The average speed of a typist is 60 to 120 words per minute. A standard word is five letters, including spaces and punctuation. The comes down to a reaction time of about a fifth to a tenth of a second for each keystroke. Each keystroke involves perceiving the letter, interpreting it, positioning the finger three-dimensionally over the key, and then pressing down with the appropriate pressure at just the right time. If neurons were not fast, typing would not be possible.
The brain has 100 billion neuron cells. Neurons also connect the brain to the rest of the body for our five senses and for activating our muscles. Some neurons are several feet long. The design problem is to get a signal from one end of a neuron to the other, quickly and reliably. The signal at one end is too weak to travel far. If it worked like electricity in a wire, it would degrade over distance. Longer neurons might not function. The actual design of neurons is really ingenious because neurons act more like digital signals than analog signals. Just think about the improvement of FM radio over AM static or digital TV over older models.
Each neuron has a sodium-potassium pump. That means that there are several ions inside and outside the long membrane of neurons that maintain a positive or negative voltage. The cell wall also has particular channels or holes in it that selectively allow some of the ions to pass and block others. When a small voltage triggers a signal at one end of the neuron, the closest sodium channels open and sodium flows into the cell, causing the voltage to go from negative to positive in an instant. That’s like flipping a switch at that particular location.
This design means that neurons are a series of on-off switches rather than a voltage level. The first switch triggers the next switch, which triggers the next one, until the signal reaches the end. Neurons work like a row of dominos falling down, rather than like a wave going across a swimming pool. No signal is lost.
This ingenious system requires the right ions, several membrane proteins, the right cell shape, and much, much more. During the first nine months of a baby’s life, 25,000 neurons are formed ever minute. Each one has to be the right shape and be positioned to connect the necessary parts of the body. All the directions for development are contained in the DNA of the first, single cell created at conception. It’s hard to imagine how many genes it takes to tell the body how to grow, right down to each sodium and potassium channel of each neuron.
That brings us to consider the idea of design by gene mutations. What process would a body go through to transform itself from not having neurons to having neurons? One favorable gene mutation has a one-in-a-hundred million chance of occurring. That needs to be multiplied by the number of genes needed to make neurons. Unfortunately for this idea, there is no way to imagine the existence of a partly-formed neuron. It’s all or nothing. Take all the time you want for your really fast neurons to think about this and really let it soak in.