Some two or three million years ago in the Pleistocene period, a great lake had occupied this part of Mongolia. The shore-line was clearly delineated by masses of fresh-water shells. We pitched our tents on a flat plain overlooking a great basin, cut and slashed by the knives of wind and frost and rain into a thousand gaping wounds. Behind us stretched a plateau which flowed away in great sweeping billows, a seemingly flat expanse. It was probable that along the borders of this inland sea there had been quicksand bogs and muddy river bottoms in those far distant days when the shovel-tusked mastodon roamed the savannahs of Mongolia. Bogs and quicksand acted as traps then just as they do today. They are one of the most fruitful sources of well-preserved fossils and we began an intensive exploration of the lake shore.
We pitched our tents on a flat plain overlooking a great basin, cut and slashed by the knives of wind and frost and rain into a thousand gaping wounds. Behind us stretched a plateau which flowed away in great sweeping billows, a seemingly flat expanse. It was only when a horse or a running antelope disappeared suddenly from the eye that one could realize that the plain was not as flat as the top of the table. We knew from previous explorations that this was a dangerous place, because for many miles in every direction it was a waterless expanse. Mongols could not live there except in winter; it was inhabited only by antelopes, wolves, and desert birds. We named our camping place Wolf Camp, because, during two months’ stay, we shot thirteen of these marauders which preyed upon the sheep and goats of the Mongols, in a village grouped about a marshy pond eight miles away on the lowlands.
Just below the tents on a narrow promontory, we discovered many outcrops of bones. When the deposit was opened, the skulls, jaws, and skeletal parts of baby mastodons far out- numbered all other animals. Evidently this had been a bog near the shore of the lake. Mother shovel-tusked mastodons with their babies had come here to drink or feed. The mud was comparatively shallow and, although both adults and young doubtless became mired, the mothers, because of their superior strength, were able to extricate themselves and sometimes get out their babies also. But others were not so fortunate and many of them had been left to die. The crowning specimen was the jaw and part of the skull of an unborn baby. It lay in the pelvic bones of an adult female, the only adult which we found in the deposit. Albert Thomson delivered the child with Walter Granger as consulting physician, while the rest of us in the clinic amused ourselves by calling them such insulting names as “palaeontological midwives.”
The most spectacular discovery of the year was made six miles to the south of Wolf Camp by Pere Teilhard de Chardin. In an amphitheater, marked by a shining dome of pure white marl, hundreds of fossils were exposed upon the The plants floating over the death trap of mud enticed the mastodon farther and farther into the water. Suddenly it found that it could not withdraw its feet. Struggling madly in the grip of the clinging mud, it sank lower and lower until the water covered its head and the last struggles were those of a drowning beast. surface but all in a very restricted locality. Granger and Thomson, with their assistants, opened the deposit. They found great numbers of shovel-tusked jaws, skulls, and bones lying in a heterogeneous mass like a heap of giant jack straws. For six weeks the men worked in this one spot, taking out the most priceless specimens day after day. I used to sit on the edge of the escarpment just above them, drifting in imagination back to those past days when the waters of a beautiful lake filled the enormous basin. Where we worked, there had been a bay on the edge of which was a deep well of soft sticky mud. Probably it was covered by three or four feet of water on which grew a luxuriant mass of tubers and succulent aquatic plants—the favorite food of the shovel-tusked mastodon. One of these gigantic beasts plowed its way slowly along the shore of the bay, dredging up masses of trailing vegetation in its great spoon-shaped jaw. Then with its trunk or mobile lips the beast delicately selected choice bits and pushed them far back into its huge mouth to be masticated by the molar teeth. The plants floating over the death trap of mud enticed the mastodon farther and farther into the water. Suddenly it found that it could not withdraw its feet. Struggling madly in the grip of the clinging mud, it sank lower and lower until the water covered its head and the last struggles were those of a drowning beast. The trap remained baited and still other mastodons were lured into the well of death. Their huge bodies sank upon those that had gone before, until the pit was choked with masses of decomposing flesh. Eventually the lake dried up, but the bones remained entombed until we came to open the grave on that brilliant day in 1930. Seventeen great spoon-shaped jaws were taken out of this single deposit. With those obtained from the “baby pit,” the Museum has a superb age series representing almost every stage in growth from the unborn young to the adult bulls with jaws five and one-half feet long. This age series is only rivaled by that of the dinosaur Protoceratops, which demonstrates its growth from the egg up to the very old males.
The expedition spent two months at Wolf Camp, busy every moment on new and interesting discoveries. We might have remained all summer at this one site, for half a dozen other places were located which doubtless would have proved as rich as those tombs we had already opened. It is only in such deposits and in the river drift of ancient stream beds that we may hope to find the remains of primitive human types.