Field Notes | National Museum of Natural History, Washington, DC

A label the size of an index card sat beside a fossil small enough to fit inside my palm, and it took two readings before I understood what the sentence was actually claiming, that Morganucodon, a creature ten centimeters long, belongs to the branch immediately adjacent to the one that became every mammal now alive, so that whatever separates its body from mine is a matter of a few million years and a great deal of luck rather than any difference in kind. Every mammal living today, including the elephant standing two rooms away and the visitor reading this label over my shoulder, descends from something that existed some two hundred million years ago, when the planet still belonged, almost without exception, to reptiles large enough to make every mammalian strategy a matter of staying invisible, ten centimeters or under, nocturnal, insectivorous, wedged into whatever crevice the day's larger animals had not yet claimed.

A mammal that stayed under ten centimeters for a hundred and fifty million years was solving the only problem actually in front of it, how to exist inside an ecology it did not design and could not renegotiate, and it solved that problem well enough that when the asteroid, or the volcanism, or whatever combination of catastrophe finally cleared the reptilian occupants out, sixty six million years ago, there was still a body plan left standing that could expand into whales, into primates, into the elephant I was about to meet three rooms further in.

What held me in front of the case longer than the fossil itself warranted was the arithmetic underneath it. Two hundred and ten million years is not a figure I can hold in any intuitive way, and yet it sits, without asking permission, beneath the body of every visitor walking past me that morning, beneath the monks I watched as a child in Qinghai lower themselves in full prostration on cold stone, beneath the elephant, beneath the fossil, beneath whatever distinction of culture or nation or species we use, day to day, to sort one body from another. The claim that we share a common origin sounds, in most conversation, like the kind of thing said to close an argument rather than open one, but the biology behind it is not sentimental at all. Every lineage of currently existing life traces back to a shared ancestor, some lineages requiring a longer trace than others, none of them requiring an infinite one.

None of this erases the violence that occurs between animals with no human presence involved at all. Predation exists. Territorial killing exists. Converting that violence into an economy, into something that requires language, law, capital, and a state apparatus to sustain itself across generations and continents, is something only human activity does. No predator has ever built a supply chain. What troubles us, when we are honest about it, is a specifically human capacity to take a living body and pass it, deliberately, through a sequence of transformations, resource, commodity, profit, power, until the body that started the sequence has become almost impossible to locate inside the object it produced.

This is where Henry, the museum's taxidermied elephant, became difficult to stand in front of, and it took me a moment to locate exactly why. It was the tusks. I already knew about the ivory trade the way one knows about most large historical crimes, at a comfortable remove, but standing there I met a fact that had never actually landed before: a tusk is a tooth, with its own nerve and its own blood supply, rooted deep and permanently into the architecture of the skull, so that removing one by force means opening a body to extract part of its own anatomy, a fact considerably harder to sit with than the image of lifting a shell off a mollusk's back.

I checked the museum's record before writing any of this down, because a reaction that strong deserves a fact underneath it rather than an assumption. Henry was killed in a legal hunt in Angola in 1955 and later donated to the Smithsonian for public education, a history that raises its own questions about who gets to hunt, who gets to donate, and what public education is doing when it uses a killed animal to teach schoolchildren about a living one. It is a different history from the poaching that continues today to kill elephants specifically for their tusks. The two histories sit differently in the body even when the ivory looks identical behind the glass, and holding that difference without collapsing it into one undifferentiated feeling of grief is, I think, part of what this kind of research actually asks of a person.

What I want to carry out of that room is the instant just before the grief, the instant in which ivory stops functioning as a word for a luxury material and turns back, briefly, into a piece of a body that was once alive. This sits close to the working claim I have been developing this month at the Folger, that a body, once it enters circulation, whether as museum specimen, ivory carving, printed illustration, or ethnographic description inside an early modern travel account, becomes what I have started calling a value-bearing media object, a body whose meaning has been transferred almost entirely into the systems that display it, price it, describe it, or classify it, so that the living tissue underneath becomes, for most purposes of the transaction, unnecessary. A museum, at its best, briefly reverses that transfer. It hands an object back its specificity for a moment, the fact that it was, once, an actual body, doing actual things, in a world that did not yet know it would end up here.

Yesterday the same question arrived through a shrine room and a national flag. Today it arrived through a tooth. Underneath both is a shape I keep circling in this research in one form or another, that before a body becomes an artifact, a specimen, a length of carved ivory, or a national symbol, it was, at some specific and locatable point, a body that was simply, actually, alive.

说明牌只有一张卡片大小，立在一块能装进手掌心的化石旁边，我读了两遍才弄清楚这句话到底在说什么。摩根齿兽，这只十厘米长的小东西，属于紧挨着那条通向今天所有哺乳动物的分支的另一条分支，两者之间隔着几百万年和相当程度的运气，而不是某种本质上的差别。今天活着的每一只哺乳动物，包括三个展厅之外的那头大象，也包括正站在我身后读这张说明牌的游客，都能追溯到大约两亿年前的某个共同祖先，那时候地球几乎完全属于体型庞大的爬行动物，哺乳动物想活下去，能用的策略只有一种，把自己压到十厘米以下，夜里出来，吃虫子，塞进那些还没被更大动物占去的石缝里。

一只哺乳动物用了一亿五千万年维持在十厘米以下，它解决的是当时唯一摆在面前的问题，如何在一个自己没有设计、也没法重新谈判的生态里活下去，它解决得足够好，好到六千六百万年前，无论是小行星还是火山还是几种灾难叠加，把爬行动物腾出位置之后，剩下的这套身体构造还能一路展开，长成鲸鱼，长成灵长类，长成我接下来要在三个展厅之外碰到的那头大象。

真正让我在那块化石前站了很久的，不是化石本身，是它底下的这个数字。两亿一千万年，我没办法用任何直觉的方式握住这个数字，可它就在那里，不需要谁的许可，压在那天早上路过我身边的每一具身体下面，压在我小时候在青海看着那些僧人五体投地磕在冰冷石板上的身体下面，压在这头大象下面，压在这块化石下面，压在我们平时用文化、国家或者物种来区分身体的那套分类下面。说我们同根同源，很多时候听起来像一句用来结束争论的话，而不是打开一场讨论的话，但它背后的生物学一点都不温情。现存的每一支生命都能追回一个共同祖先，只是有的支系要追得更远，没有一支需要追到无穷远处。

这些都不能抹去动物之间不需要人类介入也会发生的伤害，捕食存在，争夺领地的杀戮存在。把这种伤害转化成一套经济，转化成需要语言、法律、资本和国家机器才能跨越几代人和几个大陆维持下去的东西，这件事只有人类在做。没有一种捕食者建立过供应链。我们说的"自然的残酷"，多半只是后果，真正让人不安的，往往是人类这种特有的能力，把一个活着的身体依次推过一连串转化，先变成资源，再变成商品，再变成利润，再变成权力，推到最后，最初那个身体在它自己制造出来的这件物品里，几乎已经找不到了。

大象亨利那个展厅，我站在它面前开始觉得不太舒服，过了一会儿才想清楚原因。是象牙。这段历史我早就知道，一直隔着一层安全距离，作为一个抽象的贸易史存在。可站在那里，我碰到一个从没真正落地过的事实，象牙是一颗牙齿，有自己的神经，有自己的血液供应，深深地、永久地扎进头骨的结构里，暴力取走它，等于打开一个身体去摘除它自己身体结构的一部分，比从软体动物背上揭下一片壳要沉重得多。

写下这些之前我去查了博物馆的记录，一种这么强烈的反应，底下应该有一个事实撑着，不该只是一个假设。亨利是1955年在安哥拉的一次合法狩猎中被杀死的，后来捐给了史密森尼用于公共教育，这段历史本身带出一整串问题，谁有资格狩猎，谁有资格捐赠，用一头被杀死的大象去教小学生认识活着的大象，这件事在做什么。但它和今天仍在继续的、专门为了象牙而猎杀大象的盗猎，是不同的历史。这两段历史落在身体里的分量不一样，即使玻璃柜里的象牙看起来完全相同，能不把这种差别压扁成一种笼统的悲伤，我想，是这类研究真正要求的一部分。

从这个房间我想带走的，是悲伤降临前那一秒的感觉，那一秒里，象牙从一个描述奢侈材料的词，忽然变回了一头曾经活着的身体的一部分。这和我这个月在Folger做的研究里正在成形的一个判断很接近，一具身体一旦进入流通，无论是作为博物馆标本，作为象牙雕刻，作为印刷插图，还是作为早期现代游记里的民族志描述，就会变成我最近开始称之为"承载价值的媒介对象"的东西，它的意义几乎完全转移到了展示它、标价它、描述它、分类它的那套系统里，底下那层活的组织，对大多数交易目的来说，已经变得可有可无。博物馆最好的时候会短暂地把这个转移过程逆转回去，把一个已经被拉平进语言和商品的东西，还给它片刻的具体性，它曾经是一具真实的身体，做过真实的事情，活在一个还不知道自己会走到这里的世界里。

昨天这个问题是从一间法堂和一面国旗那里过来的，今天是从一颗牙齿。底下是同一个形状，我在这段研究里一直用不同的方式绕着它走，一具身体在变成文物、标本、一段象牙，或者一个国家象征之前，在某个具体的、可以指认的时间点，只是一具活着的身体。