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SCIENCE 



[N. S. Vol. UII. No. 1371 



men from the Ethiopian region, Necaior was 

 the only hookworm encountered. The search 

 was not an exhaustive one. Leiper and others, 

 however, have recorded only Necator from this 

 r^ion. 



I have not worked in Europe or northern. 

 Africa but Looss, Boycott and others report 

 the exclusive presence of A. duodenale in Eng- 

 land, western Europe, Italy and Egypt, that 

 is to say in the European moiety of the 

 Holarctic region. 



The introduction of the negro. East Indian 

 and Mediterranean peoples into America has 

 obscured the picture here and research among 

 isolated and uncontaminated Indian tribes 

 has yet to be undertaken. This research will 

 no doubt yield some interesting data, helpful 

 possibly in tracing the origin of the Amerind 

 populations; it may be possible to trace a 

 relationship for them with Mongoloids from 

 Holarctic or from Oriental r^ions. 



While there is a sharply marked out 

 regional distribution of the worms in certain 

 areas, in others time has brought about some 

 overlapping of the two species. 



The absence of Necator from Europe indi- 

 cates pretty positively that European soil has 

 not been contaminated by a Negroid race from 

 the Ethiopian region, that is Africa south of 

 the Sahara desert. The absence of A. duo- 

 denale from secluded groups of mountain 

 people in the Oriental and in Ethiopian 

 regions is explained in a similar way. In 

 mid-Java and in a few coast and river towns 

 in Fiji, East Indians have brought in large 

 numbers of A. duodenale within historic 

 times. 



The movements of negroes. Oriental and 

 Mediterranean peoples are modifying the 

 primitive worm-species-formula of non-migra- 

 tory people, hence interpretations must be 

 made from carefully selected surveys only. 



It is held by some that man and his obligate 

 parasites living in symbiosis have come along 

 through the ages together, that the relation- 

 ship has not been recently or casually ac- 

 quired. If this be true we should expect to 

 find man parasitized always by the two ob- 

 ligate forms and not to find man of the 

 Holarctic regions parasitized exclusively or 



almost exclusively by A. duodenale, while 

 man of the Oriental and Ethiopian regions 

 parasitized exclusively or almost exclusively 

 by Necator americanus. This finding in any 

 case suggests the possibility of the distribu- 

 tion of the two species of worms in distinctly 

 different zoologic as well as geographic regions 

 being due to there having been two primitive 

 races of man, each one originally parasitized 

 by a particular species of worm. Certain it is 

 that N. americanus is found more exclusively 

 among black- and brown-skinned races, while 

 A. duodenale is found exclusively or greatly 

 predominates at the present time among Cau- 

 casian and Mongoloid stocks. 



It may be that a Eurasiatic race of man, 

 possibly the Pithecanthropus of Trinil, Java, 

 became split off and furnished the stock from 

 which man of Oriental and Ethiopian regions 

 sprung. Prollopithecus emerging from Hol- 

 arctic Africa may have been not only the 

 IDarent form of man, gibbon, chimpanzee, 

 gorilla and the orang-outang, but he may have 

 harbored the parent form from which have 

 arisen the different hookworm species found 

 in the various species of anthropoids of to- 

 day. Possibly the ancestral tree of the 

 primates can be revised after a study of the 

 host relationships of their respective obligate 

 nematode parasites. At any rate we can say 

 that it seems likely from the present distribu- 

 tion of A. duodenale and N. americanus as 

 determined in surveys recently made of 

 selected groups that there were originally 

 races of man parasitized exclusively by 

 A. duodenale and inhabiting the Holarctic 

 region, that is Europe, Asia, north of the 

 Oriental region and northern Africa; and 

 that there were other races of man parasitized 

 exclusively by N. americanus and inhabiting 

 the Oriental region, that is the southern i)en- 

 insulas of Asia and Indonesia or the Malay 

 Archipelago; and also the Ethiopian region, 

 that is, Africa south of the Sahara Desert. 



The subject is an enticing one to pursue 

 but further deductions should probably not be 

 hazarded at this time by one who is merely 

 a peregrinating parasitologist. 



Samuel T. Darling 



Intebnational Health Boaed 



