The important question about what constitutes humanity in the
theological sense, image of God, &c should not be regarded as identical
with the question of who & what will be the ultimate inhabitants of
the Kingdom of Heaven. Romans 8:18-25 and Col.1:20 ("all things") do
not exclude badgers. (Note also Is.11:6-9 - very "figurative",
of course, but a figure of what?) Whatever constitutes genuine
humanity, we are human only in relationship with our the rest of the
world. Thus the promise of "new heavens and a new earth" is not just an
addendum to the hope of resurrection of human beings but is an important
part of that hope.
While the question of what constitutes humanity _is_ important,
putting it in this larger context may be helpful. That is not a
question about what ultimately counts in God's sight and what doesn't.
("Man's compassion is only for his neighbour, but the Lord's compassion
is for every living thing" [Sirach 18:13].)