posted January 2005


William H. Calvin, "The Mind's Big Bang Only 50,000 Years Ago." plenary speech, Winter Conference on Brain Research (January 2005). See also

Slides here.

William H. Calvin 
it's an image, you need to type it, not copy it (spam...)       
 University of Washington



The Mind's Big Bang Only 50,000 Years Ago

We all assume that bigger brains are better, yet our ancestors went through several million-year-long periods when toolmaking techniques didn't improve, despite a lot of brain size increase. Even after our species, Homo sapiens, was walking around Africa 162,000 years ago, we spent the next 100,000 years doing more of the same.

But gradually getting more clever is NOT what the 2.5 million year bigger-brain increase was all about. If those ancestors were getting better and better (maybe for something that doesn't show in the archeological record such as short-sentence protolanguage or more extensive sharing), it didn't feed back to improve toolmaking, long-distance trade, or even using bone as raw material for toolmaking (surely the handy-to-hand raw material at any campsite). Oops.

The burst of creativity (since maybe 75,000 to 50,000 years ago) is what we moderns associate with intelligence and our kind of consciousness. It's probably the emergence of the suite of higher intellectual functions: syntax, multi-stage planning, structured music, chains of logic, games with arbitrary rules, and our fondness for discovering hidden patterns (the search for coherence). It's likely that they share some neural machinery for handling structure and judging coherence.

If you can't speak sentences of more than 2-3 words at a time without them all blending together like a summer drink, you likely cannot think complicated thoughts either -- where you also have to resolve the ambiguities and improve the quality of the ensemble offline. That takes an ability to structure thoughts, what you also need to speak long sentences or recursively nest clauses. ("I think I saw him leave to go home.") And without quality bootstrapping aiding structuring, you can't be a poet who creates ensembles where every word resonates with the rest, just so.

So the big brain is not all about intellect.  What happened to reorganize the brain after 100,000 years at its present size, to make it more creative and versatile, back during the middle of the most recent ice age?



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