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If a body is found in a field, and the cops suspect foul play is involved, establishing the exact time of death is critical.
如果有人在田野里发现一具尸体，警察又怀疑涉嫌谋杀的话，确定确切的死亡时间就成了一个至关重要的问题。
Figuring out the deceased’s final moments can help investigators corroborate people’s stories to ultimately hone in on the killer.
弄清死者生前的最后时刻能够帮助调查人员确认有关人员是否在说谎并最终锁定凶手。
But how do you do that?
问题是，怎么才能做到这一点呢？
There are a few traditional ways to tell when someone died.
判断一个人的死亡时间一般有如下几种方法。
Forensic examiners can measure body temperature, skin color, and degree of rigor mortis.
法医可以通过测量体温、检验肤色或是检验尸体的僵硬程度（来判定死亡时间）。
Each of these changes as the body begins decomposing,
因为尸体开始腐烂后，这些因素都会随着时间有所变化，
so knowing the stage of change they can work backwards to figure out the time of death.
也就是说，知道了变化处于哪个阶段，就能倒推出死亡时间。
But all those methods only really work in the first 72 hours;
问题是，所有这些方法都只在最初的72个小时内才比较管用；
any longer and those factors have piqued,
再久这些因素就“有情绪了”，
meaning the changes have happened and there’s no more data to glean.
意思就是变化是有变化，但已经没有更多的数据可供收集了。
So, when a body has been a corpse for more than three days,
换句话说，如果尸体的死亡时间已经超过三天，
investigators have to use other methods to determine the time of death…
调查人员就得用其他办法来确定其死亡时间……
one way is to look at all the different insects that feed on dead human flesh.
办法之一就是观察以尸体为食的各种昆虫。
Insects are drawn to the gasses and fluids released from a decomposing body;
尸体腐烂时会释放出能够吸引昆虫的气体和液体；
to them, it’s fertile ground to lay their eggs and cultivate their young.
对那些昆虫而言，尸体就是它们产卵和孵化后代的沃土。
The first insect to reach a corpse is usually a blowfly, which will lay eggs within two days of the person’s death.
最先被尸体吸引过来的昆虫通常都是一种苍蝇，它们会在尸体死去后的前两天内到尸体上产卵。
Flesh flies also move in early in the decaying process.
肉蝇也是在尸体腐烂早期加入产卵队伍的成员。
Decomposing body fat attracts hide beetles and pyralid moths.
尸体的脂肪腐烂时会吸引甲虫和飞蛾。
As time go by and flesh breaks down,
随着时间流逝、尸体身上的肉不断分解，
other species of flies and beetles that have mouths to chew tougher food move in, consuming that dead flesh.
有嘴巴可以咀嚼更难咀嚼的食物的其他种类的苍蝇和甲虫就会开始迁入，消化掉剩下的尸体肉。
From there, the corpse becomes an ecosystem with insects feeding on the corpse also feeding on each other.
接着，尸体就会变成一个栖息着各种以尸体为食的昆虫，彼此形成食物链的生态系统。
This is all super gross but super important.
这个阶段的尸体真的巨恶心，但也非常非常重要。
Entomologists know the life cycles of these insects,
昆虫学家知道这些昆虫的生命周期，
specifically the all-important blowfly that lays its eggs in the dead body first.
尤其是最重要，同时也是最先在尸体上产卵的苍蝇的生命周期。
When determining time of death,
确定死亡时间时，
they can look at the stage of development of the blowfly — whether it’s an egg, larva, pupa, or adult —
昆虫学家们通过观察苍蝇的发育阶段——无论是卵、幼虫、蛹还是成虫阶段——
and take into account environmental factors like heat and insect patterns
同时考虑温度、昆虫的发育阶段等环境因素，
to work backwards and figure out approximately when the blowfly laid its eggs, which can tell them the time of death.
就能大致倒推出苍蝇产卵的时间，之后就能确定尸体的死亡时间了。
We’re really good at this, but there’s a problem…
这种推断手法我们已经很擅长了，但有一个问题……
we need to know exactly what species that larva is.
我们得确切地知道（尸体上孵化出来的）那个幼虫是哪个物种。
And they all sort of look alike.
（要命的是）那几种昆虫长得……都差不多。
The examiner needs to know the species for a better estimation of development time and time of death.
法医需要知道它是哪个物种，才能更好地估计其发育时间和尸体的死亡时间。
They can do a DNA test on an egg, but that can be pricey.
他们可以对（尸体上的）虫卵进行基因检测，但费用会比较高。
The cheaper option is to collect the egg and let it grow to adulthood in a lab to figure out the species, and work backwards from there.
更经济的办法是把虫卵收集起来弄到实验室里培养一段时间，等它们变成成虫就能辨别出它们的物种属性了，那时候再开始倒推。
Of course, if you’re trying to find out who killed someone and left them in a field…
当然了，如果你想找出是谁杀了人之后又抛尸田野的话，
waiting three or so days for a fly egg to become a fully-formed insect is stressful.
等三天左右，等苍蝇卵完全变成成虫会很有压力的。
A criminal can flee to a new country by then!
因为那个时候，凶犯可能都已经逃出国了！
Knowing the egg-identification thing is an issue,
因为知道虫卵识别的问题还很棘手，
an organic chemist teamed up with a forensic entomologist to apply real-time mass spectrometry to blowfly eggs.
一位有机化学家便与一位法医昆虫学家组了一个小团队，研究如何将实时质谱分析法应用到苍蝇卵的甄别上。
And it could be a game changer to forensic science.
二人的研究很有可能就要一举改变法医学今后的游戏规则了。
Before we get to that though, they had to learn about all these species of flies.
不过，在走这一步之前，他们需要先对所有（会在尸体上产卵）的苍蝇种类都有一个了解。
To do that, the researchers put pork liver in traps hidden around Manhattan.
为了做到这一点，两位研究人员在曼哈顿周边用猪肝布置了几个陷阱。
Yes. This is real science.
没错，这就是实打实的科学。
They attracted four species of blowfly, and trapped them before they laid their eggs.
他们一共吸引来了四种苍蝇，随后在它们产卵之前把它们都抓了起来。
They then determined their species and then put them on a fresh liver to seed with their spawn.
确定了那些苍蝇的种类，他们便把那些苍蝇重新放到新鲜的猪肝上等它们产卵。
That way they knew what species were laying eggs where.
这样他们就知道哪种苍蝇会在哪里产卵了。
The researchers then collected the eggs and tested each in a mass spectrometer to get a chemical fingerprint.
随后，研究人员又将那些虫卵收集起来分别对它们做了质谱分析，以便获得它们的化学指纹。
Mass spectrometry is really complicated to explain, but basically:
质谱分析解释起来还挺复杂的，大致的意思就是：
a sample is ionized, the atoms are sorted by mass and charge and it gives you a graph that looks like this.
先对样本进行电离处理，然后按质量和电荷对原子进行排序，排序之后就会得出一个类似这样的图表。
With this we can figure out what atoms something is made of, what they call the chemical fingerprint.
有了这个图表，我们就能摸索出某种东西是由什么原子组成的，也即摸索出它的化学指纹。
And since everything is made of atoms,
鉴于所有物体都是由原子构成的，
we can apply this technology to things like uncovering the amino acids in blowfly eggs!
那我们不就能将这项技术应用于破解苍蝇卵中的氨基酸（序列）等问题了。
Knowing the species then analyzing the eggs gave them the first ever chemically-based way to identify blowfly eggs,
知道了物种属性然后对虫卵进行分析就成了历史上首个基于化学的，识别苍蝇虫卵的办法，
and it only takes minutes to do it!
（更厉害的是）这个过程只需要几分钟就能完成！
Ideally, if this tech works, entomologists can use all the data from the crime scene
理想的情况下，也就是这项技术真的管用的情况下，昆虫学家就能通过犯罪现场的所有数据，
and a quick mass spectrometry check of the fly larvae to find an approximate time of death.
以及对苍蝇幼虫的快速质谱分析确定尸体大概的死亡时间了。
But we can’t use this to catch criminals yet.
不过，目前，我们还没办法用这项技术来抓住罪犯。
Scientists will need to measure the chemical signature of more species,
科学家还需要测量更多物种的化学特征，
and then create a database against which spectra of unknown eggs can be compared.
然后创建一个可以用来与未知虫卵的特点进行对比的数据库，
This promises to advance forensic entomology,
该研究有望推动整个法医昆虫学学科的发展，
and by extension help investigators act quickly when faced with a dead body in a field.
引申开来的话还能帮助调查人员面对田野抛尸案时加快调查节奏。
But let’s say no one found the body in the field until it was picked clean by insects…
不过，假设田野里的尸体在被昆虫吃得干干净净之前一直没被发现，
then forensic examiners have to figure out what happened using just a skull!
这时候，法医就只能通过头骨来摸索出案件的前因后果了！
I talk about that in this episode right here.
这个问题我有在这一期节目中讲。
Did you make it through this video without vomiting?
这期视频你看吐了吗？
I almost didn’t.
我反正是没忍住。
Let us know your thoughts in the comments, subscribe and come back here for more Seeker.
对于本期内容你有什么看法吗？快来评论中告诉我们吧，记得订阅，回来收看更多内容噢。
