Complex sentence: Wellman did empirical work in this area: he was part of a team (led by James Witte) that surveyed visitors to the National Geographic Society's website in 1998 and used these data to counter the dystopian argument that Internet involvement was associated with social isolation.
Split into simpler sentences: Wellman did empirical work in this area; he was part of a team (led by James Witte) that surveyed visitors to the National Geographic Society's website in 1998. Wellman's unit used these data to counter the dystopian argument that Internet involvement was associated with social isolation.