  Wind-interaction models for gamma-ray burst afterglows predict that the
optical emission from the reverse shock drops below that from the forward shock
within 100s of seconds of the burst. The typical frequency $\nu_m$ of the
synchrotron emission from the forward shock passes through the optical band
typically on a timescale of minutes to hours. Before the passage of $\nu_m$,
the optical flux evolves as $t^{-1/4}$ and after the passage, the decay
steepens to $t^{-(3p-2)/4}$, where $p$ is the exponent for the assumed
power-law energy distribution of nonthermal electrons and is typically $\sim
2$. The steepening in the slope of temporal decay should be readily
identifiable in the early afterglow light curves. We propose that such a
steepening was observed in the R-band light curve of GRB 021004 around day 0.1.
Available data at several radio frequencies are consistent with this
interpretation, as are the X-ray observations around day~1. The early evolution
of GRB 021004 contrasts with that of GRB 990123, which can be described by
emission from interaction with a constant density medium.
