Evolution is slow–until it’s fast: Genetic Load and the Future of Humanity

Source: Priceonomics

A species may live in relative equilibrium with its environment, hardly changing from generation to generation, for millions of years. Turtles, for example, have barely changed since the Cretaceous, when dinosaurs still roamed the Earth.

But if the environment changes–critically, if selective pressures change–then the species will change, too. This was most famously demonstrated with English moths, which changed color from white-and-black speckled to pure black when pollution darkened the trunks of the trees they lived on. To survive, these moths need to avoid being eaten by birds, so any moth that stands out against the tree trunks tends to get turned into an avian snack. Against light-colored trees, dark-colored moths stood out and were eaten. Against dark-colored trees, light-colored moths stand out.

This change did not require millions of years. Dark-colored moths were virtually unknown in 1810, but by 1895, 98% of the moths were black.

The time it takes for evolution to occur depends simply on A. The frequency of a trait in the population and B. How strongly you are selecting for (or against) it.

Let’s break this down a little bit. Within a species, there exists a great deal of genetic variation. Some of this variation happens because two parents with different genes get together and produce offspring with a combination of their genes. Some of this variation happens because of random errors–mutations–that occur during copying of the genetic code. Much of the “natural variation” we see today started as some kind of error that proved to be useful, or at least not harmful. For example, all humans originally had dark skin similar to modern Africans’, but random mutations in some of the folks who no longer lived in Africa gave them lighter skin, eventually producing “white” and “Asian” skin tones.

(These random mutations also happen in Africa, but there they are harmful and so don’t stick around.)

Natural selection can only act on the traits that are actually present in the population. If we tried to select for “ability to shoot x-ray lasers from our eyes,” we wouldn’t get very far, because no one actually has that mutation. By contrast, albinism is rare, but it definitely exists, and if for some reason we wanted to select for it, we certainly could. (The incidence of albinism among the Hopi Indians is high enough–1 in 200 Hopis vs. 1 in 20,000 Europeans generally and 1 in 30,000 Southern Europeans–for scientists to discuss whether the Hopi have been actively selecting for albinism. This still isn’t a lot of albinism, but since the American Southwest is not a good environment for pale skin, it’s something.)

You will have a much easier time selecting for traits that crop up more frequently in your population than traits that crop up rarely (or never).

Second, we have intensity–and variety–of selective pressure. What % of your population is getting removed by natural selection each year? If 50% of your moths get eaten by birds because they’re too light, you’ll get a much faster change than if only 10% of moths get eaten.

Selection doesn’t have to involve getting eaten, though. Perhaps some of your moths are moth Lotharios, seducing all of the moth ladies with their fuzzy antennae. Over time, the moth population will develop fuzzier antennae as these handsome males out-reproduce their less hirsute cousins.

No matter what kind of selection you have, nor what part of your curve it’s working on, all that ultimately matters is how many offspring each individual has. If white moths have more children than black moths, then you end up with more white moths. If black moths have more babies, then you get more black moths.

Source SUPS.org

So what happens when you completely remove selective pressures from a population?

Back in 1968, ethologist John B. Calhoun set up an experiment popularly called “Mouse Utopia.” Four pairs of mice were given a large, comfortable habitat with no predators and plenty of food and water.

Predictably, the mouse population increased rapidly–once the mice were established in their new homes, their population doubled every 55 days. But after 211 days of explosive growth, reproduction began–mysteriously–to slow. For the next 245 days, the mouse population doubled only once every 145 days.

The birth rate continued to decline. As births and death reached parity, the mouse population stopped growing. Finally the last breeding female died, and the whole colony went extinct.

source

As I’ve mentioned before Israel is (AFAIK) the only developed country in the world with a TFR above replacement.

It has long been known that overcrowding leads to population stress and reduced reproduction, but overcrowding can only explain why the mouse population began to shrink–not why it died out. Surely by the time there were only a few breeding pairs left, things had become comfortable enough for the remaining mice to resume reproducing. Why did the population not stabilize at some comfortable level?

Professor Bruce Charlton suggests an alternative explanation: the removal of selective pressures on the mouse population resulted in increasing mutational load, until the entire population became too mutated to reproduce.

What is genetic load?

As I mentioned before, every time a cell replicates, a certain number of errors–mutations–occur. Occasionally these mutations are useful, but the vast majority of them are not. About 30-50% of pregnancies end in miscarriage (the percent of miscarriages people recognize is lower because embryos often miscarry before causing any overt signs of pregnancy,) and the majority of those miscarriages are caused by genetic errors.

Unfortunately, randomly changing part of your genetic code is more likely to give you no skin than skintanium armor.

But only the worst genetic problems that never see the light of day. Plenty of mutations merely reduce fitness without actually killing you. Down Syndrome, famously, is caused by an extra copy of chromosome 21.

While a few traits–such as sex or eye color–can be simply modeled as influenced by only one or two genes, many traits–such as height or IQ–appear to be influenced by hundreds or thousands of genes:

Differences in human height is 60–80% heritable, according to several twin studies[19] and has been considered polygenic since the Mendelian-biometrician debate a hundred years ago. A genome-wide association (GWA) study of more than 180,000 individuals has identified hundreds of genetic variants in at least 180 loci associated with adult human height.[20] The number of individuals has since been expanded to 253,288 individuals and the number of genetic variants identified is 697 in 423 genetic loci.[21]

Obviously most of these genes each plays only a small role in determining overall height (and this is of course holding environmental factors constant.) There are a few extreme conditions–gigantism and dwarfism–that are caused by single mutations, but the vast majority of height variation is caused by which particular mix of those 700 or so variants you happen to have.

The situation with IQ is similar:

Intelligence in the normal range is a polygenic trait, meaning it’s influenced by more than one gene.[3][4]

The general figure for the heritability of IQ, according to an authoritative American Psychological Association report, is 0.45 for children, and rises to around 0.75 for late teens and adults.[5][6] In simpler terms, IQ goes from being weakly correlated with genetics, for children, to being strongly correlated with genetics for late teens and adults. … Recent studies suggest that family and parenting characteristics are not significant contributors to variation in IQ scores;[8] however, poor prenatal environment, malnutrition and disease can have deleterious effects.[9][10]

And from a recent article published in Nature Genetics, Genome-wide association meta-analysis of 78,308 individuals identifies new loci and genes influencing human intelligence:

Despite intelligence having substantial heritability2 (0.54) and a confirmed polygenic nature, initial genetic studies were mostly underpowered3, 4, 5. Here we report a meta-analysis for intelligence of 78,308 individuals. We identify 336 associated SNPs (METAL P < 5 × 10−8) in 18 genomic loci, of which 15 are new. Around half of the SNPs are located inside a gene, implicating 22 genes, of which 11 are new findings. Gene-based analyses identified an additional 30 genes (MAGMA P < 2.73 × 10−6), of which all but one had not been implicated previously. We show that the identified genes are predominantly expressed in brain tissue, and pathway analysis indicates the involvement of genes regulating cell development (MAGMA competitive P = 3.5 × 10−6). Despite the well-known difference in twin-based heritability2 for intelligence in childhood (0.45) and adulthood (0.80), we show substantial genetic correlation (rg = 0.89, LD score regression P = 5.4 × 10−29). These findings provide new insight into the genetic architecture of intelligence.

The greater number of genes influence a trait, the harder they are to identify without extremely large studies, because any small group of people might not even have the same set of relevant genes.

High IQ correlates positively with a number of life outcomes, like health and longevity, while low IQ correlates with negative outcomes like disease, mental illness, and early death. Obviously this is in part because dumb people are more likely to make dumb choices which lead to death or disease, but IQ also correlates with choice-free matters like height and your ability to quickly press a button. Our brains are not some mysterious entities floating in a void, but physical parts of our bodies, and anything that affects our overall health and physical functioning is likely to also have an effect on our brains.

Like height, most of the genetic variation in IQ is the combined result of many genes. We’ve definitely found some mutations that result in abnormally low IQ, but so far we have yet (AFAIK) to find any genes that produce the IQ gigantism. In other words, low (genetic) IQ is caused by genetic load–Small Yet Important Genetic Differences Between Highly Intelligent People and General Population:

The study focused, for the first time, on rare, functional SNPs – rare because previous research had only considered common SNPs and functional because these are SNPs that are likely to cause differences in the creation of proteins.

The researchers did not find any individual protein-altering SNPs that met strict criteria for differences between the high-intelligence group and the control group. However, for SNPs that showed some difference between the groups, the rare allele was less frequently observed in the high intelligence group. This observation is consistent with research indicating that rare functional alleles are more often detrimental than beneficial to intelligence.

Maternal mortality rates over time, UK data

Greg Cochran has some interesting Thoughts on Genetic Load. (Currently, the most interesting candidate genes for potentially increasing IQ also have terrible side effects, like autism, Tay Sachs and Torsion Dystonia. The idea is that–perhaps–if you have only a few genes related to the condition, you get an IQ boost, but if you have too many, you get screwed.) Of course, even conventional high-IQ has a cost: increased maternal mortality (larger heads).

Wikipedia defines genetic load as:

the difference between the fitness of an average genotype in a population and the fitness of some reference genotype, which may be either the best present in a population, or may be the theoretically optimal genotype. … Deleterious mutation load is the main contributing factor to genetic load overall.[5] Most mutations are deleterious, and occur at a high rate.

There’s math, if you want it.

Normally, genetic mutations are removed from the population at a rate determined by how bad they are. Really bad mutations kill you instantly, and so are never born. Slightly less bad mutations might survive, but never reproduce. Mutations that are only a little bit deleterious might have no obvious effect, but result in having slightly fewer children than your neighbors. Over many generations, this mutation will eventually disappear.

(Some mutations are more complicated–sickle cell, for example, is protective against malaria if you have only one copy of the mutation, but gives you sickle cell anemia if you have two.)

Jakubany is a town in the Carpathian Mountains

Throughout history, infant mortality was our single biggest killer. For example, here is some data from Jakubany, a town in the Carpathian Mountains:

We can see that, prior to the 1900s, the town’s infant mortality rate stayed consistently above 20%, and often peaked near 80%.

The graph’s creator states:

When I first ran a calculation of the infant mortality rate, I could not believe certain of the intermediate results. I recompiled all of the data and recalculated … with the same astounding result – 50.4% of the children born in Jakubany between the years 1772 and 1890 would diebefore reaching ten years of age! …one out of every two! Further, over the same 118 year period, of the 13306 children who were born, 2958 died (~22 %) before reaching the age of one.

Historical infant mortality rates can be difficult to calculate in part because they were so high, people didn’t always bother to record infant deaths. And since infants are small and their bones delicate, their burials are not as easy to find as adults’. Nevertheless, Wikipedia estimates that Paleolithic man had an average life expectancy of 33 years:

Based on the data from recent hunter-gatherer populations, it is estimated that at 15, life expectancy was an additional 39 years (total 54), with a 0.60 probability of reaching 15.[12]

Priceonomics: Why life expectancy is misleading

In other words, a 40% chance of dying in childhood. (Not exactly the same as infant mortality, but close.)

Wikipedia gives similarly dismal stats for life expectancy in the Neolithic (20-33), Bronze and Iron ages (26), Classical Greece(28 or 25), Classical Rome (20-30), Pre-Columbian Southwest US (25-30), Medieval Islamic Caliphate (35), Late Medieval English Peerage (30), early modern England (33-40), and the whole world in 1900 (31).

Over at ThoughtCo: Surviving Infancy in the Middle Ages, the author reports estimates for between 30 and 50% infant mortality rates. I recall a study on Anasazi nutrition which I sadly can’t locate right now, which found 100% malnutrition rates among adults (based on enamel hypoplasias,) and 50% infant mortality.

As Priceonomics notes, the main driver of increasing global life expectancy–48 years in 1950 and 71.5 years in 2014 (according to Wikipedia)–has been a massive decrease in infant mortality. The average life expectancy of an American newborn back in 1900 was only 47 and a half years, whereas a 60 year old could expect to live to be 75. In 1998, the average infant could expect to live to about 75, and the average 60 year old could expect to live to about 80.

Back in his post on Mousetopia, Charlton writes:

Michael A Woodley suggests that what was going on [in the Mouse experiment] was much more likely to be mutation accumulation; with deleterious (but non-fatal) genes incrementally accumulating with each generation and generating a wide range of increasingly maladaptive behavioural pathologies; this process rapidly overwhelming and destroying the population before any beneficial mutations could emerge to ‘save; the colony from extinction. …

The reason why mouse utopia might produce so rapid and extreme a mutation accumulation is that wild mice naturally suffer very high mortality rates from predation. …

Thus mutation selection balance is in operation among wild mice, with very high mortality rates continually weeding-out the high rate of spontaneously-occurring new mutations (especially among males) – with typically only a small and relatively mutation-free proportion of the (large numbers of) offspring surviving to reproduce; and a minority of the most active and healthy (mutation free) males siring the bulk of each generation.

However, in Mouse Utopia, there is no predation and all the other causes of mortality (eg. Starvation, violence from other mice) are reduced to a minimum – so the frequent mutations just accumulate, generation upon generation – randomly producing all sorts of pathological (maladaptive) behaviours.

Historically speaking, another selective factor operated on humans: while about 67% of women reproduced, only 33% of men did. By contrast, according to Psychology Today, a majority of today’s men have or will have children.

Today, almost everyone in the developed world has plenty of food, a comfortable home, and doesn’t have to worry about dying of bubonic plague. We live in humantopia, where the biggest factor influencing how many kids you have is how many you want to have.

source

Back in 1930, infant mortality rates were highest among the children of unskilled manual laborers, and lowest among the children of professionals (IIRC, this is Brittish data.) Today, infant mortality is almost non-existent, but voluntary childlessness has now inverted this phenomena:

Yes, the percent of childless women appears to have declined since 1994, but the overall pattern of who is having children still holds. Further, while only 8% of women with post graduate degrees have 4 or more children, 26% of those who never graduated from highschool have 4+ kids. Meanwhile, the age of first-time moms has continued to climb.

In other words, the strongest remover of genetic load–infant mortality–has all but disappeared; populations with higher load (lower IQ) are having more children than populations with lower load; and everyone is having children later, which also increases genetic load.

Take a moment to consider the high-infant mortality situation: an average couple has a dozen children. Four of them, by random good luck, inherit a good combination of the couple’s genes and turn out healthy and smart. Four, by random bad luck, get a less lucky combination of genes and turn out not particularly healthy or smart. And four, by very bad luck, get some unpleasant mutations that render them quite unhealthy and rather dull.

Infant mortality claims half their children, taking the least healthy. They are left with 4 bright children and 2 moderately intelligent children. The three brightest children succeed at life, marry well, and end up with several healthy, surviving children of their own, while the moderately intelligent do okay and end up with a couple of children.

On average, society’s overall health and IQ should hold steady or even increase over time, depending on how strong the selective pressures actually are.

Or consider a consanguineous couple with a high risk of genetic birth defects: perhaps a full 80% of their children die, but 20% turn out healthy and survive.

Today, by contrast, your average couple has two children. One of them is lucky, healthy, and smart. The other is unlucky, unhealthy, and dumb. Both survive. The lucky kid goes to college, majors in underwater intersectionist basket-weaving, and has one kid at age 40. That kid has Down Syndrome and never reproduces. The unlucky kid can’t keep a job, has chronic health problems, and 3 children by three different partners.

Your consanguineous couple migrates from war-torn Somalia to Minnesota. They still have 12 kids, but three of them are autistic with IQs below the official retardation threshold. “We never had this back in Somalia,” they cry. “We don’t even have a word for it.”

People normally think of dysgenics as merely “the dumb outbreed the smart,” but genetic load applies to everyone–men and women, smart and dull, black and white, young and especially old–because we all make random transcription errors when copying our DNA.

I could offer a list of signs of increasing genetic load, but there’s no way to avoid cherry-picking trends I already know are happening, like falling sperm counts or rising (diagnosed) autism rates, so I’ll skip that. You may substitute your own list of “obvious signs society is falling apart at the genes” if you so desire.

Nevertheless, the transition from 30% (or greater) infant mortality to almost 0% is amazing, both on a technical level and because it heralds an unprecedented era in human evolution. The selective pressures on today’s people are massively different from those our ancestors faced, simply because our ancestors’ biggest filter was infant mortality. Unless infant mortality acted completely at random–taking the genetically loaded and unloaded alike–or on factors completely irrelevant to load, the elimination of infant mortality must continuously increase the genetic load in the human population. Over time, if that load is not selected out–say, through more people being too unhealthy to reproduce–then we will end up with an increasing population of physically sick, maladjusted, mentally ill, and low-IQ people.

(Remember, all mental traits are heritable–so genetic load influences everything, not just controversial ones like IQ.)

If all of the above is correct, then I see only 4 ways out:

  1. Do nothing: Genetic load increases until the population is non-functional and collapses, resulting in a return of Malthusian conditions, invasion by stronger neighbors, or extinction.
  2. Sterilization or other weeding out of high-load people, coupled with higher fertility by low-load people
  3. Abortion of high load fetuses
  4. Genetic engineering

#1 sounds unpleasant, and #2 would result in masses of unhappy people. We don’t have the technology for #4, yet. I don’t think the technology is quite there for #2, either, but it’s much closer–we can certainly test for many of the deleterious mutations that we do know of.

The Big 6 Civilizations (Pt. 3: Indus Valley)

3. Indus Valley

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Map of the Indus Valley Civilization
Map of the Indus Valley Civilization

The Indus Valley civilization (IVC) has got to be the most obscure of the big six. If you challenged the average person to list the world’s first six relatively independent civilizations, they’d probably guess “Egypt, Mesopotamia, Greece, Rome, China, and, um, Africa? Israel?” Eventually they might hit on “Incas and Aztecs/Mayans,” which are geographically about right. But few would guess that the Indus Valley, located in modern-day Pakistan and India, was one of the world’s first three big civilizations, predating the Chinese by almost a millennium and a half.

This is partially explained by random luck: Egypt and Mesopotamia both feature in the Bible and are relatively easy to get to from Europe, (Egypt moreso than Mesopotamia,) and early archaeology appears to have been driven largely by a desire to uncover the truth behind the Homeric epics and the Bible. (And I have a much easier time accessing archaeological materials written in English.)

China is an enormous, famous country that has the resources to promote its own heritage, and the cultures of the Americas are famous because they’re nearby and because they’re included in the history of the conquering of the Americas, which we learned in school.

Pakistan, by contrast, is hard to get to, not part of the American colonial narrative, doesn’t feature in the Bible, and doesn’t have China’s fame and resources. On top of that, if the Wikipedia talk page on the Indus Valley Culture is correct, Pakistan may not be all that interested in the IVC due to it not being Muslim.

India, by contrast, proudly claims the IVC as part of its history–the IVC page is “part of a series on the history of India,” but not “part of a series on the history of Pakistan.”

Additionally, the IVC, while it left behind plenty of cities, buildings, etc., did not build the kind of monumental structures that draw tourists, like the Great Pyramids of Egypt or Chichen Itza, Mexico. More than a thousand IVC cities or settlements have been discovered, many with granaries, public baths, hydraulic systems, and obvious urban planning (their cities are laid out in grids with excellent-for-the-time sewer systems,) but almost no enormous temples, castles, pyramids, or other obviously ceremonial sites.

Indus Valley seals
Indus Valley seals

Also, we have no knowledge of their language and have yet to decipher any of their written language–if they had a written language at all. (Everything you want to know about the IVC script and why we haven’t deciphered it yet.)

The Egyptians helpfully covered their temples in hieroglyphics and left behind so many written records that we have things like Egyptian math textbooks containing fictional, satirical stories about how to not be a scribe. From Mesopotamia we have the Epic of Gilgamesh.

But from the IVC we have only short inscriptions–if they are inscriptions at all–most on small seals. Most of these inscriptions are only a few characters long, greatly hindering our ability to decipher them. We don’t know what they mean, or even if they are a written language at all.

What we do know:

IVC_MapThe IVC (aka the Harappan, after one of their chief cities,) emerged around 3,300 BC in what is now  Pakistan and India. It lasted for about 2,000 years; then essentially disappeared, its people either merging into other populations or migrating away. Over a thousand Harappan cities or settlements have been identified, most of them in Pakistan but a few in Afghanistan and a contested number in India. (Since India is eager to claim the IVC as its own, there are allegations that Indian archaeologists are inflating the number of significant sites on their side of the border.)

(Afghanistan, of course, does not have the resources for archaeology, but it is also really dry, so there probably weren’t that many sites there to start with.)

The IVC likely descended from the Mehrgarh culture (see map). Mehrgarh was a small farming settlement founded around 6,500 BC:

The earliest farming in the area was developed by semi-nomadic people using plants such as wheat and barley and animals such as sheep, goats and cattle. The settlement was established with simple mud buildings and most of them had four internal subdivisions. Numerous burials have been found, many with elaborate goods such as baskets, stone and bone tools, beads, bangles, pendants and occasionally animal sacrifices, with more goods left with burials of males. Ornaments of sea shell, limestone, turquoise, lapis lazuli and sandstone have been found, along with simple figurines of women and animals. Sea shells from far sea shore and lapis lazuli found as far away as present-day Badakshan, Afghanistan shows good contact with those areas. …

In April 2006, it was announced in the scientific journal Nature that the oldest (and first early Neolithic) evidence for the drilling of human teeth in vivo (i.e. in a living person) was found in Mehrgarh. According to the authors, their discoveries point to a tradition of proto-dentistry in the early farming cultures of that region. “Here we describe eleven drilled molar crowns from nine adults discovered in a Neolithic graveyard in Pakistan that dates from 7,500 to 9,000 years ago.”

Ouch.

Harappan toys?
Harappan toys?

Major IVC cities include Harappa, Mohenjo-daro, Dholavira, Ganeriwala, and Rakhigarhi.

[Harappa] is believed to have had as many as 23,500 residents and occupied about 150 hectares (370 acres) with clay sculptured houses

… Harappan society was not entirely peaceful, with the human skeletal remains demonstrating some of the highest rates of injury (15.5%) found in South Asian prehistory.[11] Paleopathological analysis demonstrated that leprosy and tuberculosis were present at Harappa, with the highest prevalence of both disease and trauma present in the skeletons from Area G (an ossuary located south-east of the city walls).[12] Furthermore, rates of cranio-facial trauma and infection increased through time, demonstrating that the civilization collapsed amid illness and injury.

Distribution of haplogroup L of Y-cromosome
Modern distribution of haplogroup L-M20

Genetically, Harappan skeletons belong to haplogroup L-M20, which today is found primarily in Pakistan and the west coast of India:

In Pakistan, it has highest frequency in Baluchistan.[2] In India, it has higher frequency among Dravidian castes, but is somewhat rarer in Indo-Aryan castes.[3] They make a case for an indigenous origin of L-M76 in India, by arguing that the spatial distributions of both L-M76 HG frequency and associated microsatellite variance show a pattern of spread emanating from southern India. By linking haplogroup L-M76 to the Dravidian speakers, they simultaneously argue for an Indian origin of Dravidian languages (Sengupta 2006).

There is apparently some controversy over whether the invading Indo-Europeans (who brought the Sanskrit language to India) drove the Harappans out of Pakistan and into India. India’s a big place that can absorb a lot of people, but it looks to me like many of the Harappans stayed put.

Mohenjo-Daro
Mohenjo-Daro, Pakistan

Meanwhile, in Mohenjo-Daro:

The Citadel – a mud-brick mound around 12 metres (39 ft) high – is known to have supported public baths, a large residential structure designed to house about 5,000 citizens, and two large assembly halls. The city had a central marketplace, with a large central well. Individual households or groups of households obtained their water from smaller wells. … Some houses … include rooms that appear to have been set aside for bathing, and one building had an underground furnace (known as a hypocaust), possibly for heated bathing. Most houses had inner courtyards, with doors that opened onto side-lanes. Some buildings had two stories.[citation needed]

The Great Bath of Mohenjo-daro
The Great Bath of Mohenjo-Daro

In 1950, Sir Mortimer Wheeler identified one large building in Mohenjo-daro as a “Great Granary”. Certain wall-divisions in its massive wooden superstructure appeared to be grain storage-bays, complete with air-ducts to dry the grain. … However, Jonathan Mark Kenoyer noted the complete lack of evidence for grain at the “granary”, which, he argued, might therefore be better termed a “Great Hall” of uncertain function.[13] Close to the “Great Granary” is a large and elaborate public bath, sometimes called the Great Bath. From a colonnaded courtyard, steps lead down to the brick-built pool, which was waterproofed by a lining of bitumen. The pool measures 12 metres (39 ft) long, 7 metres (23 ft) wide and 2.4 metres (7.9 ft) deep. … Other large buildings include a “Pillared Hall”, thought to be an assembly hall of some kind, and the so-called “College Hall”, a complex of buildings comprising 78 rooms, thought to have been a priestly residence.[citation needed]

Mohenjo-daro had no series of city walls, but was fortified with guard towers to the west of the main settlement, and defensive fortifications to the south. … Mohenjo-daro was successively destroyed and rebuilt at least seven times. Each time, the new cities were built directly on top of the old ones. Flooding by the Indus is thought to have been the cause of destruction.[citation needed]

Why is it all “citation needed”?

Dancing Girl of Mohenjo Daro
Dancing Girl of Mohenjo Daro

A bronze statuette dubbed the “Dancing Girl”, 10.5 centimetres (4.1 in) high[20] and about 4,500 years old, was found in ‘HR area’ of Mohenjo-daro in 1926.[20] … The archaeologist Gregory Possehl said of the statuette, “We may not be certain that she was a dancer, but she was good at what she did and she knew it”. The statue led to two important discoveries about the civilization: first, that they knew metal blending, casting and other sophisticated methods of working with ore, and secondly that entertainment, especially dance, was part of the culture.[20]

I think “dancer” is an overly-poetic interpretation of the statue, but it is a striking work.

"priest-king" statue, IVC
“Priest-King” statue, Mohenjo-daro

In 1927, this soapstone figurine, dubbed “The Priest-King,” (though we don’t know if the Mohenjo-daroians had priests or kings,) was found in a wall-niche in a “building with unusually ornamental brickwork.”

The sculpture is 17.5 centimetres (6.9 in) tall and depicts a bearded man with a fillet around his head, an armband, and a cloak decorated with trefoil patterns that were originally filled with red pigment. … Two holes beneath the highly stylized ears suggest that a necklace or other head ornament was attached to the sculpture. … Drill holes in the center of each circle indicate they were made with a specialized drill and then touched up with a chisel. The eyes are deeply incised and may have held inlay. …[22]

Dholavira, located in India:

Dholavira_LayoutOne of the unique features[14] of Dholavira is the sophisticated water conservation system[15] of channels and reservoirs, the earliest found anywhere in the world,[16] built completely of stone. The city had massive reservoirs, three of which are exposed.[17] They were used for storing fresh water brought by rains[15] or to store water diverted from two nearby rivulets.[18] This clearly came in response to the desert climate and conditions of Kutch, where several years may pass without rainfall. A seasonal stream which runs in a north-south direction near the site was dammed at several points to collect water. …

A huge circular structure on the site is believed to be a grave or memorial,[15] although it contained no skeletons or other human remains. The structure consists of ten radial mud-brick walls built in the shape of a spoked wheel.[15] … 

These hemispherical structures bear similarity to early Buddhist stupas.[5] The Archaeological Survey of India, which conducted the excavation, opines that “the kind of design that is of spoked wheel and unspoked wheel also remind one of the Sararata-chakra-citi and sapradhi-rata-chakra-citi mentioned in the Satapatha Brahmana and Sulba-sutras“.[5] …

Glyphs from the Dholavira sign board,
Glyphs from the Dholavira sign board

One of the most significant discoveries at Dholavira was made in one of the side rooms of the northern gateway of the city, and is generally known as the Dholavira Signboard. The Harappans had arranged and set pieces of the mineral gypsum to form ten large symbols or letters on a big wooden board[27] … Each sign is about 37 cm (15 in) high and the board on which letters were inscribed was about 3 m (9.8 ft) long.[28] The inscription is one of the longest in the Indus script, with one symbol appearing four times, and this and its large size and public nature make it a key piece of evidence cited by scholars arguing that the Indus script represents full literacy. A four sign inscription with big size letters on a sand stone is also found at this site, considered first of such inscription on sand stone at any of Harappan sites.[1]

More generally:

Indus Valley civilization was mainly an urban culture sustained by surplus agricultural production and commerce, the latter including trade with Sumer in southern Mesopotamia. Both Mohenjo-Daro and Harappa are generally characterized as having “differentiated living quarters, flat-roofed brick houses, and fortified administrative or religious centers.”[8] …
Distinctive seals were used, among other applications, perhaps for identification of property and shipment of goods. Although copper and bronze were in use, iron was not yet employed. “Cotton was woven and dyed for clothing; wheat, rice, and a variety of vegetables and fruits were cultivated; and a number of animals, including the humped bull, were domesticated,”[8] as well as “fowl for fighting“.[9] Wheel-made pottery—some of it adorned with animal and geometric motifs—has been found in profusion at all the major Indus sites. A centralized administration for each city, though not the whole civilization, has been inferred from the revealed cultural uniformity; however, it remains uncertain whether authority lay with a commercial oligarchy. Harappans had many trade routes along the Indus River that went as far as the Persian Gulf, Mesopotamia, and Egypt. Some of the most valuable things traded were carnelian and lapis lazuli.[10]

Obviously we don’t know much at all about IVC mathematics, but:

Excavations … have uncovered evidence of the use of “practical mathematics”. The people of the IVC manufactured bricks whose dimensions were in the proportion 4:2:1, considered favourable for the stability of a brick structure. They used a standardised system of weights based on the ratios: 1/20, 1/10, 1/5, 1/2, 1, 2, 5, 10, 20, 50, 100, 200, and 500, with the unit weight equaling approximately 28 grams … They mass-produced weights in regular geometrical shapes, which included hexahedra, barrels, cones, and cylinders, thereby demonstrating knowledge of basic geometry.[18]

The inhabitants of Indus civilisation also tried to standardise measurement of length to a high degree of accuracy. They designed a ruler—the Mohenjo-daro ruler—whose unit of length (approximately 1.32 inches or 3.4 centimetres) was divided into ten equal parts. Bricks manufactured in ancient Mohenjo-daro often had dimensions that were integral multiples of this unit of length.[19][20]

And the rather incomplete Wikipedia page on IVC hydraulics states:

Among other things, they contain the world’s earliest known system of flush toilets. These existed in many homes, and were connected to a common sewerage pipe. Most houses also had private wells. City walls functioned as a barrier against floods.

The urban areas of the Indus Valley civilization provided public and private baths, sewage was disposed through underground drains built with precisely laid bricks, and a sophisticated water management system with numerous reservoirs was established. In the drainage systems, drains from houses were connected to wider public drains.[1]

Lothal, a port city located in India, contains the world’s earliest known docks, and may have been a Harappan colony, far from the heartland of the IVC:

Before the arrival of Harappan people (c. 3000 BCE), Lothal was a small village next to the river providing access to the mainland from the Gulf of Khambhat. The indigenous people maintained a prosperous economy, attested by the discovery of copper objects, beads and semi-precious stones. … Harappans were attracted to Lothal for its sheltered harbour, rich cotton and rice-growing environment and bead-making industry. The beads and gems of Lothal were in great demand in the west. The settlers lived peacefully with the Red Ware people, who adopted their lifestyle, evidenced from the flourishing trade and changing working techniques. Harappans began producing the indigenous ceramic goods, adopting the manner from the natives.[8]

And, typical of the IVC:

The uniform organisation of the town and its institutions give evidence that the Harappans were a very disciplined people.[12] … Municipal administration was strict – the width of most streets remained the same over a long time, and no encroached structures were built. Householders possessed a sump, or collection chamber to deposit solid waste in order to prevent the clogging of city drains. Drains, manholes and cesspools kept the city clean and deposited the waste in the river, which was washed out during high tide. A new provincial style of Harappan art and painting was pioneered. The new approaches included realistic portrayals of animals in their natural surroundings. Metalware, gold and jewellery and tastefully decorated ornaments attest to the culture and prosperity of the people of Lothal.

Most of their equipment: metal tools, weights, measures, seals, earthenware and ornaments were of the uniform standard and quality found across the Indus civilization. Lothal was a major trade centre, importing en masse raw materials like copper, chert and semi-precious stones from Mohenjo-daro and Harappa, and mass distributing to inner villages and towns. It also produced large quantities of bronze celts, fish-hooks, chisels, spears and ornaments. Lothal exported its beads, gemstones, ivory and shells. The stone blade industry catered to domestic needs—fine chert was imported from the Larkana valley or from Bijapur in modern Karnataka. Bhagatrav supplied semi-precious stones while chank shell came from Dholavira and Bet Dwarka. An intensive trade network gave the inhabitants great prosperity. The network stretched across the frontiers to Egypt, Bahrain and Sumer.[11] One of the evidence of trade in Lothal is the discovery of typical Persian gulf seals, a circular button seal[13]

I love these descriptions, but given the politics involved, I remain wary that the case may be overstated.

So what happened to the IVC? There are many theories, ranging from the far-fetched (“aliens nuked it”) to the perfectly reasonable (“shifting weather patterns made the area too dry.”) Invasion by the Indo-Aryan people could also have destroyed many cities. A massive flood hit Lothal in 1900 BC, which destroyed much of the city. Wikipedia’s description of the aftermath reminds me of the post-apocalyptic nature of the collapse of Rome:

Archaeological evidence shows that the site continued to be inhabited, albeit by a much smaller population devoid of urban influences. The few people who returned to Lothal could not reconstruct and repair their city, but surprisingly continued to stay and preserved religious traditions, living in poorly built houses and reed huts. That they were the Harappan peoples is evidenced by the analyses of their remains in the cemetery. While the trade and resources of the city were almost entirely gone, the people retained several Harappan ways in writing, pottery and utensils. About this time ASI archaeologists record a mass movement of refugees from Punjab and Sindh into Saurashtra and to the valley of Sarasvati (1900–1700 BCE).[17] Hundreds of ill-equipped settlements have been attributed to this people as Late Harappans a completely de-urbanised culture characterised by rising illiteracy, less complex economy, unsophisticated administration and poverty.

New Frontiers of the Bronze Age Collapse (Pt. 2/3)

1024px-Metallurgical_diffusionYesterday we were discussing Bronze Age European/Mediterranean trade networks and civilizations. 

(Go to Part 3)

My suspicion is that these societies were more advanced and complex than we generally give them credit for, (especially the northern European ones) simply because we don’t have any written records from them and the archaeological trail is scanty.

We have amber, traded from the Baltic Sea down to Italy, north Africa, the Levant, and beyond; tin, mined in Cornwall, Spain, Brittany, and southern Germany, then traded all across Europe, north Africa, and the Middle East; and of course copper, which was mined all over.

In Egypt the bronze age was clearly glorious, but Greece and Spain also saw the rise of cities, palaces, art, and even aqueducts and sewers. Greece and Egypt had writing and were beginning to develop math (I don’t know much about the Spanish cities.)

1024px-Bronsealderens_sammenbruddAnd then, around 1200 BC, it all collapsed.

Within 50 years, almost every major city in the eastern Mediterranean was sacked, destroyed, conquered, or abandoned. The kingdoms of Mycenaen Greece, the Hittites of Syria and Anatolia,  and the New Kingdom of Egypt (and Canaan) all collapsed. The written language of Greece (“Linear B”) was completely forgotten and disappeared. The Hittite capital was burned, abandoned, and never rebuilt; Anatolia didn’t return to its former level of complexity for a thousand years. Babylon and Troy were sacked; Egypt was invaded by the Libyans.

Bronze_Age_CollapseAnd no one knows why.

The most proximate cause is the “Sea Peoples,” a motley assortment of sea-faring folks who suddenly show up in the local records (especially Egyptian) and conquer everything in sight. As Ramesses III recorded:

The [sea Peoples] made a conspiracy in their islands, All at once the lands were removed and scattered in the fray. No land could stand before their arms: from Hatti, Qode, Carchemish, Arzawa and Alashiya on, being cut off [ie. destroyed] at one time. A camp was set up in Amurru. They desolated its people, and its land was like that which has never come into being. They were coming forward toward Egypt, while the flame was prepared before them. Their confederation was the Peleset, Tjeker, Shekelesh, Denyen and Weshesh, lands united. They laid their hands upon the land as far as the circuit of the earth, their hearts confident and trusting: “Our plans will succeed!”[34]

Who were the Sea People? Where did they come from? According to Wikipedia, they were:

TofG 191The most famous Sea People were the Philistines, who appear to have hailed originally from the Aegean before being defeated by the Egyptians and settled in the southern Levant, where they came into conflict with the Israelites. There’s fairly decent evidence for the Philistine connection, because we have written accounts about them from the Egyptians and the Hebrews, plus the archaeological remains of their cities, which are full of Greek pottery.

Most of the other potential identifications are based on little more than linguistic similarity–in other words, we don’t really have any idea where a lot of them came from.

In Greece, the invaders appear to have come by land, migrating from the north, not the sea.

One of the things I’ve noticed about migrations is that once they start, (for whatever reason,) they keep going. Suppose a famine hits Group A, so they flee the area and displace Group B. Group B pushes out Group C, who take to the seas and end up destroying towns hundreds or thousands of miles away. Events in Mongolia can reverberate into Poland; a sudden abundance of food and medical care in Africa ends with migrants in Sweden.

And in exciting, potentially related news, archaeologists have uncovered the remains of a massive battle that took place in 1250 BC in, of all places, northern Germany:

Along a 3-kilometer stretch of the Tollense River, archaeologists … have unearthed wooden clubs, bronze spearheads, and flint and bronze arrowheads. They have also found bones in extraordinary numbers: the remains of at least five horses and more than 100 men. Bones from hundreds more may remain unexcavated, and thousands of others may have fought but survived.

“If our hypothesis is correct that all of the finds belong to the same event, we’re dealing with a conflict of a scale hitherto completely unknown north of the Alps,” says dig co-director Thomas Terberger, an archaeologist at the Lower Saxony State Service for Cultural Heritage in Hannover. “There’s nothing to compare it to.” It may even be the earliest direct evidence—with weapons and warriors together—of a battle this size anywhere in the ancient world. …

In one spot, 1478 bones, among them 20 skulls, were packed into an area of just 12 square meters. Archaeologists think the bodies landed or were dumped in shallow ponds, where the motion of the water mixed up bones from different individuals. By counting specific, singular bones—skulls and femurs, for example—UG forensic anthropologists Ute Brinker and Annemarie Schramm identified a minimum of 130 individuals, almost all of them men, most between the ages of 20 and 30.

Tollense battlefield
Tollense battlefield

The number suggests the scale of the battle. “We have 130 people, minimum, and five horses. And we’ve only opened 450 square meters. That’s 10% of the find layer, at most, maybe just 3% or 4%,” says Detlef Jantzen, chief archaeologist at MVDHP. “If we excavated the whole area, we might have 750 people. That’s incredible for the Bronze Age.” In what they admit are back-of-the-envelope estimates, he and Terberger argue that if one in five of the battle’s participants was killed and left on the battlefield, that could mean almost 4000 warriors took part in the fighting.

The article has some entertaining illustrations, so I urge you to take a look.

PeeneThe Tollense is a small river in north east Germany, near the Baltic Sea and fairly close to Poland. We have yet to find the remains of any bronze age cities, towns, or fortresses nearby, (the closest known settlement was 350 km away,) but somebody built a 120 meter wooden causeway across the valley.

Was the Tollense part of a major trade network the armies were fighting over? Or was this just the only road in the area? (Serbian Irish has a great post that lays out their position that the battle was actually an attack on a very large, heavily fortified trade caravan. Lots of interesting material in Serbian Irish’s post. [Their argument hinges on claims that there were women, children, and old people among the dead, which I have not seen reported elsewhere, but I also have not read the original papers the archaeologists published, so maybe Serbian Irish knows something I don’t.])

The Science article notes, hilariously, that prior to uncovering a bunch of skulls with arrowheads lodged in them and big, bashed-in holes, many archaeologists genuinely believed that real battles hadn’t occurred in the Bronze Age:

Before the 1990s, “for a long time we didn’t really believe in war in prehistory,” DAI’s Hansen says. The grave goods were explained as prestige objects or symbols of power rather than actual weapons. “Most people thought ancient society was peaceful, and that Bronze Age males were concerned with trading and so on,” says Helle Vandkilde, an archaeologist at Aarhus University in Denmark. “Very few talked about warfare.”

Peaceful arrow inside of somebody's skull, Tollense
Peaceful arrow inside of somebody’s skull, Tollense

You know, those Bronze Age chieftains just collected swords for show, kind of like people who watch too much anime.

This line of thought got started, (as far as I can tell) after WWII, when archaeologists and anthropologists began promoting the idea that war and violence were modern, Western aberrations, and that primitive peoples were all peaceful, nature-loving paragons of gender equality. Much of the accumulated evidence for prehistoric human migrations was dismissed under the slogan, “pots, not people,” an exhortation to interpret the sudden diffusion of new pots and other cultural artifacts as just evidence of trade, not the movement of people. But as I noted before, it’s looking a lot more like “People, not pots.”

This was a pretty stupid line of thought, given that we can actually count the number of homicides committed by modern hunter-gatherers, and have abundant written records of extreme violence committed within the past few centuries by one tribe against the next, from cannibalism to attempted genocide. (Heck, within the last few decades.)

totally peaceful, non-violently bashed in with a hammer skull from Tollense battlefield
Skull non-violently bashed in with a hammer or bat

At any rate, the article discusses in some detail evidence that the soldiers who died in Tollense weren’t just some local brawlers, but were trained professionals, most likely part of a large army drawn from across Europe:

And yet chemical tracers in the remains suggest that most of the Tollense warriors came from hundreds of kilometers away. … archaeologist Doug Price analyzed strontium, oxygen, and carbon isotopes in 20 teeth from Tollense. Just a few showed values typical of the northern European plain, which sprawls from Holland to Poland. The other teeth came from farther afield, although Price can’t yet pin down exactly where.

Further clues come from isotopes of another element, nitrogen, which reflect diet. Nitrogen isotopes in teeth from some of the men suggest they ate a diet heavy in millet, a crop more common at the time in southern than northern Europe. … DNA from teeth suggests some warriors are related to modern southern Europeans and others to people living in modern-day Poland and Scandinavia. …

(Now if only someone could test some Philistine DNA, so we can resolve this “Were they Greek or did they merely have Greek pots?” debate once and for all.)

Twenty-seven percent of the skeletons show signs of healed traumas from earlier fights, including three skulls with healed fractures. …

Standardized metal weaponry and the remains of the horses, which were found intermingled with the human bones at one spot, suggest that at least some of the combatants were well-equipped and well-trained. … Body armor and shields emerged in northern Europe in the centuries just before the Tollense conflict … At Tollense, these bronze-wielding, mounted warriors might have been a sort of officer class, presiding over grunts bearing simpler weapons. …

And not long after Tollense, the scattered farmsteads of northern Europe gave way to concentrated, heavily fortified settlements, once seen only to the south.

This is basically a complete revolution in our understanding of the Bronze Age in northern Europe.

Late Bronze Age cultures of Europe: Lusatian (green), German Urnfield (Orange), and Nordic (Yellow.)
Late Bronze Age cultures of Europe: Lusatian (green), German Urnfield (Orange), and Nordic (Yellow.)

Tollense is located near the apex of three different cultures: the Lusatian (centered mainly on modern Poland;) the Urnfield Cultures throughout most of Germany, (these two were related, but Wikipedia says, “The central European Lusatian culture forms part of the Urnfield tradition, but continues into the Iron Age without a notable break;”) and the Nordic cultures of the northern coast.

Interestingly, the Lusatian culture (and the Urnfield Cultures in general) arose around 1300 BC, or about 50 years before the battle. They replaced the earlier Tumulus Culture, which had interred its dead in big burial mounds (tumuli,) and disappeared right around 1200 BC. The Lusatian and Urnfield Cultures cremated their dead. (In this case, the pots are literally full of people.)

Wikipedia says of the Lusatians:

Recreation of the Biskupin fort, Lusatian Culture
Recreation of the Biskupin fort, Lusatian Culture

Metal grave gifts are sparse, but there are numerous hoards (e.g., Kopaniewo, Pomerania) that contain rich metalwork, both bronze and gold (hoard of Eberswalde, Brandenburg). Graves containing moulds, like at Bataune, Saxony or tuyeres attest to the production of bronze tools and weapons at the village level. The ‘royal’ tomb of Seddin, Brandenburg, Germany, covered by a large earthen barrow, contained Mediterranean imports like bronze-vessels and glass beads. Cemeteries can be quite large and contain thousands of graves.

Well known settlements include Biskupin in Poland, and Buch near Berlin. There are both open villages and fortified settlements (burgwall or grod) on hilltops or in swampy areas. The ramparts were constructed of wooden boxes filled with soil or stones.

Of the Urnfield:

Fortified hilltop settlements become common in the Urnfield period. Often a steep spur was used, where only part of the circumference had to be fortified. Depending on the locally available materials, dry-stone walls, gridded timbers filled with stones or soil or plank and palisade type pfostenschlitzmauer fortifications were used. Other fortified settlements used rivers-bends and swampy areas.

At the hill fort of Hořovice near Beroun (CR), 50 ha were surrounded by a stone wall. Most settlements are much smaller. Metal working is concentrated in the fortified settlements. On the Runder Berg near Urach, Germany, 25 stone moulds have been found.

Hillforts are interpreted as central places. Some scholars see the emergence of hill forts as a sign of increased warfare. Most hillforts were abandoned at the end of the Bronze Age.

And of the Bronze Age Nordic Culture:

Even though Scandinavians joined the European Bronze Age cultures fairly late through trade, Scandinavian sites presents a rich and well-preserved legacy of bronze and gold objects. These valuable metals were all imported, primarily from Central Europe, but they were often crafted locally and the craftsmanship and metallurgy of the Nordic Bronze Age was of a high standard. The archaeological legacy also comprise locally crafted wool and wooden objects and there are many tumuli and rock carving sites from this period, but no written language existed in the Nordic countries during the Bronze Age. The rock carvings have been dated through comparison with depicted artifacts, for example bronze axes and swords. There are also numerous Nordic Stone Age rock carvings, those of northern Scandinavia mostly portray elk.

Thousands of rock carvings from this period depict ships, and the large stone burial monuments known as stone ships, suggest that ships and seafaring played an important role in the culture at large. The depicted ships, most likely represents sewn plank built canoes used for warfare, fishing and trade. These ship types may have their origin as far back as the neolithic period and they continue into the Pre-Roman Iron Age, as exemplified by the Hjortspring boat.[2]

Of course, it is quite likely that the tumulus-urnfield transition had nothing to do with the Libyans invading Egypt and the fall of Troy. But the evidence so far points to the possibility of a much wider, more generalized catastrophe, that either began in one area and then prompted a cascade of peoples to invade and conquer their neighbors in multiple directions, or that affected several areas all at once.

On Thursday we’ll discuss possible reasons behind the collapse. (Go back to Part 1)