According to Dobbs, what purpose do the changes in the teenage brain serve? Why are they "adaptive" (useful for humans as a species) ?

Rewiring, sort of an ¨upgrade¨ or maturing.

They are adaptive to prepare for their next phase of evolution, the consideration of leaving home.

Explanation:

According to the researcher David Dobbs, the purpose of the massive changes that are undergone by teenage brains is with the purpose of maturing the brain within itself to face possible upcoming changes.

The process of being ¨adaptive¨ is called as such due to the fact that during this period of time, the teenage brain undergoes a ¨rewiring¨ in order to prepare for a time when the individual must face changes such as leaving the comfort zone of home and face more daring challenges like coping with daily decisions and tasks outside in the world, as well as socializing with others.