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Archiver > GENEALOGY-DNA > 2001-03 > 0983561622


From: "Dennis J. Cunniff" <>
Subject: [DNA] Re: genetics and 'ethnicity'
Date: Fri, 02 Mar 2001 14:33:42 -0500
References: <200103020500.f2250R402551@lists5.rootsweb.com>


I'm afraid I've lost track of who said what, but someone said:

> <<<<I would say the general take-home lesson is that it will
> probably be difficult to
> establish very precise ethnicity based on DNA analysis.>>>>

Very much so. Ethnicity is not a biological characteristic.

Someone else replied:

> Not difficult, just time consuming. DNA holds the key to >99% of you physical
> characteristics, and >99% of you ancestral history.

But ethnicity is a social construct, not a biological characteristic. There is little if any biological basis for racial and ethnic classification. (99%, by the way, represents a very large overestimate of the heritability of MOST characteristics.) Nor can DNA be claimed to hold 99% of your ancestral history. You have ancestors whose DNA is NOT reproduced within you. Since you have none of their DNA, you that part of your 'history' is certainly not contained within your DNA.

> You can tell a lot from
> DNA. As the databases grow, the accuracy of the information that can be
> extracted from sequence variations within the genome will greatly increase.
> From a sample of a person's DNA we WILL be able to determine eye color, hair
> color, statue, skin color, and yes, ethnicity. All with very precise accuracy.

Not true. You underestimate the importance of environmental influence and contingent history, and overestimate the importance of genetics.

Eye color probably could be determined, as the environment does not affect the genetic expression of the very few genes that would predict eye color.

Some general idea of hair color probably could also be determined, though here one would have to ignore the influence of sun exposure and of artificial coloration.

Skin color is more problematic, as it involves the expression of more genes, which interact in a complex manner, and again one would have to ignore such environmental influences as sun exposure.

Stature is determined by many factors, mostly nutritional rather than genetic. Here genetics is clearly less important than other factors.

Even an individual's sex is not COMPLETELY determined by that individual's genes. There are medical conditions in which diseases of the mother, (for example, virilizing tumors of the ovary or adrenal glands) result in genetic females with the appearance of males. This could NOT be predicted on the basis of analysis of either the child's or the mother's gene sequence.

Finally, ethnicity is not determined by genetics or by genes. It is socially defined, and not at all rigorously. The fact that people are classified in a certain way does not mean there is a genetic basis for that classification. Would you expect to find a gene for nationality?? For religious sect??

Dennis J. Cunniff.


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