  We use Big Bang Nucleosynthesis calculations and light element abundance data
to constrain the relative variation of the deuteron binding energy since the
universe was a few minutes old, $\delta Q = Q(BBN)-Q(present)$. Two approaches
are used, first treating the baryon to photon ratio, $\eta$, as a free
parameter, but with the additional freedom of varying $\delta Q$, and second
using the WMAP value of $\eta$ and solving only for $\delta Q$. Including
varying $Q$ yields a better fit to the observational data than imposing the
present day value, rectifying the discrepancy between the $^4He$ abundance and
the deuterium and $^7Li$ abundances, {\it and} yields good agreement with the
independently determined $\eta_{WMAP}$. The minimal deviation consistent with
the data is significant at about the 4-$\sigma$ level; $\delta Q/Q= -0.019 \pm
0.005$. If the primordial $^4$He abundance lies towards the low end of values
in the literature, this deviation is even larger and more statistically
significant. Taking the light element abundance data at face-value, our result
may be interpreted as variation of the dimensionless ratio
$X=m_s/\Lambda_{QCD}$ of the strange quark mass and strong scale: $\delta
X/X=(1.1 \pm 0.3) \times 10^{-3}$. These results provide a strong motivation
for a more thorough exploration of the potential systematic errors in the light
element abundance data.
