Growth Mode Jump Example

I’ve talked here before how history can be seen as a sequence of periods of steady exponential growth, separated by a few sudden jumps to new modes.  A new paper in Science offers a nice concrete model of how a new mode can be triggered by an old mode reaching a particular level.   In this case the new mode is humans using culture to share and improve complex behavior like art and tool construction.   The model says the new mode was not possible until humans were dense enough so that skill improvements from groups copying each other could overcome the tendency of a lone group’s skills to devolve.  From Science Daily:

“Our paper proposes a new model for why modern human behaviour started at different times in different regions of the world, why it disappeared in some places before coming back, and why in all cases it occurred more than 100,000 years after modern humans first appeared.  By modern human behaviour, we mean a radical jump in technological and cultural complexity, which makes our species unique. This includes symbolic behavior, such as abstract and realistic art, and body decoration using threaded shell beads, ochre or tattoo kits; musical instruments; bone, antler and ivory artefacts; stone blades; and more sophisticated hunting and trapping technology, like bows, boomerangs and nets.” …

[They] found that complex skills learnt across generations can only be maintained when there is a critical level of interaction between people. Using computer simulations of social learning, they showed that high and low-skilled groups could coexist over long periods of time and that the degree of skill they maintained depended on local population density or the degree of migration between them. Using genetic estimates of population size in the past, the team went on to show that density was similar in sub-Saharan Africa, Europe and the Middle-East when modern behaviour first appeared in each of these regions.

From the Science paper:

The origins of modern human behavior are marked by increased symbolic and technological complexity in the archaeological record. In western Eurasia this transition, the Upper Paleolithic, occurred about 45,000 years ago, but many of its features appear transiently in southern Africa about 45,000 years earlier. We show that demography is a major determinant in the maintenance of cultural complexity and that variation in regional subpopulation density and/or migratory activity results in spatial structuring of cultural skill accumulation. Genetic estimates of regional population size over time show that densities in early Upper Paleolithic Europe were similar to those in sub-Saharan Africa when modern behavior first appeared. Demographic factors can thus explain geographic variation in the timing of the first appearance of modern behavior without invoking increased cognitive capacity.

While this transition clearly let humans more quickly grow their tech abilities, it is not clear that this translated immediately into an ability to more quickly grow the number of humans.  That didn’t clearly happen until the farming revolution of about 10,000 years ago.   So did the efficient exchange of farming innovations require a different higher density threshold, or did farming require a certain minimum accumulation of tech abillities, or what?

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  • Jim Babcock

    > So did the efficient exchange of farming innovations require a different higher density threshold, or did farming require a certain minimum accumulation of tech abillities, or what?

    More likely, it required a certain accumulation of genetic adaptations in domesticated species, rather than technologies. These behave similarly, in that they require a minimum population density to sustain trade networks to carry seeds; but unlike technology, they also accumulate over time in a way that’s much harder to lose.

  • http://transhumangoodness.blogspot.com/ Roko

    So the $million question is: what does this tell us about the next transition?

  • evil mutant

    Robin,

    I recently returned to this site after an extended break and read a large number of posts in rapid succession. I noticed that a very high %, at least 6 of the last 7 posts, were about explaining some phenomena via status signaling or the desire to be associated with high status individuals.

    There are a lot of things going on, and most phenomena have a multitude of causes. This many posts about one this smells like a pet theory. That doesn’t mean any of the posts are wrong, they may all be right, but it should set off alarm bells in your head.

    • http://hanson.gmu.edu Robin Hanson

      evil, this is my person blog, and signaling is one of my interest areas. Why should I not focus my post topics on my interest areas?

  • http://entitledtoanopinion.wordpress.com TGGP

    John Hawks discusses the paper here.

  • mjgeddes

    What this tells us once again is that Eliezer Yudkowsky is wrong about everything. IQ is not the most powerful force in the universe. It’s the interaction/communication/signalling between agents that resulted in the explosion of innovation, not any increase in raw IQ.

    And what cognitive ability does interaction/communication/signalling involve? Clearly, the ability to form analogies (mappings) between between concepts – the core aspect of communication, i.e. case-based reasoning.

    The most powerful force in the universe is reflection (the ability to translate between and communicate different knowledge representations), not intelligence. It’s actually this reflective/communicative/signalling ability that’s at the heart of the growth mode jumps.

    • http://hanson.gmu.edu Robin Hanson

      mjgeddes, perhaps it escaped your attention that I not Eliezer was the author of the post, which had nothing to do with IQ? Eliezer doesn’t even post here at OB anymore. Perhaps you could take your obsession with him somewhere else?

      • ShardPhoenix

        The guy was agreeing with you (I think) and constrasting your post to what he thinks Eliezer believes. And don’t be so jealous of Eliezier stealing your thunder :/.

    • ShardPhoenix

      Elizezer is all about reflection, and I don’t think he’s ever been obsessed with “IQ” in the shallow way you’re accusing him of here.

      • mjgeddes

        ShardPhoenix,

        I’ve solved the puzzle of reflection in AI that long stumped … er certain other people… for so long. I will post a short abstract of my solution in next month’s Open Thread, publically proving once and for all that *my* Reflection trumps *his* IQ. Robin, that next post in the Open Thread will be my last on this blog – promise 😉

  • http://Brokensymmetry.typepad.com Michael F. Martin

    Nice affinities with recent work of Axelrod. Some version of Kuramoto model could be used here also.

  • Mario

    I think that technological and cultural innovation receives its main support from the luxury of leisure. Or, I suppose more accurately, the time to focus on things other than the immediate. If this were true, the first innovations would have begun simply due to economies of scale, which is what I think this shows. I’m not sure what precipitated the agricultural revolution, but I don’t think it could have happened had people not been secure enough in their situation to wait in one place for months for their main food supply to mature. You would expect similar boosts from the invention of slavery and the industrial revolution, as the returns to small inputs in labor became high enough to support more and more people working outside of the survival sector (although I’m not sure the latter is possible in a society until the former is removed).

  • http://timtyler.org/ Tim Tyler

    The traditional timeline looks something like this:

    * Hunting & Gathering;
    * Herding 15,000 BC;
    * Agricultre 10,000 BC;
    * Urban 8000 BC – cities form;

    Agriculture and group living seem fairly strongly associated with each other. Living in groups allowed humans to specialise – and move away from the shaman-hunter-gatherer-chief model into one where there were many different roles in society.