Home > Biology > How my children are growing

How my children are growing

It has been more than 3 months since I wrote my last post. While I have never been a daily poster, this is way too much delay between posts even for me. The blame (you readers, might like to use the word “credit”) goes to my two children and insane work schedules at my workplace. Though I have not been writing much, I have not stopped thinking about it. And every time I see my children I am reminded of the wonders of the universe.

“We are a way for the cosmos to know itself” – Carl Sagan

The last time it happened was when Aman was jumping standing on my tummy with me holding his hands for balance. It is almost impossible to believe that a year and a half ago, he did not even exist. A year ago, he was not more than the size of a peanut, he was not even a “he” then. But today, there they are, with all their body parts in perfect shape (more or less), the entire body working together well, growing up at an astounding pace, and slowly gaining intelligence. And that is what fills me with wonder. Let me explain.

I have talked multiple times about evolution, and how we all ended up here. Evolution by Natural Selection is fundamentally simple. Genes change randomly. And bodies change accordingly. The better suited bodies survive better, and naturally, the genes that made the better suited bodies survive too. That is the crux of evolution by natural selection. But that hides an awesomely complex phenomenon. When genes change, how do bodies change accordingly? Or, how do genes make bodies?

Darwin’s theory considers this to be a black box. It assumes that when genes change, bodies change too, which is true. But it does not talk about how that happens. It does not need to. But this area is called developmental biology. I have not read much on this, except for a single book “Endless Forms Most Beautiful” by Sean Carroll. But the feat achieved by the genes is impressive. From a single cell containing the DNA, it goes on to this 2 feet form jumping on my tummy.

Take for example the five fingers of one’s hand. Each of our fingers are different and cannot be substituted with one another. So, the body must know, that at one extreme there must be the thumb and at the other extreme there must be the little finger. And the rest of the fingers needs to be in order too. The extremes should not be mixed up either. Similarly, your hand must sprout from your shoulder and not from your hips. Every positioning has to be accurate with extremely narrow margins of error. Timing too has to be perfect. The cleft lip problem we see in children, is because of a timing issue in development. There must be a 4 dimensional map somehow, so that the body can be accurately built. How does it happen?

The entire development happens with the help of what are called switches, or from my programmer’s perspective, if-then clauses. Coming back to the example of the five fingers, there is a chemical, whose concentration varies along the entire breadth of the base of the hand (when the fingers are yet to be built). Where there is high concentration of that chemical, the genes start building a thumb, at slightly lower concentration, it builds a pointing finger, even less concentration, the middle finger, and so on till the little finger. This means, the genes that build the thumb, do their job, only if a certain amount of concentration of that chemical is achieved. If very high concentration, then thumb. If very low concentration, then little finger. It is this kind of logic that builds the entire body.

Let not this simple example of the hand, make you think, body building is a simple thing. For example, though concentration of a chemical explains the orientation of the fingers, what guarantees that this chemical does not appear near the knee or the elbow, or on the face? We will need to go one step back and then we will see, that this chemical is built by other genes, which are activated only at the base of the hands. That too is another switch.

If at the base of the hand, then release the chemical. ==> If chemical found, then build finger.

You can go one step back and ask how the body decides when a hand is built. And this questioning can continue backwards still you reach the egg. To be sure, these switches are almost never based on a single chemical. Typically they will depend on multiple circumstances. If-this-and-that-but-not-that-and-that,-then-do-this is the kind of logic we will get to see usually. These are influenced by external factors too, since what the mother eats and what she does, could lead to a change in chemical composition of the womb that could in turn affect development. That is why mothers are asked to have nutritious food and to avoid things like cigarettes, when pregnant.

The science of developmental biology is not as well known among the general public as other areas in biology, but it is interesting because it tells us how our astonishingly complex bodies that don’t miss a beat for 70-80 years, are built. I don’t have any illusions that I have explained much in that area in this post, but I hope to have evoked in you a sense of curiosity as to how indeed are bodies built from a single cell. In my next post, I will look at a different reason, this time at a cosmic level, why our very existence should be a source of wonder.

  1. November 29, 2012 at 11:31

    The wonder is summed up in one word : Curveball 🙂 They call it Magnus Effect 🙂

  1. December 28, 2012 at 16:37

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: