  Recently Venumadhav et al. (2019) proposed a new pipeline to analyze
LIGO-Virgo's O1-O2 data and discovered eight new binary black hole (BBH)
mergers, including a high effective spin, chi_{eff}, one. This discovery sheds
new light on the origin of the observed BBHs and the dynamical capture vs.
field binaries debate. Using a new statistical approach, we show that, while
isotropic models are not ruled out, the observed chi_{eff} distribution favors
field binaries, whose chi_{eff} is determined by tidal forces and wind losses,
over capture. However, given the current limited sample size, capture scenarios
(isotropic models) cannot be ruled out. Observations of roughly a hundred
merges will enable us to distinguish between the different formation scenarios.
However, if as expected, both formation channels operate it may be difficult to
resolve their exact fraction.
