Confusion over this also prompts some grownups to ask adorable questions such as, "if life evolved from simpler life forms such as cyanobacteria, why are there still cyanobacteria". And sometimes they think they've hit upon an answer and it gets published, like a recent Aug 16 article in Science.
but it also means that a species, separated into two or more non-interbreeding populations, can develop into two or more different (but closely related) species. It NEVER happens that a species has two or more independent "parent" species; the branching is always in the "downstream" direction.
It DOES happen. And it's called lateral gene transfer. And it's the reason everything at the bottom of the phylogenetic tree looks very fuzzy. And it's the reason that trees don't match when different genes are used.
I'm scratching my head... I do believe I told you these things some time ago.
Mea culpa, mea culpa. I had meant to specify the multicellular organisms, and am shamefast that I did not. Lateral gene transfer is important in microorganisms.