[lemma=we | tag=RB] [word=have] [lemma=□] □
[lemma=we | tag=RB] [word=have] [lemma=perfect] □
[lemma=we | tag=RB] [word=have] [lemma=we] □
" So that here we have perfect or even more than commonly perfect fertility , in a first cross between two distinct species . As long as we do not have perfect and complete knowledge , our scientific models must be considered tentative , and valid only within the current limits of what we know .