哺乳动物为啥变成了“哺乳”动物？

Whole-channel inclusion: 芳斯塔芙 is an honest teaching channel (title sample + 3 transcripts read: All three samples lack transcripts, but titles and descriptions indicate structured evolutionary biology explainers consistent with the channel's established teaching format.); this title passed a strict title check (sonnet) after a labelling pass.