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We’ve found a lot of stone tools. Some estimates place the number at more than 15 trillion. Is there anything we can learn from all this data apart from “our ancestors liked to make stone tools”. Well, some suggest that we may be able to track the evolution of intelligence via our technology.

This is made possible by the fact archaeologists love to categorise things. It helps turn vague interpretations into concrete groupings (or typologies). This speeds up the analysis of finds and allowing a quick and easy comparison between sites. Importantly for us, this sort of categorisation allows us to track the evolution of technology.

The mode system

This is where the mode system comes in. It’s an elegant, simple system that tracks the increasing complexity of stone tools. Since complexity correlates with time, this also seems to be the path of technological evolution.  It’s the “standard model” of Palaeolithic archaeology (palaeolithic just means “old stones,” but it sounds so much cooler in Latin).

This diagram is amazing (coincidentally, I made it myself)

From this, one can start to infer something about the mental ability of those who made the tools. A mode 2 handaxe, for example, requires that the maker (Homo erectus) has an image of the finished product in their head whereas a mode 1 flake (made by late Australopithecus/Early Homo) does not. From that, we could conclude that Homo erectus had this additional capacity.

However, here the mode system runs into many flaws, mostly because an individual can make a tool or not for reasons other than “intelligence” (in this context being used to describe the sum total of these aforementioned mental abilities).

Perhaps they simply didn’t need to make other tools (Australian Aboriginals have a simple lithic toolkit yet get along just fine) or couldn’t find the resources needed (whenever Homo erectus migrated to a new area they reverted back to making mode 1 tools) or any of a whole host of other reasons (some Australasian islanders have “forgotten” how to make some of the complex tools their ancestors could).

So when we conclude that Homo erectus was smarter than its ancestors based on the fact it made a higher mode of technology, how do we know its ancestors weren’t just as smart and, for one reason or another, made a lower mode instead?

“I could make a civilisation, I choose not too”

Intelligence and technology

To more accurately infer intelligence from tools we need some kind of metric that doesn’t vary as easily. That way its presence/absence will be more strongly correlated with intelligence as it won’t be influenced by other factors.

So ideally we are looking for something expressed in multiple tools so even if a group ceases to make one type of tool they won’t cease expressing the trait which can be measured.

It has been proposed that looking for “concepts” fits the bill. A concept is essentially an internal idea that can be expressed in a variety of external ways. Since it is internal it should be more strongly correlated with mental ability and since it can be expressed in a variety of ways it is less likely to vary.

Currently, 24 such concepts have been identified and when plotted against time show a gradual increase in “intelligence” punctuated by a few “revolutions” 2.6, 1.6 and 0.4 million years ago where multiple concepts are introduced.

The gradual increase could simply mean our ancestors gradually accumulated more knowledge (or an increased intelligence) that enabled them to do better things whilst the “revolutions” might be the result of gaining of new mental abilities.

Light grey refers to when this concept may have appeared, but is disputed. Interesting aside: many concepts are already present in the earliest stone tools

More problems

Of course, using concepts isn’t a perfect system. It’s still reliant upon artefacts and so can be influenced by all the things that influence artefact preservation. There is also little data directly linking these concepts to intelligence, limiting the firmness with which one can draw conclusions from this data.

However, it is better than the mode system and so is a step in the right direction which will hopefully be followed by great strides towards the truth.

The only downside is I now have to learn about 24 concepts rather than the easy to memorise 5 modes.


John Gowlett (2009). The Longest Transition or Multiple Revolutions? Curves and Steps in the Record of Human Origins Sourcebook of Paleolithic Transitions, 65-78 DOI: 10.1007/978-0-387-76487-0_4

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gamebak · 14th January 2012 at 5:49 pm


J.J.Brown Author · 14th January 2012 at 5:59 pm

It is an interesting distinction here between knowledge gains and revolutions. I’m also reminded of Jane Goodall’s work blurring the lines between animal and man in tool-making. Thanks for this detailed and thought provoking article.

    Adam Benton · 14th January 2012 at 6:27 pm

    Mode 1 appears as something more advanced than any chimp can make, yet this is an artefact of preservation bias. If we had access to the perishable tools our ancestors used – such as sticks – prior to the first stone tools then we would likely be able to track a gradual change from chimp like technology to human technology.

Alex Autin · 16th January 2012 at 2:29 pm

Though I know very (VERY!) little about it…I find evolution, and anything having to do with evolution, fascinating and compelling. Thanks for presenting it in a way which is completely understandable even to someone who’s never studied it….oh, and thanks also for your amazing diagrams!

    Adam Benton · 16th January 2012 at 5:11 pm

    And thank you for vindicating the existence of this blog.

Francis Griffey · 2nd May 2012 at 2:22 am

They are basing the intelligence on the complexity of the tools they produced.

    Adam Benton · 2nd May 2012 at 9:59 am

    I think that’s an oversimplification that misses many of the nuances associated with the concept system, but essentially yes.

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