darwin and modern science-第122部分

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　These　are　evidently　a　valuable　addition　to　the　means　of　recognition　of　the　two　sexes；　and　are　a　further　indication　that　the　pairing　season　has　arrived；　and　the　production；　intensification；　and　differentiation　of　these　sounds　and　odours　are　clearly　within　the　power　of　natural　selection。　　The　same　remark　will　apply　to　the　peculiar　calls　of　birds；　and　even　to　the　singing　of　the　males。〃　　Why　the　same　remark　should　not　apply　to　their　colours　and　adornments　is　not　obvious。　　What　is　obvious　is　that　〃means　of　recognition〃　and　〃indication　that　the　pairing　season　has　arrived〃　are　dependent　on　the　perceptive　powers　of　the　female　who　recognises　and　for　whom　the　indication　has　meaning。　　The　hypothesis　of　female　preference；　stripped　of　the　aesthetic　surplusage　which　is　psychologically　both　unnecessary　and　unproven；　is　really　only　different　in　degree　from　that　which　Mr　Wallace　admits　in　principle　when　he　says　that　it　is　probable　that　the　female　is　pleased　or　excited　by　the　display。

Let　us　for　our　present　purpose　leave　on　one　side　and　regard　as　sub　judice　the　question　whether　the　specific　details　of　secondary　sexual　characters　are　the　outcome　of　female　choice。　　For　us　the　question　is　whether　certain　psychological　accompaniments　of　the　pairing　situation　have　influenced　the　course　of　evolution　and　whether　these　psychological　accompaniments　are　themselves　the　outcome　of　evolution。　　As　a　matter　of　observation；　specially　differentiated　modes　of　behaviour；　often　very　elaborate；　frequently　requiring　highly　developed　skill；　and　apparently　highly　charged　with　emotional　tone；　are　the　precursors　of　pairing。　　They　are　generally　confined　to　the　males；　whose　fierce　combats　during　the　period　of　sexual　activity　are　part　of　the　emotional　manifestation。　　It　is　inconceivable　that　they　have　no　biological　meaning；　and　it　is　difficult　to　conceive　that　they　have　any　other　biological　end　than　to　evoke　in　the　generally　more　passive　female　the　pairing　impulse。　　They　are　based　on　instinctive　foundations　ingrained　in　the　nervous　constitution　through　natural　（or　may　we　not　say　sexual？）　selection　in　virtue　of　their　profound　utility。　　They　are　called　into　play　by　a　specialised　presentation　such　as　the　sight　or　the　scent　of　the　female　at；　or　a　little　in　advance　of；　a　critical　period　of　the　physiological　rhythm。　　There　is　no　necessity　that　the　male　should　have　any　knowledge　of　the　end　to　which　his　strenuous　activity　leads　up。　　In　presence　of　the　female　there　is　an　elaborate　application　of　all　the　energies　of　behaviour；　just　because　ages　of　racial　preparation　have　made　him　biologically　and　emotionally　what　he　isa　functionally　sexual　male　that　must　dance　or　sing　or　go　through　hereditary　movements　of　display；　when　the　appropriate　stimulation　comes。　　Of　course　after　the　first　successful　courtship　his　future　behaviour　will　be　in　some　degree　modified　by　his　previous　experience。　　No　doubt　during　his　first　courtship　he　is　gaining　the　primary　data　of　a　peculiarly　rich　experience；　instinctive　and　emotional。　　But　the　biological　foundations　of　the　behaviour　of　courtship　are　laid　in　the　hereditary　coordinations。　　It　would　seem　that　in　some　cases；　not　indeed　in　all；　but　perhaps　especially　in　those　cases　in　which　secondary　sexual　behaviour　is　most　highly　evolved；correlative　with　the　ardour　of　the　male　is　a　certain　amount　of　reluctance　in　the　female。　　The　pairing　act　on　her　part　only　takes　place　after　prolonged　stimulation；　for　affording　which　the　behaviour　of　male　courtship　is　the　requisite　presentation。　　The　most　vigorous；　defiant　and　mettlesome　male　is　preferred　just　because　he　alone　affords　a　contributory　stimulation　adequate　to　evoke　the　pairing　impulse　with　its　attendant　emotional　tone。

It　is　true　that　this　places　female　preference　or　choice　on　a　much　lower　psychological　plane　than　Darwin　in　some　passages　seems　to　contemplate　where；　for　example；　he　says　that　the　female　appreciates　the　display　of　the　male　and　places　to　her　credit　a　taste　for　the　beautiful。　　But　Darwin　himself　distinctly　states　（〃Descent　of　Man〃　（2nd　edition）；　Vol。　II。　pages　136；　137；　（Popular　edition）；　pages　642；　643。）　that　〃it　is　not　probable　that　she　consciously　deliberates；　but　she　is　most　excited　or　attracted　by　the　most　beautiful；　or　melodious；　or　gallant　males。〃　　The　view　here　put　forward；　which　has　been　developed　by　Prof。　Groos　（〃The　Play　of　Animals〃；　page　244；　London；　1898。）；　therefore　seems　to　have　Darwin's　own　sanction。　　The　phenomena　are　not　only　biological；　there　are　psychological　elements　as　well。　　One　can　hardly　suppose　that　the　female　is　unconscious　of　the　male's　presence；　the　final　yielding　must　surely　be　accompanied　by　heightened　emotional　tone。　　Whether　we　call　it　choice　or　not　is　merely　a　matter　of　definition　of　terms。　　The　behaviour　is　in　part　determined　by　supplementary　psychological　values。　　Prof。　Groos　regards　the　coyness　of　females　as　〃a　most　efficient　means　of　preventing　the　too　early　and　too　frequent　yielding　to　the　sexual　impulse。〃　　（Ibid。　page　283。）　　Be　that　as　it　may；　it　is；　in　any　case；　if　we　grant　the　facts；　a　means　through　which　male　sexual　behaviour　with　all　its　biological　and　psychological　implications；　is　raised　to　a　level　otherwise　perhaps　unattainable　by　natural　means；　while　in　the　female　it　affords　opportunities　for　the　development　in　the　individual　and　evolution　in　the　race　of　what　we　may　follow　Darwin　in　calling　appreciation；　if　we　empty　this　word　of　the　aesthetic　implications　which　have　gathered　round　it　in　the　mental　life　of　man。

Regarded　from　this　standpoint　sexual　selection；　broadly　considered；　has　probably　been　of　great　importance。　　The　psychological　accompaniments　of　the　pairing　situation　have　profoundly　influenced　the　course　of　biological　evolution　and　are　themselves　the　outcome　of　that　evolution。

Darwin　makes　only　passing　reference　to　those　modes　of　behaviour　in　animals　which　go　by　the　name　of　play。　　〃Nothing；〃　he　says　（〃Descent　of　Man〃；　Vol。　II。　page　60；　（Popular　edition）；　page　566。）；　〃is　more　common　than　for　animals　to　take　pleasure　in　practising　whatever　instinct　they　follow　at　other　times　for　some　real　good。〃　　This　is　one　of　the　very　numerous　cases　in　which　a　hint　of　the　master　has　served　to　stimulate　research　in　his　disciples。　　It　was　left　to　Prof。　Groos　to　develop　this　subject　on　evolutionary　lines　and　to　elaborate　in　a　masterly　manner　Darwin's　suggestion。　　〃The　utility　of　play；〃　he　says　（〃The　Play　of　Animals〃；　page　76。）；　〃is　incalculable。　　This　utility　consists　in　the　practice　and　exercise　it　affords　for　some　of　the　more　important　duties　of　life；〃that　is　to　say；　for　the　performance　of　activities　which　will　in　adult　life　be　essential　to　survival。　　He　urges　（Ibid。　page　75。）　that　〃the　play　of　young　animals　has　its　origin　in　the　fact　that　certain　very　important　instincts　appear　at　a　time　when　the　animal　does　not　seriously　need　them。〃　　It　is；　however；　questionable　whether　any　instincts　appear　at　a　time　when　they　are　not　needed。　　And　it　is　questionable　whether　the　instinctive　and　emotional　attitude　of　the　play…fight；　to　take　one　example；　can　be　identified　with　those　which　accompany　fighting　in　earnest；　though　no　doubt　they　are　closely　related　and　have　some　common　factors。　　It　is　probable　that　play；　as　preparatory　behaviour；　differs　in　biological　detail　（as　it　almost　certainly　does　in　emotional　attributes）　from　the　earnest　of　after…life　and　that　it　has　been　evolved　through　differentiation　and　integration　of　the　primary　tissue　of　experience；　as　a　preparation　through　which　certain　essential　modes　of　skill　may　be　acquiredthose　animals　in　which　the　preparatory　play…propensity　was　not　inherited　in　due　force　and　requisite　amount　being　subsequently　eliminated　in　the　struggle　for　existence。　　In　any　case　there　is　little　question　that　Prof。　Groos　is　right　in　basing　the　play…propensity　on　instinctive　foundations。　　（〃The　Play　of　Animals〃　page　24。）　　None　the　less；　as　he　contends；　the　essential　biological　value　of　play　is　that　it　is　a　means　of　training　the　educable　nerve…tissue；　of　developing　that　part　of　the　brain　which　is　modified　by　experience　and　which　thus　acquires　new　characters；　of　elaborating　the　secondary　tissue　of　experience　on　the　predetermined　lines　of　instinctive　differentiation　and　thus　furthering　the　psychological　activities　which　are　included　under　the　comprehensive　term　〃intelligent。〃

In　〃The　Descent　of　Man〃　Darwin　dealt　at　some　length　with　intelligence　and　the　higher　mental　faculties。　　（〃Descent　of　Man〃　（1st　edition）；　Chapters　II；　III；　V；　（2nd　edition）；　Chapters　III；　IV；　V。）　　His　object；　he　says；　is　to　show　that　there　is　no　fundamental　difference　between　man　and　the　higher　mammals　in　their　mental　faculties；　that　these　faculties　are　variable　and　the　variations　tend　to　be　inherited；　and　that　under　natural　selection　beneficial　variations　of　all　kinds　will　have　been　preserved　and　injurious　ones　eliminated。

Darwin　was　too　good　an　observer　and　too　honest　a　man　to　minimise　the　〃enormous　difference〃　between　the　level　of　mental　attainment　of　civilised　man　and　that　reached　by　any　animal。　　His　contention　was　that　the　difference；　great　as　it　is；　is　one　of　degree　and　not　of　kind。　　He　realised　that；　in　the　development　of　the　mental　faculties　of　man；　new　factors　in　evolution　have　supervenedfactors　which　play　but　a　subordinate　and　subsidiary　part　in　animal　intelligence。　　Intercommunication　by　means　of　language；　approbation　and　blame；　and　all　that　arises　out　of　reflective　thought；　are　but　foreshadowed　in　the　mental　life　of　animals。　　Still　he　contends　that　these　may　be　explained　on　the　doctrine　of　evolution。　　He　urges　（Ibid。　Vol。　I。　pages　70；　71；　（Popular　edition）；　pages　70；　71。）〃　that　man　is　variable　in　body　and　mind；　and　that　the　variations　are　induced；　either　directly　or　indirectly；　by　the　same　general　causes；　and　obey　the　same　general　laws；　as　with　the　lower　animals。〃　　He　correlates　mental　development　with　the　evolution　of　the　brain。　　（Ibid。　page　81。）　　〃As　the　various　mental　faculties　gradually　developed　themselves；　the　brain　would　almost　certainly　become　larger。　　No　one；　I　presume；　doubts　that　the　large　proportion　which　the　size　of　man's　brain　bears　to　his　body；　compared　to　the　same　proportion　in　the　gorilla　or　orang；　is　closely　connected　with　his　higher　mental　powers。〃　　〃With　respect　to　the　lower　animals；〃　he　says　（〃Descent　of　Man〃　（Popular　edition）；　page　82。）；　〃M。E。　Lartet　（〃