With low temperatures and a lack of food， winter is a harsh season for animals. Many animals enter hibernation to get through it.

Hibernation is when an animal goes into a state of extended inactivity. During hibernation， animals hide away from predators. Their metabolism will slow to less than a quarter of its normal rate. This cools the creature's body and slows its heartbeat to just a few times per minute， for up to months at a time.

But why don't humans hibernate？ Human hibernation doesn't exist for many reasons. Our body is not designed for hibernation. Our evolutionary ancestors were tropical animals with no history of hibernating： Humans have only migrated into temperate and subarctic latitudes in the last hundred thousand years or so. That's not quite long enough to evolve all the metabolic adaptations we would need to be able to hibernate， according to the BBC Science Focus Magazine.

冬天溫度較低、食物短缺，對(duì)于動(dòng)物來(lái)說(shuō)是一個(gè)嚴(yán)酷的季節(jié)。許多動(dòng)物靠冬眠來(lái)過(guò)冬。

冬眠指動(dòng)物進(jìn)入長(zhǎng)時(shí)間的生命活動(dòng)極低的狀態(tài)。冬眠時(shí)，動(dòng)物會(huì)避開(kāi)捕食者，將新陳代謝的速度減慢至正常速度的四分之一以下。這會(huì)讓動(dòng)物的體溫降低，心跳減慢至每分鐘幾次，而這種狀態(tài)每次會(huì)持續(xù)數(shù)月。

但是人類為什么不冬眠呢？人類不冬眠有很多原因。人類的身體不適合冬眠。我們進(jìn)化學(xué)上的祖先是沒(méi)有冬眠歷史的熱帶動(dòng)物：人類在過(guò)去大約10萬(wàn)年里，才遷移到溫帶和靠近北極地區(qū)。根據(jù)英國(guó)廣播公司的《科學(xué)焦點(diǎn)》雜志所刊載的文章，這段時(shí)間還不夠長(zhǎng)，人類無(wú)法進(jìn)化出冬眠所需的所有代謝適應(yīng)能力。

For example， waste management is a hugechallenge for human hibernation . Animals thathibernate are able to essentially stop their urinationand defecation during hibernation， sometimes througha process of reabsorption to preserve nutrients .Unfortunately， humans can't do this.

There are other challenges. Body temperaturesbelow 2.8℃ tend to disrupt the human digestive tractand may cause pain . Cold temperatures can alsosuppress the immune system， making people morevulner a ble? to? infections，? according? to? USSmithsonian Magazine.

In fact， humans don't need to sleep throughwinter. We have discovered fire， clothes， shelter，hunting and agriculture， all of which are much moreeffective ways of surviving the cold.

Could humans hibernate in the future？ For long-distance space travel， it's likely. A journey to Marswould take around months using current technology.If we hope to visit another star system， even if we could travel at the speed of light， the journey would take years. Being able to hibernate would make such distances considerably less boring for the astronauts and conserve vital resources， according to University of Oxford in the UK.

NASA is treating this question seriously. Beginning in 2014， the agency funded research on long- term hibernation as a way to facilitate long-term space travel， according to The Atlantic.

例如，處理代謝廢物就是人類冬眠面臨的巨大挑戰(zhàn)。冬眠的動(dòng)物基本上能夠在冬眠期間停止排尿、排便，有時(shí)它們還會(huì)重新吸收廢物來(lái)保存營(yíng)養(yǎng)。不幸的是，人類做不到這一點(diǎn)。

人類冬眠還面臨其他挑戰(zhàn)。人體溫度如果低于2.8℃，往往會(huì)損害人的消化道，而且可能引發(fā)疼痛。根據(jù)美國(guó)《史密森尼雜志》所刊載的文章，低溫還會(huì)降低免疫系統(tǒng)的活躍性，使得人們更容易受到感染。

實(shí)際上，人類不需要靠睡覺(jué)過(guò)冬。我們發(fā)現(xiàn)通過(guò)生火、穿衣、躲進(jìn)房屋中能夠避寒，依靠狩獵和農(nóng)耕可以果腹，所有這些手段幫助人類更有效地度過(guò)嚴(yán)寒。

未來(lái)人類會(huì)冬眠嗎？如果踏上長(zhǎng)途太空旅行，人類很可能會(huì)冬眠。憑借目前的技術(shù)，人類去往火星需要幾個(gè)月的時(shí)間。如果我們希望去到另一個(gè)星系，即使能以光速旅行，這段旅程也需要數(shù)年。英國(guó)牛津大學(xué)的研究表明，如果能夠使宇航員進(jìn)入冬眠，將大幅減少其在漫長(zhǎng)航程中的無(wú)聊感，并能節(jié)約重要的資源。

美國(guó)航空航天局（NASA）正在認(rèn)真對(duì)待人類冬眠的問(wèn)題。根據(jù)《大西洋月刊》所刊載的文章， NASA從2014年起資助了一項(xiàng)有關(guān)人類長(zhǎng)期冬眠的研究，希望以這種方式推動(dòng)長(zhǎng)期太空旅行發(fā)展。

Word Study

predator /'pred?t?（r）/ n.捕食者

temperate /'temp?r?t/ adj.氣候溫和的

The Nile Valley keeps a temperate climate throughout the year.

subarctic /s?b'ɑ?kt?k/ adj.亞北極的；靠近北極的

suppress /s?'pres/ v.壓制；抑制

vulnerable /'v?ln?r?bl/ adj.脆弱的；易受傷害的

In? cases? of food? poisoning， young? children? are especially vulnerable.

In the quest for better sleep， people often ask if they should share their bed with a pet. Before we get to that， let's take a moment to ponder the flip side： Is sleeping with you good for your pet？

In general， it is a very good thing for animals to sleep with their people， said Dr Dana Varble， the chief veterinary officer for the North American Veterinary Community

Pets who share their human's bed tend to have a higher trust level and a tighter bond with the humans that are in their lives. It's a big display of trust on their part， Varble said

Dogs and cats who are more closely bonded with their humans get additional health benefits， including increases in beneficial neurotransmitters such as oxytocin and dopamine， the feel-good hormones ，”she added .

With that important matter out of the way， let's turn to you-is it good for you to sleep with a pet？

Animals may move， bark and disrupt sleep. Sleep in dogs and cats is not continuous and they will inevitably get up and walk on the bed， stepping on people. All of that activity will lead to sleep fragmentation， said Dr vsevolodPolotsky director of sleep research and a professor in the department of medicine at Johns Hopkins University School of Medicine in theUS.

很多人都有這個(gè)疑問(wèn)：和寵物同床睡覺(jué)是否有助于睡眠？在回答這個(gè)問(wèn)題之前，我們先來(lái)看看問(wèn)題的另一面：寵物和你睡在一起，是否有利于寵物的健康？

北美獸醫(yī)社區(qū)的首席獸醫(yī)官戴娜·瓦布爾醫(yī)生說(shuō)：“總體來(lái)說(shuō)，寵物和主人一起睡覺(jué)對(duì)寵物來(lái)說(shuō)是很好的。

瓦布爾說(shuō)，和人同床而眠的寵物通?！皩?duì)主人更信任更親密。這是寵物非常信任人類的表現(xiàn)”。

她補(bǔ)充道：“與主人更親近的狗和貓還能得到額外的益處，包括會(huì)分泌更多催產(chǎn)素和多巴胺等神經(jīng)傳導(dǎo)物質(zhì)，也就是我們所說(shuō)的快樂(lè)激素。

在弄清楚這個(gè)重要問(wèn)題之后，現(xiàn)在來(lái)關(guān)注一下寵物主人：和寵物一起睡對(duì)你好不好？

美國(guó)約翰斯·霍普金斯大學(xué)醫(yī)學(xué)院醫(yī)學(xué)系教授弗謝沃洛德·波羅特斯基博士說(shuō)：“動(dòng)物會(huì)動(dòng)來(lái)動(dòng)去，大聲叫喚，而這會(huì)干擾睡眠。狗和貓的睡眠是間斷性的，睡一會(huì)兒就必然會(huì)起來(lái)走動(dòng)，并踩到主人。這些活動(dòng)都會(huì)導(dǎo)致主人的睡眠片段化。

Word Study

flip side 另一面；反面

inevitably /in'evitabli /adv.不可避免地

snuggly /'snagli /ad.溫暖舒適的

cuddly /'sAdli /ad.令人想擁抱的

He is a small， cuddly man with glasses.

insomnia /n'smni/n.失眠（癥）