只有人类才有下巴？揭秘关于人体的25个惊人事实
<p>人类的身体堪称这个世界上最神秘、最完美的杰作。科学家探索了几千年，也没能将人体完全搞清楚。你知道人类是唯一有下巴的动物吗？你知道人类为什么会起鸡皮疙瘩吗？你知道拇指有自己的脉搏吗？关于人体的25个惊人事实，跟我们一起了解一下。</p><p>1. <span word="It">It</span>’<span word="s">s</span> <span word="possible">possible</span> <span word="to">to</span> <span word="brush">brush</span> <span word="your">your</span> <span word="teeth">teeth</span> <span word="too">too</span> <span word="aggressively">aggressively</span>. <span word="Doing">Doing</span> <span word="so">so</span> <span word="can">can</span> <span word="wear">wear</span> <span word="down">down</span> <span word="enamel">enamel</span> <span word="and">and</span> <span word="make">make</span> <span word="teeth">teeth</span> <span word="sensitive">sensitive</span> <span word="to">to</span> <span word="hot">hot</span> <span word="and">and</span> <span word="cold">cold</span> <span word="foods">foods</span>.</p><p>刷牙时有可能会过于剧烈。这么做会磨损牙釉质，使得牙齿对冷热食物敏感。</p><p>2. <span word="Goose">Goose</span> <span word="bumps">bumps</span> <span word="evolved">evolved</span> <span word="to">to</span> <span word="make">make</span> <span word="our">our</span> <span word="ancestors">ancestors</span>’ <span word="hair">hair</span> <span word="stand">stand</span> <span word="up">up</span>, <span word="making">making</span> <span word="them">them</span> <span word="appear">appear</span> <span word="more">more</span> <span word="threatening">threatening</span> <span word="to">to</span> <span word="predators">predators</span>.</p><p>我们的祖先之所以会进化出鸡皮疙瘩，是为了令自己的毛发竖起来，以此对掠食者更具威胁性。</p><p>3. <span word="Wisdom">Wisdom</span> <span word="teeth">teeth</span> <span word="serve">serve</span> <span word="no">no</span> <span word="purpose">purpose</span>. <span word="They">They</span>’<span word="re">re</span> <span word="left">left</span> <span word="over">over</span> <span word="from">from</span> <span word="hundreds">hundreds</span> <span word="of">of</span> <span word="thousands">thousands</span> <span word="of">of</span> <span word="years">years</span> <span word="ago">ago</span>. <span word="As">As</span> <span word="early">early</span> <span word="humans">humans</span>’ <span word="brains">brains</span> <span word="grew">grew</span> <span word="bigger">bigger</span>, <span word="it">it</span> <span word="reduced">reduced</span> <span word="space">space</span> <span word="in">in</span> <span word="the">the</span> <span word="mouth">mouth</span>, <span word="crowding">crowding</span> <span word="out">out</span> <span word="this">this</span> <span word="third">third</span> <span word="set">set</span> <span word="of">of</span> <span word="molars">molars</span>.</p><p>智齿没有任何用处。它们只是几十万年前的遗留产物。由于早期人类的大脑逐渐增大，进而缩减了口腔内的空间，从而挤掉了第三大臼齿。</p><p><span word="molar">molar</span>['<span word="mol">mol</span>ɚ]: <span word="n">n</span>. 臼齿，磨牙</p><p>4. <span word="Scientists">Scientists</span> <span word="aren">aren</span>'<span word="t">t</span> <span word="exactly">exactly</span> <span word="sure">sure</span> <span word="why">why</span> <span word="we">we</span> <span word="yawn">yawn</span>, <span word="but">but</span> <span word="it">it</span> <span word="may">may</span> <span word="help">help</span> <span word="regulate">regulate</span> <span word="body">body</span> <span word="temperature">temperature</span>.</p><p>科学家们并不完全确定我们打哈欠的原因，但打哈欠可能有助于调节体温。</p>
页:
[1]