Here's an older thread about losing research. I know I read one before that discussed having "Research Maintenance", but I can't seem to find it in the search.
Basically, for every tech you have, you must spend 5% of it's original cost to maintain it, and the remaining points can go to new techs.
Would be interesting, since you would have to always have professors teaching the younger ones in between experiments in "high energy discharge", and races would have to decide which techs are worth the most.
Maintenance could be reduced by having a large population, too... say one RP per 10M people is assigned to reducing maintenance.
Follow the link at the top... there's a good example in there of how you could lose a tech level.