Man, so the truism goes, lives increasingly in a man-made environment. This places a special burden on human immaturity, for it

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问题   Man, so the truism goes, lives increasingly in a man-made environment. This places a special burden on human immaturity, for it is plain that adapting to such variable conditions must depend very heavily on opportunities for learning, or whatever the processes are that are operative during immaturity. It must also mean that during immaturity man must master knowledge and skills that are either stored in the gene pool or learned by direct encounter, but which are contained in the culture pool--knowledge about values and history, skills as varied as an obligatory natural language or an optional mathematical one, as mute as levers or as articulate as myth telling.
  Yet, it would be a mistake to leap to the conclusion that because human immaturity makes possible high flexibility, therefore anything is possible for the species. Human traits were selected for their survival value over a four--to five-million-year period with a great acceleration of the selection process during the last half of that period. There were crucial, irreversible changes during that final man-making period: recession of formidable dentition, 50 percent increase in brain volume, the obstetrical paradox- bipedalism and strong pelvic girdle, larger brain through a smaller birth canal--immature brain at birth, and creation of what Washburn has called a "technical-social way of life," involving tool and symbol use.
  Note, however, that hominidization consisted principally of adaptations to conditions in the Pleistocene. These preadaptations, shaped in response to earlier habitat demands, are part of man’s evolutionary inheritance. This is not to say that close beneath the skin of man is a naked ape, that civilization is only a veneer. The technical-social way of life is a deep feature of the species adaptation. But we would err if we assumed a priori that man’s inheritance placed no constraint on his power to adapt. Some of the preadaptations can be shown to be presently maladaptive. Man’s inordinate fondness for fats and sweets no longer serves his individual survival well. And the human obsession with sexuality is plainly not fitted for survival of the species now, however well it might have served to population the upper Pliocene and the Pleistocene. Nevertheless, note that the species responds typically to these challenges by technical innovation rather than by morphological or behavioral change. Contraception dissociates sexuality from reproduction. We do not, of course, know what kinds and what range of stresses are produced by successive rounds of such technical innovation. Dissociating sexuality and reproduction, for example, surely produces changes in the structure of the family, which in turn redefine the role of women, which in turn alters the authority pattern affecting the child, etc. continuing and possible acceleration change seems inherent in such adaptation. And this, of course, places and enormous pressure on man’s uses of immaturity, preparing the young for unforeseeable change-the more so if there are severe restraints imposed by human preadaptations to earlier conditions of life.  
It can be inferred that the obstetrical paradox is puzzling because ______.

选项 A、it occurred very late during the evolution of the species
B、evolutionary forces seemed to work at cross purposes to each other
C、technological innovations have made the process of birth easier
D、an increase in brain size is not an ordinary evolutionary event

答案B

解析 推论题。问题的关键词是paradox。这个单词的含义为某个“似是而非令人费解的问题”。正确的选择就是要说明这种现象为什么会令人费解。B的内容做到了这点。paradox的焦点所在就是人类朝着两个不同的方向在改变自己。一方面脑子在变大,另一方面生殖道变窄小,这样一来,造成生育困难。这让人迷惑不解,因为我们认为进化的结果会消除这种困难,结果却相反。A的内容,文章中确实提到过,说这种变化比较晚,但并没有说这让人感到吃惊。D也是一样,提到了脑子变大的事实,但并未让人感到 puzzling。至于C的内容,文中无法找到。
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