But even if life on earth turned out to have a nonevolutionary origin ( for instance , if aliens introduced the first cells billions of years ago ) , evolution since then would be robustly confirmed by countless microevolutionary and macroevolutionary studies 但是，即使地球上的生命有个与演化无关的起源（例如，最早的细胞是几十亿年前外星人送到地球上来的） ，对于生命出现以后的历史，演化依旧会是铁案如山的解释，有无数微演化与巨演化研究产生的证据支持。
