女生在一起久了 大姨媽真的會同步？

It's a belief touted in chick flicks and in university dorm rooms. But the idea that women's menstrual cycles become synchronised when they spend time together is a myth, one expert has claimed.
“女生在一起待久了，經期會同步”這個看法經常出現在年輕女性電影中和大學宿舍裏。但有專家說這個看法是錯誤的。

Dr Alexandra Alvergne, associate professor in biocultural anthropology at the University of Oxford, says this theory is flawed, and women's periods overlapping is more likely down to chance than an evolutionary adaptation.
牛津大學生物文化人類學副教授亞歷山德拉•埃爾沃格尼博士說這個理論是錯誤的，並且女性經期重疊現象更可能只是巧合而非進化過程中的適應性變化。

It is a popular belief that women who live together synchronise their menstrual cycles, and that it's mediated by their pheromones.
大多數人認爲住在一起的女性經期會同步，並且這是由她們的信息素調節的。

These are the airborne molecules that enable members of the same species to communicate non-verbally.
信息素是由空氣傳播的分子，使得相同物種能夠進行非言語交流。

The idea originated in a study published in the journal Nature in 1971, which looked at 135 American college students living in a dormitory and recorded data on when their periods began.
這種想法來自《自然》雜誌在1971年發佈的一項研究。研究觀察了住在宿舍的135名美國大學生，並且記錄了她們經期開始的時間。

The dorm had four corridors each with around 25 girls living in single and double rooms.
宿舍有四條走廊，各有約25名女生分別住在單人或雙人宿舍。

Based on the analysis of around eight menstrual cycles per woman, the study reported an increase in synchronisation - that is, a decrease in the difference between the date their period began for room mates and among closest friends.
研究分析了每個女生的大約八個月經週期，隨之發現同步率的升高。也就是說他們發現室友之間或者好朋友之間月經開始時間的差異越來越小。

But among random pairings in the dormitory, there was no decrease.
但是在那些隨意配對的宿舍裏，沒有發現差異的減少。

The author hypothesised so-called synchronisation was driven by the amount of time that women spent together, as this would allow for pheromone communication.
於是作者就假設這所謂的同步與女性相處時間的長短有關。時間越長，越有利於信息素的傳遞。

Since then, so-called 'socially mediated synchrony' has been intensely studied in various groups of women, such as room mates, co-workers, lesbian couples and women from high fertility populations – and in a number of animal species, including rats, baboons and chimpanzees.
自此，所謂的“社交性調節同步性”又在許多女性羣體中得以深入研究，如室友，同事，同性情侶以及高生育率地區的女性。人們還在一些動物中對此進行研究，比如老鼠，狒狒和黑猩猩。

The theory goes that synchronisation leads to females becoming sexually receptive - which is known as being 'on heat' in the animal kingdom - at the same time.
理論認爲同步性使得女性在同一時間易於交配，在動物世界裏，這也叫做“處於發情期”。

The most popular one is that it enables females to minimise the risk of being monopolised by a single dominant male, and thus make it easier for them to have more than one mate.
其中最普遍的理論是經期同步使得女性把她們被一個占主導地位的男性完全控制的危險降到了最低，因此她們更容易擁有一個以上的伴侶。

In fact, one analysis of 19 primate species found a dominant male had less control over reproduction if all females were receptive at the same time.
實際上，一項對十九種靈長類生物的分析顯示：如果所有的雌性都在同一時間處於發情期，唯一的佔主導的雄性對於繁殖的控制力會減弱。

However, there is now accumulating evidence that casts serious doubt on the existence of the phenomenon.
然而，越來越多的證據對此現象的存在提出了深深的懷疑。

First, the original 1971 study was criticised on methodological grounds.
首先，有人批評了1971年原始研究的方法依據。

Second, a number of studies with both human groups and non-human species failed to replicate the initial findings, with at least as many studies reporting positive results as studies reporting negative ones.
其次，一系列的研究，無論是在人類羣體還是非人類物種，都沒能復證當初的結果。得到肯定結果的研究數量和得到否定結果的數量一樣多。

Mathematical analyses have also revealed that some degree of synchrony is to be expected given shifts in female reproductive system over time.
數學分析也顯示，考慮到女性月經週期一直在不停變化，某些程度的同步性是完全有可能的。

No adaptive process needs to be invoked to explain what is observed.
不需要任何的適應性過程來解釋觀察到的現象。

In other words, synchrony - or the overlap of cycles between females - is best explained by chance.
也就是說，解釋同步性，或者女性之間經期的重疊最好的理由就是偶然性。

There is now overwhelming evidence to suggest that menstrual synchrony in humans is no more than a quirk derived from a study using flawed methods that has since turned into an urban myth.
現在越來越多的證據表明，經期同步只是因爲當初研究方法錯誤，隨後成爲了一個謠傳，實際上它只是一個偶發的事件。

Vocabulary

chick flick：針對女性的浪漫電影
menstrual cycle：月經週期
quirk：巧合