We will attempt a synthesis from various research perspectives that have analyzed the alterations that knowledge inevitably goes through while percolating into classroom activities. We will try to identify some of their causes and will illustrate them with examples in genetics. First, we will discuss some research on knowledge transformation when genetics knowledge is popularized (Staerklé and Clémence 2002), to show how knowledge is transformed in specific predictable manners as it moves from experts to general public. Then, we will draw from a large body of (French) research in didactic transposition (Chevallard 1991) in order to highlight what knowledge characteristically thrives or is lost as it percolates into school practice and learner's knowledge. We will then draw from Huberman's ("Science Communicatio," "4"(4), 478-510, 1983) analysis of knowledge use in schools the specificities of knowledge that teachers effectively use. All three perspectives reveal that cognitive and social environment are crucial determinants of what knowledge will be found in schools. An ecological metaphor explains how different cognitive environments from research into education favor knowledge "adapted" to specificities of this ecosystem. This transposition of knowledge is therefore not decay but inescapable and necessary. Ignoring this transposition has considerably reduced the effectiveness of many educational reforms. We will combine these three to propose an evolutionary perspective that could inform ways of expressing research into educational recommendations fed into the system to optimize the didactic transposition process.