# Abstract Thought Emerged After Millions of Years of Brain Expansion by Keith Devlin > “The best evidence we have from anthropology is that our ancestors acquired this capacity some time between 75,000 and 200,000 years ago. (The evidence is in the form of manufactured artifacts that early humans left behind, which indicate such a level of abstract thinking and communication.) But how — and in terms of natural selection, why — did our ancestors acquire this capacity? All we know for sure is that it came at the end of a three-and-a-half-million year period in which the average brain size of our ancestors grew to roughly its present level, approximately nine times larger than is normal for a mammal of our body size and about twice that of a present-day ape.” > **— Keith Devlin**, *2002, Edge Annual Question, “What Is Your Question? ... Why?”* ## Sources and Context - **Direct Edge response and surrounding essay:** [The hows and whys of what led to us](https://www.edge.org/response-detail/11033) — Edge published this exact passage in its 2002 Annual Question collection, *WHAT IS YOUR QUESTION? ... WHY?*. The response page preserves the surrounding argument and qualifications. - **Complete local collection index:** [[research/Edge 2002 Full Quotation Curation|Edge 2002 Full Quotation Curation]] — retained source-first record for the complete response cohort and this passage's promotion status. ## Related Articles and Collections - **Collection:** [[collections/Edge|Edge]] - **Collection:** [[collections/Machine Succession|Machine Succession]] - **Article:** [[articles/The Evolutionary Roots of Silicon Valley|Valley Roots]] - **Article:** [[articles/Digital Darwinism and the Invisible World of Machine Evolution|Digital Darwinism]] - **Article:** [[articles/We Were Never Going to Make It|Never Going to Make It!]] - **Wiki map:** [[wiki/Evolutionary Biology|Evolutionary Biology]] ## Related Topics - [[wiki/Evolutionary Biology|Evolutionary Biology]] - [[wiki/Evolutionary Dynamics|Evolutionary Dynamics]] - [[wiki/Evolvability|Evolvability]] - [[wiki/Natural Selection|Natural Selection]] ## Share on Social Media ``` “The best evidence we have from anthropology is that our ancestors acquired this capacity some time between 75,000 and 200,000 years ago. (The evidence is in the form of manufactured artifacts that early humans left behind, which indicate such a level of abstract thinking and communication.) But how — and in terms of natural selection, why — did our ancestors acquire this capacity? All we know for sure is that it came at the end of a three-and-a-half-million year period in which the average brain size of our ancestors grew to roughly its present level, approximately nine times larger than is normal for a mammal of our body size and about twice that of a present-day ape.” — Keith Devlin, 2002, Edge Annual Question, “What Is Your Question? ... Why?” https://bryantmcgill.com/simple-reminders-keith-devlin-abstract-thought-emerged-after-millions ```