Please note: This is very much a work in progress! Please read, enjoy, and then write me some feedback to BG2006 @ whiteworld. com. I'm particularly interested in which parts you find interesting and which parts you find confusing. Both are things I want to know to make this better. Thanks --Roger
The question of why evolution has developed a certain feature, and why it sustains it, is far from completely answered. There are still a lot of mysteries that Mother Nature knows the answer to that I don't. The following are some of the questions still in my "Unsolved Mysteries" file.
One day I asked my niece, who is well on her way to becoming a doctor, "Can you tell a person's age from their blood?"
Her answer was quick and direct, "No, you can't... except for a very young baby's blood. The blood of a fetus has a different kind of hemoglobin because it's getting oxygen from a placenta, not lungs."
This was not the answer I was expecting, so I thought about it... and came up with interesting thoughts.
First off, this means blood is an "ageless tissue", which makes it very different from skin, muscle, eye... almost every other tissue in the body. All these other tissues are changing constantly with age.
Second, this means that blood's performance of its bodily tasks remains almost constant throughout life. It always carries the same amount of oxygen and carbon dioxide, nutrients and waste products, and it's immune and clotting systems also remain near constant.
Third, this constant nature explains why doctors love to take blood samples and run diagnostics on them. If blood is nearly a constant, then deviations are going to be easy to measure.
Still, it's a mystery that blood doesn't rise and decline in effectiveness the way other tissues do.
Mammals, and reptiles, tend to have five digits for their feet. Why is this? I don't know. I personally have seen cats with six and seven toes, and I've seen pictures of people with four and six fingers. So, it's clear that Mother Nature could select those numbers if they were better choices. Five seems to be the right number... but I haven't yet figured out why.
In the insect, bird and reptile families, females are generally bigger than males. The strong justification for this being "right" is that it takes a lot more resource to produce eggs than it does to produce sperm, so a bigger body for egg-makers is helpful.
But in mammals, males are generally bigger than females. What I wonder is, is this a "necessary evil" that comes as part of the testoerone/estrogen sex hormone system, in effect a tradeoff for getting other valuable features of being a mammal, or is there a benefit to mammals in having large males in it's own right?
Mankind has done a lemons-to-lemon aid transformation on this phenomenon by making the males cooperative bread-winners for females. But is the larger male a benefit for the generic mammal?
This is still a mystery.
Humans and great apes do not successfully make Vitamin C, and this is very unusual. The only other familiar mammal who can't make Vitamin C is the guinea pig. Humans can't make it because there has been a single mutation to the DNA coding for a single liver enzyme.
Humans can get plenty of Vitamin C from other sources, so the mutation is neither beneficial or harmful. It is neutral. Another example of a neutral mutation is eye color -- some people have blue eyes, and some people have brown eyes, and both work equally well.
In theory a neutral mutation of a single gene should "drunk walk" in the gene pool. It should sometimes spread, and sometimes shrink. It can do either because it makes no difference. It is neutral.
But, no people synthesize Vitamin C. This means it's acting like a very favorable mutation, not a neutral mutation. Therefore, I speculate that the Vitamin C mutation is a "genetic marker" for some other very favorable mutation that has spread widely through the human gene pool.
I wonder what favorable mutation Vitamin C is a marker for? That would be a fun mystery to solve.