Journal of the Royal Geographical Society of London/Volume 34/On a few Fossil Bones from the Alluvial Strata of the Zambesi Delta
XII.—On a few Fossil Bones from the Alluvial Strata of the Zambesi Delta. By John Kirk, Esq., M.D., F.R.G.S.
Read, April 25, 1864
The following notes relate to a collection of fossil remains found in the bed of a stream which joins the Zambesi 40 miles from the present coast-line, near the head of the delta, and which carries off, during the rains, the surface-water from the plain to the coast.
The fossils occurred loose, mingled with quartz pebbles, and nodules of indurated ferruginous clay, polished and blackened. They had been transported by the rush of water from a little way inland, and were more or less rounded, but perfectly formed whenever the matrix adhered. This resembled the soil of the delta; being a clay mixed with sand, and impregnated with titanic iron.
Of Mammals, bones and teeth of large antelopes, probably the Eland and Kobus, were most abundant; next, those of the buffalo, hippopotamus, wart-hog, and lion. Among reptiles, fragments of the osseous back of the water-tortoise, and crocodile bones were found; the former being the most curious of all, with the exception of the vertebræ of antelopes. Although no entire skull or long bone was found, the vertebræ were well preserved, as also were the ribs, which made the absence of long bones of the limbs the more remarkable.
Besides bones there were many fragments of pottery, rounded on the edges and having in some cases the same clay matrix adhering to them. The surface of the ware was polished and blackened in the peculiar manner found in the tropics. A fresh fracture had the same appearance as the half-baked pottery now in use; but the surface markings differed from any known to Dr. Livingstone or myself. The presumption seemed to be that, like the bones, they had been washed from some of the clay strata cut through in the course of the creek; but, from an opportunity of following it up not presenting itself, it is doubtful whether both had come from the same locality.
Villages in that region at the present day are commonly placed near a lagoon or creek, and all refuse cast out speedily rolls down into the water. Besides, many tribes have now a superstition, which leads them to cast the bones of any animal eaten at once into the water. That these bones have never lain for many months on the plain is quite evident; for in these parts, under the powerful action of sun and moisture, disintegration speedily ensues even in solid bones. Although wounded and dying animals, such as buffalo and water-buck, often betake themselves to the shelter of a marsh and there expire, it must be seldom that their remains are favourably situated for becoming imbedded in the clay strata.
Further researches in similar situations in Africa, and in the plains left by the shrinking waters of the Nyassa Lake, may yet afford some information respecting the former inhabitants of that continent, of whom we have at present no knowledge. The present race will leave behind them nothing but such remains as those we have found in the Zambesi delta. In passing through a country which a few years before had been thickly peopled, the only signs of former settlements consisted in the stones used in grinding corn; but in a purely pastoral region even this would not have been left, while the remains of animals could have been preserved only in places where they have been cast into water and buried up speedily in mud.
The few specimens which have reached us out of the number we collected belong to species now existing in the Zambesi delta; the buffalo, the Crocodilus vulgaris, and the water-tortoise. As to the others, no difference was remarked when I examined them whilst in the country. The teeth and tusks of the hippopotamus were certainly identical with those of the species now existing in the river.
Similar phenomena were observed on the western shore of Lake Nyassa, which, in shrinking, as proved by elevated sand-beaches, has left clay-flats now crossed by affluent streams. At the mouth of one of these, portions of the frontal bone of an animal and the back of a tortoise were found semifossilised polished and blackened, along with indurated clay nodules, just as on the banks of the Zambesi.