同学们，为什么儿童会那么弱小无助呢？为什么蹒跚学步的幼儿在试着帮忙时却总是那么无用呢？小孩子拿起一把超大的扫帚（嘴里喊着“我扫！”）想努力帮忙的举动讨人喜欢，但却压根儿没有帮助。
这不仅仅是一个儿童看护人发自内心的呼唤，也是一个重大的科学问题。婴儿和幼儿是进化问题上的疑题。为什么仅就为养活自己的孩子，大型动物就必须投入那么多时间和精力呢？人类的幼儿尤其如此，他们弱小无助、依赖帮助的时间远比其他灵长类动物的幼崽要长。
One idea is that our distinctive long childhood helps to develop our equally distinctive intelligence. We have both a much longer childhood and a much larger brain than other primates. Restless humans have to learn about more different physical environments than stay-at-home chimps, and with our propensity for culture, we constantly create new social environments. Childhood gives us a protected time to master new physical and social tools, from a whisk broom to a winning comment, before we have to use them to survive.
有一种说法是，我们这种独特的漫长儿童期有助于发展我们同样独特卓越的智力。相比其他灵长类动物，我们人类的儿童期要长得多，脑袋也比它们的大得多。好动不安的人类必须要比呆在窝里的黑猩猩了解更多各式各样的自然环境；同时由于我们具有社会习性，我们还在不断创造新的社会环境。儿童期给了我们一段受保护的时间，使我们在必须依靠新的自然工具和社会工具活下去之前先掌握它们，就比如使用掸帚和发表获胜感言等等。
The usual museum diorama of our evolutionary origins features brave hunters pursuing a rearing mammoth. But a Pleistocene version of the scene in my kitchen, with ground cassava roots instead of pancakes, might be more accurate, if less exciting.
在博物馆中，描述进化起源的模型常常会展现勇猛的猎人追逐一头直立猛口象的情景。然而，我厨房中那个更新世版本的场景或许会更准确，如果它看起来并没那么激动人心的话，另外这次，薄饼被木薯根粉所替代。
Of course, many scientists are justifiably skeptical about such" just-so stories" in evolutionary psychology. The idea that our useless babies are really useful learners is appealing, but what kind of evidence could support( or refute) it? There's still controversy, but two recent studies at least show how we might go about proving the idea empirically.
当然，许多科学家也对进化心理学中这样的“假设性故事”提出了合理的质疑。我们一无用处的婴儿实际上是真正有用的学习者，这样的说法固然很有吸引力，但什么样的证据能够证明（或反驳）它呢？争议依然存在，不过最近两项研究至少向我们表明了可如何从实证层面来证明这个说法。
One of the problems with much evolutionary psychology is that it just concentrates on humans, or sometimes on humans and chimps. To really make an evolutionary argument, you need to study a much wider variety of animals. Is it just a coincidence that we humans have both needy children and big brains? Or will we find the same evolutionary pattern in animals who are very different from us? In 2010, Vera Weisbecker of Cambridge University and a colleague found a correlation between brain size and dependence across 52 different species of marsupials, from familiar ones like kangaroos and opossums to more exotic ones like quokkas.
进化心理学广泛存在的问题之一是它只关注人类，或者有时候只关注人类和黑猩猩。若要真正在进化问题上立论，就得研究类型更加丰富的不同种类的动物。我们人类的孩子既需要大力照料又拥有比较大的脑袋只是巧合吗？我们是不是会在和我们截然不同的动物中发现同样的进化模式？剑桥大学的研究人员维拉·维斯贝克及其一名同事在 52种不同的有袋类动物中，发现了脑袋大小与依赖帮助程度之间存在着关联，那些动物既包括我们熟知的袋鼠和负鼠，也包括像短尾矮袋鼠这样的更奇特的动物。
Quokkas are about the same size as Virginia opossums, but baby quokkas nurse for three times as long, their parents invest more in each baby, and their brains are twice as big.
短尾矮袋鼠的体型与弗吉尼亚负鼠相差无几，但负鼠幼崽的哺育期是短尾矮袋鼠幼崽的三倍长，且公负鼠与母负鼠对每只幼崽的照料也更多。负鼠的脑袋是短尾矮袋鼠的两倍大。
But do animals actually use their big brains and long childhoods to learn? In 2011, Jenny Holzhaider of the University of Auckland, New Zealand, and her colleagues looked at an even more distantly related species, New Caledonian crows. These brilliant big-brained birds make sophisticated insect-digging tools from palm leaves— and are fledglings for much longer than not-so-bright birds like chickens.
不过，动物真的会利用它们的大脑袋和漫长的幼龄期来学习吗？ 2011年，新西兰奥克兰大学（ University of Auckland）的研究人员詹妮·霍尔扎伊德尔( Jenny Holzhaider)及其同事对与人类亲缘关系更远的物种——新喀里多尼亚乌鸦进行了研究。这种聪明的大脑袋飞禽能将棕榈叶啄成精致的用来挑虫子的工具，它们的幼雏期比智商不那么高的禽类，比如鸡的幼雏期要长得多。
Studying the development of quokkas and crows is one way to go beyond just-so stories in trying to understand how we got to be human. Our useless, needy offspring may be at least one secret of our success. The unglamorous work of caregiving may give human beings the chance to figure out just how those darned brooms work.
在试图理解我们是如何进化为人的问题上，研究负鼠和乌鸦的进化是一个超出那些假设性故事的方法。我们毫无用处、需要照料的后代或许至少是我们进化为人的一个秘密。也许正是照料孩子这种枯燥的工作，给人类提供了弄清楚怎么使用那些可恶扫帚的机会！
