Organisms need a way to pass on their learning through time if progress is to be made and so must search for a world 1 representation of world 3 knowledge to serve this purpose. I suggest that DNA is the representation of world 3 knowledge for cells, while the brain is such a repository for organisms with central nervous systems. In mankind we see, for the first time due to the phenomenon of language, knowledge represented outside of the organism, while it is still within the evolving organic social system. This idea means that we have multiple world 1 representations of world 3 within us (e.g., within the immune system), and that many of them may so far be undiscovered.
This generalization of Popper's thinking is in line with his ideas of evolutionary knowledge and removes its anthropocentric bias. It would appear that Popper was moving radically in that direction when he wrote, in "Towards an Evolutionary Theory of Knowledge" (1990, p 35)
Can only animals know? Why not plants? Obviously, in the biological and evolutionary sense in which I speak of knowledge, not only animals and men have expectations and therefore (unconscious) knowledge, butt als plants; and, indeed, all organisms.I cannot know if Popper would have embraced this idea of a world of world 3s, as he may have seen some flaw and responded with a conjecture that moved far beyond what I am suggesting. After all, it seems like he spent a lot of time trying to explain world 3 to his audiences. However, what seems beyond dispute is that there are representations of knowledge distributed among the many cooperating systems in our bodies, regardless of whether we assign that knowledge to "world 3."
Popper, Karl R., (1990) . "Towards an Evolutionary Theory of Knowledge" in A World of Propensities, by Karl Popper, 29-51, Bristol, UK: Thoemmes.