Gotmilk?Ifyoudo,takeamomenttoponderthetrueoddnessofbeingabletodrinkmilkafteryou’reababy. Nootherspeciesbuthumanscan.Andmosthumanscan’teither. Thelonglistsoffoodallergiessomepeopleclaimtohavecanmakeitseemasifthey’rejustfinickyeaterstryingtorationalizelikesanddislikes.Notso.Eggs,peanuts,treenuts,fish,shellfishsoyandglutenallcanwreakhavocontheimmunesystemofallergicindividuals,evencausingadeadlyreactioncalledanaphylaxis. Butthoseallergicreactionsarerelativelyrare,affectinganestimated4%ofadults. Milk’sdifferent. Therearepeoplewhohavetruemilkallergiesthatcancausedeadlyreactions.Butmostpeoplewhohavebadreactionstomilkaren’tactuallyallergictoit,inthatit’snottheirimmunesystemthat’srespondingtothemilk.Instead,peoplewhoarelactoseintolerantcan’tdigestthemainsugar—lactose—foundinmilk.Innormalhumans,theenzymethatdoesso—lactase—stopsbeingproducedwhenthepersonisbetweentwoandfiveyearsold.Theundigestedsugarsendupinthecolon,wheretheybegintoferment,producinggasthatcancausecramping,bloating,nausea,flatulenceanddiarrhea. Ifyou’reAmericanorEuropeanit’shardtorealizethis,butbeingabletodigestmilkasanadultisoneweirdgeneticadaptation. It’snotnormal.Somewhatlessthan40%ofpeopleintheworldretaintheabilitytodigestlactoseafterchildhood.Thenumbersareoftengivenascloseto0%ofNativeAmericans,5%ofAsians,25%ofAfricanandCaribbeanpeoples,50%ofMediterraneanpeoplesand90%ofnorthernEuropeans.Swedenhasoneoftheworld’shighestpercentagesoflactasetolerantpeople. Beingabletodigestmilkissostrangethatscientistssayweshouldn’treallycalllactoseintoleranceadisease,becausethatpresumesit’sabnormal,instead,theycallitlactasepersistence,indicatingwhat’sreallyweirdistheabilitytocontinuetodrinkmilk. There’sbeenalotofresearchoverthepastdecadelookingatthegeneticmutationthatallowsthissubsetofhumanitytostaymilkdrinkersintoadulthood. Along-heldtheorywasthatthemutationshowedupfirstinNorthernEurope,wherepeoplegotlessvitaminDfromthesunandthereforedidbetteriftheycouldalsogetthecrucialhormone(it’snotreallyavitaminatall)frommilk. ButnowagroupatUniversityCollegeLondonhasshownthatthemutationactuallyappearedabout7,500yearsagoindairyfarmerswholivedinaregionbetweenthecentralBalkansandcentralEurope,inwhatwasknownastheFunnelBeakerculture. ThepaperwaspublishedthisweekinPLOSComputationalBiology. Theresearchersusedacomputertomodelthespreadoflactasepersistence,dairyfarming,otherfoodgatheringpracticesandgenesinEurope. Today,thehighestproportionofpeoplewithlactasepersistenceliveinNorthwestEurope,especiallytheNetherlands,IrelandandScandinavia.ButthecomputermodelsuggeststhatdairyfarmerscarryingthisgenevariantprobablyoriginatedincentralEuropeandthenspreadmorewidelyandrapidlythannon-dairyinggroups. AuthorMarkThomasofUniversityCollegeLondon’sdeptofGenetics,EvolutionandEnvironmentsays,“InEurope,asinglegeneticchange...isstronglyassociatedwithlactasepersistenceandappearstohavepeoplewithitabigsurvivaladvantage.” TheEuropeanmutationisdifferentfromseverallactasepersistencegenesassociatedwithsmallpopulationsofAfricanpeopleswhohistoricallyhavebeencattleherders. ResearchersattheUniversityofMarylandidentifiedonesuchmutationamongNilo-Saharan-speakingpeoplesinKenyaandTanzania.Thatmutationseemstohavearisenbetween2,700to6,800yearsago.TwoothermutationshavebeenfoundamongtheBejapeopleofnortheasternSudanandtribesofthesamelanguagefamilyinnorthernKenya. AccordingtothethirdsentenceofParagraph3,whichofthefollowingitemsisINCORRECT?
A.Anaphylaxis may cause people to die. B.Eggs can damage all the allergic individuals’ immune system. C.One who is allergic to gluten can not eat com. D.Tuna may cause a person who is allergic to fish to die.正确答案B