`Y Guy' Steps into Human-Evolution Debate

By Bower, B. | Science News, November 4, 2000 | Go to article overview
Save to active project

`Y Guy' Steps into Human-Evolution Debate

Bower, B., Science News

Mitochondrial Eve, meet Y-chromosome Adam. Call him Y guy--he's a younger man, after all. The scientists who tracked down Y guy see him as a potentially key figure in the debate over the location and timing of humanity's origins. Yet other investigators view Y guy as a statistical apparition generated by dubious evolutionary assumptions.

Y guy is a genetic reconstruction of the common ancestor of males today, according to a report in the November NATURE GENETICS. He resided in eastern Africa and first trekked into Asia between 35,000 and 89,000 years ago, say the researchers. In contrast, mitochondrial Eve--the hypothetical common female ancestor of all people today--lived in Africa and migrated into Asia around 143,000 years ago, other researchers have concluded from genetic analyses.

The Y and mitochondrial chromosomes apparently dispersed throughout the human population at different rates, suggest geneticist Peter A. Underhill of Stanford University and his colleagues, who published the new DNA dossier on Y guy. Nonetheless, Underhill's team says, the genetic data behind both Eve and Y guy support the theory that modern humans originated relatively recently in Africa and then spread elsewhere, replacing groups such as the Neandertals.

The researchers used 167 chemical markers to probe alterations of nucleotide sequences in the Y chromosomes in modern men. DNA samples came from 1,062 men from throughout the world. Underhill and his coworkers used a statistical program to identify men with the same sequences. They then constructed a tree of branching evolutionary relationships for men from the different parts of the world.

Men from eastern Africa fell into a genetic group at the root of the Y chromosome tree. Not only did their DNA contain a distinctive pattern, but it exhibited the greatest number of mutations. Underhill's model assumes that such mutations accumulate randomly at a relatively consistent rate over time--like a molecular clock--allowing for their calculation of Y guy's age range.

The Y chromosome segments in the new analysis exhibit much less variability than DNA regions that have been studied in other chromosomes.

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
Cite this article

Cited article

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

`Y Guy' Steps into Human-Evolution Debate


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

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?