When it comes to choosing a mate, opposites really do attract, according to a Brazilian study that found people are subconsciously² more likely to choose a partner whose genetic³ make-up is different to their own.

They found evidence that married couples are more likely to have genetic differences in a DNA⁴ region governing the immune system than were randomly⁵ matched pairs.

This was likely to be an evolutionary⁶ strategy to ensure healthy reproduction because genetic variability is an advantage for offspring, Maria da Graca Bicalho and her colleagues at the University of Parana in Brazil reported.

"Although it may be tempting⁷ to think that humans choose their partners because of their similarities, our research has shown clearly that it is differences that make for successful reproduction, and that the subconscious¹ drive to have healthy children is important when choosing a mate," Bicalho said in a statement.

Scientists said it was not clear what signals attract the body to people who are genetically⁸ dissimilar to themselves, but suggested body odor or even face structure could play a role.

Bicalho said the team compared genetic data from 90 married couples with data from 152 randomly generated control couples.

They found the real couples had significantly more dissimilarities in MHC.

"Parents with dissimilar (genetic regions) could provide their offspring with a better chance to ward⁹ infections off because their immune system genes¹⁰ are more diverse," they wrote in a summary.

Previous studies have suggested animals may use body odor as a guide to identify possible mates as being genetically similar or dissimilar, she added, but other physical factors may also be involved.

"Other cues such as face symmetry might play a role as well, but they are still in the field of speculation," she said.

人们在选择伴侣时，更容易被与自己基因差异大的人吸引。巴西一项最新研究表明，人们总是下意识地选择基因构成和自己相异的人做伴侣。

研究结果表明，与随机配对的搭档相比，夫妻二人控制免疫系统的DNA区域中基因差异更大。

巴西巴拉那大学的玛丽亚达·格拉萨·比卡卢和同事在研究报告中指出，这可能是人类确保生育健康的进化策略，因为基因的差异性对后代有利。

比卡卢在声明中称：“虽然大家更愿意相信人们会选择相似的人做伴侣，但我们的研究明确显示，存在差异的伴侣更能成功生育后代，而在选择伴侣时，这种潜在的生育健康后代的意识很重要。”

科学家称不清楚是何种身体讯息使人们吸引到基因相异的人，但表示体味甚至脸型都可能有关。

比卡卢称，研究小组将90对夫妻的基因与152对随机配对的“夫妻”的基因进行了对比。

研究人员发现，真夫妻的主要组织相容性复合体差异更显著。

研究人员在一份总结中写道：“基因相异的夫妻所生育的后代更不容易生病，因为他们的免疫系统更加多样化。”

比卡卢补充称，此前研究已证实，动物用体味来识别潜在伴侣的基因与自己的异同，但其它身体特征可能也起作用。

她说：“其它因素，比如脸型是否对称都可能与之相关，但还没有得到证实。”

Vocabulary:

ward off: 避开，挡住