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265[evol-psych] Proceedings of the National Academy of Sciences

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  • Ian Pitchford
    Aug 6, 1999
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      From the current issue of the Proceedings of the National Academy of Sciences
      of the United States of America:

      1. "What" and "how": Evidence for the dissociation of object knowledge and
      mechanical problem-solving skills in the human brain
      2. Early hominid biogeography
      3. The tempo of mass extinction and recovery: The end-Permian example
      4. Behavioral reduction of infection risk
      5. Heritability of body mass, a sexually selected trait, in an arctiid moth
      (Utetheisa ornatrix)
      6. Forty million years of mutualism: Evidence for Eocene origin of the
      yucca-yucca moth association


      Vol. 96, Issue 16, 9444-9448, August 3, 1999

      "What" and "how": Evidence for the dissociation of object knowledge and
      mechanical problem-solving skills in the human brain

      John R. Hodges, Josef Spatt, and Karalyn Patterson

      Patients with profound semantic deterioration resulting from temporal lobe
      atrophy have been reported to use many real objects appropriately. Does this
      preserved ability reflect (i) a separate component of the conceptual knowledge
      system ("action semantics") or (ii) the operation of a system that is
      independent of conceptual knowledge of specific objects, and rather is
      responsible for general mechanical problem-solving skills, triggered by object
      affordances? We contrast the performance of three patientstwo with semantic
      dementia and focal temporal lobe atrophy and the third with corticobasal
      degeneration and biparietal atrophyon tests of real object identification and
      usage, picture-based tests of functional semantic knowledge, and a task
      requiring selection and use of novel tools. The patient with corticobasal
      degeneration showed poor novel tool selection and impaired use of real objects,
      despite near normal semantic knowledge of the same objects' functions. The
      patients with semantic dementia had the expected deficit in object
      identification and functional semantics, but achieved flawless and effortless
      performance on the novel tool task. Their attempts to use this same mechanical
      problem-solving ability to deduce (sometimes successfully but often
      incorrectly) the use of the real objects provide no support for the hypothesis
      of a separate action-semantic system. Although the temporal lobe system clearly
      is necessary to identify "what" an object is, we suggest that sensory inputs to
      a parietal "how" system can trigger the use of objects without reference to
      object-specific conceptual knowledge.

      reprint requests should be addressed. E-mail: john.hodges@....


      Vol. 96, Issue 16, 9196-9200, August 3, 1999

      Early hominid biogeography

      David S. Strait and Bernard A. Wood

      We examined the biogeographic patterns implied by early hominid phylogenies and
      compared them to the known dispersal patterns of Plio-Pleistocene African
      mammals. All recent published phylogenies require between four and seven
      hominid dispersal events between southern Africa, eastern Africa, and the
      Malawi Rift, a greater number of dispersals than has previously been supposed.
      Most hominid species dispersed at the same time and in the same direction as
      other African mammals. However, depending on the ages of critical hominid
      specimens, many phylogenies identify at least one hominid species that
      dispersed in the direction opposite that of contemporaneous mammals. This
      suggests that those hominids may have possessed adaptations that allowed them
      to depart from continental patterns of mammalian dispersal.

      reprint requests should be addressed. E-mail: dstrait@....


      Vol. 96, Issue 16, 8827-8828, August 3, 1999

      The tempo of mass extinction and recovery: The end-Permian example

      Samuel A. Bowring, Douglas H. Erwin, and Yukio Isozaki

      Mass extinctions are brief episodes of greatly increased extinction, commonly
      affecting both marine and terrestrial species. Since the origin of animals some
      600 million years ago, there have been at least six major mass extinctions. The
      disappearance of the dinosaurs during the end-Cretaceous mass extinction 65
      million years ago is perhaps the best known event, but the end-Permian (ca. 251
      million years ago) extinction was, without question, the most profound.
      Although extinctions (often called background extinctions) have occurred
      throughout Phanerozoic history, they are distinct from mass extinctions. Mass
      extinctions and recoveries have played a fundamental role in animal evolution,
      comparable to natural selection, because they may trigger the demise of
      dominant species and massive reorganization of entire ecosystems. Thus
      understanding mass extinctions and their recoveries is critical for further
      developing models of evolutionary process. In particular, we seek to answer the
      following questions: (i) How rapidly do these extinction events occur? (ii)
      What caused them, and is there a single mechanism for all extinctions? (iii)
      What became extinct, what survived, and why? (iv) How did life recover in the
      aftermath of these events?

      reprint requests should be addressed. E-mail: sbowring@....


      Vol. 96, Issue 16, 9165-9168, August 3, 1999

      Behavioral reduction of infection risk

      Joseph M. Kiesecker, David K. Skelly, Karen H. Beard, and Evan Preisser

      Evolutionary biologists have long postulated that there should be fitness
      advantages to animals that are able to recognize and avoid conspecifics
      infected with contact-transmitted disease. This avoidance hypothesis is in
      direct conflict with much of epidemiological theory, which is founded on the
      assumptions that the likelihood of infection is equal among members of a
      population and constant over space. The inconsistency between epidemiological
      theory and the avoidance hypothesis has received relatively little attention
      because, to date, there has been no evidence that animals can recognize and
      reduce infection risk from conspecifics. We investigated the effects of Candida
      humicola, a pathogen that reduces growth rates and can cause death of tadpoles,
      on associations between infected and uninfected individuals. Here we
      demonstrate that bullfrog (Rana catesbeiana) tadpoles avoid infected
      conspecifics because proximity influences infection. This avoidance behavior is
      stimulated by chemical cues from infected individuals and thus does not require
      direct contact between individuals. Such facultative modulations of disease
      infection risk may have critical consequences for the population dynamics of
      disease organisms and their impact on host populations.

      To whom reprint requests should be addressed. E-mail: jmk23@....


      Vol. 96, Issue 16, 9169-9171, August 3, 1999

      Heritability of body mass, a sexually selected trait, in an arctiid moth
      (Utetheisa ornatrix)

      Vikram K. Iyengar and Thomas Eisner

      In the moth Utetheisa ornatrix (Lepidoptera: Arctiidae), females mate
      preferentially with larger males. Large body mass is advantageous to both
      sexes: large males sire more young than small males, and large females have
      higher fecundity than small females. Here we report that body mass is heritable
      in both sexes, indicating that by choosing larger males females obtain genetic
      benefits for their offspring. Choosy females also receive extra nutrient and
      defensive alkaloid by way of their partner's spermatophores, but these gifts do
      not affect the heritability of body mass. These results indicate that by
      exercising mate choice female Utetheisa receive both direct phenotypic and
      indirect genetic benefits. Forty million years of mutualism: Evidence for
      Eocene origin of the yucca-yucca moth association

      reprint requests should be addressed at: Section of Neurobiology and Behavior,
      W347 Mudd Hall, Cornell University, Ithaca, NY 14853. E-mail: te14@....


      Vol. 96, Issue 16, 9178-9183, August 3, 1999

      Forty million years of mutualism: Evidence for Eocene origin of the yucca-yucca
      moth association

      Olle Pellmyr and James Leebens-Mack

      The obligate mutualism between yuccas and yucca moths is a major model system
      for the study of coevolving species interactions. Exploration of the processes
      that have generated current diversity and associations within this mutualism
      requires robust phylogenies and timelines for both moths and yuccas. Here we
      establish a molecular clock for the moths based on mtDNA and use it to estimate
      the time of major life history events within the yucca moths. Colonization of
      yuccas had occurred by 41.5 ± 9.8 million years ago (Mya), with rapid life
      history diversification and the emergence of pollinators within 0-6 My after
      yucca colonization. A subsequent burst of diversification 3.2 ± 1.8 Mya
      coincided with evolution of arid habitats in western North America. Derived
      nonpollinating cheater yucca moths evolved 1.26 ± 0.96 Mya. The estimated age
      of the moths far predates the host fossil record, but is consistent with
      suggested host age based on paleobotanical, climatological, biogeographical,
      and geological data, and a tentative estimation from an rbcL-based molecular
      clock for yuccas. The moth data are used to establish three alternative
      scenarios of how the moths and plants have coevolved. They yield specific
      predictions that can be tested once a robust plant phylogeny becomes available.

      reprint requests should be addressed. E-mail: olle.pellmyr@....

      Ian Pitchford <Ian.Pitchford@...>
      Centre for Psychotherapeutic Studies
      School for Health and Related Research
      University of Sheffield, S10 2TA, UK