We all know that many more people today are right-handed than left-handed. Can one trace this same pattern far back in prehistory? Much of the evidence about right-hand versus left-hand dominance comes from stencils and prints found in rock shelters in Australia and elsewhere, and in many Ice Age caves in France, Spain, and Tasmania. When a left hand has been stenciled, this implies that the artist was right-handed, and vice versa. Even though the paint was often sprayed on by mouth, one can assume that the dominant hand assisted in the operation. One also has to make the assumption that hands were stenciled palm downward—a left hand stenciled palm upward might of course look as if it were a right hand. Of 158 stencils in the French cave of Gargas, 136 have been identified as left, and only 22 as right; right-handedness was therefore heavily predominant.
Cave art furnishes other types of evidence of this phenomenon. Most engravings, for example, are best lit from the left, as befits the work of right-handed artists, who generally prefer to have the light source on the left so that the shadow of their hand does not fall on the tip of the engraving tool or brush. In the few cases where an Ice Age figure is depicted holding something, it is mostly, though not always, in the right hand.
Clues to right-handedness can also be found by other methods. Right-handers tend to have longer, stronger, and more muscular bones on the right side, and Marcellin Boule as long ago as 1911 noted the La Chapelle-aux-Saints Neanderthal skeleton had a right upper arm bone that was noticeably stronger than the left. Similar observations have been made on other Neanderthal skeletons such as La Ferrassie I and Neanderthal itself.
Fractures and other cut marks are another source of evidence. Right-handed soldiers tend to be wounded on the left. The skeleton of a 40- or 50-year-old Nabatean warrior, buried 2,000 years ago in the Negev Desert, Israel, had multiple healed fractures to the skull, the left arm, and the ribs.
Tools themselves can be revealing. Long-handed Neolithic spoons of yew wood preserved in Alpine villages dating to 3000 B.C. have survived; the signs of rubbing on their left side indicate that their users were right-handed. The late Ice Age rope found in the French cave of Lascaux consists of fibers spiraling to the right, and was therefore tressed by a righthander.
Occasionally one can determine whether stone tools were used in the right hand or the left, and it is even possible to assess how far back this feature can be traced. In stone toolmaking experiments, Nick Toth, a right-hander, held the core (the stone that would become the tool) in his left hand and the hammer stone in his right. As the tool was made, the core was rotated clockwise, and the flakes, removed in sequence, had a little crescent of cortex (the core's outer surface) on the side. Toth's knapping produced 56 percent flakes with the cortex on the right, and 44 percent left-oriented flakes. A left-handed toolmaker would produce the opposite pattern. Toth has applied these criteria to the similarly made pebble tools from a number of early sites (before 1.5 million years) at Koobi Fora, Kenya, probably made by Homo habilis. At seven sites he found that 57 percent of the flakes were right-oriented, and 43 percent left, a pattern almost identical to that produced today.
About 90 percent of modern humans are right-handed: we are the only mammal with a preferential use of one hand. The part of the brain responsible for fine control and movement is located in the left cerebral hemisphere, and the findings above suggest that the human brain was already asymmetrical in its structure and function not long after 2 million years ago. Among Neanderthalers of 70,000–35,000 years ago, Marcellin Boule noted that the La Chapelle-aux-Saints individual had a left hemisphere slightly bigger than the right, and the same was found for brains of specimens from Neanderthal, Gibraltar, and La Quina.
右撇子的线索也可以通过其他方法找到。右手倾向于在右侧具有更长，更强壮和更强壮的骨骼，Marcellin Boule早在1911年就指出，La Chapelle-aux-Saints尼安德特人骨骼的右上臂骨明显强于左侧。对其他尼安德特人骨骼，如La Ferrassie I和尼安德特人本身也有类似的观察。
偶尔可以确定是否在右侧或左侧使用了石器，甚至可以评估这个特征可以追溯到多远。在石材工具制作实验中，右手的尼克·托斯（Nick Toth）左手拿着核心（即将成为工具的石头），右手拿锤石。工具制作完成后，核心顺时针旋转，顺序移除的薄片在侧面有一个新月形皮层（核心的外表面）。托斯的诀窍产生了百分之五十六右边的皮层，百分之四十四左派片。左手工具制造者会产生相反的模式。 Toth已经将这些标准应用于肯尼亚Koobi Fora许多早期地点（150万年前）的类似卵石工具，可能是由Homo habilis制造的。他在七个地点发现，百分之五十七的片子是正确的，剩下百分之四十三，这种模式几乎和今天的模式一样。
大约90％的现代人是右撇子：我们是唯一一只优先使用的哺乳动物。负责精细控制和运动的大脑部分位于左脑半球，上述发现表明，人类大脑在200万年以前的结构和功能已经不对称。在7万到35，000年前的“Ne 手”中，马塞林·布尔指出，拉夏贝尔 - 辅 - 圣人个体的左半球比右半球略大，对尼安德特人，直布罗陀人和拉基纳人的大脑也有同样的发现。
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