Question

みみ

what was it〰︎の一文の構文が分からないので教えて頂きたいです。

ear ocean. Yet upon reaching a
shh
Keeling Islands, he found an abundance of marine species
What was it, he wondered, that caused a coral island to become a fertile
oasis amid the nearly lifeless desert of the ocean around it?
This mystery, which became known as "Darwin's Paradox," has long
that the