原文已被隐藏，你可用 快捷键 - 或点击 显示原文 按钮来查看原文
第1段
1 .This is Scientific American 60-Second Science. I'm Karen Hopkin.
该句暂无译文！
2 .Why did the chicken cross the road?
该句暂无译文！
3 .Well, that's a philosophical pickle.
该句暂无译文！
4 .But if you want to know why chickens don't get cross at people-why they're content being kept in their coops-science can help.
该句暂无译文！
5 ."Domestic species are interesting because their genetic makeup has changed dramatically as part of the process of going from wild to domestic."
该句暂无译文！
6 .Liisa Loog, an evolutionary geneticist and anthropologist at the Universities of Oxford and Cambridge.
该句暂无译文！
7 ."And indeed when people have compared modern domestic animals with their wild relatives they've identified genes that do show signs of strong recent selection.
该句暂无译文！
8 .One such gene is thyroid stimulating hormone receptor, otherwise known as TSHR...
该句暂无译文！
9 .in chickens, a variant of this gene that is widespread in modern populations has been shown to directly cause chickens to be less fearful of humans and also result in reduced aggression towards conspecifics."
该句暂无译文！
10 .But when exactly did the selection for these traits-and therefore this variant-take place?
该句暂无译文！
11 ."It's been suggested because of the potential usefulness of these traits in domestic setting that selection on this gene must have happened when chickens were first domesticated around 6,000 years ago in East Asia.
该句暂无译文！
12 .But in an evolutionary timescale this is just a blink of an eye and we just don't know and don't have the resolution to tell when exactly between 6,000 years ago and now this selection happened, using data from only modern chicken populations...
该句暂无译文！
13 .but with DNA from archaeological material we can follow what happened with a gene through time and in theory spot when changes in a population occur."
该句暂无译文！
14 .Loog and her colleagues examined TSHR gene sequences in the ancient remains of about 60 chickens found in Europe" and estimated that selection at this TSHR locus happened only around 1,000 years ago, at medieval times.
该句暂无译文！
15 .That is, 5,000 years after the initial domestication of chicken.
该句暂无译文！
16 ."Interestingly this time period coincides with a...substantial increase in chicken consumption known from the archaeological record.
该句暂无译文！
17 .Historians suggest that a key driver behind these changes was the rising popularity and spread of Christian traditions, which discouraged and also on occasions even banned eating meat from four-legged animals."
该句暂无译文！
18 .But fowl were fair game.
该句暂无译文！
19 ."What is really exciting about this new study is that for the first time we can directly link genetic changes in domestic animal with cultural shifts in human food preference.
该句暂无译文！
20 .The findings appear in the journal Molecular Biology and Evolution.
该句暂无译文！
21 .This kind of plucky study is not just for the birds.
该句暂无译文！
22 .Loog says the team is collecting canine archaeological samples, so they can look at how man's best friend got divvied up into so many different breeds.
该句暂无译文！
23 .Their research will no doubt be dogged.
该句暂无译文！
24 .Thanks for listening, for Scientific American 60-Second Science. I'm Karen Hopkin.
该句暂无译文！