It is difficult to say with certainty but a number of factors could be operating.
Vaccination drives since few decades could be responsible for the resurgence of new diseases. Genetic modification of diet and an unprecedented exposure to chemicals of various kinds is another possibility.
From the evolutionary point of view, there is no doubt that from the second half of the previous century, man’s spiritual, psychological, social, and even physical evolution has picked up an unprecedented fast pace leading to lot of upsetting of norms and confusion. It is likely that this has led, on the one hand of an evolutionary lag in many who are either falling out, resisting the evolutionary push or else, as you suggest branching out into new modes of living and ways of being with dropping out of certain old faculties and emergence of some new ones. Nature is indeed in an experimental mode as never before so everything is possible in this hour of the unexpected.
Affectionately,
Alok Da
