DNA from an ancient, unidentified ancestor was passed down to humans
living today

Date:
August 6, 2020
Source:
PLOS
Summary:
A new analysis of ancient genomes suggests that different branches
of the human family tree interbred multiple times, and that some
humans carry DNA from an archaic, unknown ancestor.



FULL STORY ==========================================================================
A new analysis of ancient genomes suggests that different branches of the
human family tree interbred multiple times, and that some humans carry
DNA from an archaic, unknown ancestor. Melissa Hubisz and Amy Williams
of Cornell University and Adam Siepel of Cold Spring Harbor Laboratory
report these findings in a study published 6th August in PLOS Genetics.


========================================================================== Roughly 50,000 years ago, a group of humans migrated out of Africa
and interbred with Neanderthals in Eurasia. But that's not the only
time that our ancient human ancestors and their relatives swapped
DNA. The sequencing of genomes from Neanderthals and a less well-known
ancient group, the Denisovans, has yielded many new insights into
these interbreeding events and into the movement of ancient human
populations. In the new paper, the researchers developed an algorithm
for analyzing genomes that can identify segments of DNA that came from
other species, even if that gene flow occurred thousands of years ago
and came from an unknown source. They used the algorithm to look at
genomes from two Neanderthals, a Denisovan and two African humans. The researchers found evidence that 3 percent of the Neanderthal genome
came from ancient humans, and estimate that the interbreeding occurred
between 200,000 and 300,000 years ago. Furthermore, 1 percent of the
Denisovan genome likely came from an unknown and more distant relative, possibly Homo erectus, and about 15% of these "super-archaic" regions
may have been passed down to modern humans who are alive today.

The new findings confirm previously reported cases of gene flow between
ancient humans and their relatives, and also point to new instances
of interbreeding.

Given the number of these events, the researchers say that genetic
exchange was likely whenever two groups overlapped in time and
space. Their new algorithm solves the challenging problem of identifying
tiny remnants of gene flow that occurred hundreds of thousands of
years ago, when only a handful of ancient genomes are available. This
algorithm may also be useful for studying gene flow in other species
where interbreeding occurred, such as in wolves and dogs.

"What I think is exciting about this work is that it demonstrates what
you can learn about deep human history by jointly reconstructing the
full evolutionary history of a collection of sequences from both modern
humans and archaic hominins," said author Adam Siepel. "This new algorithm
that Melissa has developed, ARGweaver-D, is able to reach back further
in time than any other computational method I've seen. It seems to be especially powerful for detecting ancient introgression."

========================================================================== Story Source: Materials provided by PLOS. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Melissa J. Hubisz, Amy L. Williams, Adam Siepel. Mapping gene flow
between ancient hominins through demography-aware inference of
the ancestral recombination graph. PLOS Genetics, 2020; 16 (8):
e1008895 DOI: 10.1371/journal.pgen.1008895 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200806153558.htm

--- up 3 weeks, 1 day, 1 hour, 55 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)