请求讲解GWD6-Q6

GWD6-Q6:

      According to a theory advanced

       by researcher Paul Martin, the wave

       of species extinctions that occurred

Line       in North America about 11,000 years

  (5)      ago, at the end of the Pleistocene era,

can be directly attributed to the arrival

of humans, i.e., the Paleoindians, who

were ancestors of modern Native

Americans.  However, anthropologist

 (10)      Shepard Krech points out that large

animal species vanished even in areas

where there is no evidence to demon-

strate that Paleoindians hunted them.

Nor were extinctions confined to large

 (15)      animals:  small animals, plants, and

insects disappeared, presumably not

all through human consumption.  Krech

also contradicts Martin’s exclusion of

climatic change as an explanation by

 (20)      asserting that widespread climatic

       change did indeed occur at the end of

       the Pleistocene.  Still, Krech attributes

secondary if not primary responsibility

for the extinctions to the Paleoindians,

 (25)      arguing that humans have produced

local extinctions elsewhere.  But,

according to historian Richard White,

even the attribution of secondary

responsibility may not be supported

 (30)      by the evidence.  White observes that

Martin’s thesis depends on coinciding

dates for the arrival of humans and the

       decline of large animal species, and

Krech, though aware that the dates

 (35)      are controversial, does not challenge

them; yet recent archaeological

discoveries are providing evidence

that the date of human arrival was

much earlier than 11,000 years ago.

insects disappeared, presumably not

all through human consumption. 

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