The externally-derived sources of variation/novelty in the case of DNA (cosmic rays and failures in copying due to chemistry) are blind: they do not interact (epistemically) with the knowledge of the system.

The externally-derived sources of variation/novelty in the case of DNA (cosmic rays and failures in copying due to chemistry) are blind: they do not interact (epistemically) with the knowledge of the system. That is, their changes are independent of the knowledge in the system. This is what makes these sources epistemically separate.