Genetics

Recently I wrote a piece kind of throwing together the ideas of human evolution and personal genealogy, two things that clearly are ultimately connected because they both come down to simple genetics and who begat whom, but in reality are so separated in time that we cannot properly connect them. But those who accept genealogies and DNA tests for paternity have to accept evolution, because the concepts are the same. Ultimately genes work a certain way and we understand how they work quite well. Evolution is no great mystery or controversy. What is amazing is that Darwin, with no concept of genes, came up with a system that once genes were studied was found to fit very well how genes actually work. Genetics and Evolution started as separate fields, but amazingly the two separate fields merged almost perfectly. To me genealogy is simply what we can see up close of our evolutionary path. Once we get a few generations back, the branches of our ancestry become quite tangled and hard to see...but they are there. And their imprint is in our genes.

Recenly some new developments occurred in studying human evolution that I now want to fit into my previous thoughts on the subject. Slowly it seems like the path of human physical and cultural evolution is being outlined, and I am enjoying each new piece of information.

Race, ethnicity, culture, family...all important to people. But usually we think of these things completely separate from reality.

I have been reading several books that together have put some of this into perspective. Each of us are part of the whole sweep of human evolution, and we are all related in a very real, genetic way.

This man might be your ancestor:

(Ramesses II, king of Egypt, 13th century BC)

Yep, I bet lots of people today could, if only we had all the information, trace their ancestry back to this man. I would guess somewhere in the millions of people today are his descendants.

Go back far enough and we are all related. This is a fact. Or, more precisely, every little piece of our DNA ultimately derives from a common ancestor that can be traced back to some specific time and place.

This has most accurately and famously been done with our mitochondrial DNA. This DNA is something we all get from our mothers, so it is a strictly maternal descent. Men contribute nothing to it. In 1987 an amazing paper in the Journal Nature presented an analysis of modern mitochondrial DNA to show that all human beings can trace their mitochondrial DNA back to a common ancestor living in East Africa some 100-150,000 years ago. At that time some 20,000 anatomically modern humans were around.

Eye color is one of the complex genetic characteristics (called "polygenic" that defies simple Mendelean genetic patterns because multiple genes contribute. Different eye colors result from varying ratios of the two types of melanin pigment produced in the iris: eumelanin (brown/black pigment) and pheomelanin (pink/red pigment).

But recent research indicates that as much as 3/4 of the variation in human eye color comes down to 3 nucleotides of a single gene, making eye color far more simple of a genetic trait than once thought.

As reported in the American Journal of Human Genetics, and summarized in the News and Views of the November 30th, 2006 issue of Nature, a particular region of the OCA2 gene explains ths three-quarters of the variation in human eye colour, and they have found that three single-nucleotide changes in this gene are strongly associated with having blue eyes. This data came from twin studies from 3,839 twins and their family members. OCA2 is the "oculocutaneous albinism II" gene which codes for a protein called "P protein" which in some as yet undetermined way regulates the production of pigment in melanocytes, thus affecting skin and eye color.

Most of our modern crops were not selected for based on nutritional content so much as yield, ease of harvesting, appearance, etc. In other words, human agricultural endeavors have always been superficial, ignoring the inner qualities of our crops.

Turns out, modern science may allow us to improve our modern wheat strains to restore some of the nutritional qualities lost when we selected them from natural crops.

An article in the November 24th issue of Science describes the identification of a gene, Gpc-B1, coding for a protein called NAM-B1 which affects wheat grain protein, zinc, and iron content. This gene is mutated in the version of wheat (T. turgidum ssp. durum) that we use for pasta and bread and which accounts for about 20% of all calories consumed by humans worldwide. The mutation reduces the amount of protein, zinc and iron in the wheat grains by as much as 30%, meaning most of the wheat we consume is defective nutritionally compared with its wild ancestor, emmer wheat (Triticum turgidum ssp. dicoccoides). Crossing wild wheat with modern wheat crops will hopefully allow an increased protein and mineral content of the wheat we consume without affecting (we hope!) things like yield and taste.

The Jewish Genealogical Society (New York) is proud to host the 26th IAJGS International Conference on Jewish Genealogy, August 13-18, 2006 at the New York Marriott Marquis Hotel (45th and Broadway). Learn how to discover your Jewish roots (assuming you have any, of course) and meet others whose ancestors came from the same place you did. Click here for more info.

I will be speaking at the Latvian Special Interest Group Luncheon on Monday, August 14, 12:30 PM - 1:45 PM (the lunch lasts that long...hopefully not my talk!) I will talk about my efforts to restore one of the last wooden synagogues in Eastern Europe: the Green Synagogue of Rezekne. I was very honored to be invited to speak and look forward to the conference.

Studies into the "causes of homosexuality" are extremely controversial. They should not be controversial because people don't like what they imply. Rejecting science because you don't like what it tells you is similar to believing in creationism. But, scientific studies of the sort that show a "cause" of a complex behavior are always suspect. Many have later been discredited or found to be flawed. But, as a scientist I do find it surprising how complex behavior DOES seem to be linked to physical aspects of our selves, including to brain structure and genetics.

Some studies claim that homosexual men have a tiny part of their brain that looks more like the equivalent brain region in women than the male version. This work was done quite some time ago and I know that back then people considered it suggestive but flawed.

More recently, studies have linked homosexuality to having older male siblings. On the one hand such studies are very hard to do well and should always be considered with skepticism. On the other hand, a more recent study not only confirms that correlation, but also suggests that the mechainism for it is in mom.

From BBC News: