Friday, December 24, 2010
[human migration - the DNA picture]
I have recently been reading about the descent of modern humans from Neanderthals, Denisovans and Africans who lived tens of thousands of years ago. This would seem to contradict the Bible, according to which we are all descended from one man who, according to rabbinical tradition, was created 5771 years ago.
Apparently this is based on the following concept.
Let's say someone wrote a book. Afterwards, copies of the book were made by scribes who were illiterate and could not understand the book however they simply copied whatever they saw. Once in a while a spelling error would be made in the text. Later scribes using that erroneous copy would copy that error. As copies of the book are spread around the world, new errors would be made here and there. Based upon examining which spelling errors appeared in which part of the world, it would be possible to estimate how this book spread around the world. If error #1 appears in German copies and error #1 and error #2 appear in Russian copies, we could guess that the Russian copies were made based on the German copy. Furthermore, if we could estimate about how often a copiest error is made, we could estimate how far back different copies diverged and how long ago the original copy was made. For example, if present day copies contain 1,000 errors and we estimate 1 error per year, then we can assume that the book is 1,000 years old.
Human genetics is a little more complicated because each person is a combinations of genes from his father and mother. This would be similar to each scribe making a new copy based on pages mixed together from two older copies.
There are some problems with all of this however.
First of all it assumes that genetic mutations occur at a certain fairly predictable pace. Secondly, it assumes that certain DNA "spelling errors" will occur only once in history.
In general, I believe that our understanding of DNA is still in its early stages. Cases have been discovered where children did not have DNA matching their mothers' DNA. On the other hand, innocent people have been sent to prison based on false DNA matches.
It's seems questionable to me whether the new DNA studies actually reveal much more than the earlier physical anthropology, anthropometry and craniometry did. There is probably something to it but it's far from infallible.
Posted by jewish philosopher at 1:51 PM