Question

Historically, biologists assumed that the deep subsurface biosphere—a vast ecosystem of microbes thriving kilometers beneath the Earth's crust—was populated by descendants of surface-dwelling organisms. This traditional model posited that microbes were transported downward over millions of years by tectonic subduction and groundwater circulation, gradually adapting to extreme pressure and nutrient scarcity.

However, microbiologist Elena Rostova recently challenged this view, arguing that deep subsurface life originated *in situ*. Pointing to the unique metabolic pathways of these organisms, which rely on the radiometric decay of rocks rather than solar energy, Rostova contends that the subsurface biosphere represents a distinct evolutionary tree. According to her "deep genesis" hypothesis, life likely first emerged in the extreme conditions of deep hydrothermal systems and subsequently expanded throughout the crust, entirely independent of surface events.

While Rostova’s isotopic data compellingly demonstrates that the biomass in these deep rock fractures has been isolated for billions of years, her conclusion of complete evolutionary independence is premature. Recent genomic sequencing reveals that several dominant strains of subsurface archaea share a remarkably late-diverging common ancestor with surface extremophiles. This genetic overlap suggests that rather than a strict one-way descent or complete isolation, the deep biosphere has likely experienced periodic, bi-directional exchanges with the surface during major geological upheavals.

Based on the passage, which one of the following views is explicitly attributed to Elena Rostova?