As a species,humans are incredibly smart. We tell stories, create magnificent art and astounding technology, build cities, and explore space.We haven’t been around nearly as long as many other species, but in many respects we’ve accomplished more than any have before us.We eat them and they don’t eat us. We even run scientific studies on them—and are thinking about re-creating some of those that have gone extinct. But our intelligence comes with a curious caveat: our babies are among the dumbest-or, rather, the most helpless-that exist. A baby giraffe can stand within an hour of birth, and can even potentially flee predators on its first day of life. A monkey can grasp its mother and hang on for protection and nourishment. A human infant can’t even hold up its own head.

人類作為物種之一，擁有難以置信的智力。我們可以講故事，創(chuàng)造偉大的藝術(shù)和令人震驚的技術(shù)，建造城市，以及探索空間。我們與其他物種相比，遠沒有生存的更久，但是在許多方面我們都已經(jīng)超越在我們之前的物種。我們食用其他物種但是他們吃不了我們，我們甚至可以在他們身上進行系統(tǒng)的學(xué)習(xí)—并且能夠通過思考重新創(chuàng)造出已經(jīng)滅絕的生物。但是我們的智力伴隨著一個奇怪的警示：我們的嬰兒是最蠢的-或者，可以說是世界上最無助的存在。一個剛出生的長頸鹿能在一小時內(nèi)站立，并且能夠在它出生的頭一天逃避捕獵者的追殺。一直猴子能夠掛在它母親身上來吃東西和保護自己。人類的嬰兒甚至都沒有能力支撐起自己的頭部。

The evolution of human intelligence isn’t something that Celeste Kidd had ever pondered. A developmental cognitive scientist who currently works at the University of Rochester, her work had focused mostly on learning and decision-making in children. Over years of observing young children, she became impressed with the average child’s level of sophistication. But when she looked at the infants sheen countered, she saw a baffling degree of helplessness: How could they be so incompetent one second and so bright so soon thereafter? One day, she posed thequestion to her colleague Steven Piantadosi. “Both of us wondered what could possibly justify the degree of helplessness human infants exhibit,” she told me recently. “Even other primate babies, like baby chimps, which are close in evolutionary terms, can cling onto their moms.” She began to see a contradiction: humans are born quite helpless, far more so than any other primate, but, fairly early on, we start becoming quite smart, again far more so than any other primate. What if this weren’t a contradiction so much as ac ausal pathway?

人類智商的演化不是過去塞萊斯特.基德所考慮的那樣。她當(dāng)前是一位在羅徹斯特大學(xué)工作的關(guān)于認知發(fā)展科學(xué)的專家，她的工作主要集中在關(guān)于兒童學(xué)習(xí)和決策思維方面。通過多年對小孩子的觀察，她對孩子們復(fù)雜性水平的平均值逐步有了深刻的印象。但是當(dāng)她看著她所接觸過的嬰兒時，她就會困惑的看著這個無助的程度：在那一刻他們怎么會如此的無能但是在此之后在種群中又會如此的耀眼？有一天，她將這個問題帶給了她的同事皮安泰斗斯.史蒂芬?！拔覀兌枷胍页隹赡艿淖C據(jù)證明人類嬰兒的無助的合理性作為學(xué)位?！彼罱嬖V我說：“其他靈長類動物，就像大猩猩的孩子，在進化史上與人類最為接近，能夠一直堅持在他們母親身上。”她開始看到了矛盾點：人類從出生就如此無助，與其他靈長類動物相差甚遠，但是，公平的繼續(xù)下去，我們又開始變得非常聰明，又一次非常遠的將其他靈長類甩到了身后。假如沒有如此巨大的矛盾體而是因果關(guān)系呈現(xiàn)在這里，那么又會發(fā)生什么呢？

That’s theargument that Kidd and Piantadosi make in their new paper, published in a Juneissue of PNAS. Humans become so intelligent because human infants are soincredibly helpless, they argue; the one necessitates the other. The theory isstartling, but it isn’t entirely new. Researchers have been pondering thepeculiarities of our birth and its evolutionary significance for quite sometime. Humans belong to the subset of mammals, called viviparous mammals, thatgive live birth to their young. This means that infants must grow to a matureenough state inside the body to be born, but they can’t be so big that they areunable to come out. This leads to a trade-off: the more intelligent an animalis, the larger its head generally is, but the birth canal imposes an upperlimit on just how large that head can be before it gets stuck. The brain,therefore, must keep maturing, and the head must continue growing, long afterbirth. The more intelligent an animal will eventually be, the more relativelyimmature its brain is at birth.

這些論證基德和皮安塔多西發(fā)表在他們的新報紙上，出版于PNAS六月的發(fā)行物上。人類變得有智商完全是因為人類嬰兒的沒有能力，他們論證道；這些嬰兒強烈需要他人的幫助。這個理論非常讓人震驚，但是這并不是什么最新理論。很長時間以來研究者考慮到我們出生的特性以及演變過程中的意義，人類屬于哺乳類動物的子集，叫做胎生哺乳類動物，就是說在出生時已孕育出活生生的生命。這就表示嬰兒要在母體內(nèi)長到足夠成熟才能降生，但是他們又不能長得太大以免生不出來。這就產(chǎn)生了抉擇：更高智商的動物，通常都有更大的頭部，但是生育的產(chǎn)道是有最大限制的，僅能允許頭部長到被卡住前的樣子。因此大腦需要繼續(xù)成長，頭部也會在出生后繼續(xù)生長。最終，越是高智商的動物越會在出生后表現(xiàn)的更加不成熟。

Researchers have long known about this trade-off, and about the connection between brain size and neural density and intelligence. For instance, Robin Dunbar found that the ratio of neocortical volume to brain size can predict the social-group size in a number of species, including bats, cetaceans, and primates, while Simon Reader has demonstrated links in tool use and innovation to brain size in primates.Kidd and Piatadosi’s new idea is that increased helplessness in newborns mandates increased intelligence in parents—and that a runaway selection dynamic can account for both.Natural selection favors humans with large brains, because those humans tend to be smarter. This may create evolutionary incentives for babies that are born at an even earlier developmental stage, which require more intelligence to raise. This creates the dynamic: over time, helpless babies make parents more intelligent, which makes babies more helpless, which makes their parents more intelligent, and so on.

研究者對于這種交換有很深得認知，并且關(guān)于大腦的尺寸和神經(jīng)系統(tǒng)的密度以及智商三者之間的聯(lián)系也有很深的認知。舉例來說，當(dāng)西蒙.里德證明了工具使用的連接以及在靈長類動物領(lǐng)域革新了大腦的尺寸。羅賓.鄧巴發(fā)現(xiàn)通過新皮質(zhì)體積在大腦尺寸中的比例能夠預(yù)測物種在整個種群中的大小。包括蝙蝠，鯨類已經(jīng)靈長類動物?；潞推ぐ菜梦鞯男碌南敕ㄔ谟谠谛鲁錾牟溉轭悇游镏性鰪姛o助感，將會從其父母身上增強智商—一個失控選擇能夠為出生做出解釋。自然選擇偏愛人類而賜予巨大的大腦，因為如此人類趨于更加聰明。這也許為嬰兒在更早的發(fā)展階段就創(chuàng)造了演化的動機，這些都需要更多的智商去提高。這一切創(chuàng)造了動力：隨著時間的過去，無助的嬰兒讓父母更加只會，這些讓嬰兒可以更加無助，最終讓他們的父母更加只會，以此類推。（我想文中的意思可能是說，嬰兒無助的時間是大腦增長智慧的階段，也許最早的時候，這一時間沒那么長，但是隨著人類智力的提高，可以允許的這一階段也越長，嬰兒可以無助的時間也越長，也就是說，這一階段時間越長，大腦可以成長的越大。）

During their investigation, Kidd and Piantadosi realized something important that strengthened their theory. It turns out that another variable has an even higher correlation with intelligence than brain size—time to maturity, or weaning time.In other words, the time it takes to shepherd newborns through absolute helplessness to a point of relative self-sufficiency predicts primate intelligence more strongly than the best measure that has previously been proposed, namely, head circumference.Orangutans have smarter babies than baboons and they wean them longer. Baboon babies, in turn, are weaned longer,and are smarter, than lemur babies.

在基德和皮安塔多西的調(diào)查研究那個，他們相信有一些重要的東西在加強他們的理論。原來其他的變量對智商的影響比大腦的尺寸要更深遠—成熟的時間，或者說是斷奶的時間。換一種說法，剛出生的嬰兒從完全無助到自給自足之間的時間對靈長類動物智商的影響要大于測量那些建議的事情，也就是說比頭部的維度更重要。大猩猩有比狒狒更聰明的孩子，而且他們喂奶的時間更長。狒狒的孩子，反過來喂奶的時間比狐猴要長，所以他們的孩子更聰明。

Putting these facts together helped Kidd and Piantadosi develop their hypothesis. The connection between head size and intelligence does create incentives for babies to arrive earlier. But it’s the connection between weaning time and intelligence that may really be driving the cycle. You need to be smarter to care for more helpless creatures, which means that babies have to enter the world at an even more helpless stage of development, since there is a finite size to their brain at birth, mandated by the physiology of live birth. And so the cycle continues.

將這些事實擺在一起能夠幫助基德和皮安塔多西引伸處他們的假設(shè)。頭部尺寸大小和智商之間的關(guān)系是嬰兒出生的更早的動機原因。但是斷奶時間的長短和智商之間的關(guān)系可能真正決定是否能騎自行車。你需要更加智慧的去照顧那些更加無助的生物，這意味著嬰兒降生于這個世界是在一個更加無助的發(fā)展階段，直到他們的大腦在出生后長到足夠的尺寸，這是來自生物界生命降臨的指令。這個循環(huán)也因此而繼續(xù)。

Of course, thetheory is just that—a model. Ideally, to prove it you would look at head size,birth time, and intelligence over the span of human evolution, to see if wewere born earlier as we got smarter—data that are unavailable.(Kidd alsostresses repeatedly that this theory supplements, but does not supplant,earlier ones: it can coexist quite naturally with both the social-group accountof intelligence—the Dunbar approach—and what’s called the metabolic accounts ofintelligence, which posits that our digestive system has allowed for our brain’shigh metabolic needs, and that we grew smarter to be able to find and sharedifficult-to-gather food.) But there are some intriguing converging piece ofevidence. For one, other animals that are not viviparous have not evolved thesame levels of intelligence, suggesting an inherent link between live birth andbrainpower. And in modern humans, a few pieces of evidence appear to suggestthat smarter parents are more likely to have offspring that survive. In onelimited sample—two hundred and twenty-two Serbian Roma women—maternal I.Q. andchild mortality were negatively correlated (that is, higher I.Q. meant lowermortality), even controlling for education, age, and a number of other factors.In a larger sample of Californian parents, in 1978, years of education werelinked to infant-mortality rates. Global epidemiological studies suggest adecrease in mortality that equals between seven and nine per cent for each yearof a mother’s education. None of this is decisive, of course, but it issuggestive.

當(dāng)然，這個理論只是一個典型模板。觀念上來說，為了證明這個理論，需要在人類演化中的歷程中看頭部尺寸，出生時間以及智商，要看看是否我們因為我們出生早所以變得更聰明—這些數(shù)據(jù)都是難以獲取的。（基德也在理論中反復(fù)強調(diào)補充過這一點，但是無法替代，更早的一些理論：這條理論同時非常自然的在兩方面共存，智力在社會組織用途以及鄧巴途徑—就是被稱作智力的新陳代謝用途，這些就是在假設(shè)我們的消化系統(tǒng)考慮到為我們的頭腦提供更高的新陳代謝所需，并且我們變得更聰明是為了找到并分享更加難以獲取的食物。但是這里有大量的證據(jù)激起我們的興趣。其中一個，其他非胎生類動物病餓米有證明有同等的智力水平，這暗示了一種與生俱來的能夠在出生和大腦力量之間的聯(lián)系。并且在現(xiàn)代人類身上，大量的證據(jù)的出現(xiàn)暗示了更聰明的父母更有可能讓自己的后代幸存下來。在一份有限的樣本中—222位塞爾維亞羅馬女士—母親的IQ和孩子的死亡率成負相關(guān)（就是說更高的IQ意味著更低的死亡率），甚至對教育、年齡和其他相關(guān)因素進行控制的情況下也是如此。在一份加利福尼亞州父母的大樣本中，在1978年，多年教育也被關(guān)聯(lián)進了嬰兒死亡率的數(shù)據(jù)中。全球流行病研究暗示了母親受過教育孩子的死亡率會減少平均7%到9%之間。當(dāng)然這些都不是決定性因素，但是這是有影響的。

There is, ofcourse, one follow-up question: Why did this cycle happen to humans and not tolemurs? When I asked Kidd about this, she told me that their theory can notoffer an answer—like as not, it’s a matter of pure genetic luck that becameself-reinforcing. As we grew smarter, we were better able to take care of ourinfants, so they could be born more helpless and allow us to grow even smarter.

在這之上當(dāng)然還有一個問題：為什么這種循環(huán)發(fā)生在了人類身上而不是狐猴身上？當(dāng)我問基德這個問題的時候，她說她們的理論無法回答這個問題—不能給出確定的答案，這是一個純粹的遺傳幸運逐漸變得自我加強。當(dāng)我們變得更加聰明，我們就會更好的去照顧我們的嬰兒，因此他們出生后就會更加顯得無助，從而讓我們變得更加聰明。

One intriguingway to test the hypothesis further: look at twins. Typically, twins are notcarried to full term. Does that mean that twins are more intelligent thannon-twins, since they require longer weaning time—and would a mother who is atwin, in turn, give birth to smarter children?” It’s a really good question, tolook at the types of twins that run in families and whether that leads tohigher intelligence,” Kidd said. “It’s a predictable hypothesis,” and one thatthey may well include in their ongoing research on train heritability in twins.And it’s a hypothesis that came, of all places, from a five-year-old –Kidd wasbeing interviewed about twins for a podcast by the daughter of Sindya Bhanoo, aformer columnist at the Times. Dumb babies, maybe, but oh so smart, oh so soonthereafter.

一條有趣的方法去進一步測試這個假設(shè)：觀察一對雙胞胎。具有代表性的，雙胞胎沒有在足夠的空間成長。這就意味著雙胞胎比非雙胞胎有更高的智力，直到他們需要更長的斷奶時間—并且如果一個母親是這雙胞胎之一，反過來說，會生出一個更聰明的孩子嗎？“這真是一個好問題，在家庭中觀察一組雙胞胎并且看是否會產(chǎn)生更高的智力，”基德說?！斑@是一個可以預(yù)言的假設(shè)，”這其中之一也許會包含在他們持續(xù)的關(guān)于培養(yǎng)遺傳可能性雙胞胎的研究之中。并且這種假設(shè)的成立，在所有的地方都成立，來自5歲的孩子當(dāng)中—基德將與Sindya Bhanoo的女兒通過博客進行交流關(guān)于雙胞胎的事，Sindya Bhanoo是過去一名當(dāng)代專欄作家。無能的嬰兒，也許是這樣吧，但是卻如此聰明，而且會越來越聰明。