November 9, 2006

 

Neanderthals in Gene Pool, Study Suggests

By JOHN NOBLE WILFORD

 

 

Scientists have found new genetic evidence that they say may answer the longstanding question of whether modern humans and Neanderthals interbred when they co-existed thousands of years ago. The answer is: probably yes, though not often.

 

In research being published online this week by the Proceedings of the National Academy of Sciences, the scientists reported that matings between Neanderthals and modern humans presumably accounted for the presence of a variant of the gene that regulates brain size.

 

Bruce T. Lahn of the University of Chicago, the report’s senior author, said the findings demonstrated that such interbreeding with relative species, those on the brink of extinction, contributed to the evolutionary success of modern humans.

 

Other researchers in evolutionary biology said the new study offered strong support for the long-disputed idea that archaic species like Neanderthals contributed to the modern human gene pool.

 

Two other reports of DNA studies of possible mixing of human and related genes are expected to be published in the next few weeks.

 

 

Both genetic and fossil studies show that anatomically modern humans emerged 200,000 years ago in Africa and migrated into Europe 40,000 years ago. In about 10,000 years, Europe’s longtime inhabitants, Neanderthals, became extinct. The mainstream interpretation is that modern humans somehow replaced them without interbreeding.

 

In previous research, Dr. Lahn and associates discovered that a gene for brain size called microcephalin underwent a significant change 37,000 years ago. Its modified variant, or allele, appeared to confer a fitness advantage on those who possessed it. It is now present in about 70 percent of the world’s population.

 

The new research focused on the two classes of alleles of the brain gene. One appeared to have emerged 1.1 million years ago in an archaic Homo lineage that led to Neanderthals and was separate from the immediate predecessors of modern humans. The 37,000-year date for the other variant immediately suggested a connection with Neanderthals.

 

Dr. Lahn said it did not necessarily show that interbreeding was widespread. It could have been a rare, perhaps even single, event.

Name ________________________

 

Directions: Read the NY Times article about Neanderthals and Homo sapiens. Next, complete this 3-2-1 sheet.

 

 

 

3 – List three facts/ideas that you found interesting in the article.

 

 

 

 

 

 

 

 

 

 

 

 

 

2 – List two facts that you can recall from the article without looking it again.

 

 

 

 

 

 

 

 

 

 

 

1 – Write one question you have. This should be a complete sentence.

 

In previous research, Dr. Lahn and associates discovered that a gene for brain size called microcephalin underwent a significant change 37,000 years ago. Its modified variant, or allele, appeared to confer a fitness advantage on those who possessed it. It is now present in about 70 percent of the world’s population.

 

Earlier research conducted by the study’s author concluded that a dramatic change in a gene that controls brain size took place 37,000 years ago. The slightly different gene seems to give those who possess it a fitness benefit. About 70% of people now carry this variant gene.

 

The new research focused on the two classes of alleles of the brain gene. One appeared to have emerged 1.1 million years ago in an archaic Homo lineage that led to Neanderthals and was separate from the immediate predecessors of modern humans. The 37,000-year date for the other variant immediately suggested a connection with Neanderthals.

 

The study looked at two types of a variant gene, or slightly different types of the same gene that is found in the brains of modern humans, earlier ancestors with no direct link to modern humans, and Neanderthals. One variant first developed over one million years ago but was not passed on to modern humans as it died out with Neanderthals. The much younger variant that also can be traced to Neanderthals goes back just 37,000 years. Since there is no other modern human ancestor with this gene, the scientists involved with the study feel the gene is strong evidence that Homo sapiens and Neanderthals shared genetic material.

(In addition, as we know from our earlier studies in social studies, Neanderthals only lived in Europe. They would not be direct ancestors as modern humans evolved in Africa.  Modern humans did travel to Europe about 40,00 years ago. As the study indicates, at some point between 37,000 years ago and the extinction of Neanderthals about 30,000 years ago, some members of both species came to share the same gene related to brain size.)