For a real mad scientist scenario, I would anticipate that
human-chimp chimeras would be "viable"-i.e. capable of developing
through to at least the neo-natal stage. This is an extrapolation from
other successful interspecific chimeras-the "geep" (goat + sheep) for
example. What kind of a life such a being could have would give one
pause. Chimeras are produced by literally mixing together two
embryos at, say, the 8 cell blastula stage. Problems of incompatible
karyotypes do not arise.
-Lee Altenberg
Dept. of Zoology, Duke University
