Given that most systems refer to them as races rather than species...

given that most systems refer to them as races rather than species, is the general consensus that orcs/elves/dwarves etc are homo sapiens sapiens? or are they variant species under homo sapiens?

No, game makers just prefer using "race" to point other sentient beings

Most systems with standard fantasy races don't allow most of them to interbreed, and those that can show discrete racial phenotypes (IE elf, half-elf, human, no intermediate steps). This would indicate that real life genetics just don't apply to these worlds.

Which one is your picture supposed to be?

Isn't one of the definitions of a species the ability for two adults to create offspring that can also have offspring?

Half-orcs, Half-Elves, Half-dwarves, etc. usually aren't sterile in most settings, so they must be the same species.

There's a bunch of different definitions of what constitutes a species. The one you describe is the Biological definition of species, which is one of the more common. It does have points that many people dislike though- For example, polar bears and grizzly bears can produce fertile offspring, making them the same species. I guess we don't need to save the polar bears, as their species isn't endangered?

it's a fantasy setting so who cares, it's just the word used to describe what your characters are looking at and what they might look like.

This is where the concept of sub-species comes in, allowing for a more precise categorization of life.

There's also weird shit like Haldane's Rule, which is that if one gender of hybrids is missing or sterile, it's usually the gender with one copy of each chromosome, eg XY or ZW. So you have a lot of species that can interbreed but only with one gender of child, meaning... what, exactly? Tigers and lions are the same species but only when they're having daughters?

Long story short, "species" is a rough term that made perfect sense when we first started figuring this shit out, and became rapidly less useful and distinct the more we learned about it.

"When geographically separate populations of a species exhibit recognizable phenotypic differences, biologists may identify these as separate subspecies; a subspecies is a recognized local variant of a species."

This does neatly solve the polar/grizzly issue. It would seem to work for fantasy races as long as they remained geographically restricted (which is the case for some settings). Settings with high degrees of racial mixing, in which races can produce fertile offspring, pose an issue in that if these races operated off of real life genetics, the races would blend together over the course of many generations (IE being 1/8 orc, 5/8 elf and 1/4 human) which isn't what's seen. This can be solved by stating that racial mechanics are simply an abstraction, and you use the stats of the race you have the most of, while still having your complex heritage.

Trying to include the following things in a single setting:
1. Many diverse fantasy races (for now, we'll just use humans, elves, dwarves and orcs, but assume there's another dozen or so).
2. Large multiracial cities and general mixing of races (not necessarily the norm, but not unheard of)
3. Production of fertile offspring between races (both sexes of children)
4. As close to real-world genetics as possible
How do you accomplish this?

My first idea is making race act kinda like eye color, with multiple alleles with an internal pattern for what has dominance over what. This would necessitate all races having the coding for the parts of all races, and then these key alleles would determine whether you express orcy bits or elfy bits.

No.

>is the general consensus that orcs/elves/dwarves etc are homo sapiens sapiens
Short answer: No.

Long answer: Nooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo.

>IE elf, half-elf, human, no intermediate steps
I've always taken this as more of a setting/gameplay segregation. Quarter elves may exist but making rules for quarter elves, 3/4ths elves, 1/4th orcs, 3/4th orcs, etc. is tedious and adds very little. Put simply quarter elves exist in most settings, but gameplay wise they are just humans or half elves depending on what the player and DM agree to.

The only reason I could see for having tons of minor racial templates is if interbreeding is a major facet of the setting. So the setting might have a major focus on the different races, their biological and physical differences, and conflicts between them. In this case there is a reason to make a character who is 50% human, 25% elf, 25% orc since it would have a noticeable difference from a regular human presumably and could add to the story within the setting.

Even then though I would only include such a system if the differences between races were massive. Using DnD scale for comparison (10 is human average, 20 is human max)
>Elves get +6 dexterity and can max out at 26 dexterity, they also get +2 intelligence and can max out at 22 intelligence
>Dwarves get +4 strength and constitution and can max out at 24 strength and 24 constitution
>Orcs get +8 strength and can max out at 28 strength
So an average Orc is as strong as an Olympic weight lifter, while an average elf is as dextrous as a professional gymnast. Each quarter of Orc then might add +2 strength plus a fraction of whatever other abilities they have.

In general I think they just call them races because species sounds too "scientific". In my setting though they're all human subspecies that were altered by natural selection or degenerate engineering.

I'm also and agree this is a game play abstraction. However, it does have the side-effect of no one ever playing a 5/8, 2/8, 1/8 character, as that isn't a listed option for race and is never discussed in any books, even if it's a perfectly fine heritage from a setting perspective. I don't think this heritage ought to have super unique mechanics (way too much work to get that level of granularity), just that it's weird that these characters basically don't exist at all. (Human, except for one orcish grandparent and one elvish great-grandparent on the other side, etc.)

It's always bothered me how bulky orcs are. I bet he couldn't even wipe his own ass with all that bulk.

I knew a bodybuilder who never did any stretching or such and so got so bulky and restricted in his motion he couldn't wash his own hair. His arms wouldn't go above his shoulders.

I know there was a thing called ocean of cycles that broke down fantasy species into different races

Might explain why orcs are so grody.

>is the general consensus that orcs/elves/dwarves etc are homo sapiens sapiens? or are they variant species under homo sapiens?

Neither.
The general consensus is that the word 'race' holds different contextual meaning within a fantasy realm, Id Est: the word 'race' is USED to refer to the various sapient other 'species', but many people consider calling the other various peoples simply 'species' to be crass and slightly rude.
It's just like how cannibalism doesn't just mean consuming your own people, but the general eating of the flesh of any intelligent being in a fantasy world: if you're a human and you eat an elf, you're still a cannibal.

>However, it does have the side-effect of no one ever playing a 5/8, 2/8, 1/8 character, as that isn't a listed option for race and is never discussed in any books,
I have played a "human" with only traces of elven ancestry in 5e. I used the stats of a half-elf, but none of the other characters or NPCs thought of my character that way. If you learn to segregate fluff from crunch in your mind, you will have a better time..