darwin and modern science-第39节

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ns　of　the　high　plateaus　of　Peru　show　a　striking　development　of　lungs　and　thorax；　as　a　result　of　living　constantly　at　high　altitudes。

Such　special　forms　of　variation　as　arrests　of　development　（microcephalism）　and　reversion　to　lower　forms　are　next　discussed。　　Darwin　himself　felt　（〃Descent　of　Man〃；　page　54。）　that　these　subjects　are　so　nearly　related　to　the　cases　mentioned　in　the　first　chapter；　that　many　of　them　might　as　well　have　been　dealt　with　there。　　It　seems　to　me　that　it　would　have　been　better　so；　for　the　citation　of　additional　instances　of　reversion　at　this　place　rather　disturbs　the　logical　sequence　of　his　ideas　as　to　the　conditions　which　have　brought　about　the　evolution　of　man　from　lower　forms。　　The　instances　of　reversion　here　discussed　are　microcephalism；　which　Darwin　wrongly　interpreted　as　atavistic；　supernumerary　mammae；　supernumerary　digits；　bicornuate　uterus；　the　development　of　abnormal　muscles；　and　so　on。　Brief　mention　is　also　made　of　correlative　variations　observed　in　man。

Darwin　next　discusses　the　question　as　to　the　manner　in　which　man　attained　to　the　erect　position　from　the　state　of　a　climbing　quadruped。　　Here　again　he　puts　the　influence　of　Natural　Selection　in　the　first　rank。　　The　immediate　progenitors　of　man　had　to　maintain　a　struggle　for　existence　in　which　success　was　to　the　more　intelligent；　and　to　those　with　social　instincts。　　The　hand　of　these　climbing　ancestors；　which　had　little　skill　and　served　mainly　for　locomotion；　could　only　undergo　further　development　when　some　early　member　of　the　Primate　series　came　to　live　more　on　the　ground　and　less　among　trees。

A　bipedal　existence　thus　became　possible；　and　with　it　the　liberation　of　the　hand　from　locomotion；　and　the　one…sided　development　of　the　human　foot。　　The　upright　position　brought　about　correlated　variations　in　the　bodily　structure；　with　the　free　use　of　the　hand　it　became　possible　to　manufacture　weapons　and　to　use　them；　and　this　again　resulted　in　a　degeneration　of　the　powerful　canine　teeth　and　the　jaws；　which　were　then　no　longer　necessary　for　defence。　　Above　all；　however；　the　intelligence　immediately　increased；　and　with　it　skull　and　brain。　　The　nakedness　of　man；　and　the　absence　of　a　tail　（rudimentariness　of　the　tail　vertebrae）　are　next　discussed。　　Darwin　is　inclined　to　attribute　the　nakedness　of　man；　not　to　the　action　of　natural　selection　on　ancestors　who　originally　inhabited　a　tropical　land；　but　to　sexual　selection；　which；　for　aesthetic　reasons；　brought　about　the　loss　of　the　hairy　covering　in　man；　or　primarily　in　woman。　　An　interesting　discussion　of　the　loss　of　the　tail；　which；　however；　man　shares　with　the　anthropoid　apes；　some　other　monkeys　and　lemurs；　forms　the　conclusion　of　the　almost　superabundant　material　which　Darwin　worked　up　in　the　second　chapter。　　His　object　was　to　show　that　some　of　the　most　distinctive　human　characters　are　in　all　probability　directly　or　indirectly　due　to　natural　selection。　　With　characteristic　modesty　he　adds　（〃Descent　of　Man〃；　page　92。）：　　〃Hence；　if　I　have　erred　in　giving　to　natural　selection　great　power；　which　I　am　very　far　from　admitting；　or　in　having　exaggerated　its　power；　which　is　in　itself　probable；　I　have　at　least；　as　I　hope；　done　good　service　in　aiding　to　overthrow　the　dogma　of　separate　creations。〃　　At　the　end　of　the　chapter　he　touches　upon　the　objection　as　to　man's　helpless　and　defenceless　condition。　　Against　this　he　urges　his　intelligence　and　social　instincts。

The　two　following　chapters　contain　a　detailed　discussion　of　the　objections　drawn　from　the　supposed　great　differences　between　the　mental　powers　of　men　and　animals。　　Darwin　at　once　admits　that　the　differences　are　enormous；　but　not　that　any　fundamental　difference　between　the　two　can　be　found。　　Very　characteristic　of　him　is　the　following　passage：　　〃In　what　manner　the　mental　powers　were　first　developed　in　the　lowest　organisms；　is　as　hopeless　an　enquiry　as　how　life　itself　first　originated。　　These　are　problems　for　the　distant　future；　if　they　are　ever　to　be　solved　by　man。〃　　（Ibid。　page　100。）

After　some　brief　observations　on　instinct　and　intelligence；　Darwin　brings　forward　evidence　to　show　that　the　greater　number　of　the　emotional　states；　such　as　pleasure　and　pain；　happiness　and　misery；　love　and　hate　are　common　to　man　and　the　higher　animals。　　He　goes　on　to　give　various　examples　showing　that　wonder　and　curiosity；　imitation；　attention；　memory　and　imagination　（dreams　of　animals）；　can　also　be　observed　in　the　higher　mammals；　especially　in　apes。　　In　regard　even　to　reason　there　are　no　sharply　defined　limits。　　A　certain　faculty　of　deliberation　is　characteristic　of　some　animals；　and　the　more　thoroughly　we　know　an　animal　the　more　intelligence　we　are　inclined　to　credit　it　with。　　Examples　are　brought　forward　of　the　intelligent　and　deliberate　actions　of　apes；　dogs　and　elephants。　　But　although　no　sharply　defined　differences　exist　between　man　and　animals；　there　is；　nevertheless；　a　series　of　other　mental　powers　which　are　characteristics　usually　regarded　as　absolutely　peculiar　to　man。　　Some　of　these　characteristics　are　examined　in　detail；　and　it　is　shown　that　the　arguments　drawn　from　them　are　not　conclusive。　　Man　alone　is　said　to　be　capable　of　progressive　improvement；　but　against　this　must　be　placed　as　something　analogous　in　animals；　the　fact　that　they　learn　cunning　and　caution　through　long　continued　persecution。　　Even　the　use　of　tools　is　not　in　itself　peculiar　to　man　（monkeys　use　sticks；　stones　and　twigs）；　but　man　alone　fashions　and　uses　implements　DESIGNED　FOR　A　SPECIAL　PURPOSE。　　In　this　connection　the　remarks　taken　from　Lubbock　in　regard　to　the　origin　and　gradual　development　of　the　earliest　flint　implements　will　be　read　with　interest；　these　are　similar　to　the　observations　on　modern　eoliths；　and　their　bearing　on　the　development　of　the　stone…industry。　　It　is　interesting　to　learn　from　a　letter　to　Hooker　（〃Life　and　Letters〃；　Vol。　II。　page　161；　June　22；　1859。）；　that　Darwin　himself　at　first　doubted　whether　the　stone　implements　discovered　by　Boucher　de　Perthes　were　really　of　the　nature　of　tools。　　With　the　relentless　candour　as　to　himself　which　characterised　him；　he　writes　four　years　later　in　a　letter　to　Lyell　in　regard　to　this　view　of　Boucher　de　Perthes'　discoveries：　　〃I　know　something　about　his　errors；　and　looked　at　his　book　many　years　ago；　and　am　ashamed　to　think　that　I　concluded　the　whole　was　rubbish！　　Yet　he　has　done　for　man　something　like　what　Agassiz　did　for　glaciers。〃　　（Ibid。　Vol。　III。　page　15；　March　17；　1863。）

To　return　to　Darwin's　further　comparisons　between　the　higher　mental　powers　of　man　and　animals。　　He　takes　much　of　the　force　from　the　argument　that　man　alone　is　capable　of　abstraction　and　self…consciousness　by　his　own　observations　on　dogs。　　One　of　the　main　differences　between　man　and　animals；　speech；　receives　detailed　treatment。　　He　points　out　that　various　animals　（birds；　monkeys；　dogs）　have　a　large　number　of　different　sounds　for　different　emotions；　that；　further；　man　produces　in　common　with　animals　a　whole　series　of　inarticulate　cries　combined　with　gestures；　and　that　dogs　learn　to　understand　whole　sentences　of　human　speech。　　In　regard　to　human　language；　Darwin　expresses　a　view　contrary　to　that　held　by　Max　Muller　（〃Descent　of　Man〃；　page　132。）：　　〃I　cannot　doubt　that　language　owes　its　origin　to　the　imitation　and　modification　of　various　natural　sounds；　the　voices　of　other　animals；　and　man's　own　instinctive　cries；　aided　by　signs　and　gestures。〃　　The　development　of　actual　language　presupposes　a　higher　degree　of　intelligence　than　is　found　in　any　kind　of　ape。　　Darwin　remarks　on　this　point　（Ibid。　pages　136；　137。）：　　〃The　fact　of　the　higher　apes　not　using　their　vocal　organs　for　speech　no　doubt　depends　on　their　intelligence　not　having　been　sufficiently　advanced。〃

The　sense　of　beauty；　too；　has　been　alleged　to　be　peculiar　to　man。　　In　refutation　of　this　assertion　Darwin　points　to　the　decorative　colours　of　birds；　which　are　used　for　display。　　And　to　the　last　objection；　that　man　alone　has　religion；　that　he　alone　has　a　belief　in　God；　it　is　answered　〃that　numerous　races　have　existed；　and　still　exist；　who　have　no　idea　of　one　or　more　gods；　and　who　have　no　words　in　their　languages　to　express　such　an　idea。〃　　（Ibid。　page　143。）

The　result　of　the　investigations　recorded　in　this　chapter　is　to　show　that；　great　as　the　difference　in　mental　powers　between　man　and　the　higher　animals　may　be；　it　is　undoubtedly　only　a　difference　〃of　degree　and　not　of　kind。〃　　（〃Descent　of　Man〃；　page　193。）

In　the　fourth　chapter　Darwin　deals　with　the　MORAL　SENSE　or　CONSCIENCE；　which　is　the　most　important　of　all　differences　between　man　and　animals。　　It　is　a　result　of　social　instincts；　which　lead　to　sympathy　for　other　members　of　the　same　society；　to　non…egoistic　actions　for　the　good　of　others。　　Darwin　shows　that　social　tendencies　are　found　among　many　animals；　and　that　among　these　love　and　kin…sympathy　exist；　and　he　gives　examples　of　animals　（especially　dogs）　which　may　exhibit　characters　that　we　should　call　moral　in　man　（e。g。　disinterested　self…sacrifice　for　the　sake　of　others）。　　The　early　ape…like　progenitors　of　the　human　race　were　undoubtedly　social。　　With　the　increase　of　intelligence　the　moral　sense　develops　farther；　with　the　acquisition　of　speech　public　opinion　arises；　and　finally；　moral　sense　becomes　habit。　　The　rest　of　Darw