darwin and modern science-第35章

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lined！　　What　use　he　would　have　made　of　the　new　and　precious　material；　which　would　have　prevented　the　discouragement　from　which　he　suffered　when　preparing　the　second　edition　of　〃The　Descent　of　Man〃！　　But　it　was　not　granted　to　him　to　see　this　progress　towards　filling　up　the　gaps　in　his　edifice　of　which　he　was　so　painfully　conscious。

He　did；　however；　have　the　satisfaction　of　seeing　his　ideas　steadily　gaining　ground；　notwithstanding　much　hostility　and　deep…rooted　prejudice。　　Even　in　the　years　between　the　appearance　of　〃The　Origin　of　Species〃　and　of　the　first　edition　of　the　〃Descent〃；　the　idea　of　a　natural　descent　of　man；　which　was　only　briefly　indicated　in　the　work　of　1859；　had　been　eagerly　welcomed　in　some　quarters。　　It　has　been　already　pointed　out　how　brilliantly　Huxley　contributed　to　the　defence　and　diffusion　of　Darwin's　doctrines；　and　how　in　〃Man's　Place　in　Nature〃　he　has　given　us　a　classic　work　as　a　foundation　for　the　doctrine　of　the　descent　of　man。　　As　Huxley　was　Darwin's　champion　in　England；　so　in　Germany　Carl　Vogt；　in　particular；　made　himself　master　of　the　Darwinian　ideas。　　But　above　all　it　was　Haeckel　who；　in　energy；　eagerness　for　battle；　and　knowledge　may　be　placed　side　by　side　with　Huxley；　who　took　over　the　leadership　in　the　controversy　over　the　new　conception　of　the　universe。　　As　far　back　as　1866；　in　his　〃Generelle　Morphologie〃；　he　had　inquired　minutely　into　the　question　of　the　descent　of　man；　and　not　content　with　urging　merely　the　general　theory　of　descent　from　lower　animal　forms；　he　drew　up　for　the　first　time　genealogical　trees　showing　the　close　relationships　of　the　different　animal　groups；　the　last　of　these　illustrated　the　relationships　of　Mammals；　and　among　them　of　all　groups　of　the　Primates；　including　man。　　It　was　Haeckel's　genealogical　trees　that　formed　the　basis　of　the　special　discussion　of　the　relationships　of　man；　in　the　sixth　chapter　of　Darwin's　〃Descent　of　Man〃。

In　the　last　section　of　this　essay　I　shall　return　to　Haeckel's　conception　of　the　special　descent　of　man；　the　main　features　of　which　he　still　upholds；　and　rightly　so。　　Haeckel　has　contributed　more　than　any　one　else　to　the　spread　of　the　Darwinian　doctrine。

I　can　only　allow　myself　a　few　words　as　to　the　spread　of　the　theory　of　the　natural　descent　of　man　in　other　countries。　　The　Parisian　anthropological　school；　founded　and　guided　by　the　genius　of　Broca；　took　up　the　idea　of　the　descent　of　man；　and　made　many　notable　contributions　to　it　（Broca；　Manouvrier；　Mahoudeau；　Deniker　and　others）。　　In　England　itself　Darwin's　work　did　not　die。　　Huxley　took　care　of　that；　for　he；　with　his　lofty　and　unprejudiced　mind；　dominated　and　inspired　English　biology　until　his　death　on　June　29；　1895。　　He　had　the　satisfaction　shortly　before　his　death　of　learning　of　Dubois'　discovery；　which　he　illustrated　by　a　humorous　sketch。　　（〃Life　and　Letters　of　Thomas　Henry　Huxley〃；　Vol。　II。　page　394。）　　But　there　are　still　many　followers　in　Darwin's　footsteps　in　England。　　Keane　has　worked　at　the　special　genealogical　tree　of　the　Primates；　Keith　has　inquired　which　of　the　anthropoid　apes　has　the　greatest　number　of　characters　in　common　with　man；　Morris　concerns　himself　with　the　evolution　of　man　in　general；　especially　with　his　acquisition　of　the　erect　position。　　The　recent　discoveries　of　Pithecanthropus　and　Homo　primigenius　are　being　vigorously　discussed；　but　the　present　writer　is　not　in　a　position　to　form　an　opinion　of　the　extent　to　which　the　idea　of　descent　has　penetrated　throughout　England　generally。

In　Italy　independent　work　in　the　domain　of　the　descent　of　man　is　being　produced；　especially　by　Morselli；　with　him　are　associated；　in　the　investigation　of　related　problems；　Sergi　and　Giuffrida…Ruggeri。　　From　the　ranks　of　American　investigators　we　may　single　out　in　particular　the　eminent　geologist　Cope；　who　championed　with　much　decision　the　idea　of　the　specific　difference　of　Homo　neandertalensis　（primigenius）　and　maintained　a　more　direct　descent　of　man　from　the　fossil　Lemuridae。　　In　South　America　too；　in　Argentina；　new　life　is　stirring　in　this　department　of　science。　　Ameghino　in　Buenos　Ayres　has　awakened　the　fossil　primates　of　the　Pampas　formation　to　new　life；　he　even　believes　that　in　Tetraprothomo；　represented　by　a　femur；　he　has　discovered　a　direct　ancestor　of　man。　　Lehmann…Nitsche　is　working　at　the　other　side　of　the　gulf　between　apes　and　men；　and　he　describes　a　remarkable　first　cervical　vertebra　（atlas）　from　Monte　Hermoso　as　belonging　to　a　form　which　may　bear　the　same　relation　to　Homo　sapiens　in　South　America　as　Homo　primigenius　does　in　the　Old　World。　　After　a　minute　investigation　he　establishes　a　human　species　Homo　neogaeus；　while　Ameghino　ascribes　this　atlas　vertebra　to　his　Tetraprothomo。

Thus　throughout　the　whole　scientific　world　there　is　arising　a　new　life；　an　eager　endeavour　to　get　nearer　to　Huxley's　problema　maximum；　to　penetrate　more　deeply　into　the　origin　of　the　human　race。　　There　are　to…day　very　few　experts　in　anatomy　and　zoology　who　deny　the　animal　descent　of　man　in　general。　　Religious　considerations；　old　prejudices；　the　reluctance　to　accept　man；　who　so　far　surpasses　mentally　all　other　creatures；　as　descended　from　〃soulless〃　animals；　prevent　a　few　investigators　from　giving　full　adherence　to　the　doctrine。　　But　there　are　very　few　of　these　who　still　postulate　a　special　act　of　creation　for　man。　　Although　the　majority　of　experts　in　anatomy　and　zoology　accept　unconditionally　the　descent　of　man　from　lower　forms；　there　is　much　diversity　of　opinion　among　them　in　regard　to　the　special　line　of　descent。

In　trying　to　establish　any　special　hypothesis　of　descent；　whether　by　the　graphic　method　of　drawing　up　genealogical　trees　or　otherwise；　let　us　always　bear　in　mind　Darwin's　words　（〃Descent　of　Man〃；　page　229。）　and　use　them　as　a　critical　guiding　line：　　〃As　we　have　no　record　of　the　lines　of　descent；　the　pedigree　can　be　discovered　only　by　observing　the　degrees　of　resemblance　between　the　beings　which　are　to　be　classed。〃　　Darwin　carries　this　further　by　stating　〃that　resemblances　in　several　unimportant　structures；　in　useless　and　rudimentary　organs；　or　not　now　functionally　active；　or　in　an　embryological　condition；　are　by　far　the　most　serviceable　for　classification。〃　　（Loc。　cit。）　　It　has　also　to　be　remembered　that　NUMEROUS　separate　points　of　agreement　are　of　much　greater　importance　than　the　amount　of　similarity　or　dissimilarity　in　a　few　points。

The　hypotheses　as　to　descent　current　at　the　present　day　may　be　divided　into　two　main　groups。　　The　first　group　seeks　for　the　roots　of　the　human　race　not　among　any　of　the　families　of　the　apesthe　anatomically　nearest　formsnor　among　their　very　similar　but　less　specialised　ancestral　forms；　the　fossil　representatives　of　which　we　can　know　only　in　part；　but；　setting　the　monkeys　on　one　side；　it　seeks　for　them　lower　down　among　the　fossil　Eocene　Pseudo…　lemuridae　or　Lemuridae　（Cope）；　or　even　among　the　primitive　pentadactylous　Eocene　forms；　which　may　either　have　led　directly　to　the　evolution　of　man　（Adloff）；　or　have　given　rise　to　an　ancestral　form　common　to　apes　and　men　（Klaatsch　（Klaatsch　in　his　last　publications　speaks　in　the　main　only　of　an　ancestral　form　common　to　men　and　anthropoid　apes。）；　Giuffrida…Ruggeri）。　　The　common　ancestral　form；　from　which　man　and　apes　are　thus　supposed　to　have　arisen　independently；　may　explain　the　numerous　resemblances　which　actually　exist　between　them。　　That　is　to　say；　all　the　characters　upon　which　the　great　structural　resemblance　between　apes　and　man　depends　must　have　been　present　in　their　common　ancestor。　　Let　us　take　an　example　of　such　a　common　character。　　The　bony　external　ear…passage　is　in　general　as　highly　developed　in　the　lower　Eastern　monkeys　and　the　anthropoid　apes　as　in　man。　　This　character　must；　therefore；　have　already　been　present　in　the　common　primitive　form。　　In　that　case　it　is　not　easy　to　understand　why　the　Western　monkeys　have　not　also　inherited　the　character；　instead　of　possessing　only　a　tympanic　ring。　　But　it　becomes　more　intelligible　if　we　assume　that　forms　with　a　primitive　tympanic　ring　were　the　original　type；　and　that　from　these　were　evolved；　on　the　one　hand；　the　existing　New　World　monkeys　with　persistent　tympanic　ring；　and　on　the　other　an　ancestral　form　common　to　the　lower　Old　World　monkeys；　the　anthropoid　apes　and　man。　　For　man　shares　with　these　the　character　in　question；　and　it　is　also　one　of　the　〃unimportant〃　characters　required　by　Darwin。　　Thus　we　have　two　divergent　lines　arising　from　the　ancestral　form；　the　Western　monkeys　（Platyrrhine）　on　the　one　hand；　and　an　ancestral　form　common　to　the　lower　Eastern　monkeys；　the　anthropoid　apes；　and　man；　on　the　other。　　But　considerations　similar　to　those　which　showed　it　to　be　impossible　that　man　should　have　developed　from　an　ancestor　common　to　him　and　the　monkeys；　yet　outside　of　and　parallel　with　these；　may　be　urged　also　against　the　likelihood　of　a　parallel　evolution　of　the　lower　Eastern　monkeys；　the　anthropoid　apes；　and　man。　　The　anthropoid　apes　have　in　common　with　man　many　characters　which　are　not　present　in　the　lower　Old　World　monkeys。　　These　characters　must　therefore　have　been　present　in　the　ancestral　form　common　to　the　three　groups。　　But　here；　again；　it　is　difficult　to　understand　why　the　lower　Eastern　monkeys　should　not　also　have　inherited　these　characters。　　As　this　is　not　the　case；　there　remains　no　alternative　but　to　assume　divergent　evolution　from　an　indifferent　form。　　The　lower　Eastern　monkeys　are　carrying　on　the　evolution　in　one　directionI　might　almost　say　towards　a　blind　alleywhile　anthropoids　and　men　have　struck　out　a　progressive　path；　at　first　in　common；　which　explains　the　many　points　of　resemblance　between　them；　without　regarding　man　as　derived　directly　from　the　anthropoids。　　Their　many　striking　points　of　agreement　indicate　a　common　descent；　and　cannot　be　explained　as　phenomena　of　convergence。

I　believe　I　have　shown　in　the　above　sketch　that　a　theory　which　derives　man　directly　from　lower　forms　without　regarding　apes　as　transition…types　leads　ad　absurdum。　　The　close　structural　relationship　between　man　and　monkeys　can　only　be　understood　if　both　are　brought　into　the　same　line　of　evolution。　　To　trace　man's　line　of　descent　directly　back　to　the　old　Eocene　mammals；　alongside　of；　but　with　no　relation　to　these　very　similar　forms；　is　to　abandon　the　method　of　exact　comparison；　which；　as　Darwin　rightly　recognised；　alone　justifies　us　in　drawing　up　genealogical　trees　on　the　basis　of　resemblances　and　differences。　　The　farther　down　we　go　the　more　does　the　ground　slip　from　beneath　our　feet。　　Even　the　Lemuridae　show　very　numerous　divergent　conditions；　much　more　so　the　Eocene　mammals　（Creodonta；　Condylarthra）；　the　chief　resemblance　of　which　to　man　consists　in　the　possession　of　pentadactylous　hands　and　feet！　　Thus　the　farther　course　of　the　line　of　descent　disappears　in　the　darkness　of　the　ancestry　of　the　mammals。　　With　just　as　much　reason　we　might　pass　by　the　Vertebrates　altogether；　and　go　back　to　the　lower　Invertebrates；　but　in　that　case　it　would　be　much　easier　to　say　that　man　has　arisen　independently；　and　has　evolved；　without　relation　to　any　animals；　from　the　lowest　primitive　form　to　his　present　isolated　and　dominant　position。　　But　this　would　be　to　deny　all　value　to　classification；　which　must　after　all　be　the　ultimate　basis　of　a　genealogical　tree。　　We　can；　as　Darwin　rightly　observed；　only　infer　t