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by¡¡Charles¡¡Darwin

¡¡Next¡¡Chapter¡¡

Chapter¡¡1¡¡¡­¡¡Variation¡¡Under¡¡Domestication

WHEN¡¡we¡¡look¡¡to¡¡the¡¡individuals¡¡of¡¡the¡¡same¡¡variety¡¡or¡¡sub¡­variety¡¡of¡¡our¡¡older¡¡cultivated¡¡plants¡¡and¡¡animals£»¡¡one¡¡of¡¡the¡¡first¡¡points¡¡which¡¡strikes¡¡us£»¡¡is£»¡¡that¡¡they¡¡generally¡¡differ¡¡much¡¡more¡¡from¡¡each¡¡other£»¡¡than¡¡do¡¡the¡¡individuals¡¡of¡¡any¡¡one¡¡species¡¡or¡¡variety¡¡in¡¡a¡¡state¡¡of¡¡nature¡£¡¡When¡¡we¡¡reflect¡¡on¡¡the¡¡vast¡¡diversity¡¡of¡¡the¡¡plants¡¡and¡¡animals¡¡which¡¡have¡¡been¡¡cultivated£»¡¡and¡¡which¡¡have¡¡varied¡¡during¡¡all¡¡ages¡¡under¡¡the¡¡most¡¡different¡¡climates¡¡and¡¡treatment£»¡¡I¡¡think¡¡we¡¡are¡¡driven¡¡to¡¡conclude¡¡that¡¡this¡¡greater¡¡variability¡¡is¡¡simply¡¡due¡¡to¡¡our¡¡domestic¡¡productions¡¡having¡¡been¡¡raised¡¡under¡¡conditions¡¡of¡¡life¡¡not¡¡so¡¡uniform¡¡as£»¡¡and¡¡somewhat¡¡different¡¡from£»¡¡those¡¡to¡¡which¡¡the¡¡parent¡­species¡¡have¡¡been¡¡exposed¡¡under¡¡nature¡£¡¡There¡¡is£»¡¡also£»¡¡I¡¡think£»¡¡some¡¡probability¡¡in¡¡the¡¡view¡¡propounded¡¡by¡¡Andrew¡¡Knight£»¡¡that¡¡this¡¡variability¡¡may¡¡be¡¡partly¡¡connected¡¡with¡¡excess¡¡of¡¡food¡£¡¡It¡¡seems¡¡pretty¡¡clear¡¡that¡¡organic¡¡beings¡¡must¡¡be¡¡exposed¡¡during¡¡several¡¡generations¡¡to¡¡the¡¡new¡¡conditions¡¡of¡¡life¡¡to¡¡cause¡¡any¡¡appreciable¡¡amount¡¡of¡¡variation£»¡¡and¡¡that¡¡when¡¡the¡¡organisation¡¡has¡¡once¡¡begun¡¡to¡¡vary£»¡¡it¡¡generally¡¡continues¡¡to¡¡vary¡¡for¡¡many¡¡generations¡£¡¡No¡¡case¡¡is¡¡on¡¡record¡¡of¡¡a¡¡variable¡¡being¡¡ceasing¡¡to¡¡be¡¡variable¡¡under¡¡cultivation¡£¡¡Our¡¡oldest¡¡cultivated¡¡plants£»¡¡such¡¡as¡¡wheat£»¡¡still¡¡often¡¡yield¡¡new¡¡varieties£º¡¡our¡¡oldest¡¡domesticated¡¡animals¡¡are¡¡still¡¡capable¡¡of¡¡rapid¡¡improvement¡¡or¡¡modification¡£¡¡
It¡¡has¡¡been¡¡disputed¡¡at¡¡what¡¡period¡¡of¡¡time¡¡the¡¡causes¡¡of¡¡variability£»¡¡whatever¡¡they¡¡may¡¡be£»¡¡generally¡¡act£»¡¡whether¡¡during¡¡the¡¡early¡¡or¡¡late¡¡period¡¡of¡¡development¡¡of¡¡the¡¡embryo£»¡¡or¡¡at¡¡the¡¡instant¡¡of¡¡conception¡£¡¡Geoffroy¡¡St¡¡Hilaire's¡¡experiments¡¡show¡¡that¡¡unnatural¡¡treatment¡¡of¡¡the¡¡embryo¡¡causes¡¡monstrosities£»¡¡and¡¡monstrosities¡¡cannot¡¡be¡¡separated¡¡by¡¡any¡¡clear¡¡line¡¡of¡¡distinction¡¡from¡¡mere¡¡variations¡£¡¡But¡¡I¡¡am¡¡strongly¡¡inclined¡¡to¡¡suspect¡¡that¡¡the¡¡most¡¡frequent¡¡cause¡¡of¡¡variability¡¡may¡¡be¡¡attributed¡¡to¡¡the¡¡male¡¡and¡¡female¡¡reproductive¡¡elements¡¡having¡¡been¡¡affected¡¡prior¡¡to¡¡the¡¡act¡¡of¡¡conception¡£¡¡Several¡¡reasons¡¡make¡¡me¡¡believe¡¡in¡¡this£»¡¡but¡¡the¡¡chief¡¡one¡¡is¡¡the¡¡remarkable¡¡effect¡¡which¡¡confinement¡¡or¡¡cultivation¡¡has¡¡on¡¡the¡¡functions¡¡of¡¡the¡¡reproductive¡¡system£»¡¡this¡¡system¡¡appearing¡¡to¡¡be¡¡far¡¡more¡¡susceptible¡¡than¡¡any¡¡other¡¡part¡¡of¡¡the¡¡organization£»¡¡to¡¡the¡¡action¡¡of¡¡any¡¡change¡¡in¡¡the¡¡conditions¡¡of¡¡life¡£¡¡Nothing¡¡is¡¡more¡¡easy¡¡than¡¡to¡¡tame¡¡an¡¡animal£»¡¡and¡¡few¡¡things¡¡more¡¡difficult¡¡than¡¡to¡¡get¡¡it¡¡to¡¡breed¡¡freely¡¡under¡¡confinement£»¡¡even¡¡in¡¡the¡¡many¡¡cases¡¡when¡¡the¡¡male¡¡and¡¡female¡¡unite¡£¡¡How¡¡many¡¡animals¡¡there¡¡are¡¡which¡¡will¡¡not¡¡breed£»¡¡though¡¡living¡¡long¡¡under¡¡not¡¡very¡¡close¡¡confinement¡¡in¡¡their¡¡native¡¡country£¡¡¡This¡¡is¡¡generally¡¡attributed¡¡to¡¡vitiated¡¡instincts£»¡¡but¡¡how¡¡many¡¡cultivated¡¡plants¡¡display¡¡the¡¡utmost¡¡vigour£»¡¡and¡¡yet¡¡rarely¡¡or¡¡never¡¡seed£¡¡¡In¡¡some¡¡few¡¡such¡¡cases¡¡it¡¡has¡¡been¡¡found¡¡out¡¡that¡¡very¡¡trifling¡¡changes£»¡¡such¡¡as¡¡a¡¡little¡¡more¡¡or¡¡less¡¡water¡¡at¡¡some¡¡particular¡¡period¡¡of¡¡growth£»¡¡will¡¡determine¡¡whether¡¡or¡¡not¡¡the¡¡plant¡¡sets¡¡a¡¡seed¡£¡¡I¡¡cannot¡¡here¡¡enter¡¡on¡¡the¡¡copious¡¡details¡¡which¡¡I¡¡have¡¡collected¡¡on¡¡this¡¡curious¡¡subject£»¡¡but¡¡to¡¡show¡¡how¡¡singular¡¡the¡¡laws¡¡are¡¡which¡¡determine¡¡the¡¡reproduction¡¡of¡¡animals¡¡under¡¡confinement£»¡¡I¡¡may¡¡just¡¡mention¡¡that¡¡carnivorous¡¡animals£»¡¡even¡¡from¡¡the¡¡tropics£»¡¡breed¡¡in¡¡this¡¡country¡¡pretty¡¡freely¡¡under¡¡confinement£»¡¡with¡¡the¡¡exception¡¡of¡¡the¡¡plantigrades¡¡or¡¡bear¡¡family£»¡¡whereas£»¡¡carnivorous¡¡birds£»¡¡with¡¡the¡¡rarest¡¡exceptions£»¡¡hardly¡¡ever¡¡lay¡¡fertile¡¡eggs¡£¡¡Many¡¡exotic¡¡plants¡¡have¡¡pollen¡¡utterly¡¡worthless£»¡¡in¡¡the¡¡same¡¡exact¡¡condition¡¡as¡¡in¡¡the¡¡most¡¡sterile¡¡hybrids¡£¡¡When£»¡¡on¡¡the¡¡one¡¡hand£»¡¡we¡¡see¡¡domesticated¡¡animals¡¡and¡¡plants£»¡¡though¡¡often¡¡weak¡¡and¡¡sickly£»¡¡yet¡¡breeding¡¡quite¡¡freely¡¡under¡¡confinement£»¡¡and¡¡when£»¡¡on¡¡the¡¡other¡¡hand£»¡¡we¡¡see¡¡individuals£»¡¡though¡¡taken¡¡young¡¡from¡¡a¡¡state¡¡of¡¡nature£»¡¡perfectly¡¡tamed£»¡¡long¡­lived£»¡¡and¡¡healthy¡¡£¨of¡¡which¡¡I¡¡could¡¡give¡¡numerous¡¡instances£©£»¡¡yet¡¡having¡¡their¡¡reproductive¡¡system¡¡so¡¡seriously¡¡affected¡¡by¡¡unperceived¡¡causes¡¡as¡¡to¡¡fail¡¡in¡¡acting£»¡¡we¡¡need¡¡not¡¡be¡¡surprised¡¡at¡¡this¡¡system£»¡¡when¡¡it¡¡does¡¡act¡¡under¡¡confinement£»¡¡acting¡¡not¡¡quite¡¡regularly£»¡¡and¡¡producing¡¡offspring¡¡not¡¡perfectly¡¡like¡¡their¡¡parents¡¡or¡¡variable¡£¡¡
Sterility¡¡has¡¡been¡¡said¡¡to¡¡be¡¡the¡¡bane¡¡of¡¡horticulture£»¡¡but¡¡on¡¡this¡¡view¡¡we¡¡owe¡¡variability¡¡to¡¡the¡¡same¡¡cause¡¡which¡¡produces¡¡sterility£»¡¡and¡¡variability¡¡is¡¡the¡¡source¡¡of¡¡all¡¡the¡¡choicest¡¡productions¡¡of¡¡the¡¡garden¡£¡¡I¡¡may¡¡add£»¡¡that¡¡as¡¡some¡¡organisms¡¡will¡¡breed¡¡most¡¡freely¡¡under¡¡the¡¡most¡¡unnatural¡¡conditions¡¡£¨for¡¡instance£»¡¡the¡¡rabbit¡¡and¡¡ferret¡¡kept¡¡in¡¡hutches£©£»¡¡showing¡¡that¡¡their¡¡reproductive¡¡system¡¡has¡¡not¡¡been¡¡thus¡¡affected£»¡¡so¡¡will¡¡some¡¡animals¡¡and¡¡plants¡¡withstand¡¡domestication¡¡or¡¡cultivation£»¡¡and¡¡vary¡¡very¡¡slightly¡¡perhaps¡¡hardly¡¡more¡¡than¡¡in¡¡a¡¡state¡¡of¡¡nature¡£¡¡
A¡¡long¡¡list¡¡could¡¡easily¡¡be¡¡given¡¡of¡¡'sporting¡¡plants£»'¡¡by¡¡this¡¡term¡¡gardeners¡¡mean¡¡a¡¡single¡¡bud¡¡or¡¡offset£»¡¡which¡¡suddenly¡¡assumes¡¡a¡¡new¡¡and¡¡sometimes¡¡very¡¡different¡¡character¡¡from¡¡that¡¡of¡¡the¡¡rest¡¡of¡¡the¡¡plant¡£¡¡Such¡¡buds¡¡can¡¡be¡¡propagated¡¡by¡¡grafting£»¡¡&c¡££»¡¡and¡¡sometimes¡¡by¡¡seed¡£¡¡These¡¡'sports'¡¡are¡¡extremely¡¡rare¡¡under¡¡nature£»¡¡but¡¡far¡¡from¡¡rare¡¡under¡¡cultivation£»¡¡and¡¡in¡¡this¡¡case¡¡we¡¡see¡¡that¡¡the¡¡treatment¡¡of¡¡the¡¡parent¡¡has¡¡affected¡¡a¡¡bud¡¡or¡¡offset£»¡¡and¡¡not¡¡the¡¡ovules¡¡or¡¡pollen¡£¡¡But¡¡it¡¡is¡¡the¡¡opinion¡¡of¡¡most¡¡physiologists¡¡that¡¡there¡¡is¡¡no¡¡essential¡¡difference¡¡between¡¡a¡¡bud¡¡and¡¡an¡¡ovule¡¡in¡¡their¡¡earliest¡¡stages¡¡of¡¡formation£»¡¡so¡¡that£»¡¡in¡¡fact£»'sports'¡¡support¡¡my¡¡view£»¡¡that¡¡variability¡¡may¡¡be¡¡largely¡¡attributed¡¡to¡¡the¡¡ovules¡¡or¡¡pollen£»¡¡or¡¡to¡¡both£»¡¡having¡¡been¡¡affected¡¡by¡¡the¡¡treatment¡¡of¡¡the¡¡parent¡¡prior¡¡to¡¡the¡¡act¡¡of¡¡conception¡£¡¡These¡¡cases¡¡anyhow¡¡show¡¡that¡¡variation¡¡is¡¡not¡¡necessarily¡¡connected£»¡¡as¡¡some¡¡authors¡¡have¡¡supposed£»¡¡with¡¡the¡¡act¡¡of¡¡generation¡£¡¡
Seedlings¡¡from¡¡the¡¡same¡¡fruit£»¡¡and¡¡the¡¡young¡¡of¡¡the¡¡same¡¡litter£»¡¡sometimes¡¡differ¡¡considerably¡¡from¡¡each¡¡other£»¡¡though¡¡both¡¡the¡¡young¡¡and¡¡the¡¡parents£»¡¡as¡¡Muller¡¡has¡¡remarked£»¡¡have¡¡apparently¡¡been¡¡exposed¡¡to¡¡exactly¡¡the¡¡same¡¡conditions¡¡of¡¡life£»¡¡and¡¡this¡¡shows¡¡how¡¡unimportant¡¡the¡¡direct¡¡effects¡¡of¡¡the¡¡conditions¡¡of¡¡life¡¡are¡¡in¡¡comparison¡¡with¡¡the¡¡laws¡¡of¡¡reproduction£»¡¡and¡¡of¡¡growth£»¡¡and¡¡of¡¡inheritance£»¡¡for¡¡had¡¡the¡¡action¡¡of¡¡the¡¡conditions¡¡been¡¡direct£»¡¡if¡¡any¡¡of¡¡the¡¡young¡¡had¡¡varied£»¡¡all¡¡would¡¡probably¡¡have¡¡varied¡¡in¡¡the¡¡same¡¡manner¡£¡¡To¡¡judge¡¡how¡¡much£»¡¡in¡¡the¡¡case¡¡of¡¡any¡¡variation£»¡¡we¡¡should¡¡attribute¡¡to¡¡the¡¡direct¡¡action¡¡of¡¡heat£»¡¡moisture£»¡¡light£»¡¡food£»¡¡&c¡££»¡¡is¡¡most¡¡difficult£º¡¡my¡¡impression¡¡is£»¡¡that¡¡with¡¡animals¡¡such¡¡agencies¡¡have¡¡produced¡¡very¡¡little¡¡direct¡¡effect£»¡¡though¡¡apparently¡¡more¡¡in¡¡the¡¡case¡¡of¡¡plants¡£¡¡Under¡¡this¡¡point¡¡of¡¡view£»¡¡Mr¡¡Buckman's¡¡recent¡¡experiments¡¡on¡¡plants¡¡seem¡¡extremely¡¡valuable¡£¡¡When¡¡all¡¡or¡¡nearly¡¡all¡¡the¡¡individuals¡¡exposed¡¡to¡¡certain¡¡conditions¡¡are¡¡affected¡¡in¡¡the¡¡same¡¡way£»¡¡the¡¡change¡¡at¡¡first¡¡appears¡¡to¡¡be¡¡directly¡¡due¡¡to¡¡such¡¡conditions£»¡¡but¡¡in¡¡some¡¡cases¡¡it¡¡can¡¡be¡¡shown¡¡that¡¡quite¡¡opposite¡¡conditions¡¡produce¡¡similar¡¡changes¡¡of¡¡structure¡£¡¡Nevertheless¡¡some¡¡slight¡¡amount¡¡of¡¡change¡¡may£»¡¡I¡¡think£»¡¡be¡¡attributed¡¡to¡¡the¡¡direct¡¡action¡¡of¡¡the¡¡conditions¡¡of¡¡life¡¡as£»¡¡in¡¡some¡¡cases£»¡¡increased¡¡size¡¡from¡¡amount¡¡of¡¡food£»¡¡colour¡¡from¡¡particular¡¡kinds¡¡of¡¡food¡¡and¡¡from¡¡light£»¡¡and¡¡perhaps¡¡the¡¡thickness¡¡of¡¡fur¡¡from¡¡climate¡£¡¡
Habit¡¡also¡¡has¡¡a¡¡deciding¡¡influence£»¡¡as¡¡in¡¡the¡¡period¡¡of¡¡flowering¡¡with¡¡plants¡¡when¡¡transported¡¡from¡¡one¡¡climate¡¡to¡¡another¡£¡¡In¡¡animals¡¡it¡¡has¡¡a¡¡more¡¡marked¡¡effect£»¡¡for¡¡instance£»¡¡I¡¡find¡¡in¡¡the¡¡domestic¡¡duck¡¡that¡¡the¡¡bones¡¡of¡¡the¡¡wing¡¡weigh¡¡less¡¡and¡¡the¡¡bones¡¡of¡¡the¡¡leg¡¡more£»¡¡in¡¡proportion¡¡to¡¡the¡¡whole¡¡skeleton£»¡¡than¡¡do¡¡the¡¡same¡¡bones¡¡in¡¡the¡¡wild¡­duck£»¡¡and¡¡I¡¡presume¡¡that¡¡this¡¡change¡¡may¡¡be¡¡safely¡¡attributed¡¡to¡¡the¡¡domestic¡¡duck¡¡flying¡¡much¡¡less£»¡¡and¡¡walking¡¡more£»¡¡than¡¡its¡¡wild¡¡parent¡£¡¡The¡¡great¡¡and¡¡inherited¡¡development¡¡of¡¡the¡¡udders¡¡in¡¡cows¡¡and¡¡goats¡¡in¡¡countries¡¡where¡¡they¡¡are¡¡habitually¡¡milked£»¡¡in¡¡comparison¡¡with¡¡the¡¡state¡¡of¡¡these¡¡organs¡¡in¡¡other¡¡countries£»¡¡is¡¡another¡¡instance¡¡of¡¡the¡¡effect¡¡of¡¡use¡£¡¡Not¡¡a¡¡single¡¡domestic¡¡animal¡¡can¡¡be¡¡named¡¡which¡¡has¡¡not¡¡in¡¡some¡¡country¡¡drooping¡¡ears£»¡¡and¡¡the¡¡view¡¡suggested¡¡by¡¡some¡¡authors£»¡¡that¡¡the¡¡drooping¡¡is¡¡due¡¡to¡¡the¡¡disuse¡¡of¡¡the¡¡muscles¡¡of¡¡the¡¡ear£»¡¡from¡¡the¡¡animals¡¡not¡¡being¡¡much¡¡alarmed¡¡by¡¡danger£»¡¡seems¡¡probable¡£¡¡
There¡¡are¡¡many¡¡laws¡¡regulating¡¡variation£»¡¡some¡¡few¡¡of¡¡which¡¡can¡¡be¡¡dimly¡¡seen£»¡¡and¡¡will¡¡be¡¡hereafter¡¡briefly¡¡mentioned¡£¡¡I¡¡will¡¡here¡¡only¡¡allude¡¡to¡¡what¡¡may¡¡be¡¡called¡¡correlation¡¡of¡¡growth¡£¡¡Any¡¡change¡¡in¡¡the¡¡embryo¡¡or¡¡larva¡¡will¡¡almost¡¡certainly¡¡entail¡¡changes¡¡in¡¡the¡¡mature¡¡animal¡£¡¡In¡¡monstrosities£»¡¡the¡¡correlations¡¡between¡¡quite¡¡distinct¡¡parts¡¡are¡¡very¡¡curious£»¡¡and¡¡many¡¡instances¡¡are¡¡given¡¡in¡¡Isidore¡¡Geoffroy¡¡St¡¡Hilaire's¡¡great¡¡work¡¡on¡¡this¡¡subject¡£¡¡Breeders¡¡believe¡¡that¡¡long¡¡limbs¡¡are¡¡almost¡¡always¡¡accompanied¡¡by¡¡an¡¡elongated¡¡head¡£¡¡Some¡¡instances¡¡of¡¡correlation¡¡are¡¡quite¡¡whimsical£»¡¡thus¡¡cats¡¡with¡¡blue¡¡eyes¡¡are¡¡invariably¡¡deaf£»¡¡colour¡¡and¡¡constitutional¡¡peculiarities¡¡go¡¡together£»¡¡of¡¡which¡¡many¡¡remarkable¡¡cases¡¡could¡¡be¡¡given¡¡amongst¡¡animals¡¡and¡¡plants¡£¡¡From¡¡the¡¡facts¡¡collected¡¡by¡¡Heusinger£»¡¡it¡¡appears¡¡that¡¡white¡¡sheep¡¡and¡¡pigs¡¡are¡¡differently¡¡affected¡¡from¡¡coloured¡¡individuals¡¡by¡¡certain¡¡vegetable¡¡poisons¡£¡¡Hairless¡¡dogs¡¡have¡¡imperfect¡¡teeth£»¡¡long¡­haired¡¡and¡¡coarse¡­haired¡¡animals¡¡are¡¡apt¡¡to¡¡have£»¡¡as¡¡is¡¡asserted£»¡¡long¡¡or¡¡many¡¡horns£»¡¡pigeons¡¡with¡¡feathered¡¡feet¡¡have¡¡skin¡¡between¡¡their¡¡outer¡¡toes£»¡¡pigeons¡¡with¡¡short¡¡beaks¡¡have¡¡sma

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