Don't capitalise the word human, unless it's at the beginning of a sentence, or in the species variable of an infobox.
Our research has shown that the vast majority of instances of the word human in Doctor Who prose fiction aren't capitalised. We recognise that other sapient species are almost always capitalised, and that there are very occasional capitalisations of human in Doctor Who prose, as in some parts of Doctor Who and the Ark in Space. However, human isn't typically capitalised in any major range of Doctor Who print fiction, so we don't capitalise it here.