Romance with a stone

Stones are convenient to chop nuts. Many primates use them for this, some still break the shells of mollusks or shells of crabs with stones. That's all, perhaps. It is not surprising, therefore, the attention of scientists was attracted by the Cherno-lane capacins Sapajus Libidinosus , living in the Brazilian National Park of Serra-da-Capivar, which found the stones much more diverse use [1].

Monkeys not only split palm nuts and seeds with them, but also dig in their help, expand the hole in the tree trunk or gap in stones, where prey is allegedly hidden, and in this case the stone and stick are used in turn. They clearly choose stones, and do not grab the first one that came across.

Females of kaputsins during estrus attract the attention of males, throwing pebbles at them from close range. The lucky man, in which they got, should after that, as an honest capucin, mate with the female who chose him. Those prefer to aim in high-rated individuals, although not alpha male.

Such a multi-purpose use of stones allows you to expect any innovations in this area from the capucins, and scientists were not mistaken in their assumptions. These monkeys deliberately chop stones. A group of experts from Oxford, the University of San Paulo and the University College of London described in detail their stone-breeding activity [2].

Capuchins are operating in pieces of quartzite. The monkey chooses a large rounded stone and, holding it with both hands, beats with force on a different stone, interspersed into sandstone, like a hammer along the anvil (Fig. 1). The resulting piece is then often used as a hammer. In this case, the dust forms, which the capucins sniff and lick. Researchers believe that monkeys are interested in silicon as a mineral supplement and, possibly, a lichen growing on stones. Mostly males wield stones, both very young and adults. But if females take up business, they get no worse.

Capuchins use their stones many times, turn them so and that way. As a result, the surface of the anvil is covered with marks and scars, and chips are formed along the edges of the hammers. Researchers note that both the hammer and the anvils are very similar to the tools that the hominids at the dawn of the Stone Age made (Fig. 2). On the products of ancient hominids, traces of inaccurate strikes have been preserved, as well as on the stones on which the capucins were pounded. But the monkeys did not set themselves the goal of focusing a stone, they simply knocked on it and kicked. Scientists investigated 111 samples, both just discarded by monkeys and old, found during excavations in the National Park at a depth of 40-50 cm. About a quarter of all used stones are broken or chopped stone hammers. On all finds, traces of repeated blows and chips of a characteristic shape. They, like the instruments of hominids, cannot be confused with accidentally crashed stones. Capuchins even have thin records with sharp edges and traces of characteristic chips. True, no one saw them to use them as a cutting tool, pointed plates continue to grind.

It turns out that primitive stone tools can be made without a special, human structure of the brush and outstanding mental abilities. From now on, the find of knotted stones cannot serve as evidence of the deliberate manufacture of cutting tools, if there are no other objects nearby confirming targeted activity, such as pointed bones. The actions of the Capuchin Stamers support the existing point of view, according to which the manufacture and use of stone tools is not a prerogative of the genus Homo .

However, the capacins of the Serra-da-Capivar park are in an exceptional position: not every monkey has a quartzite pebble at hand and the need to crush it. Could the wisdom of the manufacture of stone tools of monkeys, which had only stones and nuts at hand? After all, if you pound a nut, you can accidentally get on a stone, there will be traces, and possibly chips.

According to the last finds on the western shore of Lake Turkan in Kenya, on the parking lot of Lomekvi-3 (Lomekwi 3), and earlier finds in Ethiopia, in the Dikika area (Dikika), primitive stone guns were used by common ancestors of hominids and chimpanzes, which lived more than 3.3 million years ago. These creatures had no more brains than in modern African humanoid monkeys, so chimpanzees can become a model for studying the behavior of manufacturers of ancient stone tools.

Scientists from Japan and Great Britain put a series of experiments on the Pan TroglodyTes chimpanze living in the Japanese sanctuary of Kumamoto. They worked with four adult monkeys (three females and one male), which have the skill of the choppers [3]. Females mastered this wisdom looking at other chimpanzes and a man was trained by a man.

Monkeys were given macadamia nuts that the inhabitants of the sanctuary know and love. This is a fairly large nut with a diameter of 23-25 ​​mm; To break it, you need to attach the strength of about 2 kN. As a hammer and an anvils of monkeys, they provided with pieces of quartzite and lava (Basalt and Trakhit) brought from the Alduvai gorge.

The monkeys broke the nuts with both hands: they held a hammer alone, the second put a nut on the anvil. There are traces on the stones, the features of which depend on whether the hammer beats along the anvil is flat or at an angle (Fig. 3). Similarly, the stones that have been used by chimpanzees living in the wild and stones with which modern people were injected. Stones remain on the stones and traces of unsuccessful blows.

On stone guns from the Olduiva gorge, a skilled Homo habilis made by man more than 2 million years ago, the fruits of monkey efforts are also similar, but there are significant differences between them (Fig. 4). Chimpanzees almost do not improve their stone hammers: they do not point chips, do not deepen cracks. The hominids clearly attached more strength and skill. Even if the chimpanzees accidentally managed to get a thin chip, the difference between him and the Olduyan guns is clearly noticeable. Monkeys do not strive for perfection and do not understand the mechanics of the process. They have a different task - to inject nuts, for this the cutting edge is not needed. And the hominids scraped meat from bones with their guns and produced bone marrow.

Researchers believe that between the primitive tools that turned out to be a stone hit on the stone, and the fertilization of thin plates existed another technological stage, not yet installed. A deep study of the material culture of chimpanzees can help in the interpretation of archaeological finds and determine the authorship of stone tools. Thus, subsequent work will be devoted to the study of stone tools made by monkeys and compare them with hominid products.

Natalia Reznik

1. Falutico T., Ottoni Eb the Manifold Use of Pounding Stone Tools by Wild Capuchin Monkeys of Serra Da Capivara National Park, Brazil // Behaviur. 2016. 153. 421–442. DOI: 10.1163/1568539X-00003357

2. Proff T., Luncz LV, Falótico T., Ottoni Eb, de la Torre I., Haslam M. Wild Monkeys Flake Stone Tools // Nature. 2016. 539 (7627). 85–88. Doi: 10.1038/Nature20112

3. Arroyo A., Hirata S., Matsuzawa T., De Latorre I. Nut Cracking Tools Used by Captive Chimpanzees ( Pan TroglodyTes ) and Their Comparison with Early Stone Age Percussive ArteFacts from Olduvai Gorge // Plos One. 11 (11): E0166788. Doi: 10.1371/Journal.pone.0166788