Showing papers on "Oldowan published in 1962"

Potassium-Argon Dating at Olduvai Gorge

Abstract: Potassium-Argon Dating At Olduvai Gorge A Progress Report by F. Clark Howell l .alllre Uuly 29, 1961) published Leakey-Evernden-Cunis on new dating which in­ dicated that the usual million years (or the evolution of man and culture might be extended to J, 750.000 years or more. Knowing our readers are interested in tbe sig­ nificance of the new dating [or theories of human evolution. we asked 26 scholars to suppose that these dates are correct and lO write a comment for CA. A few re­ sponded. but aLhers refused to do so until !.he dates can be verified. Meanwhile, von Koenigswald-Genmer-Lippolt published an article (Nature . l ovem ber 25,1961) indicating a difference in KIA dates of material [rom the same site. At this point the New Scientist ( ovember ~O. 1961) published a shan report on this controversy concluding that we should have to await new dates. F. Clark Howell has kindly prepared for CA this progress report on the dating, which both Leakey and von Koenigswald have approved. When the dates are set­ tled, we shall proceed with the symposium now held in aheyance.-EDIToR. Many Associates of CURRENT ANTHRO­ POLOGY have doubtless read or heard of the effort being made by geochemists to apply the potassium-argon (KIA) method of absolute dating to volcanic­ derived sediments of Pleistocene age. The method, when sufficiently refined and capable of consistent and accu­ rately duplicable results, promises to be a major advance toward dating the bio­ logical and cultural evolution of the Hominidae. Within the past year the method has been employed to determine the abso­ lute ages of the sediments comprising the two lower beds (I, II) at Olduvai Gorge, northern Tanganyika, a locality renowned for its splendid succession of PleistOcene mammals and early human occupation sites, and most recently for the important discoveries by Dr. and Mrs. L S. B. Leakey of early hominid skeletal remains (CA 1 :7fr77). Two series of determina tions have been made on volcanic products within or under­ lying the Olduvai series of deposits. The results of these determinations are sum­ marized in the accompanying table. W'hile there is a certain internal con­ sistency in each series of detenninations, the results from one laboratory (Max­ Planck Institute fUr Kernphysik, Heidelberg) (von Koenigswald et ai. 1961) contradict those from another laboratory (Department of Geology, University of California, Berkeley) (Leakey et al. 1961). The following points may be made with reference to these series of dates: (I) A single determination is avail­ able for a sample taken from Bed II, at a level below that known to yield an East African Chellean 3 stone industry. The determination was 360,000 years (Leakey et al. 1961). Now the Chellean 3 stone industry is known at the LLK 2 site, in the FLK locality, and this site has recently yielded a well preserved hominid cranium (Leakey 1960) which, while exhibiting some Cpithecanthro­ pine ) characters typical of early Homo~ is also very significantly larger and in some respects, especially in the occipital region, is quite unlike the East (Choukoutien) and Southeast Asiatic Uava) human populations, This KIA determination is quite comparable with two KIA determinations on phonolite tuffs from the Laacher See, Rhineland. These samples were from the upper half of the lower Main ter­ race, a feature generally assigned to the early Middle Pleistocene (or Lower Pleistocene of German workers), and probably of late Elster (Mindel or per­ haps even inter-Mindel interstadial age according to A. Frechen; but of GUnz age according to P. W01dstedt). The cor­ rected ages of the determinations are 353,000 and 388,000 years, with an aver­ age age of 370,000 years (Evernden et al. Another KIA detennination from volcanic deposits representing the ini­ tial eruptions of the Sabatino (Brac­ ciano) volcanic group, and which the late A. C. Blanc (J957) referred to as the Flaminian stage, is the third of five suc­ cessive cold stages in the Pleistocene succession of the Latium. He regarded the Flaminian as pre-Tyrrhenian (I) in age and as most probably broadly equiv­ alent to the later phases of the Elster (Mindel) Glaciation. The determina­ tion is approximately 450,000 years (Evernden 1959). (These several deter­ minations should be compared with Emiliani's (1955, 1956. 1958a, b, 1961] very tentative estimation, on the basis of the deep-sea core evidence and of as­ sumed continental equivalence, of ca. 175,000 to 205,000 years as an age for the Antepenultimate Glaciation.) Another single KIA determination is available for the Capranica tuffs in the Rome region. These were regarded by A. C. Blanc as most probably of early Tyrrhenian (I) age, that is, correspond­ ing to the Creat Interglacial (Holstein­ ian-Hoxnian) stage. The determination is approximately 230,000 years. (This determination should be compared with Emiliani's (1955, 1958b] tentative esti­ mation of the age of the Great Intergla­ cial as 130,000 to 175,000 years.) (2) Three KIA detenninations are from samples taken from deposits in Olduvai Gorge which are recognized to be ncar the top of Bed I, and certainly to postdate those sites in Bed I which have thus far yielded hominid skeletal remains. The detenninations would hence provide an approximate age for the site of the FLK N. I, a clay bed with (advanced) Oldowan industry and a rich fauna, especially many desenic rodents, but as yet no hominid remains, and which underlies the hard Marker Bed at the ,op of Bed I (Leakey 196Ia). The results of these detenninations were: 1.02 X 10- years (J,020,000 years) (Sample 1.13 X 10' years (#664R), and 1.38 X 10' years (#861), with an average age of 1.23 X 10' years (Leakeyet al. 1961). (3) Two determinations are from samples in close relation to the level in Bed I at the site of FLK I (or FLK Main) which has yielded the austra­ lopithecine skeletal remains referred to Zinjanthropus boisei Leakey, found on an extensive occupation horizon in as­ sociation with Oldowan industry and a rich fauna (Leakey 1959). The re­ sults of these determinations were: 1.89 X 10' years (#849: tuff overlying the Zinj horizon, with 20% fresh shards), and 1.64 X 10' years (#851: LUff immediately below the Zinj hori­ zon, containing numerous bone frag­ ments, a possible contaminant). Another determination is from a sample collected from the upper of two thin (2.5-5.1 em, thick) bands of ash which overlie the ( pre-Zinj ) horizon at the adjacent site of FLK NN. I. This site has recently yielded skeletal re­ mains of another, and distinct hominid (Leakey 1961a~ b), and lies some .6 m_ to 1.2 m. beloUl the FLK Main ( Zinj ) horizon. The result of this determina­ tion was: 1.78 X 10- (#850: most glass shards altered to day). Two other (unidentified) localities, situated west of the third fault on the south side of the gorge, and several miles from the FLK locality, have pro­ vided samples for age determination from a tuff series comparable with that which yielded the aforementioned skeletal remains at }~LK, The results of these determinations were: 1.63 X 10' years (#412: most glass shards altered to clay) and 1.74 X 10' years (#437: CURRENT ANTHROPOLOGY