In verse 78, it was said: ضَرَ‌بَ لَنَا مَثَلًا (And he has set up an argument about Us). Here, the expression refers to the event described above, that is, while smashing and rubbing the bone into bone meal, its revival was considered improbable. After that, it was said: وَنَسِيَ خَلْقَهُ (and forgot his own creation). It means while he was giving that example, he forgot the example of his own creation as to how he himself was created by infusing life in a lowly, impure and lifeless drop - a bland anatomy of his creation indeed. Had he not forgotten his real genetic origin, he would have never come up with such examples and would have never dared saying no to Divine power.