[BroJoeK]

Ruy Dias de Bivar: "Question: If you take two different species, but very similar, and breed them together, they will produce a hybrid species.
HOWEVER, the male of that species will be sterile.
So how did these two species reproduce?"

By definition of the word "species", different species of the same biological genus can, and occasionally naturally do, interbreed.
A good example is Polar Bears (Maritimus) & Brown Bears (Arctos), for many years classified as not just separate species, but also separate genera until...
Until confirmed examples of hybrids showed they do occasionally interbreed in the wild, and so now they are classified as just separate species of the same genus (Ursus).

Likewise with Neanderthals, they were long classified as a separate species, but now with evidence of interbreeding and very similar DNAs, they are considered just another sub-species of homo-sapiens.

That is not to suggest they were just another "race" or breed, since they were more different from us than we are from each other, but they were closely related enough to be classified in the same species.

Clear?

[gleeaikin]

I hope they will do some DNA studies soon on the Kow Marsh (Swamp?) people from Australian sites, who resemble Heidelbergensis types rather than homo sapiens sapiens, even though the remains are only 12,000 years old.