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Hits, slides, and rings

438 – 415 thousand years ago

Part of the challenge of language is coming up with some way to distinguish thousands or tens of thousands of words from one another. It would be hard to come up with that many unique sounds. What human languages do instead is to come up with phonemes and rules for stringing phonemes together into syllables, and then create words by arbitrarily pairing up one syllable, or a few, with a meaning. Phonemes are the individual sounds of a language, roughly comparable to individual letters. There are about forty phonemes in most dialects of English. (English spelling does a pretty sloppy job of matching up phonemes and letters. Finnish comes close to one phoneme per letter.)

Often in evolution organisms don’t solve new problems from scratch, but instead harness preexisting adaptations. I argued earlier that the abstract “space” of possession (“The Crampden estate went to Reginald.”) may have developed by harnessing preexisting concepts of physical space. And our abilities to recognize speech sounds may harness our preexisting capacities for recognizing the sounds of solid objects interacting. At least that’s the argument of a recent book by Mark Changizi, Harnessed: How Language and Music Mimicked Nature and Transformed Ape to Man.

Changizi notes that even though we’re mostly not aware of it, we’re very good at using our hearing to keep track of what’s going on in our physical surroundings. For example, people easily recognize the difference between someone going upstairs and someone going downstairs, and we’re pretty good at recognizing individuals by their treads. The sounds that solid objects make can be broadly categorized as hits, slides, and rings. Hits: one object collides with another and sends out a sharp burst of sound. Slides: an object scrapes against another and sends out a more extended sound. Rings: an object reverberates after a collision. Changizi argues that these correspond to the major categories of phonemes.

  • Hits = plosives, like p b t g k
  • Slides = fricatives, like s sh th f v z
  • Rings = sonorants, including sonorant consonants, like l r y w m n, and vowels

These are not the only sounds we can make with our mouths. We can do barks and pops and farts and so on. But our auditory systems are especially cued into solid object physics, so when we try to come up with easy-to-distinguish phonemes, that’s what we focus on. And a lot of rules about how phonemes hook up also follow from this principle – for example hits followed by rings are more common than the reverse.

So even if imitating nature is not the whole story of phonemes, it may at least be where they got started.

Later on when we talk about writing systems, we’ll see there’s a similar argument about how these are tuned to tickle our primate visual systems.

Speech sounds

Below are some reflections on language. There will be plenty more in days to come. For a science-fictional take on language, try Octavia Butler’s account of a world where language has disappeared, Speech Sounds. It’s one of her best. It won science fiction’s Hugo Award for best short story in 1984.

We’re now just past six months through the year 2018 at Logarithmic History. We raced through time at the rate of 754 million years a day on January 1. December 31 we’ll cover just one year (the year 2020) per day. Today, July 2, covers 26,656 years, from 487,475 to 460,819 years ago.

By today’s date, the universe is a lot more complicated than when we started. As we mentioned before, one of the major sources of complexity is the origin of new discrete combinatorial systems, made of small units that can be combined into larger units that have different properties than their constituents. Elementary particles are the first discrete combinatorial system to appear, already present in the early moments of the Big Bang. The different chemical elements are another major discrete combinatorial system. It took billions of years for enough heavy atoms, beyond hydrogen and helium, to accumulate from stellar explosions, allowing the complex chemistry and geology that we know on Earth. It may be that the paucity of heavy elements in the early Universe is what prevented earlier planetary systems from developing complex life.

With the origin of life comes another discrete combinatorial systems, or rather two connected systems: nucleotides strung together to make genes, which code for amino acids strung together to make proteins.

For the second half of the Logarithmic History year, we’ll be spending a lot of time looking at the consequences of another discrete combinatorial system: language. Or maybe, as with genes-and-proteins there are really two systems here: words strung into phrases and sentences, and concepts strung together into complex propositions in a Language of Thought.

The origin of modern human is one of the major transitions in evolution, comparable to the origin of eukaryotic cells, or of social insects. Language is crucial here: slime molds and ants organize high levels of cooperation, turning themselves into “superorganisms,” by secreting pheromones. Humans organize by secreting cosmologies.

Heidelberg and Bodo

By 600 thousand years ago we’re finding people who don’t fit comfortably into Homo erectus. A jawbone from around this time was unearthed in Germany, near Heidelberg, in 1907. Another find from the same period, often assigned to the same species, comes from Bodo, Ethiopia (below).


This guy clearly isn’t modern Homo sapiens, but his brain is starting to get out of the Homo erectus range (1200 cubic centimeters cranial capacity), and his browridge is a double arch, rather than an erectus-style straight bar. He’s also got cut marks on skull and face, from someone “defleshing” him. A respectful mortuary ritual, or did somebody really not like him?

The exact relationship of these guys to later humans has been unclear. A popular theory assigned both to an intermediate species, Homo heidelbergensis. However we just reviewed recent genetic modeling by Rogers and coworkers that suggests that a three-way split between Homo sapiens, Neanderthals, and Denisovans has already happened by this point, although the lineages haven’t had long to differentiate. So probably Heidelbergers in Europe are ancestral to Neanderthals (or at least closely related to their ancestors), while Bodo man is ancestral to our variety of Homo sapiens, or represents some kind of African side branch.

It’s a small world after all

The story of human origins is partly a story of Big Things like The Taming of Fire and  The Dawn of Speech. But it’s also the story of some odd byways and quiddities. A nice introduction to some of these is Chip Walter’s book Thumbs, Toes, and Tears: And Other Traits That Make Us Human. (His more recent Last Ape Standing is good too.) Walters considers funny bits of anatomy like our unique big toes and thumbs, and funny bits of behavior like our habits of laughing, weeping, and kissing. Toes and thumbs fossilize, but behaviors can be hard to date, evolutionarily. Presumably these behaviors appeared sometime before modern humans evolved and spread, so let’s pick today’s date. It’s also hard to figure out the exact evolutionary rationale for some of these behaviors. Humor, for example, is not a simple phenomenon: intellectually appreciating a joke, actually finding it funny and enjoying it, and finally laughing, each involve separate areas of the brain.

Laughter, specifically, is a minor human oddity that sheds an interesting light on some big events in human evolution. Robert Provine, a leading laughter researcher, spells out the argument in “Curious Behavior: Yawning, Laughing, Hiccuping, and Beyond.” Chimpanzees have a kind of laugh, a modified vocalized panting synchronized with inhalation and exhalation. Presumably laughter first resulted when panting-during-play evolved into a play signal. But the short bursts of human laughter go further, having freed themselves from synchrony with the inhalation/exhalation cycle. Laughter, in other words, is just one instance of the more general phenomenon of humans having separate controls for vocalization and for respiration. Interestingly, the most prominent examples of complex vocalization – songbirds and some other birds, whales, bats, and humans – are all found in non-quadrupeds. In quadrupeds, breathing is tightly coupled with locomotion: lungs need to be full to stiffen the thorax when the forelimbs hit the ground. Giving up quadrupedalism seems to have allowed for an “adaptive release” in the evolution of vocal abilities in a number of unrelated lineages. So the study of laughter (and other vocalizations) suggests that two key human adaptations – bipedalism and spoken language – are more closely linked than one might have expected.

Another and overlapping set of human particularities involves facial expressions of the emotions. Darwin got a whole book out of this. He concluded (admittedly based on somewhat anecdotal evidence) that different emotional expressions are largely innate. It’s an interesting illustration of his ability to reason from small facts to large conclusions that he also drew a big conclusion about human evolution from this. In Darwin’s day, there were scientists who believed that different human races had evolved from very different prehuman progenitors: one prehuman species giving rise to Europeans, another to Africans, and so on. But Darwin reasoned that the very close similarity in facial expressions (and he had traveled a lot, and witnessed a lot of expressions in a lot of places) and the very similar emotional makeup of humans around the world was evidence that human populations shared a fairly recent common ancestry. Here as in several other cases, a mixture of close reasoning and sheer luck led Darwin to the correct conclusion about evolution long before there was much solid evidence.

Darwin’s work on emotions was neglected for most of the twentieth century by anthropologists favoring a blank slate view of human behavior, but was eventually largely vindicated by a number of researchers, notably Paul Ekman. There is now good evidence for six basic facially expressed emotions: Fear, Disgust, Joy, Anger, Sadness, and Surprise.

If you’re a movie watcher, this list may seem familiar. These emotions (all except for Surprise) are all depicted as little homunculi living inside the head of an 11 year old girl in the animated feature “Inside Out.” Somebody at Pixar Studios knows their Ekman.


So the sappy song is right: There is just one moon and one golden sun, and a smile means friendship to everyone.

The 700 Club

724 – 686 thousand years ago

We’re getting to a time on the blog when Homo erectus (and Homo ergaster, if we accept that erectus-like African specimens are another species) give way to the very earliest ancestors of later species – modern humans, Neanderthals, and Denisovans. (Denisovans – known mainly from DNA rather than bones – are the contemporaries in East and Southeast Asia of Neanderthals in West Eurasia, and early sapiens in Africa.)

And what should we call the whole post-erectus gang of modern humans / Neanderthals / Denisovans / modern humans? Maybe we could call them all Homo sapiens, and use subspecies names for the three branches; then we modern humans would be Homo sapiens sapiens. Or maybe we should reserve the label Homo sapiens just for our branch. In that case, we could call the larger clade “The 700 Club,” (see below), although apparently someone else already has already taken that name.

A recent article from Alan Rogers (a colleague of mine in Anthropology at the University of Utah) and Ryan Bohlender and Chad Huff (Utah Anthropology PhDs) sheds light on this period. The authors look at the distribution of shared derived mutations in two modern human genomes (African and Eurasian) and two ancient genomes (Neanderthal and Denisovan). They fit a model involving past divergence times and population sizes to the data. The model says that about 700,000 years ago. a small population split from the rest of humanity and then quickly split again to give rise to the ancestors of Neanderthals and Denisovans. In other words, it looks like there was an Out Of Africa event in the Middle Pleistocene, well before the better known Out Of Africa event that gave rise to modern human populations around the world. The ancestors of Neanderthals and Denisovans then replaced Homo erectus in Eurasia, although the authors find signs that some erectus genes may have made it into the Denisovan gene pool. This also implies that Homo antecessor in Europe was a dead-end branch of Homo erectus, not a Neanderthal ancestor.

As paleoanthropologist John Hawks notes, in a commentary on the article, “Humans stand out among our close primate relatives as effective biological invaders. Our recent history has included range expansions into remote and harsh geographic regions, and invasions by some populations into areas long occupied by others.” We’ll be seeing more instances of this in days to come on the blog.

And here’s me on what a later history of population replacement might mean for the evolution of ethnicity and ethnocentrism.


Antecessor rising

A common way of demeaning another group is to call them cannibals. Roman pagans sometimes accused early Christians of cannibalizing infants during their secret ceremonies (a horror-show misreporting of the Christian Mass?). Later on, medieval Christians sometimes accused Jews of murdering Christian infants and mixing their blood into Passover matzohs. In response to such libels, anthropologists have sometimes swung to the opposite extreme, occasionally even denying that cannibalism (other than emergency survival cannibalism) was ever an established practice. But there is no serious doubt that human populations have sometimes practiced cannibalism, sometimes in the very recent past. In 1961, for example, Michael Rockefeller, traveling in search of tribal art, was killed and eaten by a group on the coast of New Guinea. Cannibalism can be unhealthy. For example handling and eating uncooked brains was responsible for the spread of kuru, a  gruesome prion disease, among the Fore of New Guinea. Human populations harbor genes that protect against prion diseases; this might be telling us that cannibalism was common among our ancestors.

At the Grand Dolina site in the Sierra de Atapuerca in northern Spain, the fragmentary remains of 6 people, mostly children, were discovered mixed in with animal bones and stone tools. Animal and human remains were treated the same. In both cases, cut marks show that flesh was cut from the bones. There’s no evidence that the human remains received any specially respectful treatment. Cannibalism is the most plausible explanation.

The researchers involved have proposed a new species name, Homo antecessor, for these and some other early European finds, although not everybody buys this. Whether we recognize them as a new species or not, these guys were probably an offshoot of Homo erectus, but not ancestral to later European groups, like Neanderthals.

Ice Age gear shift

810- 768 thousand years ago

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

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

Current Ice Age? Glaciers covering large parts of northern North America and northern Europe? This isn’t what the climate has been like for the past 12,0000 years. Within the current long Ice Age there have been long glacial periods and shorter interglacials, and we’re currently in an interglacial. Our own activities may have done something to prolong the interglacial, and stave off the return of the ice; more on this another day.

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

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

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

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

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

Father’s Day

906 – 858 thousand years ago

One man draws out the wire, another straights it, a third cuts it, a fourth points it, a fifth grinds it at the top for receiving the head; to make the head requires two or three distinct operations; to put it on, is a peculiar business, to whiten the pins is another; it is even a trade by itself to put them into the paper; and the important business of making a pin is, in this manner, divided into about eighteen distinct operations, which, in some manufactories, are all performed by distinct hands.

Adam Smith famously observed the enormous advantage to be gained from a division of labor in the manufacture of pins. But in one form, the division of labor is far older than Smith’s pin factory: virtually every human society has a division of labor by sex. Here’s a chart from anthropologist George Murdock on the sexual division of labor across cultures.


M Exclusively male
N Predominantly male
E Equal/equivalent for both sexes
G Predominantly female
F Exclusively female
Index is weighted average, male vs.female

The sexual division of labor is an unusual arrangement among animals: not just males and females cooperating in provisioning offspring (birds do it, wolves do it), but doing very different jobs.

It seems very likely that by today’s date on Logarithmic History, Homo erectus had a sexual division of labor, in particular a male specialization in hunting large animals. But there is a problem in figuring out how this arrangement could have gotten started. Smith listed “a tolerable administration of justice” as one ingredient in economic progress: his pin factory would have run into problems without property rights to keep people from swiping pins. In the context of the sexual division of labor, a similar problem arises if we assume that hunting is a form of “paternal provisioning.” How could this ever get off the ground, given an initial condition of promiscuity or alpha-male polygynous mating? (If we assume that monogamy is already in place, the problem is less serious. When paternal provisioning occurs in other mammalian species, it apparently evolves out of a prior condition of scattered monogamous pairs. However this sequence seems improbable for human ancestors.)

Maybe the assumption about hunting as paternal provisioning is wrong. Maybe hunting is about showing off, not providing for a family. (Hemingway is showing off; his family isn’t going to eat the lion.)

hemingway lion

But a recent article considers another possibility: a “Dad” who provisions his family may succeed in a world of “Cads” if there are strong complementarities in economic activities between males and females, i.e. a sexual division of labor. In this respect, human dads may really be something special.

Quest for fire

958 million – 907 thousand years ago

On June 3 on Logarithmic History, our ancestors had gotten as far as steak tartare. Now it’s time for an Eisenhower steak (cooked directly on the coals; see below).

What really distinguishes humans from other animals? We’ve covered some of the answers already, and will cover more in posts to come. But certainly one of the great human distinctions is that we alone use fire. Fire is recognized as something special not just by scientists, but in the many myths about how humans acquired fire. (It ain’t just Prometheus.) Claude Lévi-Strauss got a whole book out of analyzing South American Indian myths of how the distinction between raw and cooked separates nature from culture. (I admit this is where I get bogged down on Lévi-Strauss.)

Until recently the story about fire was that it came late, toward the latter days of Homo erectus. But Richard Wrangham, a primatologist at Harvard, turned this around with his book Catching Fire (which is not the same as this book), arguing that the taming of fire goes back much earlier, to the origin of Homo erectus. Wrangham argues that it was cooking in particular that set us on the road to humanity. Cooking allows human beings to extract much more of energy from foods (in addition to killing parasites). Homo erectus had smaller teeth and jaw than earlier hominins and probably a smaller gut, and it may have been fire that made this possible. Cooking is also likely to have affected social life, by focusing eating and socializing around a central place. (E O Wilson thinks that home sites favored intense sociality in both social insects and humans.)

Surviving on raw food is difficult for people in a modern high-tech environment and probably impossible for people in traditional settings. Anthropologists are always looking for human universals, and almost always finding exceptions (e.g. the vast majority of societies avoid regular brother-sister marriage, but there are a few exceptions, including Roman Egypt and Zoroastrian Iran). But cooking seems to be a real, true universal. No society is known where people got by without cooking. Tasmanians, isolated from the rest of the world for 10,000 years, with the simplest technology of any people in recent history, had lost the art of making fire, but still kept fires going and still cooked.

Recent archeological finds have pushed the date for controlled use of fire back to 1 million years ago (see today’s tweet on Wonderwerk cave), but not all the way back to the origin of Homo erectus. This doesn’t mean Wrangham is wrong. Fire sites don’t always preserve very well: we have virtually no archeological evidence of the first Americans controlling fire, but nobody doubts they were doing it. It could be that it will be the geneticists who will settle this one. The Maillard (or browning) reaction that gives cooked meat much of its flavor generates compounds that are toxic to many mammals but not (or not so much) to us. At some point we may learn just how far back genetic adaptations to eating cooked food go.

An alternative to an early date for fire, there is the recent theory that processing food, by chopping it up and mashing it with stone tools, was the crucial early adaptation.

Whenever it is exactly that humans started cooking, the date falls in (Northern hemisphere) grilling season on Logarithmic History, so you can celebrate the taming of fire accordingly. It doesn’t have to be meat you grill. Some anthropologists think cooking veggies was even more important. I recommend sliced eggplant particularly, brushed with olive oil to keep it from sticking, and with salt, pepper, and any other spices.

On the other hand, Homo erectus probably appreciated a good Eisenhower steak, cooked directly on the coals. (Yes, this actually works pretty well.)

Eisenhower Coal-Fired Steak

Named for the 34th president of the United States, who liked to cook his steaks directly on the coals, this preparation will create a crunchy, charred exterior with rosy, medium-rare meat inside.

Lump hardwood coals work better than briquettes for this recipe because they burn hotter. Be sure you use long-handled tongs. (Sorry, this method is for charcoal or wood grilling only.)

You might find an uneven exterior crust, especially when using lump charcoal, because it is irregularly shaped (unlike the uniform briquette pillows). If that happens, try to position the steak so that it is more directly on the coals and gets an even char. Clasp the steak in the tongs and rap the tongs against the edge of the grill to knock off the occasional clinging ember. If you have some ash, flick it off with a pastry brush.

Make Ahead: The steaks can be seasoned and refrigerated up to 4 hours in advance. Bring them to room temperature before they go on the fire.

  • 1 teaspoon olive oil
  • Two 1 1/2-inch-thick boneless rib-eye steaks (about 28 ounces total)
  • 2 teaspoons coarse sea salt
  • 2 teaspoons freshly cracked black pepper


Prepare the grill for direct heat. Light the charcoal; when the coals are just covered in gray ash, distribute them evenly over the cooking area. For a hot fire (450 to 500 degrees), you should be able to hold your hand about 6 inches above the coals for 2 or 3 seconds. Have a spray water bottle at hand for taming any flames. But use it lightly; you don’t want to dampen the heat too much, and some flames here are fine.

Meanwhile, brush the oil on the both sides of the steaks, then season both sides liberally with salt and pepper.

Once the coals are ready, place the steaks directly on the coals (see headnote). Cook, uncovered, for 6 minutes on one side, then use tongs to turn them over. Cook for about 5 minutes on the second side.

Transfer the steaks to a platter to rest for 10 minutes. Serve as is, or cut them into 1/2-inch-thick slices.

My handaxe

101- 959 thousand years ago

By today’s date, Acheulean tools are well developed in Africa, and found in India too. Sophisticated tools like the Acheulean hand axe probably tell us something not just about cognition in relation to tool making, but also about social cognition. You wouldn’t make a hand axe, use it, and abandon it. Nor would you go to all the trouble if the biggest, baddest guy in the group was immediately going to grab it from you. So there is probably some notion of artifacts-as-personal-possessions by the time Acheulean appears.

Possession is a social relationship, a relationship between two or more individuals with respect to the thing possessed. Robinson Crusoe didn’t “own” anything on his island before Friday came along.

Linguists have noted something interesting about the language of possession that maybe tells us something about the psychology of possession: Expressions for possession are often similar to expressions for spatial locations. Compare spatial expressions:

João went to Recife.
Chico stayed in Rio.
The gang kept Zezinho in Salvador.

and corresponding constructions for possessions:

The Crampden estate went to Reginald.
The Hampden estate stayed with Lionel.
Thag kept axe.

Of course the Crampden estate didn’t go anywhere in physical space, but it still traveled in the abstract social space of possession. In some cases just switching from inanimate to animate subject will switch the meaning from locative to possessive. The Russian preposition y means at/near when applied to a place (People are at Nevsky street) but possession when applied to a person (Hat is “at” Ivan = Ivan has hat.)

What may be going on here: people (and many other creatures) have some mental machinery for thinking about physical space. That machinery gets retooled/borrowed/exapted for thinking about more abstract relationships. So the cognitive psychology of space gets retooled for thinking about close and distant social relationships, or time ahead and behind. In other words, we may be seeing a common evolutionary phenomenon of organs evolved for one purpose being put to another purpose – reptile jaw bones evolve into mammalian inner ear bones, dinosaur forelimbs evolve into bird wings. You can find Steve Pinker making this argument in his book The Stuff of Thought. And Barbara Tversky’s recent Mind in Motion: How Action Shapes Thought seems to make the argument at greater length; I’m looking forward to reading it. For a while most of the evidence of repurposing spatial cognition for more abstract relationships came from linguistics, but there’s now some corroboration from neurology.

And I’ve made the argument for the particular case of kinship: regularities in kin terminology across cultures tell us something about pan-human ideas of “kinship space.” (My kin and mybody parts are arguably the most basic, intrinsic primitive sorts of possessions, since long before my handaxe.) This implies that the evolutionary psychology of kinship has not just an adaptive component (adaptations for calculating coefficients of relatedness and inbreeding), but also a phylogenetic component  (homologies with the cognitive psychology of space).

We’ll see other possible examples, involving e.g. the evolution of speech sounds, as we move along.