Coastal South Africa and the Coevolution of the Modern Human Lineage and the Coastal Adaptation

The fossil record indicates that Homo sapiens appears sometime around 195–160 ka (White et al. 2003; Clark et al. 2003; McDougall et al. 2005; Smith et al. 2007). Evolutionary genetics (Ingman et al. 2000; Tishkoff et al. 2007; Gonder et al. 2007; Fagundes et al. 2007; Behar et al. 2008) point to the time between 200 and 100 ka as the origin point for the modern human lineage. Modern humans have relatively very low genetic diversity that is best explained by one or more population bottlenecks late in the evolution of the lineage, with estimates for the first bottleneck ranging from 144 ka (103,535–185,642 ka 95%CI) (Fagundes et al. 2007) to 194.3 ± 32.5 ka (Gonder et al. 2007) to 203 ± 12.6 ka (Behar et al. 2008). Fagundes et al. (2007) estimate the effective population of that bottleneck at ∼600 (76–1,620 95%CI). A computer simulation by Rogers reported in (Ambrose 1998) suggests that this bottlenecked population was a single contiguous breeding group in one region, since if this population sampled a broad range of populations across Africa the original genetic variation would have been preserved. This bottleneck seems to have occurred during the glacial MIS6 (∼195–125 ka), one of the longest coldest stages of the Quaternary (Petit et al. 1999), during which time Africa would have been primarily dry with relatively few isolated refugia.