Is is possible to cheat?

[PvK]

Ya, I think it is (exceptional but) possible. The second colony tech is a clue that he has a tech partnership or at least consumed one or more AI players - not only does taking an AI get you their planets and facilities, but it also gives you +1 level in all their superior visible techs. Or, both - he could've absorbed an AI AND be partnering with someone and sharing techs and coordinating research efforts. Also, you said he was a scientist culture with superior intelligence, so I think that sounds pretty likely. He probably concentrated on religious tech to get the talismans. Best bet may be to get minsweeper tech 2 and try for a fatal stab - he may be weak in production/maintenance/repair/contrstruction and some other areas.

Or, probably wiser than an attempted strike: try to find another human player or two and explain that there is a mega-techno-alliance that needs to be countered!

PvK