user22057: I was wondering whether it is possible/advisable to split questions that are really two distinct questions. 
The 'hard case' here is an older question —Do other animals have different blood types? — which actually asked two questions:

Why have we [i.e. humans] evolved these blood types?
Do other animals have different blood types as well?

The reason I chanced on this page was a more recent question to part of which I had prepared a comprehensive answer — Do other animals have similar blood types to humans?, but which had been marked as a duplicate. Now the answers to the older question focussed on the selective advantage conundrum, with a simple 'yes' and reference to a short and shallow Wikipedia section as the answer to the second part. Fair enough for the older question, but it didn't address the question of whether the animal blood groups were the same as the human ABO system.
This is why I think it would be better to split the older question, elaborating the second part.
Not been involved long enough to know the policy thinking here.

user22057: Well, as nobody else has responded this doesn't seem to be of general concern. The answer would seem to be to jump in to modify (or suggest the poster modifies) a question when it is first posted, rather than trying to sort things out later.
Although I quoted a hard case (as suggested in the guidelines), I have come across other instances. For the hard case I guess I'll just have to add my contribution to the older question.

22057: <p>I was wondering whether it is possible/advisable to split questions that are really two distinct questions. </p>

<p>The 'hard case' here is an older question —<a href="https://biology.stackexchange.com/questions/30262/">Do other animals have different blood types?</a> — which actually asked two questions:</p>

<ul>
<li>Why have we [i.e. humans] evolved these blood types?</li>
<li>Do other animals have different blood types as well?</li>
</ul>

<p>The reason I chanced on this page was a more recent question to part of which I had prepared a comprehensive answer — <a href="https://biology.stackexchange.com/questions/44380">Do other animals have similar blood types to humans?</a>, but which had been marked as a duplicate. Now the answers to the older question focussed on the selective advantage conundrum, with a simple 'yes' and reference to a short and shallow Wikipedia section as the answer to the second part. Fair enough for the older question, but it didn't address the question of whether the animal blood groups were the same as the human ABO system.</p>

<p>This is why I think it would be better to split the older question, elaborating the second part.</p>

<p>Not been involved long enough to know the policy thinking here.</p>
 22057: <p>Well, as nobody else has responded this doesn't seem to be of general concern. The answer would seem to be to jump in to modify (or suggest the poster modifies) a question when it is first posted, rather than trying to sort things out later.</p>

<p>Although I quoted a hard case (as suggested in the guidelines), I have come across other instances. For the hard case I guess I'll just have to add my contribution to the older question.</p>
