Deep-sea hydrothermal vents were discovered only in 1977, and their discovery overturned a basic assumption of biology. (1) Until then, virtually all…

Deep-sea hydrothermal vents were discovered only in 1977, and their discovery overturned a basic assumption of biology. (1) Until then, virtually all life on Earth was understood to depend, directly or indirectly, on sunlight, since photosynthesis sits at the base of nearly every known food chain. (2) The organisms clustered around the vents, however, derive their energy not from sunlight but from the oxidation of chemicals such as hydrogen sulphide spewed out by the vents themselves, a process called chemosynthesis. (3) Entire ecosystems, including giant tube worms, blind shrimp and unique species of crab, were found thriving in what had been presumed to be a lifeless abyss. (4) Astrobiologists now cite these vent ecosystems as a reason to take seriously the possibility of life on ice-covered moons such as Europa, which never receive sunlight at their ocean floors.

Where would the following sentence best fit?

'This single finding meant that scientists had to abandon the idea that sunlight was a strict prerequisite for life anywhere on Earth, let alone elsewhere in the universe.'