你的狗多大了？我是說換算成人生的話

No one knows how it started, or where it came from, but the idea that you can convert your dog's age to human years by multiplying by seven? Total myth. But we like to contextualise our animal companions' ageing against our own lives; if nothing else, it helps us to relate to them.

沒有人知道它是怎么開始的，也不知道它是從哪里來的，但是你可以通過乘以7把狗的年齡換算成人類的年齡?完全是神話。但是，我們喜歡把動物同伴的衰老與我們自己的生活聯(lián)系起來;如果沒有別的東西，它會幫助我們與它們聯(lián)系起來。

Finding an accurate way to do so isn't easy, but a team of researchers has developed a formula. And it's based not on some arbitrary metric, but on changes to DNA over time; they've described it in a paper published on the pre-print resource bioRxiv ahead of peer review.

找到一種精確的方法并不容易，但一組研究人員已經(jīng)開發(fā)出一種公式。它不是基于任意的度量，而是基于DNA隨時間的變化;他們在同行評審之前發(fā)表在pre-print resource bioRxiv上的一篇論文中對此進(jìn)行了描述。

The team's method is based on an epigenetic mechanism called methylation. As both humans and domestic dogs (Canis lupus familiaris) age, methyl groups are added to our DNA molecules, which can change the activity of a DNA segment without altering the DNA itself.

研究小組的方法基于一種稱為甲基化的表觀遺傳機(jī)制。隨著人類和家犬(犬類狼瘡)的衰老，甲基被添加到我們的DNA分子中，它可以改變DNA片段的活性而不改變DNA本身。

This obviously has its own function, but one corollary is that DNA methylation can be used to measure age in humans. This is called the epigenetic clock.

這顯然有它自己的功能，但一個推論是DNA甲基化可以用來測量人類的年齡。這被稱為表觀遺傳鐘。

So, led by geneticists Tina Wang and Trey Ideker of the University of California San Diego, the researchers set out to compare the epigenetic clock of humans to the epigenetic clock of dogs.

因此，由加州大學(xué)圣地亞哥分校的遺傳學(xué)家蒂娜•王和特雷•艾德克領(lǐng)導(dǎo)，研究人員開始將人類的表觀遺傳時鐘與狗的表觀遺傳時鐘進(jìn)行比較。

Dog lifespans can vary wildly: from 6-7 years for some large breeds such as mastiffs to as many as 17-18 years for dogs such as chihuahuas. Despite this variation, all dogs exhibit a similar developmental, physiological, and pathological trajectory.

狗的壽命可以有很大的差異:從一些大型犬種(如獒犬)的6-7歲到吉娃娃犬的17-18歲不等。除了這些變異，所有的狗都表現(xiàn)出相似的發(fā)育、生理和病理軌跡。

A single breed offers strong genome homogeneity, which increases the chance of identifying genetic factors associated with complex traits including ageing, the team said. So they used Labrador retriever dogs for this study.

研究小組稱，單一品種具有很強(qiáng)的基因組同質(zhì)性，這增加了識別與包括衰老在內(nèi)的復(fù)雜性狀相關(guān)的遺傳因素的機(jī)會。所以他們用拉布拉多尋回犬做了這項研究。

They then compared their dog data to the published methylation profiles from the blood of 320 humans, aged between one and 103 years, and those of 133 mice.

然后，他們將狗的數(shù)據(jù)與320名年齡在1歲到103歲之間的人以及133只老鼠的血液甲基化譜進(jìn)行了比較。

"Using targeted sequencing, we characterise the methylomes of 104 Labrador retrievers spanning a 16 year age range, achieving >150X coverage within mammalian syntenic blocks," they wrote in their paper.

他們在論文中寫道：“通過靶向測序，我們對104只拉布拉多獵犬的甲基體進(jìn)行了鑒定，它們的年齡跨度為16歲，在哺乳動物的共濟(jì)區(qū)內(nèi)覆蓋率超過150倍。”。

"Comparison with human methylomes reveals a nonlinear relationship which translates dog to human years, aligns the timing of major physiological milestones between the two species, and extends to mice."

“與人類甲基體的比較揭示了一種非線性關(guān)系，這種關(guān)系將狗的年齡轉(zhuǎn)化為人的年齡，將兩個物種之間的主要生理里程碑的時間安排對齊，并延伸到老鼠身上。”

The similarities were the greatest when comparing young dogs to young humans, and elderly dogs to elderly humans.

當(dāng)比較幼犬和幼犬，老年犬和老年人時，相似性最大。

This matching of the epigenetic clocks allowed the team to derive a formula for calculating the 'human' age of dogs: human_age = 16ln(dog_age) + 31.

這種表觀遺傳時鐘的匹配使得研究小組可以推導(dǎo)出一個計算狗的“人類”年齡的公式:human_age = 16ln(dog_age) + 31。

So, multiply the natural logarithm of your dog's age in years (here's a calculator you can use) by 16, then add 31. That will give you the dog's age in 'human years'.

所以，用你的狗的年齡的自然對數(shù)乘以16(這是一個你可以使用的計算器)，然后加上31。這樣你就能知道狗狗的年齡了。

Using this formula, certain milestones matched up really well. Seven weeks in dogs was found to correspond with nine months in humans - the time when baby teeth are erupting in puppies and infants. The two species' average lifespans also matched up - 12 years for the Labradors, and 70 for humans.

使用這個公式，某些里程碑匹配得非常好。研究發(fā)現(xiàn)，狗的7周相當(dāng)于人類的9個月——幼犬和嬰兒的乳牙長出的時間。這兩個物種的平均壽命也相當(dāng)——拉布拉多犬12歲，人類70歲。

That said, other milestones didn't match up quite so well. Dogs, for instance, go through puberty and reach sexual maturity faster than humans, so the period between adolescence and middle age doesn't match up - a five-year-old Labrador is calculated at around 56 in human years. But dog methylation slows down as they age, so humans can catch up.

也就是說，其他的里程碑并不匹配得那么好。例如，狗經(jīng)歷青春期和性成熟的速度比人類快，所以從青春期到中年這段時間是不匹配的——一只5歲的拉布拉多按人類年齡計算大約是56歲。但是隨著年齡的增長，狗體內(nèi)的甲基化作用會逐漸減緩，所以人類可以迎頭趕上。

And, of course, there's that pesky problem with different breeds ageing differently. So we'll probably never have a one-size-fits-all approach - but a formula based on the epigenetic clock is considerably more useful than simply multiplying by seven.

當(dāng)然，不同品種的狗衰老的方式也不一樣。因此，我們可能永遠(yuǎn)不會有一種放之四海而皆準(zhǔn)的方法，但基于表觀遺傳時鐘的公式要比簡單地乘以7有用得多。

The team's research has been published on bioRxiv.

該團(tuán)隊的研究已經(jīng)發(fā)表在bioRxiv上。