It was always clear to me that shortsightedness cannot be genetic despite being highly heritable. It is simply too disadvantageous in a pre-glasses environment. In recent years is has become clear that lack of exposure to sunlight is one of the culprits, though near-work such as reading is also likely to blame. Myopia is maybe the most common example of our modern lifestyle disrupting developmental feedback loops and leading to developmental disorders and malformations, but there are many others.
Allergies and asthma is another example. It has long been known, that these disorders are a result of lack of exposure to … dirt, basically.
Another example is flat feet. These are due to shoes preventing foot muscles from developing the strength to support a normal arch.
Now scientist seem to start looking into the development of jaws and teeth. Crooked teeth are a uniquely modern trend. Apparently in skulls older than 500 years, teeth almost always fit perfectly together. Our modern diet leads to an underdevelopment of especially the upper jaw, which means that teeth crowd into too little space. As a result teeth grow crooked, wisdom teeth need to be removed, teeth that just wont fit need to be pulled and the rest straightened by braces.
These stories set me thinking. What more developmental feedback loops might be disrupted by our modern environment? In which ways is our mental development disrupted, which role does developmental disruption play in anorexia, depression, ADHD, autism, etc?
It also gives me a different perspective on mutational load. Many of our developmental feedback loops are probably much more resistant to random mutations than to massive disruptions of the lifestyle we evolved to lead. Hopefully, a healthcare of the future incorporates these insights into preventive care that stops this kind of damage from occurring in childhood and teenage years.