Friday, April 1, 2016

Denisovans in Paradise

Or at least Denisovan genes. From Dienekes' Blog: Denisovan ancestry in Oceanians (and some in South Asians). As usual, I continue my assumption that Denisovan women were hot, which is why they became bread into the human line, until fossil evidence proves otherwise.
The Combined Landscape of Denisovan and Neanderthal Ancestry in Present-Day Humans

Sriram Sankararaman et al.

Some present-day humans derive up to ∼5% [ 1 ] of their ancestry from archaic Denisovans, an even larger proportion than the ∼2% from Neanderthals [ 2 ]. We developed methods that can disambiguate the locations of segments of Denisovan and Neanderthal ancestry in present-day humans and applied them to 257 high-coverage genomes from 120 diverse populations, among which were 20 individual Oceanians with high Denisovan ancestry [ 3 ]. In Oceanians, the average size of Denisovan fragments is larger than Neanderthal fragments, implying a more recent average date of Denisovan admixture in the history of these populations (p = 0.00004). We document more Denisovan ancestry in South Asia than is expected based on existing models of history, reflecting a previously undocumented mixture related to archaic humans (p = 0.0013).
So the ancestors of modern man, so called "anatomically modern men" had already encountered Neandertal Men, and incorporated some of their genes, when they moved into Southern Asia and encountered the Denisovans, who they also fell in love with, or something. Early modern man was apparently not very discriminating, NTTAWWT. Or is there?
Denisovan ancestry, just like Neanderthal ancestry, has been deleterious on a modern human genetic background, as reflected by its depletion near genes. Finally, the reduction of both archaic ancestries is especially pronounced on chromosome X and near genes more highly expressed in testes than other tissues (p = 1.2 × 10−7 to 3.2 × 10−7 for Denisovan and 2.2 × 10−3 to 2.9 × 10−3 for Neanderthal ancestry even after controlling for differences in level of selective constraint across gene classes). This suggests that reduced male fertility may be a general feature of mixtures of human populations diverged by >500,000 years.
Denisovan genes caused men to be less fertile? Well, it doesn't seem to have been a big problem, as their are now a lot of people in the world with a share of Denisovan genes. You know, China.

Another interesting article at Dieneke's, this one concerning the Hobbit of Flores, that we've seen previously. New results narrow down the range of time of their occurrence: Middle (not Upper) Paleolithic hobbits
Revised stratigraphy and chronology for Homo floresiensis at Liang Bua in Indonesia

Thomas Sutikna, Matthew W. Tocheri, . . . and a bunch of other people.

Homo floresiensis, a primitive hominin species discovered in Late Pleistocene sediments at Liang Bua (Flores, Indonesia), has generated wide interest and scientific debate. A major reason this taxon is controversial is because the H. floresiensis-bearing deposits, which include associated stone artefacts and remains of other extinct endemic fauna were dated to between about 95 and 12 thousand calendar years (kyr) ago. These ages suggested that H. floresiensis survived until long after modern humans reached Australia by ~50 kyr ago. Here we report new stratigraphic and chronological evidence from Liang Bua that does not support the ages inferred previously for the H. floresiensis holotype (LB1), ~18 thousand calibrated radiocarbon years before present (kyr cal. BP), or the time of last appearance of this species (about 17 or 13–11 kyr cal. BP). Instead, the skeletal remains of H. floresiensis and the deposits containing them are dated to between about 100 and 60 kyr ago, whereas stone artefacts attributable to this species range from about 190 to 50 kyr in age. Whether H. floresiensis survived after 50 kyr ago—potentially encountering modern humans on Flores or other hominins dispersing through southeast Asia, such as Denisovans—is an open question.
Did we get it on with the hobbits too?

Wombat-socho has "Rule 5 Sunday: Time Begins on Opening Day"  ready for sampling at The Other McCain.

No comments:

Post a Comment