported to be concerned.

Learn This One Weird Trick … (Part One)

… that humans use, and now you can too!

There are people who think that human beings are nothing special. Sure (the argument goes) people have uniquely large brains. But all sorts of creatures have unique features. Elephants are the only animals with trunks. Tamarins and marmosets are the only primates that give birth to twins. Platypuses are the only venomous mammals. Spotted hyenas are the only mammals whose females sport pseudo-penises (through which they give birth!). And so on. If we could ask members of these species they’d claim that they’re the special ones.

But of course we can’t ask them, and in any case, this isn’t a very convincing argument. Human beings have an absolutely outsize impact on the Earth, and the advent of human beings looks like one of the major evolutionary transitions, comparable in importance to the origin of the eukaryotic cell or multicellular life. But even if we buy this, it still leaves open the question of whether there’s a key adaptation – a One Weird Trick – that accounts for the exceptional course of human evolution. Here are some candidates that being are being batted around these days:

1) The cognitive niche. The basic idea is at least as old as Aristotle, that human brings are defined by their capacity for Reason. A modern version of this is advocated by evolutionary psychologist John Tooby and cognitive scientist Steven Pinker. Pinker in particular has elaborated the argument that humans are uniquely adapted to acquire and share knowledge, by virtue of a suite of cognitive, social, and linguistic adaptations. We’ve already touched on several aspects of this: Human beings seem to have taken the capacity for thinking about physical space and retooled it for thinking about the abstract cognitive space of possession – a social relationship. (Other abstract cognitive spaces include kinship, time, and change-of-state.) And humans seem to harness the machinery for processing the sounds of interacting solid objects in creating major categories of phonemes. For a more complete exposition, here’s an academic article by Pinker, and a talk on youtube.

2) Culture. Rob Boyd and Pete Richerson, who’ve done a lot of mathematical modeling of cultural evolution, are skeptical about the “cognitive niche” argument. Too much culture, they argue, is things that have been learned by trial-and-error, and are passed on from one generation to the next without people understanding why they work. Boyd and Richerson appeal, as anthropologists have for generations, to the importance of culture. We mentioned earlier their argument that the frequency of climate change in the Ice Age was nicely calibrated to favor social learning rather than individual learning or instinct. Joseph Henrich provides a recent defense of the importance of culture. Contra Pinker, he thinks humans often don’t have a good cause-and-effect understanding of the things they do, but depend heavily on imitation and the accumulated wisdom of the elders. And see this post, for the importance of High Fidelity cultural transmission in the evolution of animal and human intelligence.

Coming up: Part Two. Recursion and Shared Intentionality

Ice Age gear shift

833-789 thousand years ago

Around today’s date, there was a shift in the nature of glacial cycles.

But let’s back up a bit. Earth’s climate took a turn toward cool in the transition from Eocene to Oligocene, 35 million years ago (although with some warming in the Miocene). It was probably back then that much of Antarctica started being covered by ice. The establishment of open water all the way around Antarctica may have helped isolate and freeze the continent. And declining carbon dioxide levels, partly a result of weathering of rocks in the Himalayas, probably also made a difference. But it was back at the beginning of the Pleistocene, now dated to 2.5 million years ago, that the current Ice Age truly began, with glaciers covering large parts of northern North America and northern Europe.

Current Ice Age? Glaciers covering large parts of northern North America and northern Europe? This isn’t what the climate has been like for the past 10,0000 years. Within the current long Ice Age there have been long glacial periods and shorter interglacials, and we’re currently in an interglacial. Our own activities may have done something to prolong the interglacial, and stave off the return of the ice; more on this another day.

Three astronomical cycles govern the rhythm of glacial and interglacial. There’s a 100,000 year cycle as Earth’s orbit changes from somewhat more elliptical to somewhat more circular. There’s a 40,000 year cycle as Earth’s axis shifts from slightly more tilted (24.5 degrees off vertical) to slightly less (22.1 degrees); it’s currently tilted at 23.5 degrees. And there’s a 21,000 year cycle generated as the Earth precesses – wobbles like a top. Right now the North Pole is pointed at Polaris, and the Sun very recently started rising in the constellation Aquarius at the Spring equinox: hence the Age of Aquarius.

(An even longer 400,000 year cycle might have been involved earlier in human evolution, in establishing intervals in which “amplifier lakes” flashed in and out of existence in the African rift valley. More here.)

Between 2.5 million and 800,000 years ago, the glacial/interglacial alternation was dominated by the 40,000 year cycle. But beginning about 800,000 years, there has been a gear shift: the 100,000 year cycle has been dominant and swings in climate have been more extreme. (In Africa however the 21,000 year cycle is more important for alternations between rainy and dry. Africa is in a dry state now.)

One of the startling findings to come out of the last few decades of work on ice cores from Greenland and Antarctica is that not only have there have been huge long-term changes in climate, but there have also been extreme short term shifts, probably connected with changes in ocean currents. There have been a number of occasions over the last hundreds of thousands of years during which average temperatures shifted by 10-20 degrees Fahrenheit (5-10 degrees Celsius) for a millennium, or even for a century or less! (During the last 10,000 years, however, the climate has been unusually stable.)

This is bound to have had strong effects on human beings. Two anthropologists, Robert Boyd and Peter Richerson, who work on mathematical models of cultural evolution, have a general theory of how this pattern of oscillations might have affected human evolution. They argue that human adaptation takes place on multiple time scales. On very long time scales, human beings adapt to changes in the environment genetically. On very short time scale, human beings adapt to change through individual learning. But when change happens on intermediate time scales, adaptation takes place through social learning. With changes on intermediate time scales, your ancestors may not have enough time to adapt genetically to the current climate, but things may be stable for long enough that your culture and the wisdom of the elders have a lot to teach you about how to cope. One of the really distinctive features of human beings, maybe even The Secret of Our Success is that we are, more than any other creature, a cultural animal, with high-fidelity cultural transmission; this trait may have been shaped by the nature of climate change especially over the last 800,000 years.

Toba? or the sperm whale effect?

74 thousand years ago, a big chunk of the island of Sumatra blew up. It was the biggest volcanic explosion in the past two million years, expelling 2800 times as much debris as the Mount Saint Helens eruption in Washington State in 1980. Ash from the super-eruption is found all the way from Lake Malawi to the South China Sea. The resulting Toba caldera measures about 20 by 60 miles.

toba

The Toba eruption coincides with a shift back to glacial conditions, and it may be that there’s a connection, that Earth went through a long volcanic winter after the eruption, which shifted climate to a colder equilibrium.

Did Toba have an effect on human evolution? Somewhere between 100 and 50 thousand years ago, human populations went through a bottleneck: modern humans are descended from just 1,000 to 10,000 breeding pairs from that period. It’s been argued that Toba wiped out the majority of Homo sapiens around at the time, leaving only a small group of survivors.

But the evidence that Toba is responsible for the bottleneck is equivocal. In some places humans seem to have passed through the period of the eruption without major disruptions. Also, there’s a point that gets missed in a lot of popular reporting: just because a species went through a bottleneck doesn’t necessarily mean that the population of the whole species ever shrank to that size. In the case of Homo sapiens it could be that the total population was always many times larger than 1,000-10,000. It’s just that the other tens or hundreds of thousands got replaced. In other words, we may not be looking at an external catastrophe wiping out most of humanity, and a few groups of survivors recovering. Instead, we may be looking at a small population of our eventual ancestors expanding and outcompeting other populations, so that it was our ancestors, not a volcano, who made sure that most human beings alive 74,000 years ago didn’t leave descendants.

bottleneck

This may reflect something special about human evolution: human beings typically belong to tribes and ethnic groups defined by distinctive cultures, and cultural boundaries (including language boundaries) often act as barriers to interbreeding. Several authors have suggested that this may make human beings unusually susceptible to population replacement via “cultural group selection,” and that this might account for humans having unusually low effective population size, as genes “hitchhike” along with expanding cultures. Interestingly, sperm whales, which live in populations defined by different song dialects (and other cultural differences) may show the same genetic pattern. And here’s me on kin selection and ethnic group selection, related.

In May 2015, the Toba volcano grew more active than usual, producing large emissions of steam and foul gases. Locals were reported to be concerned.