Why are children so, well, so helpless? Why did I spend a recent Sunday morning putting blueberry pancake bits on my 1-year-old grandson's fork and then picking them up again off the floor? And why are toddlers most helpless when they're trying to be helpful? Augie's vigorous efforts to sweep up the pancake detritus with a much-too-large broom ('I clean!') were adorable but not exactly effective.
This isn't just a caregiver's cri de coeur -- it's also an important scientific question. Human babies and young children are an evolutionary paradox. Why must big animals invest so much time and energy just keeping the little ones alive? This is especially true of our human young, helpless and needy for far longer than the young of other primates.
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.
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.
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.
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.
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.
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.
At first, the baby crows are about as good at digging as my Augie is at sweeping -- they hold the leaves by the wrong end and trim them into the wrong shape. But the parents tolerate this blundering and keep the young crows full of bugs (rather than blueberries) until they eventually learn to master the leaves themselves.
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.
為何兒童會，怎樣說呢，會那末弱小無助呢?為何比來某個禮拜天的淩晨我都在給一歲大的孫兒的餐叉插上零碎的藍莓薄餅碎塊，然後又把它們從地板上撿起來呢?為何盤跚學步的幼兒在試著協助時卻老是那末無用呢?奧吉(Augie)拿起一把超大的掃帚(嘴裏喊著“我掃!”)想盡力協助的舉措討人愛好，但卻壓根兒沒有贊助。
這不單單是一個兒童關照人發自心坎的召喚，也是一個龐大的科學題目。嬰兒和幼兒是進化題目上的疑題。為何僅就為贍養本身的孩子，大型動物就必需投入那末多時光和精神呢?人類的幼兒特別如斯，他們弱小無助、依附贊助的時光遠比其他靈長類動物的幼崽要長。
John S. Dykes最新研討表現，人類的孩子既須要鼎力照顧又具有比擬大的腦殼並不是偶合。有一種說法是，咱們這類奇特的漫長兒童期有助於成長咱們一樣奇特卓著的智力。比擬其他靈長類動物，咱們人類的兒童期要長很多，腦殼也比它們的大很多。好動不安的人類必需要比呆在窩裏的黑猩猩懂得更多各種各樣的天然情況;同時因為咱們具備社會習慣，咱們還在賡續發明新的社會情況。兒童期給了咱們一段受掩護的時光，使咱們在必需依附新的天然對象和社會對象活下去以前先控制它們，就好比應用撣帚和揭櫫得勝感言等等。
在博物館中，描寫進化來源的模子經常會展示英勇的獵人追趕一頭豎立猛口象的景象。但是，我廚房中誰人更新世版本的場景大概會更精確，假如它看起來並沒那末沖動民氣的話，別的此次，薄餅被木薯根粉所替換。
固然，很多科學家也對進化生理學中如許的“假如性故事”提出了公道的質疑。咱們一無用途的嬰兒其實是真正有效的進修者，如許的說法雖然頗有吸引力，但甚麽樣的證據可以或許證實(或辯駁)它呢?爭議仍然存在，不外比來兩項研討最少向咱們註解了可若何從實證層面來證實這個說法。
進化生理學普遍存在的題目之一是它只存眷人類，大概有時刻只存眷人類和黑猩猩。若要真正在進化題目上立論，就得研討範例加倍豐碩的分歧種類的動物。咱們人類的孩子既須要鼎力照顧又具有比擬大的腦殼只是偶合嗎?咱們是否是會在和咱們判然不同的動物中發明一樣的進化模式?劍橋大學(Cambridge University)的研討職員維拉•維斯貝克(Vera Weisbecker)及其一位同事在52種分歧的有袋類動物中，發明了腦殼巨細與依附贊助水平之間存在著聯系關系，那些動物既包含咱們熟知的袋鼠和負鼠，也包含像短尾矮袋鼠如許的更獨特的動物。
短尾矮袋鼠的體型與弗吉尼亞負鼠相差無幾，但負鼠幼崽的哺養期是短尾矮袋鼠幼崽的三倍長，且公負鼠與母負鼠對每只幼崽的照顧也更多。負鼠的腦殼是短尾矮袋鼠的兩倍大。
不外，動物真的會應用它們的大腦殼和漫長的幼齡期來進修嗎?2011年，新西蘭奧克蘭大學(University of Auckland)的研討職員詹妮•霍爾紮伊德爾(Jenny Holzhaider)及其同事對與人類親緣幹系更遠的物種──新喀裏多尼亞(New Caledonian)烏鴉舉行了研討。這類聰慧的大腦殼飛禽能將棕櫚葉啄成精細的用來挑蟲子的對象，它們的幼雛期比智商不那末高的禽類，好比雞的幼雛期要長很多。
一開端，那些烏鴉幼雛挑蟲子的程度就跟我孫兒奧吉掃地的程度差未幾，它們不曉得該銜住棕櫚葉的哪一頭，還把葉子啄成為了毛病的外形。不外成年烏鴉會容忍這類笨手笨腳的行動，並提供應幼雛充足的蟲子吃(固然不是奧吉吃的藍莓)，直到它們終極學會了本身處置葉子為止。
在試圖懂得咱們是若何進化為人的題目上，研討負鼠和烏鴉的進化是一個超越那些假如性故事的辦法。咱們毫無用途、須要照顧的子女大概最少是咱們進化為人的一個機密。大概恰是照顧孩子這類死板的事情，給人類供給了弄清晰怎樣應用那些可惡掃帚的機遇。
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