490 



NATURE 



[Oct. 4, 1877 



braced animals of large size, has been found in this particular 

 fauna. 



It is a noteworthy fac^t that no traces of any anthropoid apes, 

 or indeed of any Old World monkeys, have yet been detected 

 in America. Man, however, the hit^hest of the primates, has 

 left his bones and his worlcs from the Arctic Circle to I'atagonia. 

 Most of these specimens are clearly post-tertiary, although there 

 is considerable evidence pointing to the existence of man in our 

 ])liocene. All the remains yet dir^covered belong to the well- 

 marked genus Homo, and apparently to a single species, at 

 present represented by the American Indian. 



In this rapid review of mammalian life in America, from its 

 first known appearance in the trias down to the present time, I 

 have endeavoured to state briefly the introduction and succession 

 of the principal forms in eacli natural group. If time permitted, 

 I might attempt the more difficult task of trying to imlicate what 

 relations these various group; may possibly bear to each other ; 

 what connection the ancient mammals of this continent have 

 with the corresponding fams of the Old World ; and, most im- 

 portant of all, what real progre;s mammalirn life has here made 

 since the beginning of the eocene. As it is, I can only say in 

 summing up, that the marsupials are clearly the remnants of a 

 very ancient fauna, which occupied this continent millions of 

 years ago, and from which the other mammals were doubtless all 

 derived, although the direct evidence of the transformation is 

 wanting. 



The relations of the American primates, extinct and recent, to 

 those of the other hemisphere, ofl^er an inviting topic, but it is 

 not in my present province to discuss them in their mo^t sug- 

 gestive phases. As we have here the oldest and most generalised 

 members of the group, so far as now known, we may justly claim 

 America for the birth-place of the order. That the development 

 did not continue here until it culminated in man, was due to 

 causes which at present we can only surmise, ahhough the 

 genealogy of other surviving groups gives some data towards a 

 solution. Why the Old World apes, when differentiated, did 

 not come to the land of their earlier ancestry, is readily explained 

 by the then intervening oceans, which likewise were a barrier to 

 the return of the horse and rhinoceros. 



Man, however, came ; doubtless first across Behring's Straits ; 

 and at his advent became part of our faun.n, as a mammal and 

 primate. In these relations alone it is my purpose here to treat 

 him. The evidence, as it stands to-day, although not conclusive, 

 seems to place the first appearance of man in this country in the 

 pliocene, and the best proof of this has been found cm tlie Pacific 

 coast. During several visits to that region many facts were 

 brought to my knowledge which render this more than probable. 

 Man at this time was a savage, and was doubtless forced by the 

 great volcanic outbreaks to continue his migration. This was at 

 first to the south, since mountain chains were barriers on the 

 east. As the native horses of America were now all extinct, and 

 as the early man did not brmg the Old World animal with liim, 

 his migrations were slow. I believe, moreover, ihat his slow 

 progress towards civilisation wa^ in no small degree due to this 

 same cause, the absence of the h:r e. 



It is far from my intention to add to the miny theories extant 

 in regard to the early civilisations in this coantry, and their con- 

 nections with the primitive inhabitants or the later Indians, but 

 two or three facts have lately come to my knowledge which I 

 think woith mentioning in this connection. On the Columhia 

 River, I have lound evidence of tfie former existence ot inha- 

 bitants much superior to the Indians at present there, and of 

 which no tradition remains. Among many stone caivintifs which 

 I saw there were a number of heads which so strongly resemble 

 those of apes that the likeness at once suggests itself. Wtience 

 came these sculptures, and by whom were ihey made ? Another 

 fact that has interested me'very niuth is the strong resemblance 

 between the skulls of the typical mound-builders of the 

 Mississippi Valley and those of the Pueblo Indians. I had long 

 been familiar with the former, and when I recently saw the 

 latter it required the positive assurance of a friend who had him- 

 self collected them in New Mexico to convince me that they 

 ■were not from the mounds. A third fact, and I leave man to 

 the archaeologists, on who^e province I am even now trenchim'. 

 In a large collecii ^n of mound-buildes' pottery, over a thousand 

 specimens, which I have recently examined with some care, I 

 found many pieces of elaborate workmanship so nearly like the 

 ancient water-jars from Peru that no one could fairly doubt 

 that some intercourse h;.d taken place between the widely- 

 separated people that made them. 



The oldest known remains of man on this continent differ in 



no important characters from the bones of the typical Indian, 

 although in some minor details they indicate a much more 

 primitive race. These early remains, some of which are true 

 fossils, resemble much more closely the corresponding parts of 

 the highest Old World apes, than do the latter our tertiary 

 primates, or even the recent American monkeys. Various living 

 and foisil forms of Old World primates fill up essentially the 

 latter gap. The lesser gap between the primitive man of 

 America and the anthropoid apes is partially closed by still lower 

 forms of men, and doubtless also by higher apes, now extinct. 

 Analogy, and many facts as well, indicate that this gap was 

 smaller in the pi^t. It certainly is becoming wider now with 

 every generation, for the lowest races of men will soon become 

 extinct, like the Tasmanians, and the highest apes cannot long 

 survive. Hence the intermediate forms of the past, if any there 

 were, become of .still greater importance. For such misiing 

 links, we must look to the caves and later tertiary of Africa, 

 which I regard as now the most promising field for exploration 

 in the Old World. Ameri.-a, even in the tropics, can promise no 

 such inducements to ambitious explorers. We have, however, 

 an equally important field, if less attractive, in the cretaceous 

 mammals, which must have left their remains somewhere on this 

 continent. In these two directions, as I believe, lie the most 

 important future discoveries in paUvontology. 



As a cause lor many changes of structure in mamma's during 

 the tertiary ami post-tertiary, I regard as the most potent, imlural 

 sflection, in the broad sense in which that term is now used by 

 American evolutionists. Under this head, I include not merely 

 a Malthusian struggle for life among the animals themselves, but 

 the equally important contest with the elements, and all sur- 

 rounding nature. By changes in the environment, migrations 

 are enforced, slowly in some cases, rapidly in others, and with 

 change of locality must come adaptation to new conditions, or 

 extinction. The life history of tertiary mammals illustrates this 

 principle at every stage, and no o her explanation meets the facts. 



1 he real progress of mammalian life in America, from the 

 beginning of the tertiary to the present, is well idustrated by the 

 brain-growth, in which we have the key to many other changes. 

 The earliest known tertiary mammals all had very small brains, 

 and in some forms this organ was proportionally less than in 

 certaiir reptiles. There was a gradual increase in the size of the 

 brain during this perio I, and it is interesting to find that this 

 growth was mainly confined to the cerebral hemispheres, or 

 higher portion of the brain. In most groups of mammals the 

 brain has gradually become more convoluted, and thus increased 

 in quality as well as quantity. In some, also, the cerebellum 

 and olfactory lobes, the lower parts of the brain, have even 

 diminished in size. In the long struggle for existence during 

 tertiary time the big brains won, then as now ; and the increas- 

 ing power thus gained rendered us;less many structures in- 

 herited from primitive ancestors, but no longer adapted to new 

 condit ons. 



Anoilier of the interesting changes in mammals during tertiny 

 time was in the teeth, which were gradually modified with other 

 parts of the structure. The primitive form of tooth was clearly 

 a cone, and all others are derived from ihi.^. All classes of ver- 

 tebrates below mammals, namely, fishes, amphibians, reptiles, 

 and birds, have conical teeth, if any, or some simple modifica- 

 tion of this form. The edentates and cetaceans with teeth retain 

 this type, except the zeuglodonts, which appmach the dentit on 

 of aquatic carnivores. In the higher miinnnls the incisors and 

 canines retain the conical shape, and the premolars have only ir 

 part been transformed. The latter gradually change to the mors" 

 complicated molar pattern, and hence are not reduced molars, 

 but transition forms from the cone to more complex types. Most 

 of the early tertiary mammals had forty-four teeth, and in the 

 oldest forms the premolars were all unlike the molars, while 

 the crowns were short, covered with enamel, and without cement. 

 Lach stage of progress in the differentiation of the animal was, 

 as a rule, marked by a change in the teeth, one of the most com- 

 mon being the transfer, in form at least, of a premolar to the 

 molar series, and a gr,adual lengthening of the crown. Hence 

 it is often easy to decide from a fragment of a jaw, to what 

 horizon of the tertiary it belongs. The fossil horses of this 

 period, for example, gained a grinding tooth for each toe they 

 lost, one in each epoch. In the single-toed existing horses all 

 the premolars are like the molars, and the process is at an end. 

 Other dental transform.alions ate of equal interest, but this 

 illustration must suffice. 



The changes in the limbs and feet of mammals during the 

 same period were quite as marked. The foot of the primitive 



