[alexpetralia]

Evolution produces random features, which remain as long as you survive and reproduce.

So you may get totally ornamental or vestigial or obsolete features simply because they were never enough hindrance to reproduction. "Enough" is a key word - even features which are hindrances but do not offset pro-survival/pro-reproduction features will remain.

[whatshisface]

One thing I don't understand is how one species can appreciate the ornamental features of another. Human aesthetic criteria may direct the development of human features, but why do our aesthetic criteria positively appraise the features of many animals that we did not influence? One example would be birds, which are very beautiful but aren't even mammals.

[JamilD]

Ornamental features are not obsolete. Many animals are selected for their ornamental features, which may act as heuristics for fitness (both for the opposite sex in reproduction and for the same sex in combat/competitiveness). I know not all of the book is still considered wholly accurate, but Dawkins describes this at length in The Selfish Gene.

[alexpetralia]

True - ornamental was the wrong choice of wording. Ornamental features absolutely aid sexual selection.

[wellactually]

Indeed. It's alarming that such basic scientific literacy is eluding editors at the NY Times.