Variable inheritance

[Terry Reedy]

> > Virtually every creature on earth more sophisticated than a bacterium
> > inherits from two parents :-)
>
> But it never happens between CLASSES of creatures ;-)

This is the old view of evolution as producing a strictly-branching
phylogenetic tree.  However, it is only a first-approximation to the
interconnectedness of DNA-based life on earth.  Examples:

Lichens are symbiotic (and usually obligate) associations between an alga
and a fungus.

All green (chloroplast) plants are descendents of a symbiotic association
between a blue-green alga and the common ancestor(s) of all such plants.

All of us multicellular creatures with mitochondria descend from an ancient
symbiosis between the bacterium (or bacteria?) that became mitochondria and
something else.  We still inherit non-nuclear mitochondrial DNA from our
mothers.

Others have mentioned dog-wolf hybrids and persistent retroviruses.  Plants
hybridize more easily than animals, both naturally and with human
direction.

At a certain period of development, two embryos can sometines be 'mushed'
together to form one creature (a chimera -- the opposite of a twin).  For
instance, successfully combining a white mouse embryo with a black mouse
embryo produces a mouse with black and white fur patches that literally
is-a white mouse + black mouse (with 1 of 2 sets of DNA in each cell).

Genetic engineering makes it more or less possible to mix genes from any
and all creatures.  It turns out the genes do not have is-a identity other
than their sequences.

Terry J. Reedy