And despite minor differences, my, my do we show amazing conservation within our created kind!
At the same time the Sa'ami have a reputation for exceptional fertility given the right linkages.
BTW, the Sa'ami have some very clear cold climate adaptations that make them very different.
Charles Darwin himself exhibited some of those genetic adaptations, and his own children displayed approximately the same degree reproductive failure to be expected with an inappropriate Sa'ami mix (his and his wife).