For Scientific American Science Quickly, I'm Kendra Pierloos, in for Rachel Feldman.

This week we're doing something a little different. We're bringing back some of our favorite episodes of the year, starting with our 180th

anniversary special.

A scientific American celebrated the occasion by looking at times in history when science

did an about-face, a complete 180-degree turn.

Moments that had scientists saying, wait, what?

Rachel takes us back in time to some of those unexpected science pivots.

This episode first aired in August.

First up, we have a story from freelance health and life sciences journalist Diana Kwan about

nerve regeneration. For millennia, doctors and scientists believed We have a story from freelance health and life sciences journalist Diana Kwan about nerve

regeneration.

For millennia, doctors and scientists believed that any damage to the nerve cells that

carry signals throughout the body must be irreversible.

While many instances of nerve damage are indeed difficult to treat, scientists have realized

over the past couple of centuries that nerves

can and do regenerate. Throughout this evolution in our understanding of nerves, it was still

widely believed that neurons within the central nervous system, composed of the brain and spinal cord,

were incapable of healing. Now we know that even these most precious neurons can regenerate

under the right conditions. As research continues into exactly which mechanisms encourage or

block neural regeneration throughout the body, scientists are also engaged in another debate,

whether human brains are capable of producing new neurons throughout adulthood.

The phenomenon of adult neurogenesis would have been unfathomable mere decades ago,

...