So, the whole sixth lumbar vertebra has kind of been of interest to me. I did some online searching and found an interesting article which explains the abnormality some:
[A]pproximately 10% of adults, have a congenital anomaly in their lower back. One of the most common anomalies is the presence of a sixth lumbar vertebra. Having one extra lumbar vertebra provides no advantage or disadvantage to the individual and is rarely a cause of back problems… [A]nomalies such as these in the lumbar spine and sacral spine are simply variants of normal bony architecture and are typically of no consequence. In other words, it would be very rare for an abnormality such as a sixth lumbar vertebra or extra bone in the sacrum to cause back problems.
I’ll file this under “I found it on the internet so therefore it must be true.” My doctor indicated that mine wasn’t of concern since everything was all aligned. I didn’t ask what happens if it isn’t as I was afraid what the answer might be.
It would also appear that the correct term for this “L6” bone is Lumbosacral transitional vertebra.
Now this comment was particularly interesting to me:
You may be interested to find that while the homo sapien is characterized by having five lumbar vertebra but homo erectus (the first of the human skeletons found in Africa, including Lucy and australopithecus africanus skeletons) typically had 6 lumbar vertebra.
Something I was at least able to partially corroborate here. Now, before you decide to start poking fun at me for being less evolved than you, keep in mind that modern great apes have only three or four lumbar vertebrae. It’s all relative.