Why are oxygen and hydrogen two of the most abundant elements in living things

Oxygen and Hydrogen are the most abundant elements found in living beings because of their combination to form water together that builds the 70% of the living body, oxygen being used in respiration and Hydrogen being used to form other compounds as it has the simplest structure and least requirements to bond with other elements.

Explanation:

To build something, it's is important to start with the simplest formation and proceed to the complex ones. Same case applies on living beings. With the creation of all living bodies, two of the most abundant elements Hydrogen and Oxygen tends to volunteer in the formation of living bodies. Their simplest structure and least requirements to bond easily with other elements also make them suitable for the creation of living bodies.

Hydrogen consisting of only one proton and one neutron, easily collaborates with other elements and forms the complex compounds. Whereas, oxygen being processed under the respiration system, helps in developing important organs and compounds. And, most importantly not to forget point is that they both combine to make the significant compound of the living body i.e water. However, Carbon, Nitrogen and other traces are also present in the living beings but these two serve as the saviors of the war.

dopamine..

"it was found that some people who were taking the drug l-dopa to raise their levels of dopamine were developing schizophrenic-like symptoms supporting research a strength of the dopamine hypothesis is that there are many studies which have shown support for the neurochemical explanation."