November 6, 1919] 



NATURE 



213 



shown that a varied assemblage of apes lived in 

 the forests of northern India in the Miocene epoch. 

 At that time the Himalayan Mountains did not 

 exist, and the late Joseph Barrell ingeniously 

 suggested that it may have been during the uplift 

 of this mountain range at the end of the Miocene 

 and beginning of the Pliocene that primitive man 

 originated. As the land rose, the temperature 

 would be lowered, and some of the apes which 

 had hitherto lived in the warrn forest would be 

 trapped to the north of the raised area. As com- 

 paratively dry plains would there take the place 

 of forests, and as the apes could no, longer 

 migrate southwards, those that survived must 

 have become adapted for living on the ground, 

 and acquired carnivorous instead of frugivorous 

 habits. By continued development of the brain 

 and increase in bodily size, such ground-apes 

 would tend to become man. 



Unfortunately, we are still ignorant of fossils 

 to test this hypothesis. We know from fragments 

 of jaws, isolated teeth, and one limb bone that 

 generalised apes as large as chimpanzees existed 

 in Europe so far north as the latitude of Darm- 

 stadt until the end of Miocene times, but the only 

 giant ground-ape, which many have claimed to 

 be an ancestral man, was found by Dubois in 

 Java in deposits of much later age which may 

 even be Pleistocene. Pithecanthropus erectus, as 

 the Javan species is named, is still known only 

 by a cranial roof, two molar teeth, and a diseased 

 thigh-bone, which bear many resemblances to the 

 corresponding parts of the existing gibbon, and 

 are tantalising in their imperfection. 



It is, however, curious that almost the only 

 traces of true man hitherto found with distinc- 

 tively ape-like characteristics are from Western 

 Europe. The imperfect skull and mandible of 

 Eoanthropus da'wsoni discovered by the late 

 Charles Dawson at Piltdown, Sussex, represents 

 a man with the lowest of all known human brains, 

 and with an ape-like jaw in which typically human 

 molar teeth are accompanied by large canines as 

 completely interlocking as in any ape. The 

 massive lower jaw of Homo heidelbergensis from 

 Mauer, near Heidelberg, still retains much 



reminiscence of an ape in its retreating chin. The 

 fine skeleton of Neanderthal or Mousterian man 

 described by Prof. Marcellin Boule from La- 

 Chapelle-aux-Saints, France, combines more ape- 

 like features in a single individual than are 

 known in any existing man. The Piltdown and 

 Heidelberg fossils are shown by associated mam- 

 malian remains to date back at least to the begin- 

 ning of the Pleistocene, perhaps even to the end 

 of the Pliocene epoch. Neanderthal man is later, 

 and is very soon followed by typical modern man. 



As to the actual age of these various remains 

 in years or centuries there has been much dis- 

 cussion, but it must be confessed that on present 

 evidence only vague guesses are possible. It is 

 true that Penck and Bruckner have made some 

 plausible suggestions as to the length of Pleisto- 

 cene time based on their studies of the glaclation 

 of the Alps. Baron de Geer has also been able 

 to date more precisely the retreat of the Pleisto- 

 cene ice-sheet in Scandinavia by counting the 

 annual layers in the mud which its flood-waters 

 left behind. It is impossible, however, with our 

 present knowledge, to correlate the isolated 

 patches of Piltdown gravel, Mauer sands, or 

 cavern deposits with the surface phenomena of 

 distant areas ; and it is doubtful whether this 

 difficulty will ever be overcome. 



Our knowledge of the ancestry of man has, 

 indeed, progressed much during recent years, but 

 unfortunately it is necessary to depend on acci- 

 dental discoveries. Systematic exploration seems 

 to meet with little or no result. Mrs. Selenka 

 made great and prolonged excavations in Java in 

 the river-deposits whence Pithecanthropus was ob- 

 tained, without any success. The great sandpit 

 at Mauer has been continuously worked and most 

 carefully watched since the famous jaw was dis- 

 covered, but without recovering any further traces 

 of man. I have worked hard in the Piltdown 

 gravel, but for the last three seasons I have not 

 found a fragment of either bone or tooth. The 

 research needs much patience, but we may hope 

 that as interest in the subject is more widely 

 spread a larger proportion of the accidental finds 

 relating to it will escape destruction. 



THE PRESENT POSITION OF THE MUTATION THEORY. 



By Prof. Hugo de Vries. 



DARWIN assumed that species originate by 

 the gradual accumulation of infinitesimal, 

 ordinarily invisible variations on account of their 

 utility in the struggle for life. The difficulties 

 inherent in this conception have led to the theory 

 of mutation, which supposes that the production 

 of species and varieties proceeds by small but 

 distinct steps, each step corresponding to one or 

 more unit-characters. It is only after their appear- 

 ance that the environment can decide about their 

 utility. 



The new theory reduced the time necessary for 

 NO. 2610, VOL. 104] 



the evolution of organic life on earth to the limits 

 deduced by Lord Kelvin and others from physical 

 and astronomical data. It explained the appear- 

 ance of the numerous useless qualities of animals 

 and plants, and eliminated the objection that the 

 first almost imperceptible changes could scarcely 

 have any beneficial significance for their bearers. 

 It developed the doctrine of two essential types 

 of variability, which are now called fluctuating 

 vari^ility and mutability. The first of these 

 describes the small but always present differences 

 among individuals of the same stock, whereas 



