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TAXONO'vlIC CATEGOfl lES IN FOSSIL 1l0MIl\IOSERNST ~ l A Y H

Thc\mer ican \luscu'" of Natural J1istory, Ne " lo rk

It is one of the most fruitful procedures ofmodern science to bring specia l is ts of variousfields together to discuss the problems that concern the zone of overlap of their fields. ~ o possessing an y first-hand knowledge of paleoanthropology, my own contribution to the question of th etaxonomic categories of fossil man will be thatof a systematist . Significant prof!less has beenmade wi thin recent years among biological! ythinking taxonomists in th e understanding of th ecategories of subspecies, species, an d genus, andit is my hope that this knowledge may help in abetter understanding of fossil man.

The who] e problem of the origin of man depen,ls,to a considerable extent, on th e proper deflllitionan d evaluation of taxonomic categories. gut, thereis less agreement on the meaning of th e categoriesspecies an d genus in regard to nmn and th e primates than perhaps in an y other f!lonp of animals.Some anfhropologists, in fact, imply that they usespecific an d generic names merely as labels forspecimens without giving them any biologicalmeaning. Th e late Weidenreich, fo r example, statedthat in anthropology " i t always was an d still isthe custom to give generic and specifiC names toeach new type witbout mucb concern fo r the kindof relationship to other types formerly known."Broom (1950) likewise states, " I think it wil! bemuch more convenient to split the different varieties lo f South African fossil ape-man! into different genera and species than to lump them."Th e result of such standards is a simply be\\ildering diversity of names. In addition to variousso-called species of lIomo, the following namesfo r various hominid remains have been found byme in th e literature: Australopithecus, Plesi-anthropus, Paranthropus, C'oanthropus, Gigan-thopi thecus, Meganthropus, Pithecanthropus,Sinanthropus, Africanthropus, favanthropus, Pale-oanthropus, Furopanthropus, an d several others.No two authors af!lee either in nomenclature orin interpretation. It seems to me tbat an effortshould' be made to give the categories speciesand genus a new meaning in the field of anthropology, namely, the same one which in recentyears bas become the standard in other branchesof zoology.

A re-evaluation of th c tcrminology of hominidtaxonomy is facilitated by th e fact that in recentyears a magnificent body of new data has beenaccumulated by anthropologists, partly bused oncomparative anatomical studies an d partly onsignificantncw discoveries of fossil man in southeast Asia an d in eastern and souther'l Africa.

The nomenclatorial dWiculties of the anthropologists ar e chiefly due to two facts. Th e fIrstone is a very intense occupation with only a verysmall fraction of the animal kingdom which has re su i te d in the developmen t of standards that di fie I'greatly from those applied in other fields of zoology, and secondly, the attempt to express everydi flerence of morpho] ogy, even the sl ightest one,by a different name an d to do this with th e limitednumber of taxonomic categories that ar c availabl e.This difference in standards becomes very apparent if we , fo r example, compare the classification of the hominids with that of the f)rosophilaflies. Then> ilre now about (,00 species of Oroso-philo, known, al l included in a single genus. Ifindividuals of these species were enlarged to th esize of man or of a gorilla, it would be app,U'enteven to a lay person that they are probably moredifferent from each other than are the various primates an d certair ly more than th e species of th esuborder Anthropoidea. What in the case of /Jroso-ph.ila is a genus has almost th e rank of an orderor , at least, suborder i:l the primates. The discrepancy is equally great at lower categories, aswe shall presently see. It is no t mere formalismto try to harmonize the categories of anthropologywith those of the rest of zoology. Rather, theevaluation of human evolution depends to a considerable extent on the proper determination of thecategories of fossil man.

There are two recent developments in general 'systen,atics that will be particularly helpful inour e rrorts. Th e first on e is that the biologicalmeaning of the categories species and genus isnow better understood than formerly, an d second,that, in the attempt to close the gap between th ecomplexity of nature and the simplicity of categories, the nun,ber of existing categories has beenaugmented by intermediate and group categories,such as "local population" or "local races" and

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no ERNST MAYR"subspecies groups." The adoption of theseintermediate categories facilitates classificationwithout encumbering nomenclature.

THE TAXONOMIC CATEGORIESTh e work in the new systematics ha s led to a

far-reaching agreement among zoologists on th emeaning of the categories subspecies, species,genus, an d family. ]n th e following an attemptshall be made to se e how far the current usage ofthese categories ca n be extended to fossil hominids and what such a reclassification means interms of human evol ution.

The genus: The genus is a taxonomic categoryfor a group of related species. It is usually basedon a taxonomic group that can be objectively defined. However, the delimitation of these groupsagainst each other, as well as their ranking, isfrequently subjective and arbitrary. A conventionaldefinition of the genus would read about as follows: "A genus consists of one species, or agroup of species of common ancestry, which differin a pronounced manner from other groups of species and are separated from them by a decidedmorphological gap."

Hecent studies indicate that the genus is notmerely a morphological concept but that it has avei y distinct biological meaning. Species thatar e united in a given genus occupy an ecologicalsituation which is different from that occupied bythe species of another genus, or, to us e the terminology of Sewall Wright, they occupy a differentadaptive plateau. ]t is part of the task of thetaxonomist to determine the adaptive zones occupied by the various genera. The adaptive plateau of the genus is based on a more fundamentaldifference in ecology than that between the ecological niches of species.

Unfortunately, there is no such thing as a recognized or absolute generic character. This wa sknown already to th e earlier taxonomists, in fact,Linnaeus stated, ' ' It is the genus that gives th echaracters, and not the characters that make thegenus." The genus is a group category and itdefeats th e object of binomial nomenclature toplace each species into a separate genus, as ha sbeen the tendency among students of primates.

Th e acceptance of the new concept of biologically defined polytypic species (see below)necessitates the upward revision of al l other categories (Mayr, 1942). Often what was formerly agroup of allopatric species is now a single polytypic species with numerous subspecies. Toleave each of these polytypic species in a separate genus deprives the genus of it s significance

as a truly collective category. I shall illustratethis need for the combining of genera by an example. Gorilla and chimpanzee are two excellentspecies which, as Professor Schultz ha s shown,differ from each other by a wealth of characters.At one time several species of gorillas and ofchimpanzees were recognized, bu t the allopatricforms within the two species are now consideredsubspecies. Being left with one species of gorillaan d one species of chimpanzees, we are confronted by the question whether or not they aresufficiently different to justify placing them illdifferent genera. A specialist of anthropoidsimpressed by the many differences between thesespecies may \Hmt to do so . Other zoologists willconclude that the differences between the twospecies are not indicative of a generic level ofdifi'erence when measured in the standards customary in most branches of zoology. To place thesetw o anthropoids into two separate genera defeatsthe function of generic nomenclature and concealsthe close relationship of gorilla and chimpanzeeas compared with the much more difierent orangand the gibbons. Hecognizing a separate genus forthe gorilla would necessitate raising the orangand the gibbon to subfamily or family rank as hasindeed been done or suggested. This only worsensthe inequality of the higher categories among theprimates.

The same is true for the fossil hominids. Afterdue consideration of the many di fferences between\Iodern man, Java man, an d the South African apeman, I did not find an y morphological charactersthat would necessitate separating them into several genera. Not even Australopithecus ha s unequivocal claims for separation. This form ap pears to possess what might be considered theprincipal generic character of Homo, namely,upright posture .... it h it s shift to, a terrestrial !'lodeof living and the freeing of the anterior extremityfor new functions which, in turn, have stimulatedbrain evol ution. Within this type there ha s beenphyletic speciation resulting in Homo sapiens.

The claim that the many described genera ofhominids an d Australopithecines have no validity,if the same yardstick is applied that is customaryin systematic zoology, is based on two majorpoints. Both of these are admittedly somewhatvulnerable. One is the overall picture of morphological resemblance with a deliberate minimizingof the brain as a decisive taxonomic character.To this point we shall return presently. The otherpoint is the assumption that all these forms, including Australopithecus, "r e essentially membersof a single line of descent. Additional finds

might easilyth e a v a i l a b l ~logical and (the hominidsth e current n

This re-e\fossil homilcategories Eto a separatca l differenwhich theliomo are sctification foThere is evAfrican manopithecinaethose of Shominid chaothers thatas small sinoteworthy,investigatoprimitive s lthat were foful caninesthe first l o ment of thpowerful bable that mspe cializapaid apes1 he facizations hdence to pa very isoThis is bytation. Ratypical c h well be aresponsenow appeathe orangmost of ttherefore,availableman maychiIlJpanzeorang orin certainbe usedtionship.poids arean d willverge nt ,upright p

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III1

TAXONOMIC CA. TEGORIES IN FOSSIL HOMINIDS

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might easily disprove this. llowever, taking al lthe available evidence together, it seems far morelogical and consistent at the present time to unitethe hominids into a single genus than to con tinuethe current multiplicity of names.

This re-evaluation of the generic status of thefossil hominids forces us to consider also thecategories above the genus. Does Homo belongto a separate family Hominidae? Th e morphological differences between Pongo, the genus towhich the chimpanzee an d gorilla belong, andllama are so slight that there seems to be no ju stification for placing them in separate families.There is even less justification for placing SouthAfrican man in a separate subfamily, the Australopithecinae. The most primitive known hominids,those of South Africa, combine certain typicalhominid characters, such as upright posture, withothers that are usually considered simian, 8uchas small size of brain and protruding face. It isnoteworthy, however, as pointed ou t by severalinvestigators, that these hominids, even at thisprimitive stage, lack certain other simian featuresthat were formerly considered as primitive: powerful canines, large incisors, a sectorial form ofthe first lower premolar, an exaggerated development of the supra-orbitals, a simian shelf, andpowerful brachiating arms. It now appears probabl e that many of these characters are functionalspecializations which were acquired by the anthropoid apes after the hominid line had branched ofI.1 he fact that the hominids fack these specializations has been used by some authors as evidence to postulate a very early human origin anda very isolated position of the hominid branch.This is by no means the only possible interpretation. Rather it seems to me that most of thesetypical characters of the living anthropoids maywell be a single character complex evolved inresponse to a highly arboreal mode of living. Itnow appears probable that the African anthropoids,the orang, and the gibbons, may have acquiredmost of these characters independently and aretherefore, in a sense, a polyphyletic group. Th eavailable evidence seems to indicate to me thatman may be more closely related to the gorillachiplpanzee group than this group is either to theorang or to th e gibbons. The degree of similarityin certain morphological traits cannot necessarilybe used to measure degree of phylogenetic relationship. The arboreal, brachiating large anthropoids are exposed to a similar type of selectionan d will therefore evolve in a parallel, if not convergent, manner. When tIle llama-line acquiredupright posture it entered a completely different

adaptive zone and became exposed to a severelyincreased selection pressure. This must have resuI ted in a sharp accel eration of evolutionarychange leading to the well-known differences be-tween man and the iiving anthropoids. This factormust be taken into consideration when the phylogeny of man an d the anthropoids is reconstructed.It would therefore appear to be misleading from thepurely morphological-phylogenetic point of view toseparate man from the anthropoid apes as a special family. It would be equally misleading to goto the other extreme and to us e th e evidence of thesomewhat independent evolution of man and thevarious anthropoids as a means to deny theirclose relationship.

Denying the genus li omo family rank is basedon purely morphological considerations. It doesno t take into account man's unique position innature. ~ l a n ha s undoubtedly found an adaptiveplateau that is strikingly difl'erent from that ofany other animal. There ar e some \\ho feel thatthere is only one way by which to emphasize thisuniqueness of man, namely, by placing I!omo intoa separate family. The conventional standards oftaxonomy are insu fIicient to decide what is correct in this case.

From the purely biological point of view manis certainly at least as diflerent as a very goodgenus. We have thus the evolution of a newhigher category in the geologically short periodof one to two million years. This is another significant illustration for the rapidity by which onemajor taxonomic entity can be transformed intoanother one, without any jumps.

The subspecies: Before we can attempt toanswer the question how many species of fossilman have existed, we must say a few words oninfraspecific categories. Th e species of themodern systematist is polytypic and multidimensional. It ha s the geographical dimensions oflongitude and latitude and also th e time dimension. It is polytypic because it is composed oflower units, such as subspecies an d local populations. Customarily in anthropology, distinctlocal populatiorrs have been referred to as races,an d a similar custom exists in som,e branches ofzoology as, for exarr'ple, in ichthyology.

Th e amount of geographical variation and thedegree of difierence among the geographical subdivisions of a species ar e different from case tocase. Some species appear quite uniform throughout their entire range; other species have a fewor many more or less well defined subspecies.For instance, the two African forest anthropoids,chimpanzee and gorilla, 8how only a moderate

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112 ERNST iliA JRamount of geographical variation, al though bothhave well-defmed subspecies, and attempts havebeen IIlade to sp l it the chimpanzee into severalspecies. Ceographical variation is much morepronounced in the orang and even more so in someof the South American monkeys where geographica l races are often different enough to be considered full species by conservative authors.

~ I o d e r n man is comparatively homogeneous because there is much interbreeding between different tribes an d races. Still, we find in closeneighborhood to each other such strikingly different races as lmshmen an d Bantus in SouthAfrica, or the Congo pygmies and Watusi in central Africa, or th e \\edas and Singhalese in Ceylon. There is much indirect evidence that primitiveman was much more broken up into small scatteredtribes with little contact with each other, intensely subject to local selective factors.

In addition to this much greater geographicalvariation of primitive man, there is eviden ce alsoof greater individual variation (including sexualdimorphism). Th e variability of 'It. Carmel manha s been conm;ented upon in the literature. Itseems possible, if not probable, that the variousSouth African finds, Australopithecus, Plesian-thropus, an d Paranthropus, might well be ag e orse x stages of a few related tribes, notwithstanding Broom's (1950) assertions to the contrary.

Differences between young an d adult and between male and female appear to be greater in th egoriIJa and orangutan than they are in modern man.Variability may increase or decrease in the courseof evolution. Abundant proof for this staterr'entcan be found in the paleontological Ii terature. Iinterpret th e available literature to indicate thatprimitive man showed more geographical as wellas individual variation than f'lodern man.o Why primitive man should have been more variable than modern r r ~ a n is no t entirely clear. Astudy of the family structure of anthropoids mightshed son;e light on this problem. Perhars therewas a h'Teater functional difference between malean d fernaJe than in modern man. Perhaps theancestral hominids had a system of polygamy thatwould favor th e selection of secondary se x characters in th e male. \\ e don't know. Whatever thereasons, we should no t us e the variabil it y withinpopulations of modern man as a yardstick by-whichto judge the probable variability of extinctpopula tions.

This point is important because it bears onthe question whether or no t more than one speciesof hominid ha s ever existed on the earth at anyone time. Indeed, all the now available evidence

can be interpreted as indicating that, in spiteof much geographical variation, never more thanone species of man existed on th e earth at an yone time. We shall come back to this point later.

The species: As described in several publications, the concept of the species has undergonea considerable change durinf!, recent years. Th emorphological and typological species of th e earlytaxonomists ha s been rep} aced by a l,iologicalspecies. Th e species is now defmed "as a groupof actually or potentially interbreeding naturalpopulations that is reproductively isolated fromother SI l ch groups." When th is concept is appliedto man, it is at once obvious that all living populations of man are part of a single species. Notonl y a r e they conne cted everywhere by in termediate populations bnt even where strikinglydistinct human populations have come in contact,s!lch as Europeans and Hottentots, or as E ~ u r o peans an d Australian aborigines, there has beenno sign of biological isolating mechanisms, onlysocial ones.Th e problem of species delimitation is muchmore dilTicult with respect to fossil man. lIowshall we determine which populations ar e "actually or potentially interbreeding"? It is evidentthat we must usc all sorts of indirect clues. Thefirst concrete problem is what types of fossil manshould be included in the species homo sapiens.C r o - ~ l a g n o n man is so nearly identical with Homosapiens that its inclusion in that species is no tc10ubted by any serious student.

Th e problem of Neanderthal man is much moreditlicul t. Should he be in cluded in th e samespecies as modern n'an or not? V,hen the fLfst fondsof "ieanderthal man were made there seemed tobe no problem. These fossils were characterizedby distinct morphological features and wereclearl y replaced by modern wan in l

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TAXONOMIC CATEGORIES IN FOSSIL !iOMINIDS 11:3apparently incompatible views that Plod ern n,anand Neanderthal are conspeciflc and that modernman is no t a descendant of typical } ~ u r o p e a n Neanderthal? A possible clue is furnished by thehominids that were widespread in Furope in n idPleistocene. The skulls of Steinheim, Swanscombe, and of Fontechevade con,bine features ofmodern man and of Neanderthal man, together withprimitive and specialized features of their own.They lived apparently in inter-glacials and weremore closely linked with a warm climate thanNeanderthal man.

j

lf I understood the evidence correctly, it ispossible to interpret these early European fossilsas remains of populations of !Jon;o that were ancestral both to sapiens an d to "class ical" Neanderthal and from which these two forms evolvedby geographical variation. Tentatively the working hypothesis can be nlade that Neanderthal inits classical form wa s a geographical race thatoccurred in central Furope and was represented inAfrica by fihodesian man an d in Java by Njandongman, while a more sapiens-like population occurred at the same period as some of these Neanderthaloids either in north Africa or western Asiaor in some other area that has not yet yielded

I remains of fossil man. When sapiens began toI expand and spread, he eliminated the other con temporary races just as the white Polan drove ou tthe Australian aborigines and the ' \orth Americani Indians. The process of 1"1 imination of the Neanderthal characters in mixed populations was preJ sunably helped by selection preference in favorof the characters of modern man.It is very probable that additional finds will

make the delimitation of sapiens against Neanderthal even more difficult. It seems best to follow Dobzhansky's suggestion and to consider thetwo forms, as well as the ancestral group thatseems to combine their characters, as a singlespecies.Homo erectus: Java and I'eking man are suf

ficiently distinct from modern man so that theyhave to be considered a separate species, whichmust be called /lama erectus. This is true regardless of the fact that on Java, at least, Njandongand Wadjak man may have formed a practicallyunbroken chain of hominids leading from Javaman to n'odern n,an. Peking man (Ilorho erectuspekinensis) is , on the whole, so similar to Javaman that it should be cons idered merely subspecificall)' distinct, as I proposed previously (tvlayr,1944).

In spite of it s obvious similarity to Australopithecus too little is known of the still earlier

Java ,lleganthropus to assure a correct classifIcation. This is even more true of (;iganthopithecuswhom some authors consider hominid and othersanthropoid. One thing about Ciganthopithecus is ,however, very probable, naPlely, that it wa s notnecessarily a giant in spite of it s giant teeth.Jaws and teeth of early fossil Dian were relativelymuch larger than they are in modern man.

Homo transvaalensis: South l\frican ape-managain is one level further back and is suil'icientlyfar removed from Java man to be considered a fullspecies. Actually, no less than three genera andfive species of South African ape-nan were described which, in Broom's tenninolo!-,y, have thefollowing names: Australopithccus a{ricanus 1925(Taungs), A. rrometheus 1917 C\lakapan), Plesianthropus transvaalens is 1936 (Sterkfontain),Paranthropus robustus 1938 (Kromdraail, andParanthropus crassidens 1949 (Swartkrans). \Jostof these names may not have any validity, according to the Hules of Zoological "iomenclature,Article 25A, as revised in 1930. According tothese Hules a name has validity only if the description includes dia/2:nostic characters. Sinceone of these names wa s based on a child, anotheron an adult female, a third on an adult male, anenumeration of diagnostic differences is virtuallyi n ~ p o s s i b l e . Th e extant skulls are somewhataltered in shape due to crushing, and the fact thatthe cephalic index in the Taun/2:s child is 62.4while it is R3.S in the Sterkfontein IT'ale is therefore not as signifIcant as Broom thinks. ~ o isthe fact that the finds are associated with different faunas. Contemporary modern man ca n befound associated with okapis or elephants ortigers or kangaroos, or South American edentatesor with polar bears. Th e various fwds of SouthAfrican "nan are presumably not contelrporary, butthere is nothing in the evidence that has so farbeen presented (e.g. Broom, 1950) that wouldprove that more than one species is involved.

[nti l a real taxonorr;ic distinction has beenestablished, it will be safer an d more scientificto refer to the difTerent South African fossils byvernacular names. There is no dan/2:er of confusionif we speak of the Sterkfontain or \lakapan finds,while it implies an obviously erroneous conclusion, namely that of generic distinctness, ifwe refer to them as Plesianthropus and Australopithecus. i':ew discoveries are still being made inthese cave deposits and many of those that havealready been made have not ye t been fully workedout. There is good reason to believe that it willbe firmly established in the not-tao-distant futurehow many different tribes, temporal subspecies,

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114 EfUvSTI1A YRor even species of South African ape-man onceexisted. To consider them al l as one species isthe simplest solution that is consistent with th eavailable evidence.

A more important question is '" hether SouthAfrican man is ancestral to modern man or merelya specialized or aberrant sideline. The exact dating of these fossils has not ye t been achievedbu t they are believed to be very cady Pleistoceneor latest Pliocene, in fact, they presumablyranged over a considerable period of time. Thereis thus no defmite chronological reason why theSouth African ape-man could not be considereda possible ancestor of modern man. The principalobjection that has been raised is that SouthAfrican man shows a combination of charactersthat "shonlcl not" occur in an early hominid. Thisargument is based on typological considerations.Adherents of this concept believe that missinglinks should be about half-way between th e formsthe v connect an d that thev should be half-way ineve'ry respect. This unclo:lbtedly is not the casewith Australopithecus. It is apparently amazinglylike modern man in it s upright posture, structureof th e pelvis , and other features, while it is verysimian in it s massive mandibles, large molars,prognathism, and small brain. J1ustralopitheclIslacks those specializations that stamp gorilla,orang, and gibbon as typical anthropoids.

Th e peculiar combination of c h a ~ a c t e r s that isfound in ;lustralopithecus is due to the fact thatrl uring evol ution of man di Herent charactersevolved at different rates. If we would se t th epoint where th e human line branched off from th eother anthropoids as zero and the !/omo sapiensstage as 100, we might give arbitrarily the following points to the various organs of /ll1stralopithe-cus: pelvis, 90; premolars, 75; occipital condyles,RO; incisors, .5.5; th e setting of the brain case,70; shape of the tooth row, 70; th e profile of th ejaw, 30; th e molar teeth, -10; the brain, 35; etc.It is obvious that one type does not change intoanother 'type evenly and harmoniously, but thatsome features run v.ay ahead of the others.

Th e inabil ity to understand this has been thereason for \\'eidenreich's insistence that t,'oan-thropus was an artifact. lie maintained with re spect to l 'iltdown man: "Form and individualfeatures of the brain case are generally acknowledged as those of modern []lan; those of the lowerja w have anthropoid characteristics. Therefore,both skeletal elements cannot belong to the sameskulL" As a matter of fact, the skull cap is no tstrictly modern nor is the jaw strictly anthropoidand the recent luorine content determination by

Oakley (19S0) indicates that, indeed, ja w andskull ca p may be of the same geological age.

It may take a long time hefore the Piltdownpuzzle is completely cleared up. As a workinghypothesis it might be snggested that Piltdm\nman represents a geographical race of man thatwas restricted to northwestern Europe. Some ofthe characters, particularly in th e jaw, appear tobe specializations rather than indications ofprimitiveness, perhaps developed in cOllnectionwith the large size of the individual. The phylogenetic an d chrono] ogical relationship of Piltdown to the other hominid finds indicated by thethe words lleidelberg, Steinheim. Swanscombe,and Fonteehevade still remains to be determined.

The simplified nomenclature of fossil man: \{e-ducing the bewildering assortment of genera andspecies of hominids to one genus with threespecies results not only in simplicity lJUt it alsomakes certain conclusions 0bvious that were pre-viously not apparent. Before discussing theseconclusions, however, I might point out some ofthe disadvantages of such a simplifiedclassification.

There have been two trends in human evolutionas, indeed, there ar c in the evolution of al l or-ganisms. First of all, there is a continuous evoI utionary change in time, the so-called phyleticevolution, starting in the hon;inids with th e mostsimian forms and ending wi th modern man. Simul-taneously a centrifugal force ha s been operating,namely, geographical and other local variation,which tries to break up the uniform human species. Th is geographic variation leads to theformation of races an d subspecies, an d if thistrend would go to completion, to the formation ofnew separate species. There are all sorts ofintermediate stages in both these trends and itis obvious that al l th e Plany possible diITerencesan d gradations between the various kinds ofhominids cannot be expressed completel y in thesimple nomenclature of species, genus, and subspecies.

For instance, man as he exists today, ha s pro-nounced racial groups, such as th e Whites,Negroes, an d \'longoloids, which might well de serve suhspecific recognition. But there are minorracial differences within each of these subspecies.Furthermore, pre ceding modern man there havebeen types of !iomo sapiens that are now extinct,like ero-Magnon man an d his contemporaries.This, no doubt, is a different level of subspeciesfrom those of living man. Neanderthal man is athird level, an d the pre-Neanderthal man, whocombines certain features of sapiens and Nean

derthal, i!biologicaltreat eachOn the otspecies ctween thedifferenceto the levNegro. lIo

Firs t ofclassificatexpress a(of naturalcies and ghave assi,least an Egories anIsolution afrom a relcate goriesuse suchan d "locasubspeeifi(Hence, wtpractical 1'1. No t tpopulationspecifiC ra2. To gdeserve hi3. To gthose subeither geo

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115TAXOAOMIC CA TEGORIES IN FOSSIL flOMINIDSCONCL USIONSderthal, is a fourth level. It is unsatisfactory fo rw and

biological, as well as for practical reasons: to Th e arranging of al l finds of fossil hominidstreat each of these levels as a separate species. into a single genus with three species helps toOn the other hand, combining them into a single focus attention on the following conclusions.

l tdown species conceals the pronounced differences be The question of the "missing l ink." Ever sincethat tween thesc levels and reduces the taxonomic there has been an appreciation of man's anthro

of difference between Neanderthal and modern man poid origin there has been a s ~ a r c h fo r t.heto to the level of difTerence between White \lan an d "missing link." Some anthropologists may diSof Negro. How ca n this be avoided? claim this an d sa y that they realize the gradualFirst of all, we must realize that no system of evol ution of mankind but the fact remains that

phylo classification and nomenclature can ever hope to accurate criteria of humanhood are elaboratedexpress adequately the complicated relationships even in the most recent literature, such as Sirby the of natural populations. however, by giving spe Arthur Ke ith' s criterion of the brain volumecies and genus the well-defined meanings that wePilt-

of 750 cc .have assigned to these categories, we make at Th e anal ysis of this problem will be facil it a te dHe- leas t an attempt to standardize taxonomic cate by the realization that it is an oversimplificationan d gories an d make them comparable. A possible to us e in this case the uninomial al ternative

three solution of our particular difficulties may come "ape" versus "man." T a x o n o m i s t ~ kn?w. byt also from a refmement of the levels of infraspecific experience th e inadequacy of unmonlla!Jsm.

pre categories. In addition to the subspecies we may Classifying man binomially as llomo sapiens,) .." "these us e such infrasubspecdic categofles as race it at once becomes apparent that we must look

of an d "local pupulation," as well as the supra- for two missing links, namely that which connectssubspecific category of ti e "b' sapiens with his ancestor an d that which conI su species group. "Hence, we should be guided by the following nects Homo with his ancestor. Or, to expresspractical rules: this differently, the two points of interest ar e the

al l or- 1. :\ot to assign a formal name to any local on e on the phyl etic line of man where he reachedevo population or race that does not deserve sub the sapiens level and second the place where the

specific rank. llomo line branched oft from the other primates.2. To give trinomials to al l forms that do no t Let us look more closely at these two problemsdeserve higher than subspecies rank. of the origin of man. The branching oli of Homo

ting, 3. To group together as subspecies groups al l frolil the other anthropoids was a case of orthodoxthose subspecies within a species that form speciation distinguished only by the fact thatspe either geographical or chronological groups. the ne w species simultaneously reached a ne wto the Such subspecies groups in homo sapiens, for adaptive plateau. It is now evident, as has been

if this instance, might be: stated by many authors, that a change in th eof (a) modern man mode of locomotion an d a corresponding alterationof (b) 1\eanderthal group of the entire organization of the body, in other

and it (c ) pre-Neanderthal group words, the assuming of th e upright posture, were4. Not to give formal generic and specific nan,es the essential steps that le d to the evolution ofof to new fossil finds that are no t sufticiently known. Homo. This evolutionary trend apparently afiectedin th e Vernaculars, such as "Steinheim nlan" or "Pi l t first the pelvis and poster-ior extremities, followed

sub- down man," ar e just as useful and much less mis closely by the anterior extremities. The corresleading. Th e formal appl ication of generic an d ponding re-organization of the skull lagged ap s pro- specific names simulates a precision that often paren tl y behi nd . I t is therefore singular!y diflic ul tdoes not exist. To give the impression of an un- to localize both in time an d space this important

de - justified precision is as much of a methodological evolutionary step of the attainment of the uprighterror as to make cal culations to the f.fth decimal posture with the help of ja w and tooth fragments,when th e accuracy of the original data extends such as constitute most of the primate an d an

have only to the first decimal. thropoid remains in eastern Africa during PlioAnthropologists should never lose sight of th e cene and Miocene. fact th a t taxonomic categories are based on popu To determine the exact point in the phyletic

lations, not on individuals. Different names evol ut i on of fl omo where the sapiens level wasis a should never be given to individuals that are pre reached, is quite impossible. It was a verywho gradual process leading from erectus to sapienssumably members of a single variable population.Nean

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--116 ERNST MAYRand no particular form ca n be singled out as themissing link. However, there is a lower level inthe phyletic evolution of Homo that is of specialevolutionary interes t, namely, the level at whi chthe hominids first displayed those intellectualqualit ies that are considered distinctly humanrather than simian.

Attempts have been made to measure the attainment of this llama level in terms of brain size.This method is fraught with difiiculty. First ofall, brain size is to some extent correlated withbody size. If, for instance, a large gorilla shouldhave a brain of 650 cc. this is no t at all necessarily equivalent to the brain of a fossil hominidof 650 cc., if that hominid were much smaller thana gorilla. If the brain of the gorilla averages onefourth larger than that of the chimpanzee, it doesnot mean ihat he is on the average 25 pe r centmore intelligent. The correlation between br.ainsize an d intelligence is very loose. There is goodevidence that the brain size of late Pleistoceneman may have averaged larger than that of modernman. If true, this does not mean necessarily thatthere ha s been a deterioration of man's intelligence since the Pleistocene, for intelligence isdetermined not only by brain size. It is , of course,still unknown what neurological structures affectintelligence bu t the folding of the cortex and al lsorts of specializations within the cortex appearto be as important as size. It is therefore dangerous, in fact, outright misleading, to use size asan absolute criterion and to sa y that the JJamastage ~ \ ( I S reached when brain size reached aleve J of 700 or 750 cc.It has been suggested to measure the attain

ment of the human level by some cu i tural achievement, such as the us e of fIre, rather than by ananatomical standard. like brain size. This is un-questionably a superior approach, bu t has thepractical difiiculty that the flfst moment of fifemaking was no t fossilized an d can never be datedaccurately. However, the first making of fife mayhave occurred no t much after th e first use of toolsby hominids an d some lucky finds illay shed lightsomeday on the period when that occurred. SouthAfrican :nan was presumably already a user oftools, and the first us e of tools may be coincidentwith the evol ution of South African man.

Speciation in man: In the strict sense of theword, speciation means the origin of discontinuities through the origin of reproductive isolating ,nechanisms. How often ha s man speciated?Th e answer is that he ha s speciated only once ifour assumption is correct that never more thanone species of man existed on the earth at an yone time. This single event of speciation was the

branching ofT of Ilomo from the anthropoid stock.That some fairly distinct hominid remains havebeen found in approximately contemporary depositsdoes not prove t'heir specific distinctness. Thesub-division of the human speci.es in.to independent tribes favors diversification. If fossils ofCongo pygmies and of lVatusi were to be found inthe same deposit by a paleontologist, a millionyears hence, he might well think that they belonged to two different species. As stated previously, the known diversity (Jf fossil man can beinterpreted as being the result of geographicvariation within a single species of Homo. Thisle d to the evolution of such aberrant types asPiltdown man of England, bu t apparently nowhereto the simultaneous occurrence of several speciesof Homo. What is the cause for this puzzlingtrait of the hominid stock to stop speciating inspite of it s eminent evolutionary success? Itseems to me that the reason is man's great ecological diversity. Man has, so to speak, specializedin despecialization. Vlan occupies more diflerentecological niches than an y known animal. If thesingle species man occupies successfully al lth e niches that ar e open for a llama-like creature,it is obvious that he cannot speciate. This conforms strictly to Cause's Uule. Also man isapparently slow in establishing isolating mechanisms. This is indicated by the numerous in stances of incomplete speciation in the historyof the hominids. In no case was this speciationcompleted because the segregating populationswere either absorbed by intermarriage or exterminated. Man is apparently particularly intolerantof competitors. The wiping out or absorption ofprimitive populations by culturally more advancedor otherwise more aggressive invaders, which wehave witnessed so Illany times during the eighteenth and nineteenth centuries in Australia, NorthAmerica, and other places, has presumably happened many times before in the history of theearth. Th e elimination of Neanderthal man by theinvading C r o - ~ 1 a g r l o n man is merely one example.

There is one striking diHerence between manand most of the animals. In animals whenever thereis competition between two subspecies the onethat is better adapted for a specifIc locality seemsto win out. !\lan, who has reached such a high degree of independence from the environment, is lessdependent on local adaptation, an d a subspeciesof lilan can quickly spread into many geographically distant areas if it acquires generalizedadaptive improvements such as are described bythe social anthropologist. Such improvements donot need to an d probably often do not have geneticbasis. The authors who have claimed that ma n is

unique iright. Ewill conspeciesappearsthat is ,species

1. Thethan onea given

2. It ihominidwith thsapiens)

3. Theth e spec4. Thesl0wneslllechanillama intBROOM,

SouthAnthfDOBZHAI

livin(N.S.MAYH, ENew1944, 0subsp2: l l -OAKLEY,of PiSTRAUS, try.