2014-11-15

Genetic code (DNA) is not enough

Photo: wikipedia.org
Genetic code (DNA) could be seen as the best compression algorithm that we have ever seen. Just think about it: in only around 1 GBytes, DNA could store the information to create a human being, with all the general and specific characteristics and many non-educated behaviors. In 1 GBytes, the current technology could barely store a 1.5 hour movie at rather low quality, but human DNA is able to encode everything that is human in a lifetime.


Technical note: this 1 GBytes is of course an approximation. I started with 3,234 Mb (Mega-basepairs) and I encoded each pair on 2 bits (00,01,10,11), resulting 4 basepairs in each byte. So 3,234Mbasepairs could be encoded in 3,234/4 =~ 1GByte. I am expecting that future discoveries to increase the estimation of genetic information that is stored in a human zygote (the original cell from which each human being emerges). However, I am expecting that the order of magnitude to remain close. Even an 1000 times increase would not matter a lot for this argument.

So, we have a human genetic code that could easily be stored in a personal hard drive, even in your tablet. One could argue that many of the information regarding a human person might not be encoded in the DNA, it could be the result of environment, education, randomness. However, there are many attributes of a human being that cannot be the result of randomness, environment or education.

General body structure:
DNA seems to contains all the information that is needed to create a human being, with all the organs, nerves and a brain ready to learn what a human is usually able to reason. All this are formed in a distinct way for each baby born, different from a chicken or a dog. For mammals, we could question if there is any information transfer in the womb, from mother to fetus. However, the same DNA could create a bird from an egg without any contact with the mother bird (in an incubator). It is not the same complexity of the brain, however the complexity of the organs is in the same magnitude order. It is then likely that the smaller human egg contains also all the information to create the biological structure of the human being.

Body individual characteristics
A human being is born with many inherited specific characteristics (like blue eyes, a split chin, curly hair, etc). DNA also seems to contain a lot of personal physiognomy details, that stays the same in the identical twins for example.

Brain instincts and aptitudes
A human is born with the predisposition to exhibit general human behaviors, like articulate talking, logical and abstract thinking. You cannot teach a dog or even an ape to behave like a human. There must be some specific "support" for this from birth, and this must be encoded in the DNA.

Than, at maturity, there are a huge number of behaviors and rituals that are unlikely to be cultural (for example body language of emotions, mating rituals). All this should be somehow encoded in the DNA also.

Human versus computer games
This is really amazing. As a software programmer, I have no clue how to encode such huge amount of behaviors in such a relatively small program. Many computer games are bigger than a human DNA sequence but are far from exhibiting the same complexity of behaviors.

The heresy
What if not all the information about a human being is actually in the DNA? But where? I am not thinking about hidden information in the zygote cell. We could find such additional information, but it still does not reduce the wonder of encoding a full human being in a such small cell. Even a bird's egg is very small compared with the complexity of a living bird.

The fractal
We know only one artificial phenomenon that resembles with the astonishing complexity emerging from a simple seed. This are the mathematical fractals, that are starting with very simple rules and creates forms that seems very complex (although they are self-similar in nature). Some things in our body seems indeed of fractal nature, like lungs, circulatory and nervous system. This fractal structure could account for a good part of the human body complexity, but many other remains. Each body organs have a very specific structure (like lobes, valves), that is often different from the organs of other species. The human teeth is different in form from other animals and in the same time it has very well preserved attributes for humans. Each specificity must be somewhere encoded in the DNA.

The life
Leaving the human complexity alone, the complexity of any multicellular life seems to be too complex to be encoded in the DNA.

The crazy idea: 
A good part of the life structure is somehow described outside the genetic code, maybe at the Universe level. The DNA only selects some specific functions/behaviors that are preexisting in the fabric of the Universe. I developed a bit this idea in the next post, based on information theory.

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