These were the therians, like Juramaia, a toothy, shrew-like mammal known from China.

这些是兽类动物，例如 Juramaia，一种长满牙齿、长得像鼩鼱的哺乳动物，在中国广为人知。

What's interesting about syncytins is that they didn't evolve in mammals; they've been part of our genomes since before therians were even a thing.

合胞素的有趣之处在于它们不是在哺乳动物中进化而来的；在兽人出现之前， 它们就已经是我们基因组的一部分了。

Another idea is that therians followed a path similar to the monotremes, where eggs were retained in the mother's body for longer and longer periods of time.

另一个想法是， therians 遵循类似于单孔类动物的路径，卵子在母亲体内的保留时间越来越长。