Journalism grad student Karen Frantz summarizes:
Tyson argued that representations of aliens in pop culture tend to be anthropomorphized, depicting beings with similar body structures and facial features as ours. He said that it’s egocentric to assume that life on another planet would resemble life on our own, and that to him the most plausible alien character depicted in sci-fi was the Blob -- an amoeba-like villain in the classic 50’s flick.
Dawkins countered by saying that life on Earth has followed predictable paths of evolution, and we might very well expect life on other planets to take a similar course. For example, on Earth, animals on separate continents still share similar genes and characteristics -- eyes and stingers, for example -- despite having long ago split apart on the evolutionary chain.