Category Archives: Language and communication

Words and Genes

This weekend,  people in the United States set off numerous explosive devices to celebrate 239 years of independence from the United Kingdom. Since this separation, the versions of English spoken in the US and the UK have diverged considerably, but still remain (mostly) intelligible. In contrast, North and South Korea, which have only been separated for 70 years, have been more strictly isolated from one another, and as a result the versions of Korean spoken in the two countries have diverged dramatically:

differences [of mutual unintelligibility] now extend to one third of the words spoken on the streets of Seoul and Pyongyang, and up to two thirds in business and official settings.

A friend of mine who is an actual linguist drew my attention to an app that designed to translate between North and South Korean— an acute problem from people who have defected from North to South.

As Darwin and many others have noted, and as I’ve written about here, such language change bears many striking similarities with biological evolution. These similarities are interesting in their own right, and may be helpful for thinking about the long-running debate in evolutionary biology about whether natural selection acts mainly on genes, individuals, or groups.

A language, like English, or German, or French, is like a biological species. Both languages and species are made up of populations of individuals. Languages and species both have boundaries. In biology, the boundary is sex: a species is defined as a population of individuals that naturally mate and produce fertile offspring with one another. This concept is a pretty good rule of thumb, but turns out to be violated frequently in nature. Oak trees are notoriously promiscuous with oak trees from other species. Of course they mate simply by wafting their sperm into the air (tucked inside pollen grains) so they aren’t the choosiest of breeders. But even among mammals, hybrids frequently occur in nature.

In languages, the boundary is not sex but mutual intelligibility. French is considered a different language from English because, as Steve Martin says, “those French have a different word for everything!” But just as with the biological species concept, this is a useful rule of thumb, rather than an absolute rule. Speakers of closely related languages, like Danish and Swedish, can learn to understand one another with some ease.

Species have subspecies, and languages have dialects. Both are closely related to geography and geographic isolation. Languages like English and Chinese contain “dialects” that may be as mutually unintelligible as pairs of “proper” languages. Because the distinction between a language and a dialect is to some extent political, a common saying among linguists is “A language is a dialect with an army and a navy.”

Similarly, the distinction between species and subspecies in biology is somewhat arbitrary. Baboons, for example, are a widespread group of monkeys, occurring through most of Africa, with one species (Hamadryas baboons) extending their range across the Red Sea into Saudi Arabia and Yemen. Even though baboons are among the most intensively studied nonhuman primates, no one seems to about how many different baboon species there are, and what they should be called. Some people consider all baboons to be subspecies of Papio hamadryas. Other people distinguish ten or more species: Guinea baboon, Hamadryas baboon, Hauglin’s baboon, Anubis baboon, “typical” yellow baboons, Ibean yellow baboon, Kinda baboon, grey-footed baboon, Transvaal chacma baboon, and Cape & desert chacma baboon.

Jolly, C. J. (2001). A proper study for mankind: Analogies from the papionin monkeys and their implications for human evolution. Yearbook of Physical Anthropology, Vol 44. C. Ruff. New York, Wiley-Liss, Inc. 44: 177-204.
Jolly, C. J. (2001). A proper study for mankind: Analogies from the papionin monkeys and their implications for human evolution. Yearbook of Physical Anthropology, Vol 44. C. Ruff. New York, Wiley-Liss, Inc. 44: 177-204.

Interbreeding occurs among all these different kinds of baboons where their ranges overlap, so from the point of view of the traditional biological species concept, they are different species. But calling them all subspecies of Papio hamadryas seems odd because Hamadryas baboons are the most distinctive baboons of all: the males have showy capes and tufted tails, and their societies have an unusual multi-level structure quite different from the usual troops of “savanna baboons.” Moreover, as more studies are conducted of other baboons, it has become clear that each of these species (or subspecies) differs from others. For example, Guinea baboons turn out to have a social system quite similar to that of Hamadryas baboons.

So languages are similar to species, and dialects are similar to subspecies. These categories refer to populations. Within populations, individuals vary greatly, both in their language use and in their genes.

Each individual speaker of a language has her own set of words and rules: an idiolect. My idiolect may be very similar to yours, or quite different, depending on our shared vocabulary, which may include technical terms specific to our work, and idiosyncratic speech habits (which my wife complains I have in abundance).

An idiolect is similar to an individual’s genome. Each individual is unique, but at the same time, each individual speaker of a language shares a broad set of words and rules with other speakers of that language (otherwise they wouldn’t be able to communicate – and wouldn’t be considered speakers of the same language).

Continuing the analogy down to the next level, words are similar to genes. Words and genes are both combinatorial, in that they consist of sequences of smaller units combined to make larger units: syllables and letters in words, codons and nucleotides in genes.

Words are made up of syllables. Some words are made of single syllabus, such as “dog,” “cat,” and “fish.” Longer words can be made by combining syllables: “dogfish,” “catfish.”

Similarly, genes are made up of a series of codons. Unlike syllables, which can be spelled with anywhere from one to six or more letters (“a,” “-ed”, “-ing”, “ouch,” “queue,” “smooch,”), codons are always spelled with three letters.

Spelling is easier in genetics than in linguistics, because while languages may use dozens of letters (e.g., 26 in English), all genes are spelled with only 4 letters: G, A, T, and C. These letters stand for the nucleotides Guanine, Adenine, Thymine, and Cytosine.

Words are generally much shorter than genes, however, Words usually have only a few syllables, whereas genes can contain hundreds or thousands of codons.

Each 3-letter codon is translated into an amino acid; these amino acids are in turn connected up together like cars in a train to make proteins. The whole business of making proteins is very complicated, and is perhaps roughly analogous with the translation of mental representations of words into physical phenomena, such as sounds produced by the vocal tract, or signs made with the hands in sign language, or words written on a page or typed on a screen.

Linguistics Genetics
Combinatorial level Example Example Combinatorial level
Letter A, B, C, D, E, F, G… A, C, G, T Nucleotide
Syllable Dog, cat, in-, un-,-ness CAT, TAG, DAT, DCG Codon
Word Dog, cat, catness, undoglike hemoglobin, melanin, lactase, amylase Gene
Idiolect My particular speech My particular genes Genome
Dialect Upper Midwest American English Homo sapiens sapiens Subspecies
Language English Homo sapiens Species
Family Germanic, Indo-european Hominins, Primates Clade

In addition to being combinatorial, words and genes resemble one another in that they are both products of descent with modification. This is the phrase that Darwin preferred to “evolution,” and is really more precise about what happens in evolution. The descent part means that words and genes both have histories and family trees. The modification part means that both words and genes gradually change over time, across generations.

Both words and genes can undergo small changes, “mutations,” in how they are spelled. Genes can change by as little as one nucleotide. Many such mutations are “silent,” that is, they don’t affect the amino acid sequence made by the gene, because the genetic code is redundant: there are only 20 amino acids, but 64 possible codons. So some amino acids can be spelled several different ways. The amino acid serine, for example, can be spelled TCA, TCC, TCG, or TCT.

Mutations can have a wide range of effects, from not changing gene function at all, to wrecking the gene entirely. Some mutations result in slight improvements.

Words also undergo mutations. Talking about mutations in words is a little tricky in that the letters we use to spell them have an imprecise relationship to the way they are actually pronounced. In linguistics, the actual speech sounds that make up words are called phones.

Thus, “water” is spelled the same way in Dutch and English, but is pronounced slightly differently. Even within English, “water” is pronounced differently by different speakers and dialects. In the American Midwest, “water” is pronounced something like “wah-dur,” whereas in some dialects in England it is pronounced more like “wah-tuh.”

But both words and genes are robust to these small changes. They still work when altered just a little bit – which allows them to evolve.

Words and genes both accumulate small changes over time. These changes tend to cluster geographically. People who live near one another for many generations tend to speak the same language and dialect, and also tend to have more similar genes than people who live further away.

So what does all this have to do with the argument in biology about levels of selection?

In 1976, Richard Dawkins drew attention to the gene’s eye view of biology with his book, The Selfish Gene. Prior to this book, a widespread view in biology was that genes are something organisms use to accomplish certain goals. The heart pumps blood, the kidneys filter blood, and the genes store information and transmit it to the next generation. Dawkins, popularizing work by G. C. Williams and W. D. Hamilton and others, turned this view on its head: organisms are “survival machines” that genes use to make more copies of themselves. Dawkins argued that genes are ruthlessly selfish, because only those genes that succeed in getting copied are transmitted to the next generation.

Many people have objected to this view of evolution. Stephen Jay Gould, for example, argued that natural selection acts on individuals, rather than genes. Biologists including Edward. O. Wilson and David Sloan Wilson have argued that selection acts on multiple levels: genes, individuals, groups, perhaps even species. The debate continues with passionate advocates on each side.

In some ways, I think the debate is entirely sterile. Many people on both sides of the debate seem willing to agree that group selection is mathematically equivalent to kin selection. What really seems to feed the passion in this debate is the connotations that people have towards the idea of genes as “selfish” entities. Many people seem to have the impression that group selection is somehow kinder, gentler, and politically more left-leaning than gene-level selection. This view puzzles me, since plausible mechanisms of group selection are often quite nasty, such as intergroup hostility and warfare.

Genes are exotic entities, only recently discovered, and not fully understood even by professional biologists. Words, however, are familiar things that we all use all the time. So linguistic evolution might be easier to grasp for many of us than genetic evolution.

From a Darwinian perspective, a word is selfish in exactly the same way that a gene is. In both cases, versions that succeed in making more copies of themselves are the ones that persist over time.

Genes get themselves copied through reproduction. In species with sexual reproduction, they depend on their host finding a mate and (if there is any parental care) successfully rearing the resulting offspring.

Words get themselves copied in various ways. Vertical transmission is like biological reproduction, in that words are passed down from parent to child. Words differ from genes in that they are also easily passed among unrelated individuals: horizontal transmission. Horizontal transmission of genes does occur, especially in bacteria, but it is less common in complex multicellular creatures like ourselves.

Words vary among speakers, just as genes vary among individuals. Common words are shared by nearly every member of a language community, but there is still variation, among regions, social groups, interest groups, and individuals.

My idiolect, like my genome, is an ephemeral collection of words and rules. It will vanish when I die (apart from whatever words I have left behind in books and such – but even those will represent only a fraction of my actual idiolect, and will show the influence of co-authors, editors and such). My genome will also vanish when I die (parts of it will live on in my children, but all mixed up with my wife’s genes).

Words, however, have longer histories – as do genes. The word I use for H2O, “water,” comes from ancient roots. We see its cousins in words such as “Wasser” in German and the more distant cousin “voda” in Russian (whence the word “vodka,” “my dear little water”), and “uisge” in Scottish Gaelic (and its distilled descendant word in English, “whiskey”).

In language evolution, selection occurs mainly at the level of words. It is individual words that accumulate changes in their sounds and meanings. Words exist in a constant competition with other words for space in each individual’s vocabulary. Words come and go, depending on fashion, technology, and random drift.

The analogy is of course far from perfect and shouldn’t be pushed too far.

In fact, some linguists don’t like this analogy at all. In a 2014 blog post, linguist Asya Pereltsvaig complains:

words are not “just like genes” in that they are easily borrowed from language to language, even across family boundaries, are subject to conscious choice, and are not subject to natural selection.

The first point is true – sort of. The sort of genetic transmission that we are most familiar with is vertical (parent to offspring) rather than horizontal (from one unrelated individual to another). However, horizontal gene transfer turns out to be more important the people used to think.

Bacteria swap genes fairly frequently, such as when they share genes for resistance to antibiotics (like Deadheads swapping tapes of old Grateful Dead shows).

And according to one recent study, some 8% of the human genome originated in retroviruses.

So actually words and genes quite similar in this respect. Most genes, and most words, come from your parents, but some genes and words come from elsewhere, sometimes even quite unrelated sources.

The other claim, that words are not “subject to natural selection,” is also debatable. Pereltsvaig focuses attention the fact that word form is arbitrary.

As was noted by the “father of modern linguistics” Ferdinand de Saussure, the association of sound and meaning of a word is largely random: the sound of house is neither more appropriate to the concept nor better for the “survival of the fittest” than maison (French), dom (Russian), bayit (Hebrew), or iglu (Inuktitut)

It is true that the particular form of a word is basically arbitrary. But it is not true that selection has nothing to do with word form. Over time, long words that are frequently used get shortened. In both French and English, the invention of two-wheeled human-powered transportation required an accompanying new word (“vélocipède,” bicycle), which was subsequently shortened in both languages (“vélo,” bike). French teenagers commonly use “gar” for boy instead of the longer “garçon.” Words that are hard for native speakers to pronounce get changed to make pronunciation easier. Words whose meanings are transparently obvious to native speakers may generally catch on better than words whose meaning is opaque. For example, the term “earworm” (to describe a catchy tune that gets stuck in your ear) has a better chance of being understood, used, and catching on among English speakers than the original German word that it is translated from, “Ohrwurm“.

Pereltsvaig also claims, “words provide no adaptive advantage to people(s) who have them.”

But I disagree with this as well. Words are crucial to survival and reproductive success in human societies. Someone unable to use words at all would have tremendous difficulty holding a job or finding a mate. Using words well is essential, not just for those who write for a living, but also for anyone who talks with other people.

In some cases, correct understanding of a word could make the difference between life and death. One time at Gombe, an American colleague of mine thought she saw a hippo swimming in Lake Tanganyika. She grew alarmed, as several people were swimming nearby. Hippos may seem harmless but they enormous, terrifying beasts with huge sharp tusks (usually hidden inside their vast mouths). Hippos are often said to kill more people in Africa each year than crocodiles. To warn the swimmers, she shouted “Kifaru! Kifaru!” The Swahili-speaking swimmers just looked at her with a puzzled expression – since kifaru means rhinoceros in Swahili, and there was no risk whatsoever that there would be a rhino in the water. It turned out there wasn’t a kiboko (hippo) either, but if there had been, this linguistic mistake could have proved deadly.

The particular words we use tell others about our social status, our level of education, our sense of humor and style, and many other aspects that directly affect our reproductive success. Blurting out the wrong set of words can cost a person dearly (see, for example, James Watson, Tim Hunt, Donald Trump).

Looking at evolution from a gene’s eye view provides insights that simply aren’t available from other perspectives. Many aspects of biology don’t make any sense at all except from a gene’s eye view. The very existence of sex, for example. If selection occurred at the level of individuals, we should see individuals mainly making exact copies of themselves (clones). This sometimes happens in plants and animals, and is the norm for bacteria, but the widespread occurrence of sexual production is very difficult to explain, unless evolution is mainly about the replication of genes.

At the same time, words and genes both exist within incredibly complex systems in which the influence of any one word or gene may not be obvious. Just as each word contributes a tiny bit to each individual’s language output, each gene contributes a bit to each individual’s biological output. The total number of words that an individual speaker knows is estimated to be around 20,000 – 35,000. Coincidentally, this happens to be quite similar to the number of protein-coding genes in the human genome (around 20,000-25,000). Thus, in most cases, any single word or gene is likely to have only a small and subtle influence on an individual’s survival and reproductive success.

Words combine in complex ways to produce phrases, sentences, and longer things like poems, songs, articles and books. Gene products interact in complicated ways to produce living bodies and regulate the expression of other genes.

Both words and genes only make sense within the context of the complex system in which they exist. The French word “entrée” means something eaten at the start of a meal in French (the “entry” into the meal). When English speakers borrowed this word, they rather confusingly used it to refer to the main course of a meal. Similarly, the “meaning” of genes depends on the context in which the genes occur. In animals with red blood cells, the genes for hemoglobin make proteins that carry oxygen. But what would happen if these genes were inserted into a bloodless organism, such as a bacterium? Probably just an accumulation of protein that has no use whatsoever for the bacterium. (This may seem like a weirdly pointless experiment, but it has actually been done to produce and and study mammoth hemoglobin).

Additionally, just because words and genes are both “selfish,” in the sense that those that are better at getting copied are the ones that become most common in a given population, does not mean that they have to promote behavior that is selfish. Animals engage in all sorts of altruistic behavior, much of which is presumably the result of genes promoting altruism – that is in fact the central topic of The Selfish Gene.

For example, individual words might be “selfish,” in the sense that words with features that promote being copied get copied more often. But the words themselves don’t necessarily promote selfish behavior. For example, “Do unto others as you would have done unto you” is a combination of words that has been extremely successful in getting itself copied. Perhaps the great majority of the hundreds of millions of people who speak English have some version of this phrase stored in their memories; and other languages transmit equivalent versions of this phrase. The phrase is good at getting copied, but it advocates cooperative behavior, rather than selfish behavior. This is precisely why the phrase has been so successful. People who make an effort to follow the idea encoded in this phrase are likely more successful at navigating the complexities of village and urban life than people who are mean-spirited and selfish. “Selfish” words, like “selfish” genes, often promote cooperative behavior.

Language evolution and biological evolution both result from the accumulation of small changes at fundamental levels: words and genes. Words are “selfish” in exactly the same way as genes. Words and genes that have attributes that increase their likelihood of being reproduced become more common in the population. But neither words nor genes have goals, or minds, or emotions, or feelings of being selfish, altruistic, or anything else. They are just bits of information that happen to exist within copying systems. And just because these bits of information can be described as selfish doesn’t mean that they invariably code for selfish behavior.


Planet of the Apes

28 July 2014

The latest Planet of the Apes movie raises interesting many interesting questions, such as: what would it take for other apes to replace humans as the planet’s ruling primates?

Spoiler Alert: if you haven’t seen the movie yet, you might not want to read any further until you have. I try to steer clear of plot details, but if you’re the kind of person who likes to know as little as possible about a movie before seeing it, consider yourself warned.

I grew up watching the original Planet of the Apes movies. I am sure seeing movies of a world ruled by apes fueled my interest in our hairy cousins. It was a rich time for anyone interested in apes. The first movie came out in 1968, the same year that the site where Jane Goodall studied chimpanzees, Gombe, was upgraded from a game reserve to a National Park. We watched films of Jane Goodall and the chimpanzees of Gombe in elementary school. New discoveries about the apes were reported regularly in the glossy pages of National Geographic. Studies of sign-language using apes like Washoe and Koko suggested apes were on the brink of human intelligence. Movies like King Kong and the Planet of the Apes franchise presented apes as both dangerous and fascinating, blurring the boundary between human and animal.

I had a special interest this latest Planet of the Apes movie as I contributed some recordings of chimpanzee vocalizations. As a result my name shows up on the big screen for a few seconds, after Ape Extras but before Editorial Assistant, New Orleans. The Chicago Sun-Times even noticed.

(The name  Michael Wilson also shows up in the credits for the original movie, as writer of the screenplay  — though that was of course somebody else!)

I thought they did a good job with ape vocalizations in the movie. One of my complaints in general about animals in movies is that they make much more noise than animals do in real life. Movie predators, whether lions or dinosaurs, always seem to roar right before attacking their prey – something real predators would never do, as they seek to catch their prey by surprise. Roars are for warning members of your own species to stay away (and/or for attracting mates), not for chasing away your prey!

Chimpanzees can be extremely noisy, but most of the time they are very quiet. So one of my recommendations to the sound editors was to avoid extraneous calls. I was very pleased to see that for many scenes, the apes were indeed fairly quiet.

And when the apes did vocalize, I enjoyed hearing real ape calls, and different calls for each species.  I particularly liked one scene where the apes give a massive round of pant-grunts to Caesar. This is a call that chimpanzees use to show submission, and they used it in the right context for this film.

I liked that the apes mainly used sign language, and that when they did speak, they had rough, breathy voices, much like Viki the chimpanzee did when being trained to say words like “cup” and “up.”

In general, I thought the film did an excellent job building the characters and story. The main ape and human characters are complex, with understandable motives, and aren’t depicted as being either simply good or evil.

I think this might be the best movie yet in the franchise, and well worth seeing.

As an ape ecologist, though, I can’t help thinking about certain things.

For example, Muir Woods seems like a pretty rotten place for apes to live. It has trees, sure, but they are mainly redwoods and other conifers that produce no ape-friendly food. Apes are specialists in ripe fruit, which is in pretty short supply in a redwood forest. According to the Muir Woods website:

“Life in a redwood forest is determined by the low light conditions that restrict growth of plant species producing flowers, nuts, or berries. In addition, coast redwood trees contain an abundance of tannin (or tannic acid), a chemical compound that deters the presence of insects. Taken together, these conditions create an environment that is relatively low in the resources that typically form the base of a food web.”

So while it’s really cool to see apes swinging from the branches of redwoods, that forest is pretty grim habitat for apes. The gorillas might be able to subsist on herbs growing in the understory, but these are largely ferns and not very palatable. The chimps and orangutans would be pretty hungry there. They might use the forest as a temporary refuge, but would quickly move on to more suitable habitat, such as the overgrown gardens and city parks of post-apocalyptic suburbs.

If ordinary chimpanzees, gorillas and orangutans were released into the California wilderness, they would probably go their separate ways. The orangutans would forage alone. The male gorillas would compete over the female gorillas, until each silverback had a small group of females for himself. Each gorilla group would then forage separately. The chimps might start off as a single community but over time they would probably fission into several mutually hostile communities, each defending their own territory. It’s not clear why these different ape species stick together, or why they live in a village instead of sleeping up in the trees like real apes do. But of course these are retrovirus-mutated, hyper-intelligent talking apes, so they behave differently.

The film is surprisingly conservative in depicting ape romantic relationships, in that Caesar at least seems to be in a monogamous marriage with Cornelia. I suppose showing Caesar as a loyal family man makes him more appealing to viewers. However, a normal alpha male chimpanzee would try to monopolize matings with all the fertile females; and these females would try to mate with multiple males, even against the wishes of the alpha male. But perhaps the mutating retrovirus also makes apes monogamous.

But a big question relates to the film’s fundamental premise: what would it take to destroy human civilization, and clear the way for the world to be ruled by another kind of ape? (Or, in this case, a triumvirate of three different ape species.)

As Ruben Bolling points out,the Rise of the Planet Ape is a true story, and we are living it: we are the apes that have taken over the whole planet. But is human domination of the planet inevitable? How hard would humanity have to be hit to make way for other apes?

In this movie, humans are very nearly wiped out by a genetically engineered retrovirus, ALZ-113,  that makes nonhuman apes super intelligent but kills humans. (This has interesting parallels with SIVcpz, a naturally occurring retrovirus, which was transmitted from chimpanzees to humans, probably by people hunting and butchering chimpanzees for food. When contracted by people, the virus is called HIV-1 and causes the disease AIDS, which has killed many millions of people around the world. SIVcpz doesn’t make apes super intelligent, of course, and we have learned that it is also fatal to chimpanzees (Keele et al., 2009)).

According to newscasts in the movie, almost everyone who contracts the virus dies; only 1 in 500 survive. Since the virus is highly contagious and transmitted by sneezing, this leads to a much more devastating result than even the AIDS pandemic.

There are about 7 billion people on the planet today. So if 1 in 500 people died, there would still be 14 million people on the planet. Such a rapid and catastrophic epidemic would have huge impacts on the survivors, though, as food distribution systems and everything else collapsed. Say only 1 in 10 of people who survived the virus would survive the aftermath of collapsing civilization. That would bring the total population of people on the planet down to 1.4 million (which is still four to five times the total number of chimpanzees living on the planet today). This is probably a low figure, given that many people on the planet are subsistence farmers and herders of livestock.  Many people living in rural Africa, for example, would be able to survive the collapse of industrialized civilization, because they mainly live off the land without access to electricity, plumbing or fossil fuels.

In the San Francisco Bay Area, though, most people have no idea how to farm, herd livestock, or live off the land. Collapse would hurt people hard. So starting from a Bay Area population of about 7.44 million, if 1 in 500 die from disease, that leaves around 14,880 survivors. If 90% of those survivors died from starvation and post-apocalyptic fighting and such, then only around 1,488 people would be left in the Bay Area. That seems in line with the number of people crowded into the refuge of San Francisco (though as my wife noticed, the virus seems to have selectively killed all the Asians).

(Though why are they living in the middle of the city? I would think any survivors would mainly live on isolated rural farmsteads, where they can grow their own food, rather than crowding into the city center. How do these people eat? But it does look cool and dystopian to have everyone crowded together in the post-apocalypse city — maybe more so than setting it, say, on the outskirts of post-apocalypse Fresno.)

(Some other quibbles: Ten years post-apocalypse, I’m not sure anyone would still have usable manufactured clothing, eyeglasses or electronics anymore.  Even in my own family, after a year living abroad, with easy access to clothing and other supplies, the clothes we brought with us are ragged, the kids need new eyeglasses, and my son and I both need new shoes. Life post-apocalypse would certainly be much harder on such supplies. Moreover, there would certainly be no birth control or antibiotics. Sexually active women would be pregnant or nursing — which would have huge impacts on society. Weirdly, almost no young  human children, or women with nursing babies, were shown in this film.)


Based on the number of apes living in Muir Woods, they must have been reproducing at a really high rate compared to normal apes. This wiki states that there are 2,000 apes living in the ape village. Now that’s a lot of apes. Currently there are only about 2,000 captive chimpanzees in the United States. The starting population in Muir Woods must have been a lot less than that, since they started with apes escaping from just two captive colonies, and it would be hard for apes from other parts of the country to find out about the Muir Woods population, much less travel there.

Is it realistic to have 2,000 apes in ape village just 10 years after the ape revolution?

One key to the success of humans is demography. We can reproduce much faster than other apes. For example, suppose by coincidence that both the surviving human population in San Francisco, and the chimpanzee population in Muir Woods, started out at about 1,000 individuals. (Gorillas reproduce more quickly than chimpanzees, and orangutans reproduce more slowly, but since in the movie most of the apes are chimps, I’ll focus on them.) In a best case scenario, chimpanzee populations could potentially grow at about 2% per year. (Most wild chimpanzee populations “grow” at about 0% per year, though, because mortality is high and food supplies are limited — which in turn limits fertility and growth.)

Projected populations of humans and chimpanzees post-apocalypse, starting from 1000 individuals in each population.
Projected populations of humans and chimpanzees post-apocalypse, starting from 1000 individuals in each population.

So starting out with 1,000 chimps, in ten years there would be only about 1,221 chimps (if they somehow found food and didn’t suffer high mortality from predation, warfare etc.). Human hunter-gatherers, though, can grow at much faster rates, such as around 4%, even without medical care and with all of the hardships that hunter-gatherers face. At this rate, starting with 1,000 humans, we’d have around 1,492 people by the end of ten years — so about 270 more humans than chimps. And realistically, survivors in California would be farmers, not hunter-gatherers, with potentially even faster population growth. So if Ape Village apes are reproducing like normal chimpanzees, and if the starting population was in the hundreds, a population of 2,000 ten years later is not realistic.

Why can human populations grow so much faster than chimpanzees?

In some ways it is surprising that this can even be possible. After all, humans take longer to reach maturity than chimpanzees. Female chimpanzees have their first birth around age 14 (males reach full size around age 16, but for population growth, it’s females that matter more). Humans hunter-gatherers take longer to mature, with an average age of first birth at 18-20 (Hill & Kaplan 1999). Moreover, even though humans live longer than chimpanzees, human females stop reproducing in their forties — so their reproductive careers are, on average, shorter than those of chimpanzees.

However, once humans do grow up, they can reproduce quickly.  Chimpanzees have an average interval of around 5 years (Jones et al., 2010), whereas hunter-gatherers have an interbirth interval of only 4 years (Hill & Kaplan 1999).

How can women reproduce more quickly than chimpanzees? A big part of the answer must be cooking. Thanks to fire, humans can extract more energy from the environment, by increasing the energy available from food, and by making otherwise unpalatable foods safe to eat (Wrangham et al., 1999). Cooking likely helps children grow faster, by providing soft, energy rich foods from a young age, whereas chimpanzee children continue drinking their mother’s milk for longer, as they gradually add tough, hard adult foods to their diet. This surely has a big impact on human fertility and growth rates.

In the movie, the apes in Ape Village had fires in each house, so maybe they were cooking? That would certainly help them reproduce more quickly.

Another reason human populations can grow so much faster than chimpanzee populations is that humans have much lower mortality than chimpanzees, even in hunter-gatherer populations without access to medicine. Hunter-gatherers regularly live into their 50s, whereas the median age of survival for wild chimpanzees is about 30, and few live into their 40s. What accounts for this difference?

I suspect cooking is probably important for reducing mortality as well.  Cooking and other food extraction and preparation technology likely help people obtain food even in difficult times of the year, whereas chimpanzees in seasonal environments may become weak and more likely to die from diseases. Cooking also must help people live longer by providing soft foods that they can continue to eat into old ages, as their teeth wear down.

So super-intelligent mutant apes potentially *could* take over the world, but only if most of the humans are killed off, and apes learn how to cook.


Works cited:

Jones, J. H., M. L. Wilson, C. M. Murray and A. E. Pusey (2010). “Phenotypic quality influences fertility in Gombe chimpanzees.” Journal of Animal Ecology 79(6): 1262-1269. get pdf

Keele, B. F., J. H. Jones, K. A. Terio, J. D. Estes, R. S. Rudicell, M. L. Wilson, Y. Li, G. H. Learn, T. M. Beasley, J. Schumacher-Stankey, E. E. Wroblewski, A. Mosser, J. Raphael, S. Kamenya, E. V. Lonsdorf, D. A. Travis, T. Mlengeya, M. J. Kinsel, J. G. Else, G. Silvestri, J. Goodall, P. M. Sharp, G. M. Shaw, A. Pusey, E. and B. H. Hahn (2009). “Increased mortality and AIDS-like immunopathology in wild chimpanzees infected with SIVcpz.” Nature 460: 515-519. get pdf

Hill, K. and H. Kaplan (1999). “Life history traits in humans: Theory and empirical studies.” Annual Review of Anthropology 28: 397-430. get pdf

Wrangham, R. W., J. H. Jones, G. Laden, D. Pilbeam and N. Conklin-Brittain (1999). “The raw and the stolen: cooking and the ecology of human origins.” Current Anthropology 40(5): 567-594. get pdf






Is English a Virus from Outer Space?

Last week, I attended talks for the Society of Anthropology of Paris meeting here in Montpellier. This has been an interesting experience for many reasons. For one, the talks have shown some interesting differences in the politics of anthropology in France compared to the United States.

The society was founded by Paul Broca in May, 1859, six months before Darwin published the Origin of Species. Broca discovered the language-associated area of the brain that bears his name, and was the one of the first to study the Cro-Magnon fossils, discovered in France in 1868.

While the society carries the general name of Anthropology, it now focuses on Biological Anthropology. The talks were mainly what in America we would call archaeology: analysis of bones and food residues from historic and prehistoric graves and occupation sites. Interesting stuff, but a bit narrow in scope. Few talks focused on human behavior, apart from a session of evolutionary psychology talks Thursday morning. In contrast to the American Physical Anthropology meetings, there were no talks on nonhuman primates. Most strikingly, there was no sociocultural anthropology at all; they have different meetings. Apparently, the divide between quantitative, evolutionary anthropology and qualitative, interpretive anthropology is even more stark in France than in the US. It seems more like an old, nearly-forgotten divorce than the uncomfortable marriage-on-the-verge-of-separation that still exists in American anthropology.

Another interesting aspect of the meetings was the use of language. The audience was mainly French, so I expected all the talks and slides to be in French. One speaker, based in England but not a native English speaker, gave her talk in English, but most of the language on her slides was French. The other speakers spoke in French, but for many of the talks, some or even all of the slides were in English. They frequently used English for technical terms, or when citing the title or findings from papers published in English. This was all very typical of what I have been seeing in departmental seminars at the University of Montpellier. The audience is mainly French, and most of the talks are in French, but visiting speakers usually give their talks in English, which everyone in the audience seems to understand reasonably well. And even when the speakers are French, their slides are sometimes entirely in English.

Before coming here, I had the impression that the French were highly protective of their language. They have laws requiring the use of French in commercial communications. They have L’Académie française, which tries to keep the language contaminated from foreign words like “le sandwich” and “les airbags.”  Government agencies strive to come up with replacements for English words like “buzz,” “chat,” and “newsletter.” And in a recent study, France ranked right at the bottom of the heap of European countries for English language proficiency. And there’s a stereotype that the French are hostile towards people who can’t speak French properly (meaning most of us Americans).

In contrast to what I expected, though, most of the people I’ve encountered seem to have a very positive attitude towards English. People who know some English are eager to practice it. It’s not like northern Europe, where almost everyone in the cities seems to speak perfect English, but enough people speak English that in many situations, I have to make an effort to keep using French. The books in the lab library are mainly in English. My French colleagues read and publish their papers in English-language journals. Lab meetings and social interactions are mainly in French, but everyone can switch to English when needed (like when I give up in my struggle to explain something in French, which often happens). Outside of academia, English words and phrases occur in ads and on signs, and English-language songs dominate the radio (which is required by law to have 40% of songs in French during prime hours).

On a global scale, French has fallen dramatically from its 19th Century peak as a major language of empire, diplomacy, learning and culture. The percentage of American and British students studying French as a foreign language has dropped dramatically in recent decades. In much of North America, place names from Indiana (La Fontaine) to Minnesota (the redundantly named Mille Lacs Lake) reflect a long-lost empire, where French has been reduced to a declining minority language in Louisiana and even in Canada, where the proportion of native French speakers has dropped to 22% of the population. Even in Africa, where France had a vast colonial empire, French may be losing ground compared to other languages. In formerly French North Africa, Arabic competes with French for status as the primary language. South of the Sahara, French is still widely used as an official language, but Rwanda dropped French in favor of English, both in protest to French actions during the Rwandan genocide, and as part of an effort to build closer ties to the Anglophone East African Community. English is an official language of Africa’s most populous country (Nigeria) and the biggest economy (South Africa), and is the language of higher education in Africa’s second most populous country, Ethiopia, even though Ethiopia was never part of the British Empire. In Asia, English is widely spoken in South and Southeast Asia, including the second most populous country on the planet, India, whereas French has a small and declining number of speakers in former French Indochina.

In the thousand year-old rivalry between English and French, English seems to be gaining the upper hand.

Which has me wondering: what makes a language expand or contract? Does it mainly have to do with features outside the language, such as politics, demography, military conquest, and migration? Or does it also depend, at least to some extent, on features of the language itself?

I remember a night more than twenty years ago, during my first field season in Africa, studying baboons in Kenya. Gathered around the dinner table with American and Kenyan researchers, eating by the warm glow of kerosene lanterns, conversation turned to why English was so widely spoken. One of my American colleagues suggested that it was because English was so open to new words and ideas. Instead of trying to keep out foreign words, English readily adopts new words, like America adopts new immigrants.

I thought this was a funny thing to be saying in Kenya, where English was widely spoken not because the language is so open and friendly, but because it was the language of the British Empire, which colonized Kenya and much of the rest of Africa, as well as most of North America. The reason Kenyans and Americans had English as a common language had more to do with British seafaring, commerce, and military might than with any particular virtues of the language they spoke.

Similarly, all sorts of languages that might be hard for non-native speakers to learn have spread widely due to non-linguistic factors, such as the military might and demographic growth of their speakers. English speakers generally consider Russian, Chinese, and Arabic all hard to learn, but that didn’t stop these languages from spreading widely as their respective empires expanded.

All the same, thinking more about language from a Darwinian perspective makes me wonder whether, in the competition among languages, languages might change in ways that affect their relative competitive ability.

A language, like a biological species, has a life cycle, and is in competition with other languages. A language may spread widely and diversify, leaving numerous descendant languages, as Latin gave rise to the Romance languages, or Sanskrit to many modern Indian languages. Or it may shrink and die.

Growth or decline for languages occurs much the same way as it does for species: through births, deaths, and migration. Each time a child is born and learns her mother tongue, a new speaker is added to the language. If a language is no longer being transmitted to the young, but is only spoken by old people, the language will die with the last aging speakers.

Languages also migrate with their speakers. One reason English is spoken so widely is because seafaring English speakers established colonies around the world. In some of these colonies, English speakers became numerous and eventually swamped not only the native populations but also all subsequent immigrants. Some linguists call America a “language graveyard” because speakers of so many different languages come to America, only to have their children learn English and forget their mother tongue.

The total population of French speakers appears to be growing. In evolution, though, what really matters is relative growth rate. Genetic fitness, for example, is essentially a measure of relative growth rate of particular variants of genes (“alleles”) in a population. Alleles that have a high relative growth rate become increasingly common in the population, and may eventually reach fixation, present in essentially all members of the population. An allele, or a language, can become less common in the population if it is increasing at a slower rate than the population as a whole.

But unlike genes, language isn’t transmitted only from parents to offspring. Language can also be transmitted to completely unrelated people. In this way, a particular language is more like an infection.

As William S. Burroughs wrote and Laurie Anderson sang, “language is a virus from outer space.”

This is a thought-provoking image. Like a virus, a particular language is not part of the host’s own genome, but it uses the host to spread itself. However, it is wrong on two counts.

First, even though human language is an extremely peculiar and probably unique form of communication among earth species, invoking space aliens as an explanation is sort of the reverse of Occam’s razor: “among competing hypotheses, the hypothesis with the fewest assumptions should be selected.”

Second, even though language has some virus-like properties (it is can be transmitted from one person to another), it is really more like a plasmid than a virus.

Viruses are parasites that hijack the cellular machinery of other organisms to make more copies of themselves. But they usually don’t do anything to help the host, and in fact they often harm the host. A cold virus has been making the rounds of my family, and it has done nothing good for any of us. Instead, it lurks in our cells, churning out more copies of itself, and manipulates our bodies to ooze those copies out into the world to be spread to other people through coughing, sneezing, and running noses.

In contrast, at least as far as transmission is concerned, a language is more like a plasmid than a virus. Plasmids are little circular bits of DNA found in the cells of bacteria and other organisms.

Plasmids encode genes that provide handy tricks for the host, such as resistance to an antibiotic, or the ability to make a toxin. Plasmids can enable their hosts to live in what would otherwise be a hostile environment. Plasmids are useful to the host, rather than harmful, probably because of their mode of transmission: they can only be transmitted when the host reproduces (by dividing, in the case of bacteria) or when the host connects to another cell specifically to obtain new genes.

Like a plasmid, a language can do all sorts of useful things for its host. So much so that I’ve been making considerable effort to infect myself with a new one (French).  The infection is far from complete (and is progressing rather more slowly than I might have hoped), but it’s far enough along that I can do a number of useful things with it, like order coffee and chocolate croissants, or renew my commuter rail pass, or get a new inner tube for the wheel of my jogging stroller, all of which would be harder to do using only the infection that I inherited (English).

The idea of language as a virus, or plasmid, or other transmissible agent is closely related to the term “meme,” which Richard Dawkins coined in The Selfish Gene, to make an analogy between cultural and biological evolution. The word has caught on, happily, to refer to Internet pictures of LOLcats and such, which are memes in exactly the sense that Dawkins originally meant: little bits of information that are able to get themselves propagated, and which undergo mutations and evolve overtime in branching lineages, just as genes do. In this sense, a language is basically a big complex of memes.

In this view, the individual words in a language are memes. Like genes, they evolve, becoming more or less frequent in a population over time, and undergoing mutations, and sometimes becoming extinct.  Words compete with other words in the meme-pool.

The word computer, for example, is a Latinate word that came into English from French around 1646. At that time, the word “computer” referred to a person, not a machine: someone whose job it was to do calculations. Three hundred years later, when electronic calculating machines were invented, English speakers described the machines as “computers.” This sense of the word spread from English into a number of other languages, like Russian (kompyuter) and Swahili (kompyuta). But in France, the original home of the term “computer,” they instead use “ordinateur,” a word created in 1955 at the bequest of IBM France, because the term “computer” seemed “too restrictive in regard to the possibilities of these machines.”

So while languages have memes like viruses have genes, and like viruses they can be transmitted from one person to another, languages are usually useful to their host, rather than harmful. Why is that the case?

One reason might be the mode of transmission. A virus that is transmitted via saliva and snot is mainly interested in making its host produce lots of saliva and snot, and sneezing and smearing those fluids as widely as possible. The virus doesn’t share any genes in common with the host, and its reproductive success doesn’t depend on the reproductive success of the host. (Except for sexually transmitted viruses; though here, the interests of the host and virus still diverge, since the host doesn’t necessarily reproduce each time it has sex. A sexually transmitted virus benefits if the host lives long enough to keep having sex with more partners, but its own success doesn’t depend on whether the host actually reproduces successfully.)

In contrast, the surest means of language transmission is through the reproduction of the speaker. Languages take a long time to acquire (as I am painfully aware), and even though people say little kids learn languages quickly, it still takes years from them to learn their mother tongue properly, and from what I’ve seen in my own family, acquiring a new language is no trivial matter even when young. Because transmitting language from parent to child depends on successful raising of the child,  the interests of the language closely coincide with the interests of the host.

But unlike a host’s own genome, a language can be transmitted horizontally as well as vertically: from host to host, rather than just host to offspring. It is in this respect that a language is more like a plasmid than either a virus. Like a plasmid, a language is useful to its host, it is transmitted to the host’s offspring, and it can also be transmitted to other unrelated hosts.

Of course, languages aren’t exactly like plasmids. It’s just an analogy, and any analogy can be pushed too far. But to me it seems a helpful analogy for thinking about the relative growth rates of different languages.

In an environment full of a particular antibiotic, such as penicillin, bacteria that acquire the penicillin-resistance plasmid will survive and reproduce, whereas bacteria without that plasmid will die out.

Likewise, in a world where English provides access to information, jobs, and money, people will have a strong incentive to acquire English.

On balance, I would guess that most of the reasons for the success of English have little to do with any particular properties of English. English is not, of course, intrinsically a “better” language than French, or Swahili, or Basque, or any other language. All of these languages can be used to communicate any idea. Most of the current advantages of English have to do with the social and political environment, which depends more on the happenstance of the British Empire spreading English across the world and planting colonies in fertile places, and the resulting the wealth and power of the United States and its impacts on global commerce, popular culture, science and technology. Currently a huge factor must be frequency dependent selection. As English becomes more widely spoken, it becomes increasingly advantageous to know it. This produces a snowball effect, benefiting English at the expense of other languages.

Still, are there some linguistic features that have helped English become widespread? Has English itself evolved in ways that make it more contagious? Perhaps the early history of contact with other languages, like Brythonic, Old Norse, and Norman French, helped to eliminate some features that were harder for non-native speakers to learn (most aspects of gender and case, for example). Elimination of tricky features seems to have happened with other languages. Swahili, for example, emerged as a trading language between Africans speaking Bantu languages and traders from Arabia, Persia and elsewhere. Many Bantu languages related to Swahili have tones, but Swahili doesn’t, perhaps as a result of interaction with Arabic and other languages.

Perhaps the combination of Germanic grammar and Romance vocabulary helps to make English easier for speakers of these two major branches of European languages to learn.

And also, given that much of the innovation in science, technology, and other ideas happens in Anglophone countries, and is communicated in Anglophone channels, English is rich in vocabulary useful for talking about these new things and ideas.

But another way that English might help propagate itself is through the production of little bits of language that are highly infections in their own right: songs, books, movies, and the like.

Popular music, and music videos, seem especially virus-like. A pop song doesn’t provide obvious benefits to the listener. Instead, it exploits the listener’s sensory biases in ways that make the listener want to repeat the experience.

Take the music video for Gangnam Style, for example. I watched it many times.  I haven’t learned anything useful from it, except perhaps an explanation for why all the kids at the disco are dancing like they are riding ponies. This mainly Korean language video went viral, in part due to its catchy little hook of weird English.

In the book Plagues and Peoples, historian William H. McNeil argued that a key factor in history was the diseases carried by different peoples. The Eurasian landmass provided a massive Darwinian breeding ground for particularly nasty infectious agents, passed from domestic animals to people, and transmitted over thousands of miles of steppe by mobile horsemen. When Europeans first traveled to the Americas, they carried these highly infectious agents with them, with disastrous results for the Native Americans.

In a similar way, the vast Anglophone world serves as a global breeding ground for particularly infectious memes. I’ve talked with people who say they learned their English from listening to rap, or watching TV.

Perhaps official efforts to protect French actually serve to weaken the language, reducing its ability to resist infection, and reducing pressure on the producers of songs, books, movies and other cultural artifacts to be maximally infectious.



La Vie en France

Currently I am on sabbatical in France, hosted in the lab of Michel Raymond at the University of Montpellier-2.

I have been working on papers on chimpanzees and aggression, but also trying to learn French, which has me thinking a lot about language, including the evolution of language, and parallels between biological evolution and linguistic evolution.

I didn’t study French in school, apart from a few weeks in grad school, but over the years have tried, in fits and starts, to learn the language on my own. I have studied two evolutionary cousins of French, Spanish and Italian, which both helps and hurts. There are lots of similarities in the vocabulary and grammar of these languages, but my wife complains that I speak French like a Spaniard.

Languages are like biological species, in that they change over time, and are related to other languages in a tree-like pattern. Just like humans and chimpanzees share a common ancestor that lived around 6 million years ago, French and English share a common Indo-European ancestor that was spoken something like five or six thousand years ago, before the Italic and Germanic branches of Indo-European diverged.
Indo-European Language Evolution







Words are a bit like genes, in that they are units of inheritance. A language is made up of words, much like a genome is made up of genes. Like genes, words change gradually over time, in their meaning and pronunciation. With written languages, we can track these changes with spelling, just as we can track genetic changes with differences in the letters of the genetic alphabet of base pairs (A, T, G and C).

Like our genes, we usually get our language from our parents. But unlike genes, we can also get bits and pieces of language, and even entire languages, from people who are completely unrelated to us.

Unlike animal species (but like some organisms, like bacteria), languages can “mate” freely and exchange words. Thus, English and French have been exchanging words freely over the past thousand years, even though they are from different branches of the Indo-European language family.

One of the fascinating (and sometimes frustrating!) things about French is this long history of interaction with English. After the French-speaking Normans invaded England in 1066, French enjoyed several hundred years as the primary language of the ruling class in England, and English borrowed many thousands of words from French. As a result, written French looks a bit more like English than other Romance languages do; and written English looks rather more like a Romance language than other Germanic languages do. And ever since the Norman invasion, English and French have been trading words back and forth.

Like genes, words accumulate tiny changes over time. Over long periods of time, words with a shared ancestry can drift apart and become very different in spelling, pronunciation, and/or meaning.

Just like in biological evolution, when populations are separated, they gradually begin to accumulate differences and diverge. Just like these changes can lead to the formation of distinct species, they can lead to the formation of distinct languages.

Over time, these repeated branchings from common ancestors lead to tree-like patterns for both languages and species. Historical linguists were the first to appreciate this, for example in this very early depiction of language evolution, which appeared about 60 years before Darwin published an evolutionary tree as the only figure in his Origin of Species.

Tree of Languages by Félix Gallet, c. 1800
Tree of Languages by Félix Gallet, c. 1800


Dawin's Tree
Dawin’s Tree








Just like in biological speciation, the process is gradual and boundaries are often fuzzy. American English is a bit different from British English. French people tell me they need subtitles to understand French movies from Quebec.

Many words are spelled pretty much the same in both French and English, especially anything ending in –tion (nation, séduction, production) or –ism(e) (capitalisme, socialisme). These are often words that were recently invented and borrowed.

Older borrowings, which have had more time to evolve, can look quite different. For example, castle and château both come from the Latin common ancestor, “castellum.” The English word is still pretty similar to the Old North French word “castel,” while in French, the hard “c” has turned to a soft “ch” sound and the “s” has disappeared, signaled only by a sort of fossil of an accent mark, the circumflex (ˆ) on the “a,”  which shows there used to be an “s” there.

French has borrowed lots of words from English, which are sometimes obvious (le sandwich, le weekend, le cocktail) but not always: le foot (football), le pull (pullover, sweater).

Many words that English borrowed from French mean quite different things in modern French. Sometimes this is because the English adopted a quite different meaning of the word from how it is used in French. (An entrée is the entry to a meal in French, just a light little starter course, but for some reason an entrée has come to mean the main dish in English.)

But sometimes this is because the French word has continued to evolve in its own course, or been abandoned altogether for another word.

Like dandelion. English borrowed this from the French phrase, dent-de-lion, “lion’s tooth,” a lovely name that must refer to the toothy looking leaves. But apparently, the French don’t call dandelions “dent-de-lions” anymore. Instead, they call them pissenlit – literally, piss-in-bed, because of the plant’s diuretic properties.

Pissenlits in bloom.
Pissenlits in bloom.

Thanks a lot, evolution.