1.Only you: Human lips are different from those of all other animals because they are everted, meaning that they purse outward.
1.人類的嘴唇是外翻的，這一點(diǎn)和所有其他動(dòng)物都不一樣。

2.But we are not the only species to engage in kissing-like behaviors. Great apes press their lips together to express excitement, affection, or reconciliation.
2.但人類并不是唯一一個(gè)會(huì)做出“接吻”行為的物種。類人猿（包括大猩猩、黑猩猩、長臂猿等）在表達(dá)興奮、喜愛或和解的時(shí)候也會(huì)將彼此的嘴唇貼在一起。

3.Scientists are not sure why humans kiss, but some think the answer lies in early feeding experiences. Through nursing and (in some cultures) receiving pre-chewed food from a parent's mouth, infants may learn to associate lip pressure with a loving act.
3.科學(xué)家們并不確切知道人類為什么要接吻，但一些人認(rèn)為接吻行為和早期哺乳經(jīng)歷有關(guān)。通過哺乳——在一些文化中母親還會(huì)將嚼碎的食物嘴對嘴喂給嬰兒——嬰兒可能學(xué)會(huì)了將嘴唇接觸和表達(dá)愛意聯(lián)系起來。

4.Another possibility: Smelling a loved one's cheek has long served as a means of recognition in cultures around the world, from New Zealand to Alaska. Over time, a brush of the lips may have become a traditional accompaniment.
4.另一種可能是：在世界各地——從新西蘭到阿拉斯加——嗅聞所愛之人的臉頰一直都是表達(dá)認(rèn)可的一種方式，久而久之，可能就伴隨著發(fā)展出了碰觸嘴唇這樣一種傳統(tǒng)禮儀。

5.And yet kissing is not universal, leading some experts to think it might actually be a learned behavior.
5.但接吻行為也并不是全球通行的，因此有一些專家認(rèn)為它可能是一種后天習(xí)得的行為。

6.The Roman military introduced kissing to many non-kissing cultures; later it was European explorers who carried the torch.
6.古羅馬軍隊(duì)將接吻行為帶到了許多沒有這種傳統(tǒng)的文化中；后來歐洲的探險(xiǎn)家們又將它帶到了新大陸。

7.Being close enough to kiss helps our noses assess compatibility. In a landmark study, biologists reported that women prefer the scents of men whose immunity-coding genes are different from their own. Mixing genes that way may produce offspring with a stronger immune system.
7.在近到足夠接吻的距離下，我們的鼻子能夠判斷對方是否適合相處。在一項(xiàng)里程碑式的研究中，生物學(xué)家們發(fā)現(xiàn)女人能夠靠氣味識(shí)別出那些免疫系統(tǒng)編碼基因與自己不同的男人，從而影響她們對伴侶的選擇，因?yàn)榛旌系幕蚩梢宰尯蟠鷵碛懈鼜?qiáng)的免疫系統(tǒng)。

8.Love Is the Drug: Dopamine, a neurotransmitter associated with feelings of desire and reward, spikes in response to novel experiences, which explains why a kiss with someone new can feel so special.
8.多巴胺是一種神經(jīng)遞質(zhì)，負(fù)責(zé)傳遞欲望和興奮等感覺，在經(jīng)歷新事物的時(shí)候活動(dòng)最為強(qiáng)烈。這就可以解釋為什么跟某個(gè)新認(rèn)識(shí)的人接吻感覺如此不同。

9.In some people, a jolt of dopamine can cause a loss of appetite and an inability to sleep, symptoms commonly associated with falling in love.
9.對某些人來說，少量多巴胺就會(huì)引起食欲下降和失眠，而這些癥狀通常被當(dāng)做墜入愛河的征兆。

10.Holding hands and kissing reduces levels of the stress hormone cortisol, thereby lowering blood pressure and optimizing immune response.
10.牽手和接吻可以降低“壓力荷爾蒙”皮質(zhì)醇的水平，因此可以降低血壓和提高免疫反應(yīng)。

11.And a passionate kiss has the same effect as belladonna in making our pupils dilate.
11.一個(gè)深情的吻可以和顛茄（一種有毒植物）一樣讓人的瞳孔擴(kuò)大。

12.Prelude to a Kiss: Two-thirds of all people turn their head to the right when kissing. This behavior may mirror the head-turning preference observed in babies and even in fetuses.
12.三分之二的人在接吻時(shí)會(huì)將頭轉(zhuǎn)向右邊。這和嬰兒甚至胎兒在轉(zhuǎn)頭時(shí)的偏好是一致的。

13.Evolutionary psychologists have discovered that men are far more likely to prefer sloppy tongue kisses than women.
13.進(jìn)化論心理學(xué)家發(fā)現(xiàn)，男人比女人更喜歡濕乎乎的舌吻。

14.Always brush and floss, boys. Evolutionary psychologists found that when deciding whether to kiss someone, women pay much closer attention than men do to the breath and teeth of their partner.
14.進(jìn)化論心理學(xué)家還發(fā)現(xiàn)，在決定是否要同一個(gè)人接吻時(shí)，女人會(huì)比男人更加注意對方的呼吸和牙齒。所以小伙子們，記得好好刷牙。

15.You Give Love a Bad Name: One milliliter of saliva contains about 100,000,000 bacteria.
15.但是無論如何，一毫升唾液中還是有大約10億個(gè)細(xì)菌。

聲明：雙語文章中，中文翻譯僅代表譯者個(gè)人觀點(diǎn)，僅供參考。如有不妥之處，歡迎指正。