View Full Version : Wallace Line and Denisovan Admixture

13-01-16, 20:40
Wallace Line (another variant called Huxley Line) is the boundary between Sahulian animals and Oriental animals:


The Wallace Line or Wallace's Line is a faunal boundary line drawn in 1859 by the British naturalist Alfred Russel Wallace that separates the ecozones of Asia and Wallacea, a transitional zone between Asia and Australia. West of the line are found organisms related to Asiatic species; to the east, a mixture of species of Asian and Australian origin is present. Wallace noticed this clear division during his travels through the East Indies in the 19th century. The line runs through Indonesia, between Borneo and Sulawesi (Celebes), and through the Lombok Strait between Bali and Lombok. The distance between Bali and Lombok is small, about 35 kilometres (22 mi). The distributions of many bird species observe the line, since many birds do not cross even the smallest stretches of open ocean water. Some bats have distributions that cross the line, but other mammals are generally limited to one side or the other; an exception is the crab-eating macaque. Other groups of plants and animals show differing patterns, but the overall pattern is striking and reasonably consistent. Flora do not follow the Wallace Line to the same extent as fauna.[1]


But it corresponds almost exactly also to the extent of Denisovan admixture in indigenous populations of the region:



Apparently the mixing between humans and Denisovans took place only in areas to the east of the line. Or - alternatively - it is also possible that Denisovan-admixed populations living to the west of the line, were later replaced by non-admixed populations.

It can be noted that Negritos in the Andaman Islands (AN - Onge people, etc.) do not have any Denisovan ancestry:


13-01-16, 23:19
there were multiple migrations from into Sahul 55.000 till 3.000 years ago
the first migrations must have been heavy on Denisovan admixture, which was diluted by later arrivals
from 5.500 years on HG in Sundaland were displaced by incoming rice farmers from China, many of these HG fled to Sahul
these probably didn't have Denisovan admixture, otherwise it would have been found in Sundaland as well

14-01-16, 03:57
It seems the Negritos of the Andaman islands and the people living east of the Wallace line dont share any Y dna lineages, its possible that they were simply part of two separate out of Africa groups and the ancestors of the Onge simply didnt mix with any denisovans. Groups west of the wallace line do have small amounts of denisovan heritage like the Tibetans who happen to carry Y dna D like the Onge. Its likely the Onge's ancestors took a root that didnt cross paths with the denisovans and the rest of the asian denisovan lineage from the mainland was largely lost during later migrations of people from Africa which groups east of the Wallace line weren't impacted as strongly by.

14-01-16, 19:15
The existence of Homo Floriensis, which may be a dwarf version of Homo Erectus, is proof that archaics lived beyond the Wallace Line. Maybe the Wallace Line did serve as a barrier and thus saved the last archaics from the same fate as the Neanderthals for a while.

14-01-16, 19:17
Ha! Maybe Homo Floriensis IS a Denisovan! Two attempts have been made to extract DNA that failed. Damn shame.