I'm not sure I understand you perfectly. A phylogenetic tree (which is essentially a family tree, but for multiple species or even all of life) can certainly b

I'm not sure I understand you perfectly. A phylogenetic tree (which is essentially a family tree, but for multiple species or even all of life) can certainly be constructed on the basis of DNA alone. But I guess you mean it won't tell us (for example) what our ancestor 100 million years ago looked like, which is true enough.