The speaker is trying to work out where "I" comes from. Is the self just inherited, a bit of DNA from Andy and Elsie, or is it shaped by where a person lives and what they do? The poem never settles this, and the speaker admits that separating the two is "difficult" and "intricate."
The image of melted tin dropped into water suggests a sudden hardening into one fixed shape, as if the self appears in a single moment. But the speaker immediately thinks of the "infinitely others" who might have formed instead. The pun on "re-fuse/refuse" hints at a missing chance to melt down and reshape, or to push back, which leaves the speaker feeling it is "too late."
The closing question is whether the self is "recombinant," a remix of what came before, or "emergent," something new that arises from it. The mood is thoughtful and uncertain, with a quiet unease, and the last word is left hanging alone.