Hi David, Wikipedia defines addiction as: Addiction is the continued use of a mood altering substance or behavior despite adverse dependency consequences, or a neurological impairment leading to such behaviors. (http://en.wikipedia.org/wiki/Addiction) I suppose that you could argue that oxygen deprivation causes a definite and dramatic but short-lived mood disturbance, but the key difference I see is that while oxygen is critically necessary to all human life, addictive substances are only necessary to life in some people and under a few special circumstances. These might include, but are not limited to mitigating severe pain, the need for sedation for surgery, or sometimes, in the context of an established addiction. The mild addictions I was talking about, with respect to bata casomorphins 5 and 7, seem to have several predisposing facets: We are born with a leaky gut. This means that during the first months of life human infants lack an effective intestinal barrier in the gut. This barrier slowly develops during those early months when infants are mostly reliant on breast milk. In those early months, the sedating effect of those opioids might well provide a selective advantage. The casomorphins in breast milk behave like morphine. They attach to the same receptors and they have a sedating effect. The children I have observed, when they had a clean diaper, usually fall asleep while suckling or almost immediately after being fed. It seems to me that when hiding from predators, it would be very useful to be able to quickly sedate an infant in order to reduce the risk of detection. Weaning is a difficult time because infants crave breast milk. However, the gradual increase in integrity of the gut barrier probably produces a gradual reduction in the casomorphins that reach the bloodstream, and then, the brain. So we have a built-in weaning mechanism that may persist even up to 3 or 4 years of age. This elegant adaptation reflects the intricate dance between our environment and our hominid or early human forebears. Perhaps suckling at the breast predisposes to addiction in later life. The various social lubricants such as alcohol, nicotine, and even weed, may all be ingested in a similar fashion. These socially acceptable substances often involve a suckling action. Whether a joint, a cigarette, a cigar, a pipe, a bottle, a straw, or a can, these addictive substances can all be ingested by the same suckling action that was imprinted on our brains from the time of each of our births. I am awed by each new insight into natural selection but I really don't think that I misused the term addiction. Please explain how it became a "throw-away word" in my usage of it. best wishes, Ron ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++ Addiction seems like it has become a throw-away word. Everything gets turned into an addiction. The biggest addiction seems to be the drug oxygen. We are all addicted to oxygen. Just look at the withdrawal symptoms when we run out of our oxygen fix. -David H