One can speculate as to why no multienzyme com­plexes have evolved to immediately convert toxic inter­mediates into polar, nontoxic metabolites. In any case, it is an almost unsolvable problem because the properties of the metabolites would have to be predicted for each xenobiotic. Amodication that leads to improved water solubility in one compound can cause amutagenic effect in another. For their own protection, humans have, in fact, mechanisms for trapping reactive metabolites. Here glutathione and glutathione transferase must be men­tioned because they detoxify electrophiles particularly well (Sect.27.7). Perhaps toxic or carcinogenic effects were not aparticularly decisive theme for evolution un­til now. Tumors play asecondary role for most animals because of their short lifespan. Up until just afew gener­ations ago, war and infectious diseases were the primary causes of death in humans. It has only been in recent times that the average life expectancy has increased. In the sense of evolution, aging individuals play only asec­ondary role. Once reproduction is complete, the parents are only necessary for the care of their young until early adulthood. One only needs to think of female spiders that consider their mates to be nothing more than their next prey immediately after copulation!