Why Are Babies So Dumb

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.

人类作为物种之一，拥有难以置信的智力。我们可以讲故事，创造伟大的艺术和令人震惊的技术，建造城市，以及探索空间。我们与其他物种相比，远没有生存的更久，但是在许多方面我们都已经超越在我们之前的物种。我们食用其他物种但是他们吃不了我们，我们甚至可以在他们身上进行系统的学习—并且能够通过思考重新创造出已经灭绝的生物。但是我们的智力伴随着一个奇怪的警示：我们的婴儿是最蠢的-或者，可以说是世界上最无助的存在。一个刚出生的长颈鹿能在一小时内站立，并且能够在它出生的头一天逃避捕猎者的追杀。一直猴子能够挂在它母亲身上来吃东西和保护自己。人类的婴儿甚至都没有能力支撑起自己的头部。

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?

人类智商的演化不是过去塞莱斯特.基德所考虑的那样。她当前是一位在罗彻斯特大学工作的关于认知发展科学的专家，她的工作主要集中在关于儿童学习和决策思维方面。通过多年对小孩子的观察，她对孩子们复杂性水平的平均值逐步有了深刻的印象。但是当她看着她所接触过的婴儿时，她就会困惑的看着这个无助的程度：在那一刻他们怎么会如此的无能但是在此之后在种群中又会如此的耀眼？有一天，她将这个问题带给了她的同事皮安泰斗斯.史蒂芬。“我们都想要找出可能的证据证明人类婴儿的无助的合理性作为学位。”她最近告诉我说：“其他灵长类动物，就像大猩猩的孩子，在进化史上与人类最为接近，能够一直坚持在他们母亲身上。”她开始看到了矛盾点：人类从出生就如此无助，与其他灵长类动物相差甚远，但是，公平的继续下去，我们又开始变得非常聪明，又一次非常远的将其他灵长类甩到了身后。假如没有如此巨大的矛盾体而是因果关系呈现在这里，那么又会发生什么呢？

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.

这些论证基德和皮安塔多西发表在他们的新报纸上，出版于PNAS六月的发行物上。人类变得有智商完全是因为人类婴儿的没有能力，他们论证道；这些婴儿强烈需要他人的帮助。这个理论非常让人震惊，但是这并不是什么最新理论。很长时间以来研究者考虑到我们出生的特性以及演变过程中的意义，人类属于哺乳类动物的子集，叫做胎生哺乳类动物，就是说在出生时已孕育出活生生的生命。这就表示婴儿要在母体内长到足够成熟才能降生，但是他们又不能长得太大以免生不出来。这就产生了抉择：更高智商的动物，通常都有更大的头部，但是生育的产道是有最大限制的，仅能允许头部长到被卡住前的样子。因此大脑需要继续成长，头部也会在出生后继续生长。最终，越是高智商的动物越会在出生后表现的更加不成熟。

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.

研究者对于这种交换有很深得认知，并且关于大脑的尺寸和神经系统的密度以及智商三者之间的联系也有很深的认知。举例来说，当西蒙.里德证明了工具使用的连接以及在灵长类动物领域革新了大脑的尺寸。罗宾.邓巴发现通过新皮质体积在大脑尺寸中的比例能够预测物种在整个种群中的大小。包括蝙蝠，鲸类已经灵长类动物。基德和皮安塔得西的新的想法在于在新出生的哺乳类动物中增强无助感，将会从其父母身上增强智商—一个失控选择能够为出生做出解释。自然选择偏爱人类而赐予巨大的大脑，因为如此人类趋于更加聪明。这也许为婴儿在更早的发展阶段就创造了演化的动机，这些都需要更多的智商去提高。这一切创造了动力：随着时间的过去，无助的婴儿让父母更加只会，这些让婴儿可以更加无助，最终让他们的父母更加只会，以此类推。（我想文中的意思可能是说，婴儿无助的时间是大脑增长智慧的阶段，也许最早的时候，这一时间没那么长，但是随着人类智力的提高，可以允许的这一阶段也越长，婴儿可以无助的时间也越长，也就是说，这一阶段时间越长，大脑可以成长的越大。）

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调查研究那个，他们相信有一些重要的东西在加强他们的理论。原来其他的变量对智商的影响比大脑的尺寸要更深远—成熟的时间，或者说是断奶的时间。换一种说法，刚出生的婴儿从完全无助到自给自足之间的时间对灵长类动物智商的影响要大于测量那些建议的事情，也就是说比头部的维度更重要。大猩猩有比狒狒更聪明的孩子，而且他们喂奶的时间更长。狒狒的孩子，反过来喂奶的时间比狐猴要长，所以他们的孩子更聪明。

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.

将这些事实摆在一起能够帮助基德和皮安塔多西引伸处他们的假设。头部尺寸大小和智商之间的关系是婴儿出生的更早的动机原因。但是断奶时间的长短和智商之间的关系可能真正决定是否能骑自行车。你需要更加智慧的去照顾那些更加无助的生物，这意味着婴儿降生于这个世界是在一个更加无助的发展阶段，直到他们的大脑在出生后长到足够的尺寸，这是来自生物界生命降临的指令。这个循环也因此而继续。

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.

当然，这个理论只是一个典型模板。观念上来说，为了证明这个理论，需要在人类演化中的历程中看头部尺寸，出生时间以及智商，要看看是否我们因为我们出生早所以变得更聪明—这些数据都是难以获取的。（基德也在理论中反复强调补充过这一点，但是无法替代，更早的一些理论：这条理论同时非常自然的在两方面共存，智力在社会组织用途以及邓巴途径—就是被称作智力的新陈代谢用途，这些就是在假设我们的消化系统考虑到为我们的头脑提供更高的新陈代谢所需，并且我们变得更聪明是为了找到并分享更加难以获取的食物。但是这里有大量的证据激起我们的兴趣。其中一个，其他非胎生类动物病饿米有证明有同等的智力水平，这暗示了一种与生俱来的能够在出生和大脑力量之间的联系。并且在现代人类身上，大量的证据的出现暗示了更聪明的父母更有可能让自己的后代幸存下来。在一份有限的样本中—222位塞尔维亚罗马女士—母亲的IQ和孩子的死亡率成负相关（就是说更高的IQ意味着更低的死亡率），甚至对教育、年龄和其他相关因素进行控制的情况下也是如此。在一份加利福尼亚州父母的大样本中，在1978年，多年教育也被关联进了婴儿死亡率的数据中。全球流行病研究暗示了母亲受过教育孩子的死亡率会减少平均7%到9%之间。当然这些都不是决定性因素，但是这是有影响的。

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.

在这之上当然还有一个问题：为什么这种循环发生在了人类身上而不是狐猴身上？当我问基德这个问题的时候，她说她们的理论无法回答这个问题—不能给出确定的答案，这是一个纯粹的遗传幸运逐渐变得自我加强。当我们变得更加聪明，我们就会更好的去照顾我们的婴儿，因此他们出生后就会更加显得无助，从而让我们变得更加聪明。

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.

一条有趣的方法去进一步测试这个假设：观察一对双胞胎。具有代表性的，双胞胎没有在足够的空间成长。这就意味着双胞胎比非双胞胎有更高的智力，直到他们需要更长的断奶时间—并且如果一个母亲是这双胞胎之一，反过来说，会生出一个更聪明的孩子吗？“这真是一个好问题，在家庭中观察一组双胞胎并且看是否会产生更高的智力，”基德说。“这是一个可以预言的假设，”这其中之一也许会包含在他们持续的关于培养遗传可能性双胞胎的研究之中。并且这种假设的成立，在所有的地方都成立，来自5岁的孩子当中—基德将与Sindya Bhanoo的女儿通过博客进行交流关于双胞胎的事，Sindya Bhanoo是过去一名当代专栏作家。无能的婴儿，也许是这样吧，但是却如此聪明，而且会越来越聪明。