Where did I put my car keys, and when did civilization begin?

Some mysteries, like "Where did I put my car keys?" can be solved by discovering new information.  Some of the more interesting ones, though, may resolve by realizing you were asking the wrong question in the first place.

For example, physicists spent a long time trying to understand the medium that light waves propagated in.  Just like ocean waves propagate in water and sound waves propagate in all kinds of material -- but not in a vacuum -- it seemed that light waves must propagate in some sort of medium.  "Luminiferous aether", they called it.

But that brought up questions of what happens to light if you're moving with respect to that medium.  Sounds in the air will sound higher-pitched if you're moving through still air toward the sound, or if the wind is blowing and you're downwind, and so on (examples of the Doppler effect).

There didn't seem to be a "downwind" with light.  The Earth orbits the Sun at about 0.001% of the speed of light, not much, but enough that a careful measurement should detect a change in frequency depending on which direction light is moving and where the Earth is in its orbit.  But it didn't, and people spent a lot of time trying to figure out what was happening with the aether until Einstein put forth a theory (special relativity) that started with the idea that there was no aether.

I just got done scanning through the older posts on this blog to see whether I'd discussed a question that comes up from time to time, in various forms, when discussing human prehistory: "What happened a few thousand years ago in human evolution, that enabled us to move from hunter-gatherer societies to full-blown civilization?"  The closest I could find was a comment at the end of a post on change in human technology:

How did civilization and technology develop in several branches of the human family tree independently, but not to any significant extent in others?

This is not quite the same question, but it's still not a great question because it's loaded with similar assumptions.   All societies have technology and rules of living together, so we're really talking about who has "advanced technology" or "higher forms of social organization" or whatever, which are not exactly the most objective designations.  But even taking those at face value, I think this is another "wrong question" like "What happens if you're moving with respect to the aether?"

Even if you try to stick to mostly objective criteria like whether or not there are cities (civilization ultimately derives from the same roots as Latin civitas -- city -- and civis -- citizen), or whether a particular group of people could smelt iron, once you go back a few thousand years there's a lot we don't know about what happened where, and even where we think we do know, the definitions are still a bit fuzzy.  How big does a settlement have to be to be considered a city?  How much iron do you have to smelt before you're in the "iron age"?  Any amount? Enough to make a sword?  Enough to manufacture swords by the hundred?

Wikipedia (at this writing) defines a civilization as "any complex society characterized by the development of a state, social stratification, urbanization, and symbolic systems of communication beyond natural spoken language (namely, a writing system)" with eight separate supporting citations.  I didn't check the page history, but one gets the impression that this definition evolved over time and much discussion.

By this definition, civilizations started appearing as soon as writing appeared.  In other words, writing is the limiting factor from the list above.  The first known examples (so far) of writing, Sumerian cuneiform and Egyptian hieroglyphs, are about 5400 years old.  By that time there had been cities for thousands of years.  Terms like "state" and "social stratification" are harder to pin down from hard archeological evidence, or even to define objectively in a way people can agree on, but it's pretty clear that, however you slice it, they came well before cuneiform and hieroglyphics.

It may be hard to pin down exactly what a state is, but it's not hard to find examples that people will agree are states.  Most of the world's population now lives in places that most people agree are states, even though there are disagreements about which people are subject to the rules of which state or whether a particular nation's government is effectively functioning as a state.  Nonetheless, if you asked most political scientists whether, say, New Zealand, Laos or Saint Lucia is a state, you'd get a pretty resounding "yes".  Likewise, most people familiar with the subjects would agree that, say, Ancient Rome, the Shang Dynasty and the Inca Empire were states.

The problems come when you try to extract a set of criteria from the examples.  While Wikipedia defines a state as "a centralized political organization that imposes and enforces rules over a population within a territory" it goes on in the very next sentence to say "There is no undisputed definition of a state" (with two supporting references). Wikipedia does not claim to be an authoritative source on its own and I suppose it's possible that the page editors missed the One True Definition of "state", but it seems unlikely.  More likely there really isn't one.

Going with the "centralized political organization ..." definition for the moment, things get slippery when you try to pin down what it means to "impose and enforce rules".  For one thing, except (probably) in the smallest city-states, say Singapore or the Vatican, there is always a tension among various levels of government.

In the US, for example, the federal government is supreme over state and local governments, but in practice it's local laws that mostly determine where you can build a house, how fast you can drive your car on which streets and any of a number of other things that have more visibility in most people's day-to-day life than, say, federal standards for paraffin wax (I checked, there are several).

Certainly the supremacy clause of the Constitution means something, and few would disagree that the federal government imposes and enforces rules throughout the US, or that the US is a state, but on the other hand we also call 50 constituent parts of the US "states" and they impose and enforce their own rules within their boundaries.  Is the State of Wyoming a "state", then, in the sense given above?  If so, is the city of Cheyenne?

This may seem like splitting hairs over definitions, but when you consider something like the Roman Empire, where it could take weeks or months to get a message from the center of government to the far-flung provinces, and the people in those provinces often didn't speak the official language and largely practiced their local religions and customs, and the local power structure was largely still in place, though with some sort of a governor, who may or may not have been Roman, nominally in charge, it's a legitimate question what it might mean to be "part of the Roman Empire" or in what exact territory the imperial state could actually impose and enforce rules at any particular time.

If all you have to go on is excavated ruins without any written records, it's harder still to say what might or might not be a state.  There are monumental constructions going back at least 10,000 years, that would have required cooperation among fairly large numbers of people over years or decades, but that doesn't necessarily mean there was (or wasn't) a centralized government.  So far, no one has found any strong indication that there was.  It's possible that ancient monuments were built at the command of a centralized leadership, but again, there doesn't seem to be any strong evidence to support that, as there definitely is for, say, the Egyptian pyramids.

Likewise for cities.  It's hard to tell by looking at the ruins of a city whether there was a centralized government.  One of the earliest cities known, Çatalhöyük, shows no obvious signs of, say, a City Hall or anything other than a collection of mud-brick houses packed together, though the houses themselves have their own fascinating details.  But then again, neither would any number of large villages / small towns today show obvious signs of a central government.  There may have some sort of centralized government, somewhere, imposing and enforcing rules on Çatalhöyük, but there could very well not have been.  Current thinking seems to be there wasn't.

Empires like the Mongol or Macedonian ones built cities, but most cities in these empires already existed and were brought into the empire by conquest.  If we didn't have extensive written records, it would be much harder to determine that, say, present-day Uch Sharīf, Pakistan, was (possibly) founded by Alexander as part of the Macedonian Empire and was later (definitely) invaded by the Mongols.  While it's a fairly small city of around 20,000 people, it contains a variety of tombs, monuments and places of worship.  If it were suddenly deserted and all writing removed from it, and everything else in the surrounding area were covered in dirt, an archeologist who didn't know the history of the surrounding regions would have a lot of work to do to figure out just what went on when.

Present-day archeologists trying to understand human culture from 10,000 or more years ago are up against a similar situation.  What sites have been discovered are often isolated and what survives has a lot more to do with what sorts of things, like stonework and pottery, are likely to endure for millennia than what was actually there.

In addition, it's clear that while there were cities thousands of years before  Mesopotamian civilization, it's pretty clear most people didn't live in them, but in the surrounding areas, whether nomadically or in villages, and whatever traces they left behind are going to be much harder to find, if they can be found at all.  There's probably at least some selection bias, in that until perhaps recently, there has been more focus on finding signs of civilization, that is, cities, than looking for signs of villages or nomadic peoples.

The result is that we really just don't know that much about how Neolithic people organized themselves.  There are some interesting clues, like the existence of "culture regions" where the same technologies and motifs turn up over and over again across large areas, but it's hard to say whether that's the result of a central government or just large-scale trade and diffusion of ideas (current thinking seems to be that it's probably trade and diffusion).

One of the basic assumptions in talking about civilizations is that civilization requires stable and abundant food supplies so that people can remain in one place over the course of years and at least some people have time to do things besides procuring food.  The converse isn't true, though.  You can have stable and abundant food supplies, and at least the opportunity for people to develop specialized roles, without civilization developing, and that seems to be what actually happened.

Rice was domesticated somewhere between 8,000 and 14,000 years ago, and wheat somewhere in the same range.  Permanent settlements (more technically, sedentism) are at least as old, and there were cultures, such as the Natufian, that settled down thousands of years before showing signs of deliberate agriculture.  Overall, there is good evidence of

• Permanent settlements without signs of agriculture over periods of millennia (Natufian culture)
• Large-scale organization without signs of agriculture or permanent settlements (monuments at Göbekli Tepe about 10,000 years old, not to mention later examples such as Stonehenge)
• Cities without writing, or signs of centralized government (Çatalhöyük, about 9,000 years ago at its peak)
• Agriculture without large-scale cities, over periods of millennia (domestication of rice and wheat)
• Food surpluses without grain farming
• Large-scale trade without evidence of states

Putting this all together

• There's not really a widely-accepted single definition of what civilization is, particularly since there's no widely-accepted single definition of what concepts like "state" and "social stratification" mean
• It's hard to say for sure how people organized themselves 10,000 years ago because there's no written record and the physical evidence is scattered and incomplete
• There are clear signs, particularly monumental structures, that they did organize themselves, at least some of the time
• There are clear signs that they interacted with each other, whether directly or indirectly, over large areas
• The various elements of what we now call civilization, particularly agriculture and permanent settlements, didn't arise all at once in one place, but appeared in various combinations over large areas and long periods of time

In other words, there was no particular time and place that civilization began, and questions like the ones I gave at the beginning aren't really meaningful.

Human knowledge has continually evolved and diffused over time.  People have been busy figuring out the world around them for as long as there have been people, and as far as we can tell, people's cognitive abilities haven't changed significantly over the past few dozens of millennia.

Overall, we've become more capable, because, overall, knowledge tends to accumulate over time.  The ability to create what we now call civilization has been part of that, but there was no particular technological change, and certainly no genetic change, that brought about the shift from foraging societies to civilization, because it's not even accurate to talk about "the shift".  There wasn't some pivotal change.  There have been continual changes over large areas and long periods of time that have affected different groups of people in different ways.  We can choose to draw lines around those now, but the results may say more about how we draw lines than about how people lived.

None of this is to say that terms like "civilization" or "state" are meaningless, or that civilizations and states are inherently bad (or good).  Rather, it seems more useful to talk about particular behaviors of particular groups of people and less useful to argue over which groups had "advanced technology" or were "civilized", or to try to say when some group of people crossed some magical boundary between "uncivilized" and "civilized" or when some collection of settlements "became a state".

Among other things, this helps avoid a certain kind of circular reasoning, such as asserting that the people who built Stonehenge must have had an advanced society because only an advanced society could build something like Stonehenge.  What's an advanced society?  It's something that can build monuments like Stonehenge.  I don't think this really represents the current thinking of people who study such things, but such arguments have been made, nearly as baldly.  Better, though, to try to understand how Stonehenge was built and how the people who built it lived and then try to see what led to what.

This also helps avoid a particular kind of narrative that comes up quite a bit, that there is a linear progression from "early, primitive" humanity to "modern, advanced societies".  In the beginning, people lived in a state of nature.  Then agriculture was discovered, and now that people had food surpluses, they could settle down.  Once enough people settled down, they developed the administrative structures that became the modern nation-state as we know it, and so forth.

None of those assertions is exactly false, leaving aside what exactly a "state of nature" might be.  Agriculture did develop, over periods of time and in several places.  Eventually, it enabled higher population densities and larger centers of population, and, in practice, that has involved more elaborate administrative structures.

But that isn't all that happened.  People raised domesticated plants, and eventually animals, and otherwise modified their environments to their advantage, for hundreds or thousands of years at a stretch without building large cities.  Cities arose, but for almost all of human history, as in prehistory, most people didn't live in them -- that's a very recent development.

One problem with this kind of linear narrative is that it can give the impression that there was a sort of dark age, before civilization happened, where people weren't doing much of anything.  If we put the origins of modern humans at, say, 70,000 years ago -- again, at least to some extent this is a matter of where we choose to draw lines, but it couldn't have been much later than that -- then why did it take so long to get from early origins to civilization?  As far as anyone knows, that's a span of over 60,000 years.  What were we doing all that time?

If you require a sharp dividing line between "nothing much going on" and "civilization", this seems like a mystery.  If you don't need such a line, the answer seems pretty mundane, because we were doing pretty much the same thing all the way through:  steadily developing culture, including technology and art.  Eventually, at various times and places, what we now call civilization becomes possible, and some time after that, at some smaller number of times and places, it happens.

One note: This post draws fairly extensively from points made in The Dawn of Everything.  Along with discussing human history, that book explores what implications deep human history might have on how present-day societies might be structured.  I'm not trying to promote or refute any of that here.  Here, I'm more interested in deep human history itself, the stories we tend to build around what we know about it, and how the two can differ.

Pan proiiciens

Humans have several unique qualities (and many more not-so-unique), but one that may not come readily to mind is that we throw things, and we throw them very well.  No other animal we know of could come remotely close to doing this, or this, or this.  Even an average human's throwing abilities are far beyond anything else in the natural world.  If I said that I'd seen someone throw a ball 50 meters, no one would think twice.  If I said that I'd seen a horse throw a ball 50 meters, the most likely response would probably be "No, you didn't", maybe followed by "How??"

If you think about it, it's actually somewhat surprising that humans would be unique when it comes to throwing things.  It's a very useful skill.  If you can bring down a small mammal with a well-aimed rock, you'll eat much better than if you have to run it down.  Even if you're a very good runner-downer, it still takes way less energy to throw a rock.  Throwing a rock can also get a high-hanging fruit out of a tree (though not easily).  Throwing is a good way to get something you're carrying up onto a high ledge that you can then get to with all your limbs free, and so forth.  You'd think something would have stumbled on it before our ancestors did.

On the other hand, a lot of body plans just aren't that well suited to throwing.  Birds have one set of limbs serving as landing gear and for locomotion when not airborne, and the other given over to wings.  That leaves the head and beak as all-purpose picker-uppers, severely limiting throwing potential.  Birds can throw things by picking them up and then heaving the head and letting go, but not very far or forcefully.

Fish and other sea creatures live in a viscous medium where throwing is not particularly useful.  Most mammals have all four limbs specialized for walking, running, jumping and so forth, leaving them in much the same spot as birds.  Lizards are also pretty well tied to the ground or other surface they're traveling on -- particularly the limbless ones, to say nothing of actual snakes (snakes are closely related to lizards, but there are also some proper lizards that lack limbs).

There's an obvious common thread here: To throw effectively you need a free limb, one not specialized to supporting your weight.  You need hands, as opposed to front feet.  You don't need to be fully bipedal, though that clearly ought to help, but you do need to be able to grab something, stand up on your hind limbs and let fly.

There aren't many animals in that category, but several primates are, by virtue of having hands (and feet, and tails) adapted to grabbing and swinging from tree branches instead of always walking on all fours.  Putting all this together, perhaps it's not so surprising that throwing would have only evolved recently, in a branch of the primate family tree, itself relatively recent.

It is a principle of evolution that behavior tends to change first, and then anatomy follows.  First certain fish started coming up out of the water, whether to escape from other fish who couldn't or to move from a shallow, drying-up pond to a deeper one, or for whatever reason. Later came Tiktaalik and its kin with pectoral fin bones (and other features) better adapted to life out of water.

Once the new niche was established on land, there was plenty of selection pressure to reshape the body for living on land, and eventually lose the older adaptations for water living entirely.  More strictly speaking, the new behavior of coming up on land meant that fish with more land-adapted bodies could have better survival chances.

In the case of primates throwing, it's not that other primates don't throw.  Some species of monkeys are well-known to throw excrement at others of their species, and chimps will throw things as a threat.  It doesn't seem to matter much to them what they throw, but it will generally be branches and occasionally rocks.  Chimps don't show signs of throwing with the same purposes we do, but it's significant that some sort of throwing behavior is established in our near relatives.  It's therefore plausible, though not certain, that it was also established in our common ancestors.

While chimps are known to hunt, and are known to throw things, and are known to be reasonably intelligent, they are not known to throw for purposes of hunting.  This is not completely shocking, as they tend to hunt small monkeys in trees when they hunt.  The strategy is to go in as a group, block off escape routes and send one member of the hunting party in for the kill.  Rock throwing would probably not help much in such a situation.  You'd have to encumber a hand carrying a rock up into the trees, and then you'd only have one rock, a bunch of branches in the way, and a monkey that would not be well-inclined to staying still in the path of a hurtling rock.

But imagine a tribe of ancestral chimps a couple of million years ago venturing out of the forest.  These wouldn't be exactly like today's chimps, of course, but today's chimps appear to resemble these ancestors much more closely than we do, so we can consider them ancestral chimps here.  In 1993, William Calvin laid out a hypothesis that a good way for such creatures to get food would be to stake out a water hole and go after the herds that gathered there to drink -- as several other predators do.

Naturally, herds of gazelles and such are adapted to dealing with predators around water holes.  The main strategy is to stampede away, which works well, except that any animal that trips or falls is likely to be trampled by the herd and left behind as an easy meal.  This actually works reasonably well for the herd as a whole (from an individual's view, if you have this behavior you're more likely to be one of the survivors than if you don't), and it works for the hunters as well.  It just doesn't work particularly well for the particular animal left behind.

Now suppose you hit upon a way to make a herd stampede, and at the same time make one of its members stumble and likely be trampled.  That would work even better for you, though again not so well for the unlucky victim.  Calvin's idea is that there's an easy way to do this, that those ancestral chimps could have done with the mental and physical abilities they had: Throw a reasonably-sized rock into the herd.  If it hits one member, that member will stumble, the herd will startle and, with a bit of luck, trample the stumbler.   This doesn't have to happen every time, just enough to make it noticeably easier to get food from the herds gathered at the water hole.

At that point, we're off to the races.  Any change, whether in behavior or anatomy,  that improves throwing force or accuracy, will make for better hunting and better-fed primates.  Richard Young cites paleontological evidence to support a claim that exactly this happened during the past couple million years -- the body, and the hand in particular, became better and better suited to throwing (and to clubbing, another area where we excel).  Doing these well requires a number of changes from the long-fingered, short-thumbed tree-branch-hooking hands of the rest of the chimp family.

Calvin, for his part, speculates that the famous Archeulean hand axe was actually an improved weapon to throw into a herd, as it would be more likely to cut into the prey's hide and cause it to instinctively collapse, making it more likely to be trampled.  As always, this doesn't imply that the hunters were thinking it through in that much detail.  It's enough that throwing a sharp rock works better than throwing one that isn't, and that some in the population had an innate proclivity for chipping away at rocks and so making them sharper.

It's been argued repeatedly that, if we weren't the ones doing the classifying, or weren't so subject to a certain prideful feeling of distinctness from the rest of nature,  we would be classified in the same genus as chimps and bonobos.  Either they would be Homo troglodytes and Homo paniscus, or we would be Pan sapiens.  Under the latter scheme, those savanna-dwelling rock throwers might best be called Pan proiiciens -- throwing Pan, the name Pan being taken from the Greek god of the forest, used to designate the forest-dwelling chimps and bonobos.  Except these particular Pan would be leaving the forest.

Behavior drives anatomical change, but anatomy limits behavior.  Just as only some fish had the right anatomy to even try moving on land, only some animals had the right kind of body to try throwing things.  Primates happened to be close enough, again likely because their hands had already adapted for something else besides walking, something that allowed for grabbing and flinging.  This is a common pattern in evolution.  It used to be called pre-adaptation, but that gives the impression that, for example, primate hands evolved for grabbing tree branches so that they could later evolve for throwing and clubbing.  That's not how it works, so the ungainly but unbiased term exaptation is preferred.

There is another interesting point that Calvin makes.  It's not enough to have the anatomy.  You need to be able to control it.  It takes around a tenth of a second for our bodies to carry out a conscious command.  To throw a projectile accurately [as we do now, as opposed to lobbing rocks into a herd -- D.H. Sep 2015], you need to time your movements within about a hundredth of a second.  Once you've decided to throw something, it's far, far too late to make adjustments as you go along.  You have to have the whole program ready to go ahead of time, adjusted for where your target is -- or will be when the projectile reaches it.  Calvin speculates that this sort of plan-ahead was re-purposed into our control structures for things like language.

I'm not sure I quite buy this.  I doubt that throwing is the only thing in evolutionary history that requires this sort of plan-ahead.  Surely when a hawk dives for a mouse or a cheetah jumps for a gazelle it is doing the same sort of thing under similar constraints.  Nonetheless, it's an interesting idea, and plausible in a general sense, that the original behavior change of throwing things would have brought on a host of other changes, in both behavior and anatomy, that led to wholly new behaviors like speech and large-scale planning (for lack of a better term for the type of planning that we do and other animals don't).

On the pace of change in human technology

Lately, I've been listening to the BBC podcast of A History of the World in 100 Objects.  The program is full of all sorts of illuminating information about the history of humanity, but I want to focus here on three of the eariler objects

• An Oldowan stone chopping tool found in the Olduvai Gorge in Tanzania, about 2 million years old
• An Archeulean stone hand axe, also found there, but about 1.2 million years old
• A Clovis spear point, found in Arizona, about 13,000 years old

At first glance, these seem pretty similar.  They're pieces of hard stone that have had pieces knocked off of them to make tools.  The hand axe and the spear point have the same general form, though the spear point is considerably smaller.  If you had to guess what kind of creature made each object, you might well think that the hand axe and the spear point were made by the same creature, or at least similar, while the chopping tool was made by something much less sophisticated.  But that's not quite the case.

All three objects were made by members of our genus, Homo.  That is, they were made by primates that walked upright like us and, at least by comparison with other primates, had skulls and teeth more or less like ours, and so on.  However, the humanoids who made the chopping tool were definitely not modern humans.

Why not?  First, they didn't look like us, even if they looked more like us than like other apes.  The chopping tool is found with the bones of Homo habilis, which, while it walked upright, had longer arms than us and a smaller skull, was considerably smaller overall, and showed a greater size difference between male and female than humans do.  If we'd seen a group of habilis out walking around, we would probably have thought "Those are interesting-looking apes.  Almost human, even." and not "Those people look weird."

Second, Homo habilis doesn't seem to have been able to make much else out of stone.  Yes, several other kinds of tools are found at the same site, but not many kinds, and all made basically the same way: Take a more-or-less hand-sized rock and knock a small number of chips off it.  The end result looks much like the original piece of stone.  In fact, it's also possible that what we see as a chopping tool is actually just the leftover and it's the sharp flakes that the makers were after.  Or they could have used both.  In any case, the formula is simple: Knock one rock with another, use what you end up with.

Despite appearances, it's also quite clear that the makers of the Archeulean hand axe were not human.  From skeletal remains, they were Homo ergaster (or African Homo erectus, depending on your classification).  To be sure, the tools found with them are the result of a more elaborate process than habilis's chopping tools.  After hammering the core stone with another stone to flake parts of it off, the stone is then worked with bone, wood or antler to refine the shape.  This gives longer, sharper edges than Oldowan tools have, and the hand axe is much more symmetrical than the chopper, but again, there are only a few basic tools in the toolkit, and this toolkit remains the same for hundreds of thousands of years.  [As one would expect from an area of active inquiry, there has been some new information about hand-axes and such since I first wrote this, but the basic picture is still a small repertoire of tools with little or no change for thousands of generations.  I may return to this topic ... --D.H. 15 Oct 2014]

The simplest explanation for the the Oldowan and Acheulean toolkits is that they were the product of instinct, not some general tool-making ability.

I think, if we weren't talking about human ancestry here, this would be an open-and-shut case.  Since we are, I suppose I should elaborate on that a bit.  Because the chopping tool and hand axe are being presented as early human tools, it's natural to look at them and think, especially in the case of the hand axe, "Of course.  They're too complex and sophisticated to be the result of instinct, and they were clearly meant to be used as tools.  That implies a mind capable of intention and forethought."

It's natural to think that, but all kinds of natural, common-sense conclusions turn out not to be true.  This is most likely one of them.

First, consider complexity.  It's hard to say how an Archeulean hand axe is any more complex than, say, a weaver bird nest, beehive or pufferfish circle, to take a few examples.  You could argue that weaving a nest, or making a beehive or circular pattern in the sand is merely a matter of performing a simple behavior repeatedly according to a predetermined recipe -- leaving aside how "simple" that might actually be -- but so too is hitting one rock with another in a symmetrical pattern.

Fair enough, but a hand axe is not just a passive structure.  It is a tool built to be used to help manipulate the environment to a particular purpose.  But other animals do this, too, without any evident abstract forethought.  While there are not a lot of examples of this, there are several well-known ones: a capuchin monkey using a stick to get at termites, for instance, or an otter using rocks to break open a shellfish.

There are even a few known cases of other animals making tools to be used.  Elephants will strip the bark off of branches to make a better switch for swatting flies.  Chimps will do likewise with termite-fetching sticks.  For that matter, building a nest or burrow is no better or worse an argument for forethought.  Both are built for future use.  This is not the same as building a particle accelerator, or even a well-fletched arrow, but it's clearly something.

And yet, there is no particular reason to think that a bird building a nest is consciously thinking "I will build this nest so that I can sleep and brood eggs here."  It's not out of the question, but it doesn't seem at all necessary to assume intent in order to explain the behavior.

In that light, the chopping tool and hand axe look like just another example of animal tool use, perhaps unique in the particular combination of making and using the tool, but not a huge leap from other animal examples.

Let me be clear that I'm not arguing that the Oldowan and Archeulean tools are the product of instinct because they are in some way "simple".  Modern archeologists have learned the "knapping" technique used to produce these tools, and it's harder than it might look.  Rather, I'm arguing that instinctive behavior is not necessarily simple, other animals do similarly complex things instinctively, and in both cases the behavior carries on, essentially unchanged, for generation after generation.

But hold on.  Couldn't we just as well say that the Clovis spear point is the product of instinct?  Sure, we know that we make tools intentionally, but maybe the Clovis people didn't.  The Clovis tool kit is remarkably uniform over the Americas, and most (but not all) finds comprise a handful of different designs of tools made by the same stone-knapping techniques as the hand axe and the chopping tool.

However, there are two big clues that this is not the case, and one even has to do with the title of this post.

First, the Clovis people came along well after humans began to disperse from Africa.  People alive today share a large number of common characteristics unique to humans, such as language with pronouns and other heavy linguistic machinery, music, art, jewelry and, of course, tool-making as we know it.  The most recent common ancestor of all people alive today lived somewhere in the vicinity of 50,000 years ago.

Genetic studies of modern Native Americans in North America show that they share a common ancestor at least as far back as the Clovis people and, of course, belong to the same family tree as everyone else.  There is no plausible way that the Clovis people were not ancestors of people alive today, and no plausible way that those ancestors are not descendants of the original human population.

Why would the Clovis artifacts seem to closely resemble those of habilis and ergaster, then?  Why no Clovis art, beyond a few markings on bone?  Why no evidence of jewelry, or other kinds of artifact found in European sites from thousands of years earlier?

A survey paper by Ryan Ellsworth of the University of Missouri puts forth a plausible explanation:  The Clovis people spread very quickly, over a period of a few hundred years, over a previously uninhabited area, which would explain the uniformity.  They were nomadic, and tended to camp at the kill sites of the megafauna (mastodons and such) that they brought down.  They would not have built permanent dwellings, much less villages or cities, would have had no reason to carry anything bulky and non-functional with them, and probably preferred easy-to-work but more perishable materials for any art or jewelry they did carry.  This is not too far from hunter-gatherer societies encountered in modern times [Much of this type of narrative has been called into serious question, but that'll have to go in a different post -- D.H Jan 2022].

There is still a lot to be learned about the Clovis culture, and there are several competing theories as to who arrived when and did what, but Ellsworth's hypothesis fits the known evidence and is in line with a fair bit of other work.  Even if that particular account doesn't turn out to be the definitive answer, there's no need to reach too far to explain why a population of behaviorally modern humans might leave traces such as we find for the Clovis people.

Which brings me to the second big clue, and the title: Clovis culture is succeeded immediately by a number of other cultures which show a steady development of tools, regional variations and, eventually, the full array of human artifacts, from cities with huge monuments to houses to carved beads.  This happens over a period of thousands of years, much, much too quickly to be explained by genetic change.  Even if some disaster had wiped out humanity in the Americas before Europeans arrived, we would know that these later artifacts were made by people, and the early ones by their ancestors.

In short, the rate of change by itself is enough to make it clear that a generalist tool-user was at work.

This still leaves plenty of questions unanswered.  What happened between Homo ergaster and Homo sapiens [and our cousins such as Denisovans and Neanderthals] to make that shift from instinctive behavior to cultural behavior, learned and passed down from generation to generation?  Why is it that, while other animals can learn new behavior, and to some extent transmit it, we only see this sort of ratcheting effect, of each generation building on the last, in our species?  How did civilization and technology develop in several branches of the human family tree independently, but not to any significant extent in others?  Why does the pace of technological change appear to be accelerating?  Will this continue?

All interesting questions, and I may get to them some time.  Or back to them.  I've had a couple of stabs at some of them already.