Luz Bone

Our sages teach that there is a special bone called a "Luz bone" which is indestructible, for never having taken nourishment from the fruit of the "tree of knowledge". Accordingly, God will use it in the future as the means to spark off the resurrection of the body.

There are Torah sources which identify the elusive "luz bone" as the vertebrae at the bottom of the spine (see "Ta'amei HaMinhagim"). The Ari z"l is quoted as teaching the opposite, that it's located at the top of the spine. To me this reads like two end points or poles which define a line. In this case, it defines the line we know of as the spinal cord.

In "Tal Orot", Rabbi Ya'akov Meir Shpielman explains that both parents produce "seed" (reproductive cells) which are enlivened by sparks drawn from the lower edge of the parents' own souls. These sparks originally reside in the mind/brain, the seat of the soul. They then travel down the spine to give life to each parents' "seed". 

At fertilization, the two sparks, one from each parent, merge to form a "starter soul" for the zygote. As development progresses, the fetus' own soul descends and the "starter soul" remains as a garment around it. This is likely the garment referred to in Tanya I, chapter 2, whose spiritual quality can be affected by the thoughts of the parents during the reproductive act.

So by identifying the  "luz bone" as indestructible and as somehow part of the spine, our sages might really be referring to the reproductive sparks within the spine, as they are sufficiently spiritual to be out of physical reach. Though we bury bodies is ways contemplated to ease their resurrection, sadly there were holy martyrs whose bodies were likely physically destroyed. Yet, even about them we say that their "luz bone" remains. Possibly, this supports the notion that it's not in physical reach. Interestingly, in Spanish "luz" means light, which can also be extended to mean spiritual light.

The idea of a non-physical "luz bone" works nicely with the Ramchal's teaching that before Adam and Eve ate the fruit, they weren't physical as we know it. Rather, their version of physical is what we would consider spiritual (see "Da'at Tevunot"). Therefore, if there is a body part which wasn't nourished by the fruit, it's likely that it did not physicalize together with the rest of their bodies.  

If this understanding is correct, then in the future, the human body will be resurrected by its very own reproductive forces. Whether it will be from what's associated with the top of the spine or the bottom, might be a question of the person's own level of holiness. 

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