23. Why were they transformed into monkeys?

These verses (2:65, 5:60, 7:166) of the Quran convey the message that those who disregarded the order not to go fishing on Saturdays were transformed to monkeys by God. 

This may raise a question within oneself, ‘is going fishing on Saturdays a grave crime’. Please refer to clarification point 146 regarding this. 

Some may even wonder if there is a link existing between the monkeys of yesteryears and the present ones. In this regard we need to bring into mind Prophet Muhammad’s saying ‘Whoever Allah transforms would not bestow upon them the ability to create progeny’

Hadith Book Muslim: 5176, 5177. 

Hence the conclusion that those who were transformed into monkeys are extinct without procreation, and there is no chance of any link with the present-day beings.