- 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.
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.
