The nature of this great and mysterious thing that is heredity - the passing on through a bloodline, perpetuated from generation to generation, of a rich ensemble of material and spiritual assets, the continuity of a single physical and moral type from father to son, the tradition that unites members of one same family across the centuries - the true nature of this heredity can undoubtedly be distorted by materialistic theories. But one can, and must also, consider this reality enormously important in the fullness of its human and supernatural truth.

One certainly cannot deny the existence of a material substratum in the transmission of hereditary characteristics; to be surprised at this one would have to forget the intimate union of our soul with our body, and in what great measure our most spiritual activities are themselves dependent upon our physical temperament. For this reason Christian morality never forgets to remind parents of the great responsibilities resting on their shoulders in this regard.

Yet of greater import still is spiritual heredity, which is transmitted not so much through these mysterious bonds of material generation as by the permanent action of that privileged environment that is the family, with the slow and profound formation of souls in the atmosphere of a hearth rich in high intellectual, moral, and especially Christian traditions, with the mutual influence of those dwelling under the same roof, an influence whose beneficial effects endure well beyond the years of childhood and youth, all the way to the end of a long life, in those elect souls who are able to meld within themselves the treasures of a precious heredity with the addition of their own merits and experiences.

Such is the most prized patrimony of all, which, illuminated by a solid faith and enlivened by a strong and loyal practice of Christian life in all its demands, will raise, refine, and enrich the souls of your children.

- from the 1941 Allocution to the Roman Patriciate and Nobility

Even taking into account specific context and audience of the allocution, the ideas self-evidently have much wider application. It is not as if his praise for "the continuity of a single physical and moral type from father to son" can be treated as applying to the nobility only. He even says that parents have a great responsibility in this regard.

How do these ideas alter our interpretation of the following well-known (on this forum) passage from Mit Brennender Sorge?

Whoever exalts race, or the people, or the State, or a particular form of State, or the depositories of power, or any other fundamental value of the human community - however necessary and honorable be their function in worldly things - whoever raises these notions above their standard value and divinizes them to an idolatrous level, distorts and perverts an order of the world planned and created by God; he is far from the true faith in God and from the concept of life which that faith upholds.

Isn't it spelled privileged?

I always want to spell sacrifice as sacrafice, too.

In her Way of Perfection, Theresa of Avila said that she titles of nobility, bloodlines, and things like that were obstacles to holiness.  

So are earthly goods.  It does not mean that earthly goods are not good.

No but too much of an attachment to them is an obstacle to holiness

Belief in the descent of man from apes.

Ahh good one!

How about some others?

Some groups practice very high levels of endogamy for reasons of maintaining a type.

I think the Pope is mainly speaking against biological reductionism.

Theories of heredity that rely too much on the idea of a struggle for survival determining traits, and that would aim for some sort of long term eugenesis as though such a process could overturn original sin.