I've noticed the focus on being able to transition and combine cultures as a prominent theme of Humankind, and I would like to offer some suggestions on the presentation of race within a civilization. While Civilization 6 had the aspect of having military units reflect the ethnicity of their civililzation, Humankind has the opportunity to expand on such a principle in several possible ways. 

One would be to dynamically change the racial status of the units of a civilization, by shifting in new ethnicities depending on which cultures are adopted. This would be a novel game mechanic that would allow players to see their civilization diversify in a visible way over the course of time, and could serve to further express the multicultural aspect of the game design. Although a downside to this would ultimately be late game civilizations looking roughly the same by the end of the game(unless you could implement a system to have the race changes be proportional, i.e. adding population weight to cultural shifts, or mass migration if a neighboring culture were to be under siege, or have a revolution). 

The second method for race being showcased in the game would rely more on the players input, mainly through the customizable leader option teased in the trailer. Such a method would rely on the stated race for the custom leader, and having it reflected in the game. This would allow for entirely new spins on existing civilizations, such as african vikings, chinese egyptians, or many other interesting iterations. This personal touch could allow players to feel they have attained a unique spin on what might have been( prepare for the eventual ethnostate comments), and quite literally add a palette of color to the dynamics of a players civilization. 

The third method(my personal favorite), doesn't necassarily conflict with the other two but could provide additional identity to regions of the game. This would mean designating certain races to be native to certain biomes(to a degree at least), which could be explored in many ways. For example, the territory of the starting region adheres to the race of either the culture, the player's taste, or the region itself, while expansion of the civilization could diminish the presence of other races depending on policy. Military factions could colonize regions, and introduce their own race, or enslave the natives. The options for the effects on a native race could be wildly more dynamic, such as ethnicities producing more in their homeland or home continent. Races of colonized regions might produce less until they are successfully integrated, and committing genocide could negatively impact fame. Being unable to assimilate a race in an occupied region could lead to a civil war, or a mass exodus of that population. 

Humankind has a lot of potential for becoming a more vibrant and interactive game, and I hope they do give some attention to race as an important aspect of it.  

The developers wrote in the comments on Twitter:

Your culture's skin color will resemble a mix between your avatar and the culture you've chosen.

KonungBalt wrote:

The developers wrote in the comments on Twitter:

Your culture's skin color will resemble a mix between your avatar and the culture you've chosen.

I wish it could more fully adapt in that case, having more customization seems like it would be a fun option

Yes, both your Culture and your Avatar will play a role in the appearance of your units. We're not ready to dive into details about that yet, though.

I believe that the implementation of slavery into the game won't ever be a reality, and could cause some unnecessary conflict when combined with a more fluid system in regards to culture and race. This being said, certain world settings could make interesting scenarios, similar to the different generation settings in Civilization that could have all cultures start on one landmass while the rest are open to colonization later in the game. Whether this would involve "tribes"(I imagine them as less powerful versions of civilizations, such as in Endless Legend. Though repeating that dynamic could be quite stale, we don't want to conquer and pacify all minor factions, it would serve better as a potential facet of a growing culture.), or just leaving such continents vacant, gives an opportunity for much greater replayability. There are many roads you could go down with race as a mechanic, but I believe the most important thing for Amplitude to nail is the feel of a unique culture that the player helps to shape. Regardless, I am beyond excited for this game.

LastMonarchist wrote:

I believe that the implementation of slavery into the game won't ever be a reality, and could cause some unnecessary conflict when combined with a more fluid system in regards to culture and race. This being said, certain world settings could make interesting scenarios, similar to the different generation settings in Civilization that could have all cultures start on one landmass while the rest are open to colonization later in the game. Whether this would involve "tribes"(I imagine them as less powerful versions of civilizations, such as in Endless Legend. Though repeating that dynamic could be quite stale, we don't want to conquer and pacify all minor factions, it would serve better as a potential facet of a growing culture.), or just leaving such continents vacant, gives an opportunity for much greater replayability. There are many roads you could go down with race as a mechanic, but I believe the most important thing for Amplitude to nail is the feel of a unique culture that the player helps to shape. Regardless, I am beyond excited for this game.

Slavery appears in the civic tree so it would deffinitly be there in one form or another ! 

In all honesty, props to Amplitude for making the decision to put Slavery in the game. After diving deeper into ES2, I think the race mechanic will mostly closely represent how ES2 handled population. That would make the most sense for me if captured cities/tribes could be enslaved as units of population, though I would still hope for the ability to have some level of customization over what your civilizations population units look like(i.e. icons, clothing, etc).