First, on page 45, Moalem states, "When rats are exposed to freezing temperatures, their bodies become resistant to their own insulin. Essentially, they become what we would call diabetic in response to the cold." Okay, when I read that I interpreted it as "temporary diabetes". The following statement says, "In areas with cold weather, more diabetics are diagnosed in colder months... Children are most often diagnosed with Type 1 diabetes when temperatures start to drop in late fall." I understand that, too. Now here's my question; children diagnosed with Type 1 diabetes, would that be considered also a "temporary" diagnosis? That may seem like a foolish question, but the reading has not been able to answer that for me. I am curious to know how the children's blood levels are when temperatures are high.
Next, in chapter 3 page 64, Moalem writes, "heavy evolutionary pressure can breed a that into - or out of - a population's end pool in just a generation or two". That is really interesting, but it seems like he is making is sound a lot easier than what it really is. For example, the ACHOO syndrome; I understand it isn't heavy evolutionary pressure to get rid of it, but it seems kind of pointless now, right? Moalem even says it's very dangerous if someone is driving under a tunnel and has a sneezing frenzy when they get out. If this is something that has happened "way back when our ancestors spent more time in caves", wouldn't it not be in our genes? I guess I don't really have a direct question for this topic perhaps just clarification.
Ok, I by no means claim to be an expert on diabetes or genetics, but I think I may have an answer to your questions Rosario. First of all, on the diabetes thing, Moalem says on the bottom of page 25 that "inheritance definitely causes a predisposition to diabetes that can be triggered by some other factor. In the case of Type 1 diabetes, that trigger may be a virus or even an environmental trigger." So I think that in reference to the children who are diagnosed with Type 1 diabetes in the winter, it is not a "temporary" diagnosis, but rather that environmental factors are triggering the emergence of a disease that they had the propensity for all along.
ReplyDeleteAlso, I looked at www.diabetes.co.uk and found that in people who have already been diagnosed with diabetes, their HbA1c levels tend to spike during winter. HbA1c is a compound that occurs when glucose sticks to hemoglobin in the blood, and so it is an indicator of blood sugar levels. This doesn't mean that these people only have diabetes during the winter, but rather that their diabetes becomes a little harder to control during the winter. This interaction between biology and environment seems to support Moalem's hypothesis.
Next, on the issue of evolution within a generation or two, I think it's helpful to look at what Moalem says on the bottom of page 46/top of page 47: "When natural selection goes to work, it doesn't favor adaptations that make a given plant or animal 'better' - just whatever it takes for it to increase the chances of survival in its current environment. And when there's a sudden change in circumstances that threatens to wipe out a population - a new infectious disease, a new predator, or a new ice age - natural selection will make a beeline for any trait that improves the chance of survival." So even though sneezing in the sunlight may be pointless now and even dangerous in some rare instances, if it is not causing large numbers of people with that genetic tendency to die before they are able to reproduce, it will not be eliminated from the gene pool. Similarly, if there is a sudden and drastic change in environment, it is conceivable that all (or most) of the people in that environment without a certain genetic tendency could die off within one or two generations, thus leading to a drastic increase in the rates of that genetic tendency within the population.
To sum up, our body does not intentionally mutate its genes in order to adapt to a certain environment, rather genetic mutations occur randomly and then the environment determines whether or not these mutations will help someone to survive and reproduce. This in turn determines whether or not these genetic mutations will be prevalent in a given population in a given environment. So something won't get removed from our gene pool unless it causes everyone who has it to be unable to reproduce. I hope this helps to clarify what you were confused about.
"This doesn't mean that these people only have diabetes during the winter, but rather that their diabetes becomes a little harder to control during the winter." didn't even think of that, but your answer has definitely cleared up any questions I had with regards to the reading. Thank you very much, I appreciate it!
ReplyDeletep.s. after looking at my post, I must have been drunk (not really, don't take that seriously) when I wrote it because there are so many errors!