user4108: Let's consider this post as a study case. I think, the question is fully answered on the wikipedia page linked in the comments.
A one-link-only answer is usually not accepted and I don't feel like rephrasing everything that is said on the wikipedia page. So how can we deal with this question? We cannot close a post because the answer exists somewhere else. We cannot close a post as a duplicate of a wiki page. Should it be closed as too broad? Should someone write a one-link-only answer? Should we leave this post unanswered?

user791: My $0.02: If it's a good question, but you don't have time (or the desire) to answer it fully, just toss it an upvote and leave it alone. Maybe leave a comment with the wiki link (as you did) so the next person who comes along who does have the time to kill, and maybe a hankering for reputation points, has a jumping-off point to start from. 
In my opinion the fact that the answer is easy to find on Wikipedia does not make the question worth closing. If the question should be closed based on its own merits - if it is, in fact, hard to tell what the asker is looking for - then naturally it should be closed. But the question shouldn't be judged on the quality of its answers (or lack thereof). 

user3340: Though we keep using the term "Available on Wikipedia" for trivial, it has to be noted that wikipedia has grown a lot and some articles are every elaborate and detailed. Some journal (Landes Bioscience if I am not wrong) puts the information of your paper in a wikipedia article. Many active researches update wikipedia pages related to their topics. 
Which means just because a topic has a wikipedia page does not mean it is trivial.
I think it is for the experienced users to judge if a question is trivial or not. If it is not trivial and has a wiki article it is best to get the actual references (doi indexed) from wikipedia and cite them. 
So I think link only answer is okay if the article cited is doi indexed and the article is the exact answer of the question. 

4108: <p>Let's consider <a href="https://biology.stackexchange.com/questions/17261/is-there-an-evolutionary-explanation-for-depression">this post</a> as a study case. I think, the question is fully answered on the wikipedia page linked in the comments.</p>

<p>A one-link-only answer is usually not accepted and I don't feel like rephrasing everything that is said on the wikipedia page. So how can we deal with this question? We cannot close a post because the answer exists somewhere else. We cannot close a post as a duplicate of a wiki page. Should it be closed as too broad? Should someone write a one-link-only answer? Should we leave this post unanswered?</p>
 791: <p>My $0.02: If it's a good question, but you don't have time (or the desire) to answer it fully, just toss it an upvote and leave it alone. Maybe leave a comment with the wiki link (as you did) so the next person who comes along who does have the time to kill, and maybe a hankering for reputation points, has a jumping-off point to start from. </p>

<p>In my opinion the fact that the answer is easy to find on Wikipedia does not make the question worth closing. If the question should be closed based on its own merits - if it is, in fact, hard to tell what the asker is looking for - then naturally it should be closed. But the question shouldn't be judged on the quality of its answers (or lack thereof). </p>
 3340: <p>Though we keep using the term <strong>"Available on Wikipedia"</strong> for <strong>trivial</strong>, it has to be noted that wikipedia has grown a lot and some articles are every elaborate and detailed. Some journal (<a href="http://www.tandfonline.com/action/authorSubmission?journalCode=krnb20&amp;page=instructions#.VLD4TB0vBX8" rel="nofollow">Landes Bioscience</a> if I am not wrong) puts the information of your paper in a wikipedia article. Many active researches update wikipedia pages related to their topics. </p>

<p>Which means just because a topic has a wikipedia page does not mean it is trivial.</p>

<p>I think it is for the experienced users to judge if a question is trivial or not. If it is not trivial and has a wiki article it is best to get the actual references (doi indexed) from wikipedia and cite them. </p>

<p>So I think link only answer is okay if the article cited is doi indexed and the article is the exact answer of the question. </p>
