ISSN:1060-1538    

DOI:10.1002/evan.1360010502

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

ISSN:1060-1538    

DOI:10.1002/evan.1360010503

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

ISSN:1060-1538    

DOI:10.1002/evan.1360010504

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractOur species colonized North and South America last of all the major land masses, thereby ending the spread that began a million years earlier when ancestral members of the genusHomofirst ventured out of Africa. But who were the first Americans? When did they arrive? Did they come in one migration or many? How quickly and by what adaptive strategies did they move across the environmentally diverse and trackless New World? How do they relate to contemporary native Americans? We have plenty of answers to these questions. Unfortunately, we can't agree which ones are right. This much is certain: the first Americans wereHomo sapienswho came from northeast Asia via the Bering Straits (Fig. 1). They may have walked from Siberia to Alaska across Beringia, the land bridge formed when vast Pleistocene glaciers froze 5% of the world's water,1lowering global sea levels and exposing the shallow continental shelf between Asia and America. These hunter‐gatherers were present throughout the Americas by 11,500 years ago, in time to witness the climatic and ecological changes, including the extinction of thirty‐five genera of megafauna, that signalled the end of the Pleistocene. Beyond those bare facts there is controversy. Here, then, is a brief summary of the state of the argument over the peopling of the Ameri

ISSN:1060-1538    

DOI:10.1002/evan.1360010505

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe protruding chin is an attribute that defines modernHomo sapiensto the exclusion of all other primates, including fossil hominids. The functional significance of the chin has been contemplated for most of the 20th century, but as yet no compelling functional argument for its evolution has withstood careful scrutiny. Consequently, the human chin is often cited as an example of a nonadaptive trait. Past attempts to explain the chin in a functional or mechanical context have failed, largely as a result of an incomplete understanding of in vivo masticatory biomechanics. When the morphology of the chin is considered in light of experimental data on mastication, its evolution can be interpreted as a consequence of recent changes in mandibular proportions that have altered the relative importance of different masticatory stresses. Hypotheses proposing that chin morphology is the result of sexual selection or spatial constraints may be untestable. As with arguments that posit no functional role for the chin, the credibility of these hypotheses has depended, to a large degree, on the refutation of previous biomechanical explanations.

ISSN:1060-1538    

DOI:10.1002/evan.1360010506

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe interests of evolutionary anthropologists, behavioral ecologists, and demographers converge on the ecology of human fertility. Ecological conditions influence the optimum pattern of maternal effort. Patterns of abortion, neglect, and infanticide vary with mothers' ability to invest in their children and children's ability to use that investment. As in most other mammals, the ecology of human fertility varies between the sexes: status and resource control are important for males, whereas reproductive value is crucial for females. In pre‐industrial societies, and even in monogamous societies in demographic transition, wealthy men had more children than did poorer men. This correlation, often assumed to have disappeared, persists today, with richer men still having more sexual access than others. Sex differences in the ecology of fertility mean that sex of the offspring, as well as birth order, influences parental investment. Because individual fertility varies with environment, it is not surprising that “natural” (uncontrolled) fertility varies across societies or that demographic transitions proceed locally, with occasional reverses, as individuals strive to maximize their lifetime reproductive success in changing, competitive, condi

ISSN:1060-1538    

DOI:10.1002/evan.1360010507

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

ISSN:1060-1538    

DOI:10.1002/evan.1360010508

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

ISSN:1060-1538    

DOI:10.1002/evan.1360010501

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY