How did modern humans settle the world?

How did modern humans settle the world?

In lieu of lots of text, above is a stylized representation of the routes which Neo-Africans took ~50 thousand years ago from their point of departure to parts unknown. The two colors represent two models. The red lines show two major streams issuing out of Africa, a northern route which pushed into the heart of Central Asia, and a southern oceanic one, which pushed all the way into Australia. The second differs, with eastern and western branches of non-African humanity. The models really start to break down within the last ~10,000 years. For example, by either model India has seen an admixture even between the two branches in the Holocene. Additionally, there may have been “false dawns” and admixtures.

In the early 2000s I accept the probable likelihood of the first model. But today I am more leaning toward the second. What’s your stance, and why? I’ll give my rationale below….

The primary reason I’m skeptical of the northern vs. southern route is that Melanesians are clearly southerners, while East Asians and Europeans are northerners. But the phylogenetic stuff I’ve run myself and that I’ve seen using autosomal data sets indicate that …

Razib Khan