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1、实用文档Lesson1Wecanreadofthingsthathappened5,000yearsagointheNearEast,wherepeoplefirstlearnedtowrite.Buttherearesomepartsoftheworldwhereevennowpeoplecannotwrite.Theonlywaythattheycanpreservetheirhistoryistorecountitassagas--legendshandeddownfromonegenerationofstory-tellerstoanothe
2、r.Theselegendsareusefulbecausetheycantellussomethingaboutmigrationsofpeoplewholivedlongago,butnonecouldwritedownwhattheydid.AnthropologistswonderedwheretheremoteancestorsofthePolynesianpeoplesnowlivinginthePacificIslandscamefrom.Thesagasofthesepeopleexplainthatsomeofthemcamefro
3、mIndonesiaabout2,000yearsago.Butthefirstpeoplewhowerelikeourselveslivedsolongagothateventheirsagas,iftheyhadany,areforgotten.Soarchaeologistshaveneitherhistorynorlegendstohelpthem文案大全实用文档tofindoutwherethefirst'modernmen'camefrom.Fortunately,however,ancientmenmadetoolsofstone,es
4、peciallyflint,becausethisiseasiertoshapethanotherkinds.Theymayalsohaveusedwoodandskins,butthesehaverottedaway.Stonedoesnotdecay,andsothetoolsoflongagohaveremainedwheneventhebonesofthemenwhomadethemhavedisappearedwithouttrace. Lesson2Why,youmaywonder,shouldspidersbeourfriends?Be
5、causetheydestroysomanyinsects,andinsectsincludesomeofthegreatestenemiesofthehumanrace.Insectswouldmakeitimpossibleforustoliveintheworld;theywoulddevourallourcropsandkillourflocksandherds,ifitwerenotfortheprotectionwegetfrominsect-eatinganimals.Weowealottothebirdsandbeastswhoeat
6、insectsbutallofthemputtogetherkillonly文案大全实用文档afractionofthenumberdestroyedbyspiders.Moreover,unlikesomeoftheotherinsecteaters,spidersneverdotheleastharmtousorourbelongings.Spidersarenotinsects,asmanypeoplethink,norevennearlyrelatedtothem.Onecantellthedifferencealmostataglancef
7、oraspideralwayshaseightlegsandaninsectnevermorethansix.Howmanyspidersareengagedinthisworkonourbehalf?OneauthorityonspidersmadeacensusofthespidersinagrassfieldinthesouthofEngland,andheestimatedthatthereweremorethan2,250,000inoneacre,thatissomethinglike6,000,000spidersofdifferent
8、kindsonafootballpitch.Spidersarebusyforatleasthalfthey
