>>12575418there were two groups of pre-human hominid: the coastal hominid, and the grassland hominid. coastal hominids lived on the water, ate seafood frequently, regularly built and utilized boats, and lived a more nomadic lifestyle. grassland hominids lived a much more static lifestyle, getting their water from watering holes and utilizing endurance hunting to catch mammalian prey.
the two groups, while distinct, regularly interbred. traits that benefited both lifestyles, such as bipedalism, were selected for at a much faster rate than normal. traits that benefited one group, but didn't harm the other (such as vernix caseosa in coastal humans, an at-birth coating only found in humans and sea lions) got to hang around as well.
eventually, these two groups jointly evolved into the pre-modern human ethnic groups. at some point, the nomadic coastal humans started travelling more broadly into other parts of the eurasian continent, and eventually were cut off from the grassland humans in africa; a divide that didn't reconnect until the last few thousand years, and only with ecological impact within the last few hundred.
