  Stellar evolution theory restricted to single stars predicts a minimum mass
for core-collapse supernovae (CCSNe) of around eight solar masses; this minimum
mass corresponds to a maximum age of around 45 million years for the progenitor
and the coeval population of stars. Binary evolution complicates this
prediction. For example, an older stellar population around 100 million years
could contain stellar mergers that reach the minimum mass for core collapse.
Despite this clear prediction by binary evolution, there are few, if any CCSNe
associated with a distinctly older stellar population...until now. The stellar
population within 150 pc of the Vela Pulsar is inconsistent with single-star
evolution only; instead, the most likely solution is that the stellar
population is $\ge$80 Myr old, and the brightest stars are mass gainers and/or
mergers, the result of binary evolution. The evidence is as follows. Even
though the main sequence is clearly dominated by a $\ge$80-Myr-old population,
a large fraction of the corresponding red giants is missing. The best-fitting
single-star model expects 51.5 red giants, yet there are only 22; the Poisson
probability of this is $1.7 \times 10^{-6}$. In addition, there is an
overabundance of bright, young-looking stars (25-30 Myrs old), yet there is not
a corresponding young main sequence (MS). Upon closer inspection, the vast
majority of the young-looking stars show either past or current signs of binary
evolution. These new results are possible due to exquisite Gaia parallaxes and
a new age-dating software called {\it Stellar Ages}.
