I am not an expert but I will attempt to answer your question. Firstly the concept of someone being accountable at puberty is not unique to Islam but is prevalent in most religions of the world including Christianity and Judaism. Please refer to the following link http://en.wikipedia.org/wiki/Coming_of_age
Now coming to the fact about Islam not being relevant because of recent findings of Science, you yourself have quoted that the human mind is not "fully" developed till age of 25. But does that mean that no one will be accountable for his actions till then. So for eg if a 24 yr old man commits rape, robbery, we should pardon him because of this scientific theory.
And finally, please find the following article which attempts to explain how Islam and Science are non-contradictory