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Lettris is a curious tetris-clone game where all the bricks have the same square shape but different content. Each square carries a letter. To make squares disappear and save space for other squares you have to assemble English words (left, right, up, down) from the falling squares.
Boggle gives you 3 minutes to find as many words (3 letters or more) as you can in a grid of 16 letters. You can also try the grid of 16 letters. Letters must be adjacent and longer words score better. See if you can get into the grid Hall of Fame !
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1.a stone tool with a cutting edge; the stone is held in the hand and used for chopping
||This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. Please help to improve this article by introducing more precise citations. (November 2011)|
A hand axe, today often known by the more neutral term biface, is a stone tool with two faces typical of the lower (Acheulean) and middle Palaeolithic (Mousterian), and is the longest-used tool of human history.
For the purposes of this article, four classes are defined :
While Class IV hand axes are referred to as "formalized tools", bifaces from any stage of a lithic reduction sequence may be used as tools. (Also, other biface typologies make five divisions rather than four).
Examples of hand axes first appeared 1.6mya in the later Oldowan (Mode I), called the "developed Oldowan" by Mary Leakey, but became more abundant in mode II Acheulean industries that appear in what is now Southern Ethiopia around 1.4 million years ago, although some of the best examples come from 1.2 million year old deposits in Olduvai Gorge. They are also known in Mousterian industries. In North America, hand axes make up one of the dominant tool industries, starting from the terminal Pleistocene and continuing throughout the Holocene. For example, the Folsom point and Clovis point traditions (collectively known as the fluted points) are associated with Paleo Indians, some of the first people to colonize the new world (see Models of migration to the New World). Further, hand axe technology is almost unknown in Australian prehistory.
Oldowan hand axes appeared sometime between 1.6 and 1.4 million years ago. They are most closely associated with Homo ergaster. The average hand axe from H. ergaster was 15 cm (6 in), but some were as long as 30 cm (12 in). Unlike earlier stone tool technology, hand axes have three distinctive shapes; hand axes, cleavers, and picks. Hand axes were shaped like a tear drop, with two cutting edges and a sharp point. Cleavers were like hand axes, but with the point broken off and replaced with a cutting edge. Picks were thicker, more triangular hand axes. These three shapes are very uniform. For example, the ratio of the length and width of hand axes is fairly consistent across hand axes from this period. These hand axed tools were possibly used in five ways by H. ergaster.
Older hand axes were produced by direct percussion with a stone hammer and can be distinguished by their thickness and a sinuous border. Later Mousterian handaxes were produced with a soft billet of antler or wood and are much thinner, more symmetrical and have a straight border.
An experienced flintknapper needs less than 15 minutes to produce a good quality hand axe. A simple hand axe can be made from a beach pebble in less than 3 minutes.
Several basic shapes, like cordate, oval, or triangular have been distinguished, but their chronological significance is not agreed upon.
As most hand axes have a sharp border all around, there is no firm agreement about their use. Interpretations range from cutting and chopping tools to digging implements, flake cores, even the use in traps and a purely ritual significance (such as courting behaviour). The current majority scientific view of their use however, is some form of chopping or tool for general purpose use, probably for cutting meat and extracting bone marrow (which would explain the pointed end) and general hacking through bone and muscle fiber. Experiments at Boxgrove appear to back this up.
H.G. Wells proposed in 1899 that handaxes were used as missile weapons to hunt prey - an interpretation supported by William H. Calvin. Calvin maintains that some of the rounder examples could have served as "killer frisbees" meant to be thrown at a herd of animals at a water hole so as to stun one of them. There are few indications of hand axe hafting, and some artifacts are far too large for that. However a thrown hand axe would not usually have penetrated deeply enough to cause very serious injuries. Additionally many hand axes are very small. There is very little evidence of impact damage in most handaxes.
Tony Baker suggested that the hand axe was not a tool, but a core from which flakes had been removed and used as tools(http://www.ele.net/acheulean/handaxe.htm flake core] theory). However, hand axes are often found with retouch such as sharpening or shaping, casting doubt on this idea.
Other theories suggest the shape is part tradition and partly a byproduct of the way it is manufactured. Since many early hand axes appear to be made from simple rounded pebbles (from river or beach deposits), it is necessary to detach a 'starting flake', often much larger than the rest of the flakes (due to the oblique angle of a rounded pebble requiring greater force to detach it), thus creating an asymmetry in the hand axe. When the asymmetry is corrected by removing extra material from the other faces, a trend toward a more pointed (oval) form factor is achieved. (Knapping a completely circular hand axe requires considerable correction of the shape.) Studies in the 1990s at Boxgrove, in which a butcher attempted to cut up a carcass with a hand axe, revealed that the hand axe was perfect for getting at bone marrow.
Marek Kohn and Steven Mithen have independently arrived at the explanation that symmetric handaxes have been favored by sexual selection as fitness indicators. Kohn in his book As we know it wrote that the handaxe is "a highly visible indicator of fitness, and so becomes a criterion of mate choice." Evolutionary psychologist Geoffrey Miller follows on their example and has said that handaxes have characteristics which make them suitable for being subject to sexual selection forces, such as that they were made for over a million years throughout Africa, Europe and Asia, they were made in large numbers, and most were impractical for utilitarian use. He says that a single design persisting across such a span of time and space cannot be explained by cultural imitation and draws a parallel between bowerbirds' bowers (built to attract potential mates and used only during courtship) and Pleistocene hominids' handaxes. He calls handaxe building a "genetically inherited propensity to construct a certain type of object." He discards the idea that they were used as missile weapons as there were more efficient weapons at the time, such as javelins, and although he accepts that some handaxes may have been used for practical reasons, he agrees with Kohn and Mithen who have shown that many handaxes show a considerable degree of skill, design and symmetry beyond the demands for utility, some were too big (such as the handaxe found in Furze Platt, England which is over a foot long) or too small (less than two inches, therefore of little practical use), they feature symmetry far beyond practical use and show evidence for excessive attention to form and finish. Miller thinks that the most important clue is that most handaxes show no signs of use or evidence of edge wear under electron microscopes. Furthermore, handaxes can be good handicaps in Amotz Zahavi's handicap principle theory: the learning costs are high, there are risks of injury, they require physical strength, hand-eye coordination, planning, patience, pain tolerance, and resistance to infection from cuts and bruises when making or using such a handaxe. 
|This article may be expanded with text translated from the corresponding article in the Spanish Wikipedia. (March 2009)
Don't speak Spanish? Click here to read a machine-translated version of the Spanish article.
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