Verified answer

There are human hermaphrodites in the sense that they have both a penis and vagina, but at most only one of their sex organs is functional.

Even if both sex organs were fertile, the baby would not be a clone of the parent, because each sperm or egg cell has a different combination of genetic material. So any baby would have "doubles" of some parental DNA and none of other DNA. Having two copies of large portions of DNA typically leads to all sorts of problems of the type you get with babies born from incestual relationships (birth defects, mental retardation, etc. - not exactly prime material for "inifinitely populating the earth").

Also, hermaphrodites result largely from developmental errors, not because of genes. That is, even if a hermaphrodite of the type we are imagining was able to have a self-fertilized baby, that baby would be very unlikely to be a hermaphrodite itself.