If science proves facts that conflict with Buddhist understanding, Buddhism must change accordingly. We should always adopt a view that accords with the facts.
To define Buddhism without a lot of words and phrases, we can simply say, 'Don't cling or hold on to anything. Harmonize with actuality, with things as they are.'
Buddha taught kindness towards lower beings; and since then there has not been a sect in India that has not taught charity to all beings, even to animals. This kindness, this mercy, this charity - greater than any doctrine - are what Buddhism left to us.