A model that had a single common ancestor and allowed for some gene - swapping among species was even better than a simple tree of life.

一个拥有单一共同祖先且允许物种间部分基因彼此交换的模式甚至更优于树形生命模式。

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Any new flu carries the risk of gene-swapping that can form mutant viruses, and this one has some swine and avian genes that, before this April, had never been seen in humans.

任何新流感都有基因转换从而产生变异病毒的危险，而这次的病毒包含有部分猪流感和禽流感的基因，在今年4月之前从未在人身上发现过。

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