Human Genetic Origins Go Nuclear

By Bower, Bruce | Science News, July 22, 1995 | Go to article overview
Save to active project

Human Genetic Origins Go Nuclear


Bower, Bruce, Science News


A new method of "absolute genetic dating," announced by scientists last week, promises to rejuvenate molecular studies of the evolution of humans and other animals. While it has not yet resolved disputes over humanity's origin, the technical advance has undoubtedly shifted the terms of the debate.

David B. Goldstein of Pennsylvania State University in University Park and his colleagues devised a way to measure genetic variation between populations at certain sites in nuclear DNA. This enabled them to calculate that an initial split in human evolutionary development probably occurred between Africans and non-Africans about 156,000 years ago.

"Our genetic data suggest that modern humans originated in Africa and spread from there to the rest of world sometime during the last 150,000 years or so, lending strong support to the out-of-Africa theory of modern human origins," Goldstein and his coworkers conclude in the July 18 Proceedings of the National Academy of Sciences.

Most prior studies of genetic evolution used mitochondrial DNA, which is found outside the cell nucleus. Although this approach often supported the out-of-Africa model, statistical flaws undermined it (SN: 2/22/92, p.123).

Supporters of multiregional evolution argue instead that Homo sapiens evolved simultaneously in different parts of the world, beginning 1 million or more years ago (SN: 6/20/92, p.408).

Goldstein's group studied nuclear DNA segments called microsatellites. Nuclear DNA consists of 23 pairs of strandlike chromosomes, built up from structural units called nucleotides. At microsatellite sites, chromosome pairs carry repeated nucleotide sequences; these sites often contain between two and five nucleotide repeats, but the number can reach 40 or more.

Several thousand microsatellites have been identified over the past decade. No one understands their functions fully. Because nucleotide repeat sequences often get added or deleted as a unit, the researchers theorize that the extent of population differences at microsatellite sites marks the passage of time since groups halted consistent interbreeding.

The rest of this article is only available to active members of Questia

Sign up now for a free, 1-day trial and receive full access to:

  • Questia's entire collection
  • Automatic bibliography creation
  • More helpful research tools like notes, citations, and highlights
  • Ad-free environment

Already a member? Log in now.

Notes for this article

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
Loading One moment ...
Project items
Notes
Cite this article

Cited article

Style
Citations are available only to our active members.
Sign up now to cite pages or passages in MLA, APA and Chicago citation styles.

Cited article

Human Genetic Origins Go Nuclear
Settings

Settings

Typeface
Text size Smaller Larger
Search within

Search within this article

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

While we understand printed pages are helpful to our users, this limitation is necessary to help protect our publishers' copyrighted material and prevent its unlawful distribution. We are sorry for any inconvenience.
Full screen

matching results for page

Cited passage

Style
Citations are available only to our active members.
Sign up now to cite pages or passages in MLA, APA and Chicago citation styles.

Cited passage

Welcome to the new Questia Reader

The Questia Reader has been updated to provide you with an even better online reading experience.  It is now 100% Responsive, which means you can read our books and articles on any sized device you wish.  All of your favorite tools like notes, highlights, and citations are still here, but the way you select text has been updated to be easier to use, especially on touchscreen devices.  Here's how:

1. Click or tap the first word you want to select.
2. Click or tap the last word you want to select.

OK, got it!

Thanks for trying Questia!

Please continue trying out our research tools, but please note, full functionality is available only to our active members.

Your work will be lost once you leave this Web page.

For full access in an ad-free environment, sign up now for a FREE, 1-day trial.

Already a member? Log in now.

Are you sure you want to delete this highlight?