Featured Research

from universities, journals, and other organizations

Using human genomes to illuminate the mysteries of early human history

Date:
September 21, 2011
Source:
Cornell University
Summary:
Researchers are utilizing the complete genome sequences of people alive today to shed light on events at the dawn of human history, such as the times of divergence of early human populations and of the "out of Africa" migration of the ancestors of modern Europeans, Asians and other non-African groups.

The study shows that the San people -- like the man shown here -- split from other African populations about 130,000 years ago.
Credit: iStockphoto/Giuseppe Masci

Cornell researchers have developed new statistical methods based on the complete genome sequences of people alive today to shed light on events at the dawn of human history.

They applied their methods to the genomes of individuals of East Asian, European, and western and southern African descent. They analyzed only six genomes, but made use of the fact that these genomes contain traces of genetic material from thousands of human ancestors, which have been assembled into new combinations over the millennia by genetic recombination.

The main finding of the study, published Sept. 18 in Nature Genetics, is that the San, an indigenous group of hunter gatherers from southern Africa, diverged from other human populations earlier than previously thought -- about 130,000 years ago. In comparison, the ancestors of modern Eurasian populations migrated from Africa only about 50,000 years ago.

Previous studies of human demography have primarily relied on mitochondrial DNA from the maternal line or Y-chromosome data passed from fathers to their sons, but those studies are limited by small numbers of genomic positions. This study uses the full genome of each individual, providing a richer, more complete picture of human evolution, according to the researchers.

"The use of genomewide data gives you much more confidence that you are getting the right answer," said Adam Siepel, associate professor of biological statistics and computational biology, and senior author of the paper. "With mitochondrial DNA, you are only looking at one family tree [the maternal line], with one pathway from each individual to its ancestors. We are sampling from all possible pathways."

"What's unusual about our methods is that, not only do they use complete genome sequences, but they consider several populations at once," said Ilan Gronau, the paper's lead author and a postdoctoral associate in Siepel's lab. "This is the first paper to put all of these pieces together," he added.

Previous studies using mitochondrial DNA, Y chromosomes and other markers have estimated that anatomically modern humans arose roughly 200,000 years ago in eastern or southern Africa; and that the indigenous hunting-and-gathering central and southern African San people -- one of the most genetically divergent human populations -- diverged from other Africans about 100,000 years ago.

But this study shows that the San people split from other African populations about 130,000 years ago (somewhere between 108,000 and 157,000 years ago). The estimate of an "out of Africa" migration of about 50,000 years ago (somewhere between 38,000 and 64,000 years ago) is consistent with recent findings using other methods, the researchers said.

To conduct the study, the researchers began with a statistical approach that was originally developed to infer divergence times for related but distinct species, such as the human, chimpanzee and gorilla. They faced a number of challenges in adapting these methods for use with human genome sequences. For example, the great ape genome method assumes that gene flow stops after two species diverge, because they can no longer mate. That is not true for distinct human populations, and without accounting for gene flow, the divergence times would have been underestimated, Siepel said.

Gronau used mathematical techniques to work around that problem and then created elaborate computer simulations to demonstrate that the new method worked within known parameters of human divergence.

The study was funded by the Packard Foundation, National Science Foundation and National Institutes of Health.


Story Source:

The above story is based on materials provided by Cornell University. The original article was written by Krishna Ramanujan. Note: Materials may be edited for content and length.


Journal Reference:

  1. Ilan Gronau, Melissa J Hubisz, Brad Gulko, Charles G Danko, Adam Siepel. Bayesian inference of ancient human demography from individual genome sequences. Nature Genetics, 2011; DOI: 10.1038/ng.937

Cite This Page:

Cornell University. "Using human genomes to illuminate the mysteries of early human history." ScienceDaily. ScienceDaily, 21 September 2011. <www.sciencedaily.com/releases/2011/09/110921120122.htm>.
Cornell University. (2011, September 21). Using human genomes to illuminate the mysteries of early human history. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2011/09/110921120122.htm
Cornell University. "Using human genomes to illuminate the mysteries of early human history." ScienceDaily. www.sciencedaily.com/releases/2011/09/110921120122.htm (accessed July 30, 2014).

Share This




More Fossils & Ruins News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Rodents Rampant in Gardens Around Louvre

Rodents Rampant in Gardens Around Louvre

AP (July 29, 2014) Food scraps and other items left on the grounds by picnickers brings unwelcome visitors to the grounds of the world famous and popular Louvre Museum in Paris. (July 29) Video provided by AP
Powered by NewsLook.com
London's Famed 'Gherkin' Goes on Sale for 650 Mln

London's Famed 'Gherkin' Goes on Sale for 650 Mln

AFP (July 29, 2014) London's "Gherkin" office tower, one of the landmarks on the British capital's skyline, went on sale for about 650 million ($1.1 billion, 820 million euros) on Tuesday after being placed into receivership. Duration: 00:36 Video provided by AFP
Powered by NewsLook.com
Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Newsy (July 28, 2014) The asteroid that killed the dinosaurs struck at the worst time for them. A new study says that if it hit earlier or later, they might've survived. Video provided by Newsy
Powered by NewsLook.com
Tourists Disappointed to Find Rome Attractions Under Restoration

Tourists Disappointed to Find Rome Attractions Under Restoration

AFP (July 26, 2014) Tourists visiting Italy at the peak of the summer season are disappointed to find some of Rome's most famous attractions being restored and offering limited access. Duration: 01:01 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins