在哥斯达黎加的一家动物园里，人们发现了首个美洲鳄单性繁殖的案例。这只雌性美洲鳄产下的胎儿与母亲的基因相似度达 99.9% 。

The egg was laid by an 18-year-old female American crocodile in Parque Reptiliana in January 2018. The foetus inside was fully formed, but stillborn, so didn't hatch. The mother was obtained by the reptile park when she was just two years old and was kept apart from other crocodiles for her entire life.

2018年1月，一只18岁的雌性美洲鳄在哥斯达黎加的爬行动物公园产下了这颗蛋。当时，蛋内的幼鳄胚胎已完全发育成型，但因死产而未孵化。这只鳄鱼母亲在两岁时被哥斯达黎加爬行动物公园收养，一生都在与其它鳄鱼隔离的环境下生活。

Because of this, the park scientific team contacted US researchers from Virginia Polytechnic, which specialises in such virgin births, known scientifically as parthenogenesis. They analysed the foetus and found that it was more than 99.9 percent genetically identical to its mother, confirming that it had no father.

正因如此，爬行动物公园的科学团队联系了美国弗吉尼亚理工学院的研究人员，该团队专门研究这种单性生殖现象，科学术语为 “孤雌生殖”。他们对幼鳄胚胎进行了分析，发现它与其母亲的基因相似度超过99.9%，证实了胚胎没有父亲。

Research team hypothesises that this ability was inherited from a common evolutionary ancestor, suggesting that dinosaurs may also have been capable of reproducing in this way.

研究团队提出了这样一种假说：这种孤雌生殖能力是从鳄鱼和恐龙的一个共同祖先那里遗传下来的，这表明恐龙可能也有以这种方式繁殖的能力。

词汇表

foetus 胎儿，胚胎
stillborn 死产的
virgin birth 单性生殖
parthenogenesis 孤雌生殖，单性生殖
genetically （基因）遗传上地
hypothesises 假设
inherited 遗传下来的
ancestor 祖先

阅读理解：请在读完上文后，回答下列问题。

1. Why didn't the crocodile egg hatch?

2. Why did scientists believe the crocodile foetus had no father?

3. Which other creatures could have reproduced by themselves?

4. Where does the research team think this ability to self-reproduce was inherited from?

答案

1. Why didn't the crocodile egg hatch?

The foetus inside the egg was fully formed, but stillborn.

2. Why did scientists believe the crocodile foetus had no father?

Scientists found that the foetus was more than 99.9 percent genetically identical to its mother, confirming that it had no father.

3. Which other creatures could have reproduced by themselves?

It's possible dinosaurs may also have been capable of reproducing in this way.

4. Where does the research team think this ability to self-reproduce was inherited from?

Research team hypothesises that this ability was inherited from a common evolutionary ancestor.