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Computational Complexity and the Evolution of Homo Sapiens


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In recent decades, the Neo-Darwinian Synthesis has been quietly expanded to embrace the evolution of complex systems (living and non-living) and the information on which they are based (e.g., Adami 2011; Mayfield 2013). The expanded theoretical framework is especially appropriate—perhaps essential—for understanding the evolution of modern humans, who represent major changes in the way that information is stored, transmitted, translated, and manipulated (Maynard Smith and Szathmáry 1995). Modern humans may be distinguished from earlier forms of Homo by an enhanced faculty for manipulation of information (i.e., computation) that permits generation of a potentially infinite variety of combinations of hierarchically-organized units of information. This faculty is most commonly manifest in the computations that underlie spoken and unspoken language (Hauser et al. 2002), which may be considered a form of information technology. Spoken or imagined words are “material symbols” (Clark 2008) manipulated in the brain to facilitate complex computation in a manner analogous to the beads of an abacus.

If technology is viewed as a form of computation (i.e., manipulation of objects and materials), this faculty also is evident in the artifacts produced by modern humans, which exhibit an increasingly complex, hierarchical organization with a potentially infinite variety of combinatorial possibilities. Because the acquisition of syntactic language requires a lengthy "critical period" of exposure during childhood, the computational complexity of language appears to be linked to the significantly delayed maturation of the modern human brain (which is only 25% of its adult volume at birth). Greenfield (1991) found that the manipulation of objects exhibits increasing complexity (i.e., more hierarchical levels of organization) during childhood and noted overlap in areas of the brain activated for language and object manipulation. The enhanced faculty for manipulation of information and objects (i.e., increased computational complexity) found in modern humans is thus plausibly tied to the delayed growth of the brain and extended childhood, which begins to evolve after about 0.5 million years ago, but apparently is not comparable to that of living people until after 0.2 million years ago (Smith et al. 2007; Smith et al. 2010). The evolution of enhanced computational complexity in modern humans transformed existing systems of communication and technology, yielding an open-ended syntactic form of language and potentially infinite variety of hierarchically structured artifacts. Modern humans created new forms of information, including visual art (analog) and notation (digital), and colonized most terrestrial habitats on Earth by designing their own adaptive “traits” (e.g., tailored clothing) based on complex technological computations.

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Computational Complexity and the Evolution of Homo Sapiens

  1. 1. Computational complexity and the evolution of Homo sapiens John F Hoffecker Institute of Arctic and Alpine Research University of Colorado at Boulder American Anthropological Association Washington DC • December 2014
  2. 2. HYPOTHESIS: Homo sapiens is characterized by a faculty for performing computations with symbols (words and numbers) in the brain on a more complex level than other forms of Homo. The appearance of the modern human anatomy in the fossil record reflects an increase in computational complexity related to epigenetic changes in the timing and pattern of early brain growth.
  3. 3. computation in modern humans
  4. 4. “A complex train of thought can no more be carried on without the aid of words, whether spoken or silent, than a long calculation without the use of figures or algebra” Charles Darwin (1871: 57–58) “. . . the material structures of language both reflect, and then systematically transform, our thinking and reasoning about the world” Andy Clark (2011: 59) language as cognitive scaffolding words & numbers = “material symbols”
  5. 5. “. . . the fundamental purpose of brains is to produce future” Daniel C. Dennett (1991: 177) “material symbols” of language allow computation about objects and events outside immediate spatial and temporal setting of individual
  7. 7. how is complexity measured? Simon (1962) proposed a hierarchical measure of complex systems
  8. 8. Chomsky (2006: 129) syntactic language as computation LEVEL 1 LEVEL 2 LEVEL 3
  9. 9. modern humans also perform computations through visual- tactile coordination of the hands with material objects as with the products of the computations that underlie syntactic language, artifacts and features may exhibit a complex hierarchical structure and potentially infinite variations
  10. 10. LEVEL 1 LEVEL 2 LEVEL 3 Conard 2009: 248, fig. 1
  11. 11. LEVEL 1 LEVEL 2 LEVEL 3
  12. 12. adapted from Sato 2009: 33 Udehe snare (Russian Far East) LEVEL 1 LEVEL 2 LEVEL 3
  14. 14. alarm calls: matching sound and meaning evolutionary roots of language in Homo ter2 64/Items/SD226_2_section4
  15. 15. KNM-ER 1470: ~1.9 million years old 1470 endocast: reorganization of frontal lobe (third inferior frontal convolution, Broca’s area) (Tobias 1987; Holloway 1995; Falk et al. 2000)
  16. 16. early Homo expansion into less productive habitat ~2 mya
  17. 17. Dominguez-Rodrigo et al. 2010: 322, fig. 6 FLK Zinj main excavation (Leakey 1971)
  18. 18. Beekman and Lew (2007) addressed problem of “when does it pay to dance?” ● dancing beneficial when it allows colony to focus on high-quality patches ecological modeling & information-center foraging strategy: honeybee colony foraging
  19. 19. Primary kin Primary kin Hill et al. 2011: 1288, fig. 2
  20. 20. Lieberman 2011: 505, fig. 12.9
  21. 21. Lalueza-Fox et al. 2011: 251, table 1
  22. 22. Lalueza-Fox et al. 2011: 251, table 1
  23. 23. “social brain hypothesis” (Dunbar 1996, 1998)
  24. 24. H. sapiens in sub-Saharan Africa 200–75 ka (1367–1510 cm3) 1250–1299 cm3 adapted from Lieberman 2011: 566, fig. 13.12a
  25. 25. Homo sapiens (Jebel Irhoud, Morocco) ~160,000 years old Smith et al. 2007: figs. 1 & fig. 2 Coqueugniot et al. 2004: 299–300, figs. 1 & 2 Homo erectus (Modjokerto, Java) ~1.8 million years old 1.0–1.5 years old: brain volume = 72–84%
  26. 26. Gunz et al. 2011: fig. 5
  27. 27. archaeology of the social brain Clark 1993: 155, fig. 1 Bouzouggar et al. 2007: 9967, fig. 3