Saturday, January 31

"Unnatural" Selection

Article Review: The Future of Man - by Peter Ward

It is hard to argue against the fact that so-called “natural” selection has at least significantly slowed, if not come close to a complete halt. All one has to do is look at infant mortality rates today compared to even a few generations ago, let alone a few hundred years ago. Today, people with genetic disorders and/or weak immune systems due to heritable factors, can live to maturity - giving them essentially the same odds of reproducing as individuals with superior genes. Furthermore, another “natural” force driving evolutionary change in "natural populations – adaptations to different geographical environments, or niches – has been effectively negated by recent inventions, i.e. planes, trains, and automobiles. The reason increased mobility negatively effects the rate and quantity of change is that for rare adaptations - such as those that arise in small populations as a result of a niche environment - to persist and become prominent, there must be reproductive isolation. Otherwise, genes that are beneficial only in a niche environment will be diluted out by more prominent genes from immigrants, or lost due to migration of individuals who inherit said genes. In other words, THE DAYS OF “NATURAL” FORCES/PREDATORS SHAPING OUR EVOLUTION ARE ESSENTIALLY OVER.

The article (click the picture, title of the post, or here for the link) discusses the forces driving human evolution today, and some of the possible outcomes. What Ward claims, and I agree, is that THE STRONGEST DRIVING FORCE IN OUR EVOLUTION TODAY IS CULTURE. Meaning the strongest factor affecting what evolutionary biologists define as “fitness” – or the ability to reproduce – is the ability to “fit in.” This doesn’t necessarily mean being cool, but rather being able to find your niche in a particular society or culture. Some people may argue that human behaviors/personalities are not inherited - and therefore cannot influence evolution. However, there is increasing evidence that at least certain behavioral traits – ADHD for example, or tendency towards alcoholism and addiction – are in fact highly heritable traits.

While certainly not all behavioral traits are simply inherited (and therefore highly heritable), and those that are simply inherited are influenced by other factors like random chance and environmental factors, it is my belief that future discoveries will reveal that a significant portion of personality is in fact heritable. Psychologist Eric Turkheimer is quoted in the article “My Genome, My Self,” by Steven Pinker (discussed in the previous post), going as far as to say that,
When it comes to the future, Ward discusses two possible scenarios, both quite science-fiction in nature, but both rational possibilities. One is the infamous artificial intelligence (AI) scenario, in which we create robots with the ability to think for themselves, which then leads to the (inevitable?) ironic ending in which the machines we create, and ultimately come to depend on for survival, end up taking over. All I can say about the AI scenario is: I like to watch movies about the topic. But I certainly don’t have the expertise to speculate about the acumen of any arguments for, or against, the possibility.

The second scenario involves genetic modification, a topic with which I am much more familiar. But before I start , I want to preface my comments by saying that the proceeding concepts (along with AI) are still not feasible, and probably won’t be for quite some time (see previous post).

Now, genetic modification can be broken down into two categories: somatic cell modification (or gene therapy as it is often called) and germ-cell “therapy”. Somatic cell modification will absolutely be a reality at some point in the future, and probably far before germ-cell modification. And when it comes to somatic cell therapy, I personally have no objections (at this point – though I reserve my right to change my opinion – but I certainly have no “moral” objections to the concept). I’m sure, however, that when the possibility does become a reality it will be a hot topic for debate - as there will surely be plenty who feel strongly against it, just as there are many against genetically modified plants now.

When it comes to germ-cell genetic modification, all I really want to say is that, even when our great, great, great…grandchildren have a much better understanding of the human genome, I hope they are smart enough not to mess with germ-cells. What’s to keep every couple expecting a child to have the DNA analyzed to find what to fix. And if you ask me, that scenario can only play out to one end: everyone will be beautiful and intelligent, with an agreeable disposition – after all, WHO WOULD CHOOSE FOR THEIR KID TO BE UGLY AND STUPID?!? That's not to say the human race would turn into a completely homogenous group of “clones,” but it would be a very real possibility - and that’s one of the more benign forecasts when it comes to the possible consequences of messing with germ-cells.

Friday, January 30

Can your genes tell you who you are?

Article Review: My Genome, My Self - by Steven Pinker

It has now been almost exactly 13 years since the cloning of the first mammal (remember Dolly), and in case you haven’t realized, the genomics revolution is in full swing. For the price of a semester's worth of books, you can have your genome scanned for disease risks, ancestry data, and a small sample of traits; for the price of a luxury car, you can get a “complete” sequence (I use quotations because by complete what is really meant is the 1% that codes for proteins). And unlike most things these days, these prices are dropping precipitously. So the obvious questions are: WHAT CAN OUR GENES TELL US ABOUT WHO WE ARE, and what will be the consequences (good and/or bad) of having that information? Steven Pinker, a Harvard College professor of psychology, recently wrote the cover story for The New York Time Magazine on the topic (to link to the article, click on the title of the post - for some reason a direct link doesn't work, but you should be able to get to it from the page you are directed to).

According to Pinker, the two main concerns that have been raised are:

1) Possible discrimination based on genetic data

2) The possibility of companies taking advantage of hypochondriacs by “turning dubious probabilities into Genes of Doom”

In my opinion, the concerns, while something to be aware of, won’t cause significant problems. Bush has already passed a law against using genetic information as a basis for discrimination in the workplace or for healthcare - and there are many diseases for which tests already exist that can determine your susceptibility, so why should the same info coming from a different source cause a new problem? On top of that, I will explain below how discrimination based on genetic information is (like many forms of discrimination) simply a result of ignorance.

As for advantages, the two most obvious are:

1) The possibility for personalized medicine in which drugs are prescribed according to an individual's unique biochemistry

2) Possibility of being able to focus screening and prevention measures on those with the highest risk

Unfortunately, MOST OF THE POTENTIAL BENEFITS OF PERSONAL GENOME SEQUENCING WON'T BE REALIZED IN OUR LIFETIME. What most people don’t understand (including those who championed in the idea of eugenics, popular with many until relatively recently - Hitler being the most famous) is that there are two basic types of inheritance. The first is called Mendelian (aka qualitative, simple) inheritance.

Mendelian inheritance refers to traits that are the result of a single gene with two different versions. The classic example is from Mendel’s work with peas (hence Mendelian inheritance), in which height is controlled by a single gene with two versions, short and tall. In cases such as this, the trait (height) of an individual can be accurately predicted by which versions of the gene it possesses; tall version = tall plant, small version = small plant (another form of Mendelian inheritance has three classes in which 2 talls = tall, 1 tall + 1 short = medium, and 2 shorts = short). While there are a few examples of human traits that are inherited in this manner (diseases such as eye color, cystic fibrosis, Tay-Sachs; also dwarfism), most follow a much more unpredictable mode of inheritance referred to as non-Mendelian (aka quantitative, complex, polygenic) inheritance.

Non-Mendelian inheritance refers to traits that are a result of many different genes, each contributing only slightly. This is the case for most traits in humans, including intellegence and height. Although we can all appreciate the fact that height is a highly heritable trait - “no one thinks Kareem Abdul-Jabbar just ate more Wheaties growing up than Danny DeVito,” - the reason that there aren’t just two or three classes of people (tall, medium, and short) is because dozens to hundreds of genes control human height, each contributing a small amount. This is the case for probably 99% of human traits.

On top of the fact that most traits are controlled by the small effects of many genes, in both kinds of inheritance, traits are also influenced by two other factors that can’t be predicted by your genome sequence: the environment and random chance. This means that even for Mendelian inheritance, where having a particular form of a gene directly determines the physical form of the trait, there will still be variation. This is inherently clear for anyone who has known identical twins. Their genomes are identical, but their personalities, and even physical appearances, are not. These differences are therefore a result of environment and/or random chance (there are actually many other factors that could cause variation, but I'm probably already getting more technical than I should).

Speaking of random chance, the last point I want to bring up is this: MANY MATHEMATICIANS CONSIDER THE PROBABILITY OF A SINGLE EVENT TO BE A MEANINGLESS CONCEPT. For example, when Pinker had his genome sequenced, he discovered he had a gene conferring upon him an 80% chance of baldness. But he’s not bald and shows no signs of balding being a problem in the future. The problem is trying to apply the proportion of people in a sample to an individual person – as Pinker says, “I’m not 80% bald, or even 80% likely to be bald. The most charitable interpretation of the number when applied to me is, ‘If you knew nothing else about me, your subjective confidence that I am bald, on a scale of 1-10, should be 8'.”

I know this post is a bit more than a nugget, but the overall point is this: don’t expect your genome to tell you much more about yourself than you can already find out by other means. In fact, old school means such as aptitude tests (like IQ scores for intelligence, or time in the fifty meter dash for athletic speed), are still much more accurate and informative - and will continue to be so for quite some time. I don't know about you, but I find some comfort in that. I mean, I think its nice to know that your genome can't tell you who you are, or as someone more poetic than I put it, "YOUR GENES ARE NOT YOUR DESTINY."