I think almost all of them are on deep branches of life that we don't know anything about.

我认为几乎所有的人都处于我们不了解的生命的深层分支。

The Danish researchers determined that the mastodons in Greenland two million years ago belonged to a deep branch of the mastodon family tree, one that was previously unknown.

丹麦研究人员确定，200万年前格陵兰岛的乳齿象属于乳齿象家族树的一个深分支，这在以前是未知的。