  The Oklo phenomenon, natural fission reactors which had taken place in Gabon
about 2 billion years ago, provides one of the most stringent constraints on
the possible time-variability of the fine-structure constant $\alpha$. We first
review briefly what it is and how reliable it is in constraining $\alpha$. We
then compare the result with a more recent result on the nonzero change of
$\alpha$ obtained from the observation of the QSO absorption lines. We suggest
a possible way to make these results consistent with each other in terms of the
behavior of a scalar field which is expected to be responsible for the
acceleration of the universe.
