
First off, just in case there are those who are going to be confused or not aware of what I'm going for in the title... Here is what we'll be discussing.
I've noticed that most player race seems to be based on the classic human morphology, with the additional of the occasional fin or feather. Looking at a basic view of dimorphism in primates:

The current D&D dimorphism seems to be somewhere between types A and B (Gibbon and Chimp).
Of course we no longer have gender specific stats in D&D for most humanoids... But why not change the way that occasional humanoids are portrayed?
What if Goblin males were Orcs? A male 'goblin' may practice a pride-like existence, dispatching weaker males to have a coterie of females and goblin whelps. To take it further the male's pheremones may produce infertile neuters for protection of the pride, in the form of Ogres or Orogs.
The dimorphism could continue through the races. The female drow of old controlled a matriarchal spiderlike society... Perhaps their males are treated in the same way as certain spider species, being used for reproduction, having shorter lifespans, and lacking the lifespan of their matriarchs, being reduced to the lifespan of a human.
Dark elf males are sent out in sorties, easily replaced and constantly trained to the art of arms and spellcraft but lacking in the overall mystic strength and clerical powers.
Of course you can always choose this for your own races, and you could really go wild. What about an entire society of fertile humanoids of an ancient tree, the tree being a source of reproduction through its pollen or fruits. Mating displays through coloration, plumage/hair, and other features could vary between. 50/50 sexual societies may be a norm, but the idea of a society of infertile Dragonborn produced from the 'teeth' of a dragon (small unfertilized enamel deposits that still reproduce a humanoid but not a dragon).
As has been discussed with dwarves coming from stones, spontaneous generation is another option.
So what are your ideas on dimorphism in D&D and options of reproductive modes within the common and homebrewed races in your setting?
Slainte,
-Loonook.