tpo 真題打印版-54-44

1、托福 托福 TPO 真題打印版 真題打印版1 / 1855454-R-1The Commercialization of LumberIn nineteenth-century America, practically everything that was built involved wood. Pine was especially attractive for building purposes. It is durable a

2、nd strong, yet soft enough to be easily worked with even the simplest of hand tools. It also floats nicely on water, which allowed it to be transported to distant markets across the nation. The central and northern reach

3、es of the Great Lakes states—Michigan, Wisconsin, and Minnesota—all contained extensive pine forests as well as many large rivers for floating logs into the Great Lakes, from where they were transported nationwide.By 186

4、0, the settlement of the American West along with timber shortages in the East converged with ever-widening impact on the pine forests of the Great Lakes states. Over the next 30 years, lumbering became a full-fledged en

5、terprise in Michigan, Wisconsin, and Minnesota. Newly formed lumbering corporations bought up huge tracts of pineland and set about systematically cutting the trees. Both the colonists and the later industrialists saw ti

6、mber as a commodity, but the latter group adopted a far more thorough and calculating approach to removing trees. In this sense, what happened between 1860 and 1890 represented a significant break with the past. No longe

7、r were farmers in search of extra income the main source for shingles, firewood, and other wood products. By the 1870s, farmers and city dwellers alike purchased forest products from large manufacturing companies located

8、 in the Great Lakes states rather than chopping wood themselves or buying it locally.The commercialization of lumbering was in part the product of technological change. The early, thick saw blades tended to waste a large

9、 quantity of wood, with perhaps as much as a third of the log left behind on the floor as sawdust or scrap. In the 1870s, however, the British-invented band saw, with its thinner blade, became standard issue in the Great

10、 Lakes states' lumber factories. Meanwhile, the rise of steam-powered mills streamlined production by allowing for the more efficient, centralized, and continuous cutting of lumber. Steam helped to automate a variety

11、 of tasks, from cutting to the carrying away of waste. Mills also employed steam to heat log ponds, preventing them from freezing and making possible year-round lumber production.For industrial lumbering to succeed, a wa

12、y had to be found to neutralize the effects of the seasons on production. Traditionally, cutting took place in the winter, when snow and ice made it easier to drag logs on sleds or sleighs to the banks of streams. Once t

13、he streams and lakes thawed, workers rafted the logs to mills, where they 托福 托福 TPO 真題打印版 真題打印版3 / 185significant difference in the Americas 11,000 years ago was the presence of human hunters of these large mammals. Was

14、this coincidence or cause-and-effect?We do not know. Ecologist Paul S. Martin has championed the model that associates the extinction of large mammals at the end of the Pleistocene with human predation. With researcher J

15、. E. Mosimann, he has co-authored a work in which a computer model showed that in around 300 years, given the right conditions, a small influx of hunters into eastern Beringia 12,000 years ago could have spread across No

16、rth America in a wave and wiped out game animals to feed their burgeoning population.The researchers ran the model several ways, always beginning with a population of 100 humans in Edmonton, in Alberta, Canada, at 11,500

17、 years ago. Assuming different initial North American big-game-animal populations (75-150 million animals) and different population growth rates for the human settlers (0.65%-3.5%), and varying kill rates, Mosimann and M

18、artin derived figures of between 279 and 1,157 years from initial contact to big-game extinction.Many scholars continue to support this scenario. For example, geologist Larry Agenbroad has mapped the locations of dated C

19、lovis sites alongside the distribution of dated sites where the remains of wooly mammoths have been found in both archaeological and purely paleontological contexts. These distributions show remarkable synchronicity (occ

20、urrence at the same time).There are, however, many problems with this model. Significantly, though a few sites are quite impressive, there really is very little archaeological evidence to support it. Writing in 1982, Mar

21、tin himself admitted the paucity of evidence; for example, at that point, the remains of only 38 individual mammoths had been found at Clovis sites. In the years since, few additional mammoths have been added to the list

22、; there are still fewer than 20 Clovis sites where the remains of one or more mammoths have been recovered, a minuscule proportion of the millions that necessarily would have had to have been slaughtered within the overk

23、ill scenario.Though Martin claims the lack of evidence actually supports his model—the evidence is sparse because the spread of humans and the extinction of animals occurred so quickly—this argument seems weak. And how c

24、ould we ever disprove it? As archaeologist Donald Grayson points out, in other cases where extinction resulted from the quick spread of human hunters—for example, the extinction of the moa, the large flightless bird of N

25、ew Zealand—archaeological evidence in the form of remains is abundant. Grayson has also shown that the evidence is not so clear that all or even most of the large herbivores in late Pleistocene America became extinct aft

26、er the appearance of Clovis. Of the 35 extinct genera, only 8 can be confidently assigned an extinction date of between 12,000 and 10,000 years ago. Many of the older genera, Grayson argues, may have succumbed before 12,